Procedure for Disinfection of Drinking Water in Ontario (2022)

Preamble

This procedure is a supporting document for Ontario legislation and regulations related to drinking water and specific to water disinfection and any pre-disinfection processes that may be necessary to ensure effectiveness of disinfection. (Note: Provisions of Ontario Regulation 170/03, "Drinking-Water Systems", ("Regulation") a regulation under the Safe Drinking Water Act, 2002 ("SDWA"), adopt this Procedure by reference. For instance, the Procedure is adopted by reference in the provisions in Schedules 1 and 2 to the Regulation that deal with requirements for primary and secondary disinfection.) This procedure supersedes the MOE Procedure B13-3, "Chlorination of Potable Water Supplies in Ontario, January 2001."

The specific requirements in the Regulation to which this procedure pertains are as follows:

  • all municipal drinking-water systems and regulated non-municipal drinking-water systems that are required to provide a minimum level of treatment must have a treatment process that consists of disinfection as a minimum, if the system obtains water from a raw water supply which is ground water;
  • all regulated drinking-water systems that obtain water from a raw water supply which is surface water or ground water under the direct influence of surface water, must provide a minimum level of treatment consisting of chemically assisted filtration and disinfection or other treatment capable of producing water of equal or better quality;
  • all drinking water entering a distribution system that has been treated and is otherwise ready for consumption must contain a disinfectant residual that persists throughout the distribution system unless a point of entry treatment approach is used as permitted by the Regulation; and,
  • effectiveness of the provided treatment must be adequately monitored.

The underlying reasons for these requirements are: to ensure an adequate level of removal or inactivation of pathogenic organisms that may be present in the raw water; to prevent re-contamination of drinking water within the distribution system; and, to maintain drinking water quality throughout the distribution system.

Disinfection is the key element to the achievement of these goals, and any need for pre or post-disinfection treatment related to the achievement of these goals derives from the limitations of the disinfection process. For this reason, although it also addresses these pre- or post-disinfection processes, this procedure is referred to as a disinfection procedure.

The intent of this Procedure is to ensure that new microbiological challenges and new developments in treatment technologies and practices are addressed both in the design of new drinking-water systems and in the upgrading, expansion, and maintenance of existing systems.

1. Disinfection of drinking water

1.1 Introduction

This Procedure provides guidance for:

  • disinfection (primary disinfection), including any pre-disinfection treatment necessary to achieve the required level of removal or inactivation of pathogens potentially present in the source water;
  • the maintenance of a disinfectant residual in a distribution system (secondary disinfection);
  • control of disinfection by-products; and,
  • disinfection following drinking-water system construction or repair.

A clear distinction is made between primary disinfection and secondary disinfection, which are often completely separate treatment processes and provide different outcomes. The former is intended to provide disinfection before the water is delivered to the first consumer and the latter ensures maintenance of a disinfectant residual throughout the distribution system.

1.2 Design and construction of disinfection facilities

The design and construction of both primary and secondary disinfection facilities should normally conform to the criteria set out in the Recommended Standards for Water Works ("Ten State Standards") published by the Great Lakes - Upper Mississippi River Board of State and Provincial Public Health and Environmental Managers (of which Ontario is a member) or, when a site-specific application of an alternative design has been approved by the Ministry, to the construction, operation, and performance requirements criteria stipulated in the approval.

The design recommendations in the Ten State Standards should be considered as representing sound principles of good engineering practice. Variance from the detailed design recommendations may be appropriate, depending on site-specific circumstances associated with an individual drinking-water system. In this context, the Ten State Standards document should be considered as a guideline in the Ontario regulatory framework.

In assessing an application for approval of a drinking-water system, the Ministry’s review team will also be regarding the design recommendations in the Ten State Standards as representative of sound engineering principles and a proponent may be required to demonstrate that any submitted design addresses the issues otherwise addressed by a 'Ten State' recommendation.

The Ten State Standards also include administrative procedures, policy statements, and reporting requirements (including Engineers' Reports) as recommendations. It is important to note that while these may also represent sound principles and good practices, the specific requirements of Ontario legislation, regulations, policies, processes and procedures will prevail over these recommendations.

It is further recognized that the Ten State Standards document focuses on public water supplies which include larger systems; however, many principles and recommended standards contained within the document will also have relevance to even the smallest of drinking-water systems. The designer of a drinking-water system that does not require an approval, and the Professional Engineer undertaking an Engineering Evaluation Report for the system in accordance with regulatory requirements, should have regard to the design recommendations of the Ten State Standards, but also use professional expertise to determine the site-specific relevancy and appropriateness of any single requirement in the context of the drinking-water system being designed or assessed.

The requirements contained elsewhere in this procedure are critical to the design or assessment of treatment processes for all drinking-water systems.

2. Pathogen removal/disinfection requirements

Drinking water disinfection and any pre-disinfection treatment requirements in Ontario are specific to the type of raw water supply a drinking-water system will be relying upon. Design of the treatment processes should consider the characterization, variability and vulnerability of the raw water supply. All water supplies should be individually assessed by measuring relevant water quality parameters and utilizing, where chemical disinfection is used, the CT tables1 provided to determine the appropriate disinfectant dosage. This section outlines the disinfection (primary disinfection) requirements by the type or raw water supply, with variations based on vulnerability of the raw water supply, and includes any applicable pre-disinfection treatment (filtration) requirements.

2.1 Ground water

For the purpose of this document, a raw water supply which is ground water means water located in subsurface aquifer(s) where the aquifer overburden and soil act as an effective filter that removes micro-organisms and other particles by straining and antagonistic effect, to a level where the water supply may already be potable but disinfection is required as an additional health risk barrier, unless the Director has granted a drinking-water system relief, or requirements for exemption have been met in accordance with Ontario Regulation 170/03, "Drinking-Water Systems".

Where the drinking-water system obtains water from a raw water supply which is ground water, the treatment process must, as a minimum, consist of disinfection and must be credited with achieving an overall performance that provides, at a minimum 2-log (99%) removal or inactivation of viruses before the water is delivered to the first consumer.

For example, with ground water of pH 7-8 and temperature 7-10 degrees Celsius (°C), this requirement can be met by a minimum chlorine residual of 0.2 mg ⁄ L, measured as free chlorine, after 15 minutes of contact time determined as T10 at maximum flow rate. For ground water whose conditions are outside this range of pH or temperature, higher CT values may be needed to achieve the required minimum virus inactivation.

2.2 Surface water and ground water under direct influence of surface water

Surface water2 means water bodies (lakes, wetlands, ponds - including dug-outs), water courses (rivers, streams, water-filled drainage ditches), infiltration trenches, and areas of seasonal wetlands.

Ground water under the direct influence of surface water means ground water having incomplete or undependable subsurface filtration of surface water and infiltrating precipitation. The following drinking-water systems are deemed by the Drinking-Water Systems Regulation, to be drinking-water systems that obtain water from a raw water supply that is ground water under the direct influence of surface water:

  • A drinking-water system that obtains water from a well that is not a drilled well or that does not have a watertight casing that extends to a depth of at least 6 metres below ground level.
  • A drinking-water system that obtains water from an infiltration gallery.
  • A drinking-water system that is not capable of producing water at a rate greater than 0.58 litres per second and that obtains water from a well, any part of which is within 15 metres of surface water.
  • A drinking-water system that is capable of producing water at a rate greater than 0.58 litres per second and that obtains water from an overburden well, any part of which is within 100 metres of surface water.
  • A drinking-water system that is capable of producing water at a rate greater than 0.58 litres per second and that obtains water from a bedrock well, any part of which is within 500 metres of surface water.
  • A drinking-water system that exhibits evidence of contamination by surface water.
  • A drinking-water system in respect of which a written report has been prepared by a professional engineer or professional hydrogeologist that concludes that the system’s raw water supply is ground water under the direct influence of surface water and that includes a statement of his or her reasons for reaching that conclusion.

Drinking-water systems that obtain water from a raw water supply which is surface water or ground water under the direct influence of surface water must have a treatment process that is capable of producing water of equal or better quality than a combination of well-operated chemically assisted filtration and disinfection processes would provide. This treatment process must achieve an overall performance that provides at a minimum a 2-log (99%) removal or inactivation of Cryptosporidium oocysts, a 3-log (99.9%) removal or inactivation of Giardia cysts and a 4-log (99.99%) removal or inactivation of viruses before the water is delivered to the first consumer.

At least 0.5-log removal or inactivation of Giardia cysts and 2-log removal or inactivation of viruses must be provided through the disinfection portion of the overall water treatment process.

Chemically assisted direct or conventional filtration and disinfection, and slow sand filtration and disinfection processes operating in accordance with performance criteria provided in subsections 3.4.1, 3.4.2 and 3.4.3 that have been credited with a 3-log (99.9%) removal or inactivation of Giardia cysts, will also be credited with 2-log (99%) removal or inactivation of Cryptosporidium oocysts. Where chlorination is used for primary disinfection, the 2-log removal credit for Cryptosporidium oocysts is considered to be attributed to these filtration processes because chlorine at reasonable doses and contact times is considered to be essentially ineffective in inactivating Cryptosporidium oocysts.

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In the case of membrane and cartridge filtration or other filtration processes that only rely on physical characteristics of the filtration medium, the 2-log removal or inactivation of Cryptosporidium oocysts can only be assigned to the process specifically tested and confirmed by an independent testing agency or the approving Director for this removal or inactivation of Cryptosporidium oocysts or removal of surrogate particles.

Higher log removal or inactivation may be needed for a raw water supply where there is a presence of sewage effluent or other sources of microbial contamination - runoff from livestock operation, manure storage, handling or spreading, etc.

The determination of any additional log removal or inactivation required may also be based upon pathogen monitoring of raw water. This process may be subject to errors, however, when carefully planned, applied and interpreted, it may represent a useful tool in making process design decisions3. Where drinking-water systems are required to have an approval, these considerations should be further discussed during pre-submission consultation to determine the sources of microbial contamination.

For drinking-water systems that are subject to an approval and that rely on a raw water supply which is ground water under the direct influence of surface water, the approving Director may accept that disinfection alone is capable of producing water of equal quality if:

  • a hydrogeologist report, prepared in accordance with the Ministry’s "Terms of Reference for Hydrogeological Study to Examine Ground Water Sources Potentially Under Direct Influence of Surface Water. October 2001" concludes that adequate in-situ filtration is provided by the aquifer overburden, and,
  • wellhead protection measures are being, or will be, implemented in accordance with conditions imposed in the approval.

Should the approving Director concur that it is acceptable that the required treatment is achieved through disinfection alone, the disinfection process or combination of disinfection processes used in these circumstances must be capable of providing an effective inactivation of oocysts, cysts, and viruses. In this context, primary disinfection may need to use both ultraviolet disinfection and chemical disinfection. In this connection, the reader’s attention is directed to section 3.2 of this procedure, Ultraviolet (UV) Disinfection.

3. Disinfection (primary disinfection)

Disinfection (primary disinfection) is a process or a series of processes intended to inactivate human pathogens such as viruses, bacteria and protozoa, potentially present in influent water before the water is delivered to the first consumer.

The entire process of primary disinfection must be completed within the water treatment component of the system, which may include a dedicated part of the piping upstream of the first consumer connection. Where point of entry treatment units are permitted by the Regulation, primary disinfection must be completed within the point of entry treatment unit. Be aware that if point of entry treatment units are to be used at a drinking-water system, the Regulation imposes specific requirements in relation to such units, and these requirements should be carefully reviewed.

Effective disinfection of adequately filtered influent water or raw water of suitable quality can be accomplished by either chemical or physical means such as the use of chlorine, chlorine dioxide, ozone or ultraviolet light. However, the disinfection processes will not be as effective on influent waters of inferior quality.

Because of this limitation in the effectiveness of disinfection processes, in order to achieve the required level of inactivation of pathogens potentially present in a particular raw water supply, depending on the quality of the raw water as well as certain other site-specific conditions, it may be necessary to introduce some additional contamination barriers and/or treatment processes ahead of the primary disinfection stage. These additional requirements will be addressed as part of the Ministry approval or as part of the Engineer’s consideration during the preparation of the Engineering Evaluation Report for systems that do not require an approval.

The following subsections identify specific requirements related to the use of different disinfection processes; the need for and use of different pre-disinfection treatment processes; as well as the pathogen removal or inactivation credits given to these processes and the criteria the processes must meet to qualify for these credits.

3.1 Chemical disinfection

The selection of an appropriate disinfection process depends upon site-specific conditions and raw water characterization that is unique to each drinking-water system. Process selection decisions must consider and balance the need to inactivate human pathogens while minimizing the production of disinfection by-products. Commonly accepted chemical disinfectants are free chlorine, monochloramine, chlorine dioxide and ozone.

Free chlorine residual disinfection ("Chlorination") is the application of chlorine to water to produce a free chlorine residual4 (directly or through oxidation of any naturally present ammonia and/or other nitrogenous substances).

Free chlorine, in the form of hypochlorous acid, is considered a powerful disinfectant that is effective against a very broad range of pathogens. The free chlorine residual from primary disinfection may also be used to maintain a persistent residual within the water distribution system (secondary disinfection). In this case, where ammonia and other nitrogenous substances are present in the influent water, the application of chlorine should be such that the resulting free chlorine residual, at the end of the primary disinfection process, comprises more than 80% of the total chlorine residual5 as only the free chlorine residual is considered a disinfectant for the purpose of secondary disinfection. In situations where breakpoint chlorination is being practiced (to oxidize natural raw water ammonia by the break-point chemistry), it will be effectively complete before the water leaves the disinfection equipment. If this provision were not in place, it is possible that the residual required to protect the water in the distribution system might be prematurely and rapidly lost through continuing break point chemistry.

Free residual chlorination may be achieved through the use of chlorine gas, sodium hypochlorite, calcium hypochlorite or free chlorine producing electrochemical process.

Combined chlorine residual disinfection ("Chloramination") is the application of ammonia and chlorine, with the ammonia addition downstream of the application of chlorine at the mass ratio of chlorine to ammonia of approximately 4.5:1 to produce a combined chlorine residual6 predominantly in the form of monochloramine. Table 14 presents CT values for the inactivation of viruses by chloramines during primary disinfection. This table is only applicable for indicating virus inactivation efficiencies if chlorine is added prior to ammonia.

Monochloramine is a weak disinfectant and it is rarely suitable for use as a primary disinfectant, because at the normally used concentrations it requires very long contact time to achieve adequate disinfection. Because of its high persistence characteristics, monochloramine is more commonly used as a secondary disinfectant to maintain chlorine residual in the water distribution system. In the secondary disinfection process, the sequence of addition of chlorine and ammonia does not affect the efficiency or effectiveness of the formation of combined chlorine residual. In fact, the chemicals can be added in any sequence, or simultaneously, provided proportioning is correctly balanced and a rapid mixing occurs immediately subsequent to the addition.

Chlorine dioxide disinfection involves on-site generation of chlorine dioxide through the reaction of sodium chlorite with chlorine gas, hypochlorous acid or hydrochloric acid, or through the use of an electrochemical process. Chlorine dioxide is a powerful disinfectant that is generally more rapidly effective than chlorine, but less than ozone. The chlorine dioxide residual from primary disinfection may also be used to maintain a residual through part or all of the water distribution system.

Ozone disinfection involves on-site generation of ozone through electrical treatment of oxygen or dry air. Although ozone is a highly effective disinfectant, it does not produce a persistent residual, and is not suitable for the purpose of the maintenance of disinfectant residual in the water distribution system. There is a potential for distribution system biofilm proliferation unless a biofiltration step is included downstream of ozone application.

Note: Where primary chemical disinfectants other than free chlorine are selected, the suitability and effectiveness of these processes must be established on a site-specific basis and the rationale for the selection should be documented by the designer of the drinking-water system or the professional engineer who is responsible for preparing a report on the system.

3.1.1 CT Disinfection concept

The CT disinfection concept uses the combination of a disinfectant residual concentration (in mg ⁄ L) and the effective disinfectant contact time (in minutes), to quantify the capability of a chemical disinfection system to provide effective pathogen inactivation to the required level. The use of this concept involves determining the CT values required at the actual, often variable, operating conditions (flow, temperature, and pH) and ensuring that the employed disinfection process achieves these values at all times.

Chemical disinfection CT values are calculated by multiplying the disinfectant residual concentration (in mg ⁄ L) by the disinfectant contact time (in minutes).

CT = Concentration (mg ⁄ L) × Time (minutes)

The chemical disinfectant residual is measured at the end of each treatment step (e.g., clarification, if a portion of the overall disinfection process is accomplished before filtration) and the contact time used is T10 - the length of time during which not more than 10% of the influent water would pass through that process. The use of T10 ensures that 90% of the water will therefore have a longer contact time.

Actual T10 values can be significantly different from calculated hydraulic detention times (T) and should be determined by a tracer study, mathematical modeling or by calculations using typical baffle conditions. The following table summarizes factors applicable to typical baffle conditions.

Typical baffle conditions
Baffle ConditionT10/T RatioBaffle Description
Unbaffled (mixed flow) separate inlet/outlet0.1No baffles, agitated basin, very low length to width ratio, high inlet and outlet flow velocities
Poor0.3Single or multiple unbaffled inlets and outlets, no intra-basin baffles
Average0.5Baffled inlet or outlet with some intra-basin baffles
Superior0.7Perforated inlet baffle, serpentine or perforated intra-basin baffles, outlet weir or perforated launders
Perfect (plug flow)1Very high length to width ratio (pipeline flow)

CT values can be determined for each process step of the treatment train and summed, where the pH level and chlorine residual remain constant. Calculations should be based on the disinfectant residual concentration as continuously measured at the end of, or at intermediate points within, each process step. Disinfectant concentrations will be assumed to be constant upstream of any monitoring station, at all upstream points up to the next upstream monitoring location or the disinfectant addition point.

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The summed total (calculated) CT value is then compared to the required CT value, which is determined from the CT tables appended to this procedure. The tables7 identify the free chlorine and other chemical disinfectants CT values required for specific values of log inactivation of Giardia cysts and target viruses (hepatitis A) at specific temperatures and pH levels.

The calculated CT value should, at all times during plant operation, be equal to or greater than the required overall CT value.

Where pH and chlorine levels change significantly in different sections of the disinfectant exposed treatment, a more accurate estimate of the overall treatment is obtainable by adding log inactivation values for each type of microbial threat in each section.

Where appropriate, the Integrated Disinfection Design Framework (IDDF)8 method for accounting disinfection decay and true process hydraulic should be used for determining the CT values and associated logs of microbial inactivation in the interest of maximizing pathogen control while minimizing disinfection by-product formation.

3.2 Ultraviolet (UV) Disinfection

The application of ultraviolet (UV) light is an acceptable primary disinfection process. A particular type and design of UV reactor may be considered acceptable if it has been shown to achieve the required level of disinfection through reactor biodosimetry testing using MS-2 bacteriophage and/or Bacillus subtilis spores to establish the flow maxima that the equipment can deliver under different UV transmittances and still achieve the target design dose. Where the considered technology uses UV light source providing radiation at wavelengths different from continuous monochromatic 254 nm wavelength light that is close to the maximally effective germicidal wavelengths of 260-265 nm, the dose delivered by the considered technology must be validated also by empirical biodosimetry testing and the dose must be expressed as a 254 nm-equivalent UV dose.

For drinking-water systems that do not require an approval, as a consideration during the preparation of the Engineering Evaluation Reports, the Engineer should refer to published standards for the UV equipment being considered in order to demonstrate that the required level of disinfection is met for the use of the equipment in question. For point of entry treatment units, ANSI / NSF Standard 55A or equivalent can be referred to for the purposes of the report.

UV facilities should be designed taking into account appropriate reliability and redundancy measures, and the light transmission and scale formation/fouling potential in the UV reactor specific to the quality of the raw water supply. Particular attention is drawn to the recommendations contained with the 'Ten State Standards' for UV systems.

While the use of UV light may be acceptable for the purpose of primary disinfection, it does not provide a disinfectant residual. Where the regulation requires the provision of secondary disinfection for a drinking-water system, primary disinfection must be followed by another process, normally chlorination, which introduces and maintains a persistent disinfectant residual throughout the distribution system.

3.2.1 Ground Water

For ground water which is not under the direct influence of surface water, UV light is acceptable as a primary disinfection process, provided that the UV reactor’s 254 nm-equivalent UV pass through dose of at least 40 mJ ⁄ cm2 is maintained throughout the life time of the lamp.

3.2.2 Surface Water and Ground Water under Direct Influence of Surface Water

Drinking-water systems that obtain water from a raw water supply which is surface water or ground water under the direct influence of surface water must have a treatment process that is capable of producing water of equal or better quality than a combination of well-operated chemically assisted filtration and disinfection. The use of UV light may only be acceptable as a primary disinfection process in combination with chemically assisted filtration (or an equivalent treatment process). UV light on its own is not an acceptable substitute for the chemically assisted filtration step. Where there is a presence of sewage effluent, a primary disinfection process (following chemically assisted filtration) using UV light alone may not be adequate to inactivate certain viruses (e.g., adenovirus). In such cases, a two-stage primary disinfection process consisting of UV light and chemical disinfection, with a proper contact time may be needed. When monochromatic 254 nm wavelength UV light is used in combination with chlorine it does not interfere significantly with the chlorine based disinfection process.

For some drinking-water systems that are subject to an approval and that rely on a raw water supply which is ground water under the direct influence of surface water, the approving Director may accept that disinfection without chemically assisted filtration is capable of producing water of equal quality if:

  • a hydrogeologist report, prepared in accordance with the Ministry’s "Terms of Reference for Hydrogeological Study to Examine Ground Water Sources Potentially Under Direct Influence of Surface Water, October 2001", concludes that adequate in-situ filtration is provided by the aquifer overburden, and,
  • wellhead protection measures are being implemented in accordance with conditions imposed by the approval.

For drinking-water systems meeting the above criteria, the approving Director may concur that the required treatment performance can be achieved through disinfection alone, a two stage primary disinfection process consisting of UV light (UV reactor’s 254 nm-equivalent UV pass through dose of at least 20 mJ ⁄ cm2) combined with chemical disinfection so as to provide an overall 4.0 log inactivation of viruses.

3.3 Other Disinfectants

In the case of other disinfectants or a combination of disinfectants other than those discussed in this procedure it must be demonstrated and documented that the disinfection process in conjunction with filtration (where required) achieves the required level of pathogen removal or inactivation.

3.4 Filtration Process Pathogen Removal Credits

This subsection identifies various filtration technologies and the associated specific pathogen removal credits. These credits only apply when a professional engineer, exercising his or her professional judgement, concludes that the technology design satisfies the Recommended Standards for Water Works ("Ten State Standards") or when a site-specific application of the alternative design has been approved by the Ministry and the operation meets the required performance criteria as discussed in the following subsections. Where possible, the filtration system should be designed and operated to reduce turbidity levels as low as possible, with a goal of treated water turbidity of less than 0.1 NTU at all times. The credits in the following table represent the minimum log removal efficiencies as opposed to average removal efficiencies.

Pathogen removal credits
Treatment TechnologyLog Removal Credit: Giardia CystsLog Removal Credit: VirusesLog Removal Credit: Cryptosporidium Oocysts
Conventional Filtration2.522
Direct Filtration212
Slow Sand Filtration222
Diatomaceous Earth Filtration212*
Membrane Filtration3.0 +0.0 to 2.0 +2*
Cartridge/Bag Filters2.0 +02*

* Applies only when the process has been specifically tested and confirmed for this removal/inactivation or cryptosporidium cysts or removal of surrogate particles.

3.4.1 Conventional Filtration

Conventional filtration is the most common treatment process currently used by drinking-water systems that rely on raw water supplies which are surface water. This treatment process consists of chemical coagulation, rapid mixing, flocculation, and sedimentation followed by rapid sand filtration.

In order to be considered conventional filtration and meet or exceed the 2.5 log Giardia cyst removal, the 2.0 log Cryptosporidium oocyst removal and 2.0 log virus removal credits, the filtration process must meet the following criteria:

  • use a chemical coagulant at all times when the treatment plant is in operation;
  • monitor and adjust chemical dosages in response to variations in raw water quality;
  • maintain effective backwash procedures, including filter-to-waste or an equivalent procedure during filter ripening to ensure that the effluent turbidity requirements are met at all times;
  • continuously monitor filtrate turbidity from each filter; and,
  • meet the performance criterion for filtered water turbidity of less than or equal to 0.3 NTU in 95% of the measurements each month.

3.4.2 Direct Filtration

Direct filtration process consists of chemical coagulation, rapid mixing and flocculation followed by rapid sand filtration. It is very similar to a conventional filtration process but without the sedimentation step prior to filtration. Generally, the use of direct filtration process is limited to raw water supply sources with water turbidity of less than 20 NTU and colour less than 40 TCU. In order to meet or exceed the 2.0 log Giardia cyst removal, the 2.0 log Cryptosporidium oocyst removal and 1.0 log virus removal credit, the direct filtration process must meet the conventional filtration criteria above.

3.4.3 Slow Sand Filtration9

Slow sand filtration is a biological and physical process, equivalent to chemically assisted filtration, where the processes of adsorption and biological flocculation that take place in the gelatinous microbial growth formed in the upper sand layer eliminate the need for chemical coagulation and flocculation. Generally, the use of a slow sand filtration process is limited to raw water supply sources (or influent water after pretreatment) having turbidity of less than 10 NTU and colour less than 15 TCU.

In order to meet or exceed the 2.0 log Giardia cyst removal, the 2.0 log Cryptosporidium oocyst removal and 2.0 log virus removal credits, the slow sand filtration process must meet the following criteria:

  • maintain an active biological layer;
  • regularly carry out effective filter cleaning procedures;
  • use filter-to-waste or an equivalent procedure during filter ripening periods;
  • continuously monitor filtrate turbidity from each filter or take a daily grab sample; and,
  • meet the performance criterion for filtered water turbidity of less than or equal to 1.0 NTU in 95% of the measurements each month.

3.4.4 Diatomaceous Earth Filtration (DE)

Filtration using diatomaceous earth involves the passage of water through a layer of diatomite media supported on a fine metal screen, a porous ceramic material or a synthetic fabric supported on a septum. The initial diatomite layer is usually supplemented by a continuous feed of diatomite. Generally, the use of a DE filtration process is limited to raw supply water sources (or influent water after pretreatment) having turbidity of less than 20 NTU and colour less than 15 TCU.

In order to meet or exceed the 2.0 log Giardia cyst removal, the 2.0 log Cryptosporidium oocyst removal and 1.0 log virus removal credit, the DE filtration process must meet the following criteria:

  • maintain a minimum thickness of pre-coat;
  • maintain effective filter cleaning procedures;
  • maintain full recycle or partial discharge to waste of water flow during filter precoat until the recycle stream turbidity falls to below 1.0 NTU;
  • continuously monitor filtrate turbidity from each filter; and,
  • meet the performance criterion for filtered water turbidity of less than or equal to 1.0 NTU in 95% of the measurements each month.

3.4.5 Cartridge/Bag Filters

This technology is designed to meet the low flow demands of small systems. These filters can effectively remove particles from water in the size range of Giardia cysts (5-10 microns) and Cryptosporidium oocysts (2-5 microns). Cartridge filters do not remove any significant proportion of influent viruses. Generally, the use of cartridge/bag filtration processes is limited to raw water supply sources (or influent water after pretreatment) having turbidity of less than 5 NTU and colour less than 5 TCU.

Cartridge and bag filters are made from fibre, and unlike membranes, have a broad range of pore/opening sizes which allow penetration of a few larger sized particles than the filter rating. This small penetration rate by oversized particles should be taken into consideration along with the quality of the raw water supply.

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In order to claim the 2.0 log Cryptosporidium oocyst removal credit, the cartridge/bag filtration process must meet the following criteria:

  • use filter elements and housing certified for surrogate particle removal evaluation in accordance with testing procedures and manufacturing quality control specified in ANSI/NSF Standard 53 or equivalent;
  • continuously monitor filtrate turbidity from each filter or take a daily grab sample; and
  • ensure that differential pressures across the filter medium do not exceed manufacturer’s rating and materials coming in contact with water conform to ANSI/NSF Standard 61.

Normally, the filter should meet the performance criterion for filtered water turbidity of less than or equal to 0.2 NTU in 95% of the measurements each month. Where it can be shown that turbidity results from the presence of inorganic particles of a size less than 2 microns, higher turbidity may be acceptable.

3.4.6 Membrane Filtration

Membrane filtration processes involve passage of the water through a thin synthetic organic polymer film in a straining filtration step. Membranes that require moderate to low pressures for adequate flow (micro and ultra-filters) must have chemically formed and uniformly sized pores that are 1 micron or less in diameter. Higher pressure membrane filters (nano and reverse osmosis filters) have no pores but allow water to permeate or diffuse through the membrane. Virus removal capability will vary with type and manufacturer of a particular membrane.

In order to claim 2.0+ log Cryptosporidium oocyst removal credit, the membrane filtration process must meet the following criteria:

  • maintain effective backwash procedures, including filter-to-waste or an equivalent procedure, to ensure that the effluent turbidity requirements are met at all times;
  • monitor integrity of the membrane by continuous particle counting or equivalently effective means (e.g., intermittent pressure decay measurements);
  • continuously monitor filtrate turbidity; and,
  • meet the performance criterion for filtered water turbidity of less than or equal to 0.1 NTU in 99% of the measurements each month.

3.4.7 Other Filtration Technologies

In the case of the provision of a filtration technology other than those discussed in this procedure, before using the technology, it must be demonstrated and documented that the filtration technology in conjunction with disinfection achieves the required level of pathogen removal or inactivation.

4. Disinfectant residual maintenance (secondary disinfection)

The maintenance of a disinfectant residual in the distribution system (secondary disinfection) is intended to maintain (or introduce and maintain) a persistent disinfectant residual to protect the water from microbiological re-contamination, reduce bacterial re-growth, control biofilm formation, and serve as an indicator of distribution system integrity (loss of disinfectant residual indicating that the system integrity has been compromised). Only chlorine, chlorine dioxide and monochloramine provide a persistent disinfectant residual and can be used for the maintenance of a residual in the distribution system.

Where the provision of secondary disinfection is required by the Regulation, the drinking-water system’s distribution system must be operated such that at all times and at all locations within the distribution system, where there is a daily flow, there is at least a free chlorine residual of 0.05 mg ⁄ L at a pH 8.5 or lower10 , or chlorine dioxide residual of 0.05 mg ⁄ L, or where monochloramine is used, a combined chlorine residual of 0.25 mg ⁄ L.

The maximum chlorine residual at any time and at any location within the distribution system should not exceed 4.0 mg ⁄ L when measured as free chlorine, 0.8 mg ⁄ L when measured as chlorine dioxide, and 3.0 mg ⁄ L when measured as combined chlorine. (Note: A combined chlorine residual of 3.0 mg ⁄ L is equivalent to the maximum acceptable concentration of 3.0 mg ⁄ L for chloramines allowed by the Ontario Drinking-Water Quality Standards.)

The recommended optimum target for free chlorine residual concentration in a water distribution system is 0.2 mg ⁄ L at a pH 8.5 or less. The recommended optimum target for combined chlorine residual for systems designed to operate with chloramination is 1.0 mg ⁄ L at all locations within the distribution system to suppress bacterial activity that converts ammonia to nitrite and nitrate.

Drinking-water systems using only chloramination as a secondary disinfection, where addition of ammonia is properly adjusted as required, would not show any free chlorine residual in tests of distribution system samples. For such systems the measurement of total chlorine residual only would be adequate to represent the value of combined chlorine residual.

In larger water distribution systems, maintenance of the minimum required residual may not be possible without the operation of re-chlorination facilities at one or more points within the distribution system. Rapid decay of a disinfectant residual may occur as a result of a number of other causes such as heavy encrustation or sediment accumulation and biofilm activity and may require investigation and specific corrective action such as engineered flow velocity increases, and swabbing or pigging/lining and/or main replacement.

Note: The application of disinfectant for the maintenance of a residual does not require contact time.

5. Disinfection of drinking-water systems after construction or repairs

All parts of drinking-water systems in contact with drinking water which are taken out of service for inspection, repair or other activities that may lead to contamination before they are put back in service, must be disinfected in accordance with the provisions of the AWWA Standard for Disinfecting Water Mains (C651), AWWA Standard for Disinfection of Water Storage Facilities (C652), AWWA Standard for Disinfection of Water Treatment Plants (C653), and AWWA Standard for Disinfection of Wells (C654) or an equivalent procedure that ensures the safety of drinking water that is delivered to consumers.

6. Monitoring

6.1 Primary Disinfection

All systems providing primary disinfection must ensure that routine monitoring of the relevant parameters associated with the performance of the disinfection process is being carried out to ensure that water that is directed to consumers is being properly disinfected. Primary disinfection facilities for all municipal residential drinking-water systems must be equipped with continuous disinfection process monitoring and recording devices with alarms unless otherwise specified in the Regulation.

For drinking-water systems that are not required by the Regulation to have continuous monitoring equipment11, it is strongly recommended that such systems consider installing such equipment. Non-municipal systems that do not have continuous monitoring equipment installed must analyze manual grab samples on a daily basis for the parameters specified in the Regulation.

Where appropriate instrumentation is available, consideration may be given to using continuous monitoring data to provide a real-time and recorded display of the relevant CT data and microbial inactivation/removal logs being achieved by the overall treatment process for all targeted microbial threats.

6.1.1 Free Chlorine Residual Disinfection

Except for situations identified below, the free chlorine residual analyzer(s) installed for the purpose of continuous monitoring of a primary disinfection process utilizing free chlorine residual, must take a continuous sample at the downstream end of the primary disinfection process. Where the complete primary disinfection is accomplished through a series of distinct disinfection processes/steps, a continuous sample must be taken at the downstream end of each such distinct process/step. In all cases, the location must be ahead of the point of addition of any post-disinfection chemicals, including those intended for the purpose of ensuring maintenance of disinfectant residual in the distribution system or preventing corrosion in the distribution system. For non-municipal or municipal non-residential systems where continuous monitoring devices are not installed, daily monitoring using manual grab samples at the same locations must be performed.

Where the chlorine contact time necessary to complete the process of primary disinfection is provided by a dedicated section of the piping upstream of the first consumer connection, the chlorine residual analyzer installed for the purpose of monitoring completion of the primary disinfection process may take a continuous sample at an intermediate location, between the point of the addition of chlorine and the down-stream end of the section of the piping used for the primary disinfection contact time, provided that the continuous sample adequately simulates the contact time.

For a raw water supply which is ground water, where the chlorine consumption characteristics of the influent water is sufficiently stable to allow establishment of a reliable chlorine depletion algorithm, a grab sample or a continuous sample may be taken at a location other than the downstream end of the section of the piping used for the primary disinfection contact time. In such a case, based on the established chlorine depletion algorithm, a minimum chlorine residual concentration, necessary to maintain the residual at the end of the dedicated chlorine contact section of the piping must be maintained at the level required for complete primary disinfection.

Every free chlorine residual analyzer installed for the purpose of monitoring a primary disinfection process utilizing free chlorine residual, must be calibrated at a frequency necessary to ensure appropriate operation of the analyzer within a quality control band of plus/minus 0.05 mg ⁄ L at a chlorine concentration up to and including 1.0 mg ⁄ L or plus/minus 5.0% at a chlorine concentration greater than 1.0 mg ⁄ L.

6.1.2 Chlorine Dioxide Residual Disinfection

The location and installation of chlorine dioxide residual analyzer(s)12 for continuous monitoring of a primary disinfection process utilizing chlorine dioxide residual should follow the recommendations provided in section 6.1.1. In addition, at frequencies appropriate for site-specific conditions (type of chlorine dioxide generator, water quality, etc.), grab samples should be taken from the same location and analyzed for chlorite and chlorate concentrations.

6.1.3 Monochloramine Residual Disinfection

The location and installation of total and free chlorine residual analyzer(s) for continuous monitoring of a primary disinfection process utilizing monochloramine chlorine residual should follow the recommendations provided in section 6.1.1. In addition, at frequencies appropriate for site-specific conditions and water quality, grab samples should be taken from the same location and analyzed for total chloramines and monochloramine concentrations.

6.1.4 Ultraviolet (UV) Light Disinfection

All UV disinfection facilities must continuously monitor such parameters that allow the operator to determine that the target design 254 nm-equivalent UV pass through dose or higher is being delivered, and all systems must provide annunciated failure alarms when this design dose is not being delivered.

Equipment that records test results of the continuous monitoring equipment is strongly recommended for drinking-water systems using a surface water supply or a groundwater supply under the direct influence of surface water. All sensors that constitute part of the monitoring system must be calibrated at a frequency that maintains their necessary sensitivity and reliability in ensuring that the design UV dose is being achieved. Calibration frequencies are to be determined as part of the process of obtaining Ministry approval or should be provided to the owner by the Engineer in the Engineering Evaluation Report, with specific regard to the manufacturer’s instructions.

6.1.5 Turbidity

Regulated drinking-water systems that obtain their water from a raw water supply that is surface water or ground water under the direct influence of surface water, may be required by the Regulation to be equipped with continuous water turbidity monitoring and recording devices with alarms on each filter effluent line.

(Video) How-to analyze monochloramine and free ammonia in a drinking water sample

If a drinking-water system is not required by the Regulation to have continuous monitoring equipment to monitor turbidity, it is, nonetheless, strongly recommended. Systems not required to have continuous monitoring and which choose not to install such equipment must ensure that a water sample is taken at least once a day on each filter effluent line and is tested for turbidity.

Water turbidity analyzers installed at water treatment plants utilizing a raw water supply which is surface water or ground water under direct influence of surface water, should take a continuous sample upstream of the primary disinfection process. For systems where continuous monitoring equipment is not installed, the daily water sample should be taken from this same location.

Every water turbidity analyzer installed for the purpose of monitoring the effectiveness of the filtration process (usually ahead of the primary disinfection process) must be calibrated at a frequency necessary to ensure the appropriate operation of the analyzer.

6.2 Maintenance of disinfectant residual in a distribution system

Information obtained through the monitoring of disinfectant residual in the distribution system in accordance with the Regulation, should be used to assess the effectiveness of secondary disinfection throughout the distribution system, as well as to control the level of disinfectant in the water leaving the water treatment plant and any re-chlorination facilities located within the distribution system.

It is recommended that the facilities provided for the purpose of the introduction, change, or adjustment of disinfectant residual in the distribution system at re-chlorination facilities or at the water treatment plant, be provided with equipment for continuous monitoring of the operation of the facilities and an alarm system.

Where a treatment process that is operated downstream of natural or engineered filtration produces turbidity solely due to oxidation or chemical precipitation, the turbidity does not present a health hazard. For aesthetic reasons, however, it is recommended that turbidity levels be maintained below 5.0 NTU. In such cases, turbidity may be monitored with grab samples taken at the entrance to the distribution system.

7. Disinfection by-products

Chemical disinfectants may be capable of producing by-products13 in quantities that may present long-term health risks to the drinking water consumer. The concentrations of disinfection by-products (DBPs) produced are specific to the type of disinfectant, the chemical make-up of the naturally occurring organic precursors and their concentrations in water prior to chlorine (or other chemical disinfectant) addition, the concentration of the disinfectant in water, and the retention time in the drinking-water system before reaching the consumer’s tap.

The claim for CT credits related to chemical disinfection should be supported by evidence that the treatment processes are designed and operated for efficient DBP precursor removal before the primary disinfection process. Chemical disinfectant addition should not take place upstream of the precursor removal process(s), unless the use of prechlorination can be justified by the raw water source quality including active mussel veliger content, measurement of DBP formation potential, and other site specific conditions.

To control the formation of DBPs in the drinking-water systems, the following should be considered:

  • source water protection, including nutrient and algal management;
  • DBP precursor removal by optimization of chemical and physical treatment process prior to chemical disinfection; and,
  • disinfection strategy selection involving adjusting, and where possible, delaying and reducing the usage of, and minimizing, active chemical disinfectant contact and treated water storage time. When there is evidence to suggest such adjustments may be insufficiently effective, consideration should be given to the use of one or more disinfectants or pre-disinfection process steps selected from the following: disinfection with UV light, alternative chemical disinfection with chlorine dioxide or ozone, optimization of pretreatment oxidation, if present, or, using monochloramine as the distribution system disinfectant. It should be noted that the use of ozone in a pre-disinfection process has a potential for greater disinfection by-product formation when chlorine is added downstream.

Notwithstanding the above, the treatment processes must be designed and always operated to achieve the required removal or inactivation of pathogens as a priority with the minimization of disinfection by products formation as a secondary objective.

Table 1 – CT values for inactivation of Giardia cysts by free chlorine at 0.5°C or lower (pH 6)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.423466991114137
0.624477194118141
0.824487397121145
125497499123148
1.2255176101127152
1.4265278103129155
1.6265279105131157
1.8275481108135162
2285583110138165
2.2285685113141169
2.4295786115143172
2.6295888117146175
2.8305989119148178
3306091121151181
Table 1 – CT values for inactivation of Giardia cysts by free chlorine at 0.5°C or lower (pH = 6.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4275482109136163
0.6285684112140168
0.8295786115143172
1295988117147176
1.2306090120150180
1.4316192123153184
1.6326395126158189
1.8326497129161193
2336699131164197
2.23467101134168201
2.43468103137171205
2.63570105139174209
2.83671107142178213
33672109145181217
Table 1 – CT values for inactivation of Giardia cysts by free chlorine at 0.5°C or lower (pH = 7)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4336598130163195
0.63367100133167200
0.83468103137171205
13570105140175210
1.23672108143179215
1.43774111147184201
1.63875113151188226
1.83977116154193231
23979118157197236
2.24081121161202242
2.44182124165206247
2.64284126168210252
2.84386129171214257
34487131174218261
Table 1 – CT values for inactivation of Giardia cysts by free chlorine at 0.5°C or lower (pH = 7.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.44079119158198237
0.64080120159199239
0.84182123164205246
14284127169211253
1.24386130173216259
1.44489133177222266
1.64691137182228273
1.84793140186233279
24895143191238286
2.25099149198248297
2.45099149199248298
2.651101152203253304
2.852103155207258310
353105158211263316
Table 1 – CT values for inactivation of Giardia cysts by free chlorine at 0.5°C or lower (pH = 8)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.44692139185231277
0.64895143191238286
0.84998148197246295
151101152203253304
1.252104157209261313
1.454107161214268321
1.655110165219274329
1.856113169225282338
258115173231288346
2.259118177235294353
2.460120181241301361
2.661123184245307368
2.863125188250313375
364127191255318382
Table 1 – CT values for inactivation of Giardia cysts by free chlorine at 0.5°C or lower (pH = 8.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.455110165219274329
0.657114171228285342
0.859118177236295354
161122183243304365
1.263125188251313376
1.465129194258323387
1.666132199265331397
1.868136204271339407
270139209278348417
2.271142213284355426
2.473145218290363435
2.674148222296370444
2.875151226301377452
377153230307383460
Table 1 – CT values for inactivation of Giardia cysts by free chlorine at 0.5°C or lower (pH = 9)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.465130195260325390
0.668136204271339407
0.870141211281352422
173146219291364437
1.275150226301376451
1.477155232309387464
1.680159239318398477
1.882163245326408489
283167250333417500
2.285170256341426511
2.487174261348435522
2.689178267355444533
2.891181272362453543
392184276368460552
Table 2 – CT values for inactivation of Giardia cysts by free chlorine at 5°C (pH 6)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4163249658197
0.61733506783100
0.81734526986103
11835537088105
1.21836547189107
1.41836557391109
1.61937567493111
1.81938577695114
21939587797116
2.22039597998118
2.420406080100120
2.620416181102122
2.821416283103124
321426384105126
Table 2 – CT values for inactivation of Giardia cysts by free chlorine at 5°C (pH = 6.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.42039597898117
0.620406080100120
0.820416181102122
121426383104125
1.221426485106127
1.422436587108130
1.622446688110132
1.823456890113135
223466992115138
2.223477093117140
2.424487295119143
2.624497397122146
2.825497499123148
3255076101126151
Table 2 – CT values for inactivation of Giardia cysts by free chlorine at 5°C (pH = 7)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.423467093116139
0.624487295119143
0.824497397122146
125507599124149
1.2255176101127152
1.4265278103129155
1.6265379105132158
1.8275481108135162
2285583110138165
2.2285685113141169
2.4295786115143172
2.6295888117146175
2.8305989119148178
3306191121152182
Table 2 – CT values for inactivation of Giardia cysts by free chlorine at 5°C (pH = 7.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4285583111138166
0.6295786114143171
0.8295888117146175
1306090119149179
1.2316192122153183
1.4316294125156187
1.6326496128160192
1.8336598131163196
23367100133167200
2.23468102136170204
2.43570105139174209
2.63671107142178213
2.83672109145181217
33774111147184221
Table 2 – CT values for inactivation of Giardia cysts by free chlorine at 5°C (pH = 8)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4336699132165198
0.63468102136170204
0.83570105140175210
13672108144180216
1.23774111147184221
1.43876114151189227
1.63977116155193232
1.84079119159198238
24181122162203243
2.24183124165207248
2.44284127169211253
2.64386129172215258
2.84488132175219263
34589134179223268
Table 2 – CT values for inactivation of Giardia cysts by free chlorine at 5°C (pH = 8.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.43979118157197236
0.64181122163203244
0.84284126168210252
14387130173217260
1.24589134178223267
1.44691137183228274
1.64794141187234281
1.84896144191239287
24998147196245294
2.250100150200250300
2.451102153204255306
2.652104156208260312
2.853106159212265318
354108162216270324
Table 2 – CT values for inactivation of Giardia cysts by free chlorine at 5°C (pH = 9)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.44793140186233279
0.64997146194243291
0.850100151201251301
152104156208260312
1.253107160213267320
1.455110165219274329
1.656112169225281337
1.858115173230288345
259118177235294353
2.260120181241301361
2.461123184245307368
2.663125188250313375
2.864127191255318382
365130195259324389
Table 3 – CT values for inactivation of Giardia cysts by free chlorine at 10°C (pH 6)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4122437496173
0.6132538506375
0.8132639526578
1132640536679
1.2132740536780
1.4142741556882
1.6142842556983
1.8142943577286
2152944587387
2.2153045597489
2.4153045607590
2.6153146617792
2.8163147627893
3163248637995
Table 3 – CT values for inactivation of Giardia cysts by free chlorine at 10°C (pH = 6.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4152944597388
0.6153045607590
0.8153146617792
1163147637894
1.2163248637995
1.4163349658298
1.6173350668399
1.81734516784101
21735526987104
2.21835537088105
2.41836547189107
2.61837557392110
2.81937567493111
31938577594113
Table 3 – CT values for inactivation of Giardia cysts by free chlorine at 10°C (pH = 7)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.41735526987104
0.61836547189107
0.81837557392110
11937567593112
1.21938577695114
1.41939587797116
1.62040607999119
1.820416181102122
221416283103124
2.221426485106127
2.422436586108129
2.622446687109131
2.822456789112134
323466991114137
Table 3 – CT values for inactivation of Giardia cysts by free chlorine at 10°C (pH = 7.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.421426383104125
0.621436485107128
0.822446687109131
122456789112134
1.223466991114137
1.423477093117140
1.624487296120144
1.825497498123147
2255075100125150
2.2265177102128153
2.4265279105131157
2.6275380107133160
2.8275482109136163
3285583111138166
Table 3 – CT values for inactivation of Giardia cysts by free chlorine at 10°C (pH = 8)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.425507599124149
0.6265177102128153
0.8265379105132158
1275481108135162
1.2285583111138166
1.4285785113142170
1.6295887116145174
1.8306090119149179
2306191121152182
2.2316293124155186
2.4326395127158190
2.6326597129162194
2.8336699131164197
33467101134168201
Table 3 – CT values for inactivation of Giardia cysts by free chlorine at 10°C (pH = 8.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4305989118148177
0.6316192122153183
0.8326395126158189
1336598130163195
1.23367100133167200
1.43469103137172206
1.63570106141176211
1.83672108143179215
23774111147184221
2.23875113150188225
2.43877115153192230
2.63978117156195234
2.84080120159199239
34181122162203243
Table 3 – CT values for inactivation of Giardia cysts by free chlorine at 10°C (pH = 9)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.43570105139174209
0.63673109145182218
0.83875113151188226
13978117156195234
1.24080120160200240
1.44182124165206247
1.64284127169211253
1.84386130173216259
24488133177221265
2.24590136181226271
2.44692138184230276
2.64794141187234281
2.84896144191239287
34997146195243292
Table 4 – CT values for inactivation of Giardia cysts by free chlorine at 15°C (pH 6)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.481625334149
0.681725334250
0.891726354352
191827354453
1.291827364554
1.491828374655
1.6101928374756
1.8101929384857
2101929394858
2.2102030394959
2.4102030405060
2.6102031415161
2.8102131415262
3112132425363
Table 4 – CT values for inactivation of Giardia cysts by free chlorine at 15°C (pH = 6.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4102030394959
0.6102030405060
0.8102031415161
1112132425363
1.2112132435364
1.4112233435465
1.6112233445566
1.8112334455768
2122335465869
2.2122335475870
2.4122436486072
2.6122437496173
2.8122537496274
3132538516376
Table 4 – CT values for inactivation of Giardia cysts by free chlorine at 15°C (pH = 7)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4122335475870
0.6122436486072
0.8122437496173
1132538506375
1.2132538516376
1.4132639526578
1.6132640536679
1.8142741546881
2142842556983
2.2142843577185
2.4142943577286
2.6152944597388
2.8153045597489
3153046617691
Table 4 – CT values for inactivation of Giardia cysts by free chlorine at 15°C (pH = 7.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4142842556983
0.6142943577286
0.8152944597388
1153045607590
1.2153146617792
1.4163147637894
1.6163248648096
1.8163349658298
21733506783100
2.21734516885102
2.41835537088105
2.61836547189107
2.81836557391109
31937567493111
Table 4 – CT values for inactivation of Giardia cysts by free chlorine at 15°C (pH = 8)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4173350668399
0.61734516885102
0.81835537088105
11836547290108
1.21937567493111
1.41938577695114
1.61939587797116
1.82040607999119
220416181102122
2.221416283103124
2.421426485106127
2.622436586108129
2.822446688110132
322456789112134
Table 4 – CT values for inactivation of Giardia cysts by free chlorine at 15°C (pH = 8.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.42039597998118
0.620416181102122
0.821426384105126
122436587108130
1.222456789112134
1.423466991114137
1.624477194118141
1.824487296120144
225497498123147
2.2255075100125150
2.4265177102128153
2.6265278104130156
2.8275380106133159
3275481108135162
Table 4 – CT values for inactivation of Giardia cysts by free chlorine at 15°C (pH = 9)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.423477093117140
0.624497397122146
0.8255076101126151
1265278104130156
1.2275380107133160
1.4285583110138165
1.6285685113141169
1.8295887115144173
2305989118148177
2.2306091121151181
2.4316192123153184
2.6316394125157188
2.8326496127159191
3336598130163195
Table 5 – CT values for inactivation of Giardia cysts by free chlorine at 20°C (pH 6)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.461218243036
0.661319253238
0.871320263339
171320263339
1.271320273340
1.471421273441
1.671421283542
1.871422293643
271522293744
2.271522293744
2.481523303845
2.681523313846
2.881624313947
381624313947
Table 5 – CT values for inactivation of Giardia cysts by free chlorine at 20°C (pH = 6.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.471522293744
0.681523303845
0.881523313846
181624313947
1.281624324048
1.481625334149
1.681725334250
1.891726344351
291726354352
2.291827354453
2.491827364554
2.691828374655
2.891928374756
3101929384857
Table 5 – CT values for inactivation of Giardia cysts by free chlorine at 20°C (pH = 7)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.491726354352
0.691827364554
0.891828374655
191928374756
1.2101929384857
1.4101929394858
1.6102030394959
1.8102031415161
2102131415262
2.2112132425363
2.4112233435465
2.6112233445566
2.8112234455667
3112334455768
Table 5 – CT values for inactivation of Giardia cysts by free chlorine at 20°C (pH = 7.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4102131415262
0.6112132435364
0.8112233445566
1112234455667
1.2122335465869
1.4122335475870
1.6122436486072
1.8122537496274
2132538506375
2.2132639516477
2.4132639526578
2.6132740536780
2.8142741546881
3142842556983
Table 5 – CT values for inactivation of Giardia cysts by free chlorine at 20°C (pH = 8)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4122537496274
0.6132639516477
0.8132640536679
1142741546881
1.2142842556983
1.4142843577185
1.6152944587387
1.8153045597489
2153046617691
2.2163147627893
2.4163248637995
2.6163249658197
2.8173350668399
31734516784101
Table 5 – CT values for inactivation of Giardia cysts by free chlorine at 20°C (pH = 8.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4153045597489
0.6153146617792
0.8163248637995
1163349658298
1.21733506783100
1.41734526986103
1.61835537088105
1.81836547290108
21837557392110
2.21938577594113
2.41938587796115
2.62039597898117
2.82040607999119
320416181102122
Table 5 – CT values for inactivation of Giardia cysts by free chlorine at 20°C (pH = 9)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.41835537088105
0.61836557391109
0.81938577594113
12039597898117
1.220406080100120
1.421416282103123
1.621426384105126
1.822436586108129
222446688110132
2.223456890113135
2.423466992115138
2.624477194118141
2.824487295119143
324497397122146
Table 6 – CT values for inactivation of Giardia cysts by free chlorine at 25°C (pH 6)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.44812162024
0.648121620
0.84913172226
14913172226
1.25914182327
1.45914182327
1.65914192328
1.851015192429
251015192429
2.251015202530
2.451015202530
2.651016212631
2.851016212631
351116212732
Table 6 – CT values for inactivation of Giardia cysts by free chlorine at 25°C (pH = 6.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.451015192429
0.624510151924
0.851016212631
151016212631
1.251116212732
1.461117222833
1.661117222833
1.861117232834
261218232935
2.261218232935
2.461218243036
2.661219253137
2.861219253137
361319253238
Table 6 – CT values for inactivation of Giardia cysts by free chlorine at 25°C (pH = 7)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.461218232935
0.629612182329
0.861219253137
161219253137
1.261319253238
1.471320263339
1.671320273340
1.871421273441
271421273441
2.271421283542
2.471422293643
2.671522293744
2.881523303845
381523313846
Table 6 – CT values for inactivation of Giardia cysts by free chlorine at 25°C (pH = 7.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.471421283542
0.635714212835
0.871522293744
181523303845
1.281523313846
1.481624313947
1.681624324048
1.881625334149
281725334250
2.291726344351
2.491726354352
2.691827354453
2.891827364554
391828374655
Table 6 – CT values for inactivation of Giardia cysts by free chlorine at 25°C (pH = 8)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.481725334250
0.691726344351
0.891827354453
191827364554
1.291828374655
1.4101929384857
1.6101929394858
1.8102030405060
2102031415161
2.2102131415262
2.4112132425363
2.6112233435465
2.8112233445566
3112234455667
Table 6 – CT values for inactivation of Giardia cysts by free chlorine at 25°C (pH = 8.5)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4102030394959
0.6102031415161
0.8112132425363
1112233435465
1.2112234455667
1.4122335465869
1.6122335475870
1.8122436486072
2122537496274
2.2132538506375
2.4132639516477
2.6132639526578
2.8132740536780
3142741546881
Table 6 – CT values for inactivation of Giardia cysts by free chlorine at 25°C (pH = 9)
Free Chlorine Concentration mg ⁄ L0.5 log1 log1.5 log2 log2.5 log3 log
0.4122335475870
0.6122437496173
0.8132538506375
1132639526578
1.2132740536780
1.4142741556882
1.6142842567084
1.8142943577286
2152944597388
2.2153045607590
2.4153146617792
2.6163147637894
2.8163248648096
3163249658197
Table 7 – CT values for inactivation of viruses by free chlorine
Temperature (°C)Log Inactivation: 2 (pH: 6 to 9)Log Inactivation: 2 (pH: 10)Log Inactivation: 3 (pH: 6 to 9)Log Inactivation: 3 (pH: 10)Log Inactivation: 4 (pH: 6 to 9)Log Inactivation: 4 (pH: 10)
0.56459661290
5430644860
10322433645
15215322430
20111216322
2517111215
Table 8 – CT values for inactivation of Giardia cysts by chlorine dioxide
InactivationTemperature 1 °CTemperature 5 °CTemperature 10 °CTemperature 15 °CTemperature 20 °CTemperature 25 °C
0.5 log104.343.22.52
1.0-log218.77.76.353.7
1.5-log321312107.55.5
2.0-log42171513107.3
2.5-log52221916139
3.0-log632623191511
Table 9 – CT values for inactivation of viruses by chlorine dioxide
InactivationTemperature 1 °CTemperature 5 °CTemperature 10 °CTemperature 15 °CTemperature 20 °CTemperature 25 °C
2-log8.45.64.22.82.11.4
3-log25.617.112.88.66.44.3
4-log50.133.425.116.712.58.4
Table 10 – CT values for inactivation of Cryptosporidium by ozone
Log creditTemperature 1 °CTemperature 2 °CTemperature 3 °CTemperature 5 °CTemperature 7 °CTemperature 10 °CTemperature 15 °CTemperature 20 °CTemperature 25 °C
0.512109.57.96.54.93.121.2
123211916139.96.23.92.5
1.53531292420159.35.93.7
2464238322620127.84.9
2.5585248403325169.86.2
369635747393019127.4
Table 11 – CT values for inactivation of Giardia cysts by ozone
InactivationTemperature 1 °CTemperature 5 °CTemperature 10 °CTemperature 15 °CTemperature 20 °CTemperature 25 °C
0.5 log0.480.320.230.160.120.08
1.0-log0.970.630.480.320.240.16
1.5-log1.50.950.720.480.360.24
2.0-log1.91.30.950.630.480.32
2.5-log2.41.61.20.790.60.4
3.0-log2.91.91.430.950.720.48
Table 12 – CT values for inactivation of viruses by ozone
InactivationTemperature 1 °CTemperature 5 °CTemperature 10 °CTemperature 15 °CTemperature 20 °CTemperature 25 °C
2-log0.90.60.50.30.250.15
3-log1.40.90.80.50.40.25
4-log1.81.210.60.50.3
Table 13 – CT values for inactivation of Giardia cysts by chloramine at pH 6-9
InactivationTemperature 1 °CTemperature 5 °CTemperature 10 °CTemperature 15 °CTemperature 20 °CTemperature 25 °C
0.5 log635365310250185125
1.0-log1270735615500370250
1.5-log19001100930750550375
2.0-log2535147012301000735500
2.5-log3170183015401250915625
3.0-log38002200185015001100750
Table 14 – CT values for inactivation of viruses by chloramine at pH 6-9
InactivationTemperature 1 °CTemperature 5 °CTemperature 10 °CTemperature 15 °CTemperature 20 °CTemperature 25 °C
2-log1243857643428321214
3-log206314231067712534356
4-log288319881491994746497

1 The definition of the T10 contact time and explanation of the CT value concept are provided in subsection 3.1.1 (CT Disinfection Concept).

2 In a multi-barrier system for providing safe drinking water, the selection and protection of a reliable, high-quality drinking water source is the first barrier. In this context, many locations described as surface water would be unsuitable as a source water supply but are included in the description for full consideration as they may impact ground water.

3 Reference should be made to US EPA's guidance manuals (Long Term 1 Enhanced Surface Water Treatment Rule and Long Term 2 Enhanced Surface Water Treatment Rule)

4 Free (available) chlorine residual: The amount of chlorine available as dissolved gas (Cl2), hypochlorous acid (HOCl), and hypochlorite ion (OCl–), that is not combined with ammonia (NH3) or other compounds in water.

5 Total chlorine residual: The total amount of chlorine residual present after a given contact time in a water sample, regardless of the form of chlorine.

6 Combined (available) residual chlorine: The concentration of residual chlorine that is combined with ammonia (NH3), organic nitrogen, or both in water as chloramine (or other chloroderivative), yet is still available to oxidize organic matter and act as a disinfectant. Combined chlorine can be accurately estimated as the difference between the measured total chlorine and measure or known free chlorine residual.

7 US EPA "Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources", and Long Term 2 Enhanced Surface Water Treatment Rule for the table providing the CT values for inactivation of Cryptosporidium by ozone.

8 IDDF method is published by Awwa Research Foundation and American Water Works Association, 1998.

9 Because of the selective mechanisms of slow sand and DE filtration processes, filtrate turbidity levels exceeding 1.0 NTU can occur as a result of passage of inorganic particles through the filter without influencing the effective removal of harmful organisms. Temporary filtrate turbidity levels of over 1.0 NTU therefore should not be interpreted as indicating an adverse water condition with these processes in the absence of additional supporting evidence.

10 A maximum water pH of 8.5 is recommended for free chlorine residual maintenance for two reasons; the disinfecting power of free chlorine is rapidly and progressively reduced as pH levels rise over 7.0, and, pH levels tend to rise naturally in distribution systems as a result of biofilm activity.

11 Continuous monitoring equipment is equipment that, at intervals appropriate for the process and parameter being monitored, automatically tests for the parameter directly in the stream (or in the case of UV disinfection, through the stream) of water being treated or distributed, or in a continuous sample taken from the stream of water being treated or distributed, where a continuous sample is a continuous stream of water flowing from the stream of water being treated or distributed to the continuous monitoring equipment.

12 In circumstances where chlorine dioxide generation and chlorine dioxide demand is stable, consideration may be given to an alternative to continuous chlorine dioxide monitoring using continuous redox potential monitoring supplemented by intermittent assay of disinfectant chemical components.

13 Unlike chemical disinfectants, UV light appears not to form detectable amounts of potentially toxic by-products.

FAQs

How is drinking water treated in Ontario? ›

Chlorine is used in the drinking water process to control bacteria, algae and viruses. The range of chlorine used is set by the Provincial Safe Drinking Water Act and is continuously monitored by the City to ensure the water is safe to drink.

What are the 3 main ways of disinfection in the water treatment? ›

Chlorination, ozone, ultraviolet light, and chloramines are primary methods for disinfection.

What is used for disinfection of drinking water? ›

Chlorine is a highly effective method of disinfection. However, while in the pipes it produces small amounts of chemicals (called “disinfection by-products”) if the source water has higher levels of dirt or germs that may react with chlorine. Chlorine is also used up quickly in water systems.

How does Ontario process water? ›

Conventional filtration is the most common treatment process currently used by drinking-water systems that rely on raw water supplies which are surface water. This treatment process consists of chemical coagulation, rapid mixing, flocculation, and sedimentation followed by rapid sand filtration.

What is Ontario's Safe Drinking Water Act? ›

The Act recognizes that the people of Ontario are entitled to expect their drinking water to be safe and provides for the protection of human health and the prevention of drinking-water health hazards through the control and regulation of drinking-water systems and drinking-water testing.

How clean is Ontario water? ›

Since the events in Walkerton, the Province's chief drinking water inspector has consistently found that about 99.9% of the water testing results from municipal residential drinking water systems met Ontario's strict drinking water quality standards.

What are the 5 steps of water treatment? ›

Public water systems often use a series of water treatment steps that include coagulation, flocculation, sedimentation, filtration, and disinfection.

What are the 4 steps of water treatment? ›

4 Steps of Community Water Treatment
  1. Coagulation and Flocculation. ...
  2. Sedimentation. ...
  3. Filtration. ...
  4. Disinfection.

What are 2 methods of disinfection? ›

Generally, two methods of disinfection are used: chemical and physical. The chemical methods, of course, use chemical agents, and the physical methods use physical agents. Historically, the most widely used chemical agent is chlorine.

What is the process of disinfection? ›

Disinfection describes a process that eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects (Tables 1 and 2). In health-care settings, objects usually are disinfected by liquid chemicals or wet pasteurization.

What are three types of disinfection? ›

Regulatory Framework for Disinfectants and Sterilants
  • Steam Sterilization.
  • Flash Sterilization.
  • Low-Temperature Sterilization Technologies.
  • Ethylene Oxide “Gas” Sterilization.
  • Hydrogen Peroxide Gas Plasma.
  • Peracetic Acid Sterilization.
  • Microbicidal Activity of Low-Temperature Sterilization Technologies.

Why is disinfection important in water treatment? ›

Why Do We Need Disinfection? Disinfection of drinking water and wastewater is critical to the protection of public health. All water and wastewater systems should use some form of disinfection process to remove or inactivate microorganisms (pathogens) that can cause disease in humans and animals.

Who regulates drinking water in Ontario? ›

There are three bodies that regulate Ontario's water supply: the Ontario Ministry of the Environment, the Ontario Ministry of Natural Resources, and the federal government. This factsheet deals with provincial legislation that protects drinking water in Ontario.

Who is responsible for clean water in Ontario? ›

The Ministry of the Environment is responsible for protecting water. 1 This is the oversight agency for the protection of source water to municipal systems, not small drinking water systems. The operational agency for source water protection committees is local conservation authorities.

How many water treatment plants are there in Ontario? ›

In Ontario, there are 423 sewage treatment plants. The provincial Crown operates 244 STPs and municipalities operate 179 STPs.

Is clean drinking water a human right in Ontario? ›

Access to water is a human right under international law, and Canada's Constitution Act of 1982 provides for “essential public services of reasonable quality.” This means that the authorities have an obligation—as well as a moral imperative—to uphold this right.

What is the Ontario Environmental Protection Act? ›

The Environmental Protection Act is the key legislation for environmental protection in Ontario. It grants the Ministry of the Environment, Conservation and Parks broad powers to deal with the discharge of contaminants causing negative effects.

What is the Safe Drinking Water Act in Canada? ›

The Safe Drinking Water for First Nations Act came into effect in 2013. The Act allows the Government of Canada, in collaboration with First Nations, to develop federal regulations to ensure access to safe, clean and reliable drinking water and the effective treatment of wastewater.

Is water free in Ontario? ›

Water bills in Ontario are usually issued once every two months for most residential properties. Irrespective of the volume used, the water utility bill has these fixed charges on it: Water (distribution, collection, treatment, and infrastructure maintenance and renewal.)

What is the best water to drink in Canada? ›

Montellier is by far the water with the lowest pH, coming in at 4.30 on the meter test (no surprise, since it is a natural carbonated spring water). Marketed as Canada's Carbonated Natural Spring Water, this water comes in both cans and bottles in flavoured and unflavoured varieties.

What is good drinking water quality? ›

Total Dissolved Solids (TDS)

The EPA recommends that water containing more than 500 mg/l of dissolved solids not be used if other less mineralized supplies are available. However, water containing more than 500 mg/l of TDS is not dangerous to drink.

What are the 7 steps of water treatment? ›

They typically consist of several steps in the treatment process. These include: (1) Collection ; (2) Screening and Straining ; (3) Chemical Addition ; (4) Coagulation and Flocculation ; (5) Sedimentation and Clarification ; (6) Filtration ; (7) Disinfection ; (8) Storage ; (9) and finally Distribution.

What are the 7 methods of water treatment? ›

Figure 5.2 The seven steps often used in the large-scale treatment of water.
  • 1 Screening. ...
  • 2 Aeration. ...
  • 3 Coagulation and flocculation. ...
  • 4 Sedimentation. ...
  • 5 Filtration. ...
  • 6 Chlorination. ...
  • 7 Supplementary treatment.

How do you clean drinking water? ›

Boil. If you don't have safe bottled water, you should boil your water to make it safe to drink. Boiling is the surest method to kill disease-causing germs, including viruses, bacteria, and parasites. adding a pinch of salt for each quart or liter of boiled water.

What is the most important step in water treatment? ›

It is, however, an important primary step in the water treatment process, because coagulation removes many of the particles, such as dissolved organic carbon, that make water difficult to disinfect. Because coagulation removes some of the dissolved substances, less chlorine must be added to disinfect the water.

What is an example of disinfection? ›

Disinfecting uses chemicals (disinfectants) to kill germs on surfaces and objects. Some common disinfectants are bleach and alcohol solutions. You usually need to leave the disinfectant on the surfaces and objects for a certain period of time to kill the germs.

What is the most effective disinfectant? ›

The best disinfectants for viruses are alcohol, bleach, hydrogen peroxide, and quaternary ammonium compounds. These active ingredients are the most common on the EPA's list of registered disinfectants against the coronavirus.

What is the most common disinfectant? ›

Hypochlorites, the most widely used of the chlorine disinfectants, are available as liquid (e.g., sodium hypochlorite) or solid (e.g., calcium hypochlorite).

What is meant by disinfection of water? ›

The term “disinfection” is used to mean the destruction of infective organisms in water to such low levels that no infection of disease results when the water is used for domestic purposes, including drinking.

What is the acceptable range of pH for potable water in Ontario? ›

The operational guideline for pH is a range of 7.0 to 10.5 in finished drinking water.

Who owns water in Ontario? ›

4 Crown land ownership and requirements under the Public Lands Act. The ownership or exclusive right to use water is not vested in the Crown in right of Ontario. Water in Ontario is considered a right in common and cannot be privately owned.

When was the Ontario Safe Drinking Water Act passed? ›

The Ontario government passed the Clean Water Act in 2006 to implement some of the recommendations of the Walkerton Inquiry. The Act ensures communities protect their municipal drinking water supplies through prevention -- by developing collaborative, watershed-based source protection plans based on science.

What is the process at a water treatment plant? ›

The 5 major unit processes include chemical coagulation, flocculation, sedimentation, filtration, and disinfection (described below).

What is the water treatment system? ›

A wide variety of water treatment systems and devices exist that remove or reduce unwanted chemicals and/or microorganisms through disinfection, physical filtration, adsorptive filtration, oxidation/reduction and chemical exchange reactions in order to make water potable or improve the aesthetics of the water.

Where does wastewater Go Ontario? ›

Sanitary sewers transport wastewater released from a drain, toilet, sink or appliance such as a clothes or dishwasher. This wastewater from residences and businesses flows to treatment plants where it is cleaned before being released into Lake Ontario.

Who regulates drinking water in Ontario? ›

There are three bodies that regulate Ontario's water supply: the Ontario Ministry of the Environment, the Ontario Ministry of Natural Resources, and the federal government. This factsheet deals with provincial legislation that protects drinking water in Ontario.

Who regulates water quality in Ontario? ›

The Ministry of Environment and Energy's legislative authority to manage water comes primarily from two acts, the Ontario Water Resources Act ( OWRA ) and the Environmental Protection Act ( EPA ).

How is the water in Mississauga treated? ›

The system consists of two water treatment plants — The system consists of two water treatment plants — Lakeview and Lorne Park. Both plants treat water going to Mississauga and Brampton and Lakeview also sends water to southern parts of Caledon as well as to York Region, which purchases the water from Peel.

How is town water purified? ›

During filtration, the clear water passes through filters that have different pore sizes and are made of different materials (such as sand, gravel, and charcoal). These filters remove dissolved particles and germs, such as dust, chemicals, parasites, bacteria, and viruses.

Is clean drinking water a human right in Ontario? ›

Access to water is a human right under international law, and Canada's Constitution Act of 1982 provides for “essential public services of reasonable quality.” This means that the authorities have an obligation—as well as a moral imperative—to uphold this right.

What is the acceptable range of pH for potable water in Ontario? ›

The operational guideline for pH is a range of 7.0 to 10.5 in finished drinking water.

Who owns water in Ontario? ›

4 Crown land ownership and requirements under the Public Lands Act. The ownership or exclusive right to use water is not vested in the Crown in right of Ontario. Water in Ontario is considered a right in common and cannot be privately owned.

This document outlines procedures for disinfecting water mains as part of an addition, modification, replacement, extension, planned maintenance, or emergency repair in a municipal residential drinking water system. The procedures are required to be followed in order to satisfy conditions imposed by the Director in a drinking water works permit. Download PDF Published in August 2020

New watermains For watermains, including temporary watermains, that are added to, modified, re-aligned, replaced or extended within a Drinking Water System, Operating Authorities shall ensure that the requirements of ANSI / AWWA Standard C651 are followed as modified by this procedure.. Backflow Prevention requirements for new watermains The Backflow Prevention provisions within Section 4.8.9 of ANSI / AWWA Standard C651 shall be mandatory for the installation of new watermains except for Connections (see section 1.1.4).. Table 1: Chlorine concentrations* and contact times for disinfecting new watermains Disinfection method Minimum contact timeInitial chlorine concentrationMaximum allowable decrease in chlorine concentrationTablet or Continuous Feed24 hours ≥ 25 mg/L 40% of the Initial Chlorine Concentration to a maximum of 50 mg/L **Slug3 hours ≥ 100 mg/L 25 mg/L Spray30 minutes ≥ 200 mg/L Measurement Not Required* At concentrations over 10 mg/L , measurements of total chlorine and free chlorine shall be deemed equivalent.. A flow meter shall be installed to measure flow through the new watermain; A sampling point shall be installed at the end of the new watermain (additional sampling points may also be installed along the length of the watermain); and Flow shall be established, and samples shall be taken from the sampling point(s) at intervals that are calculated to represent the lengths of the watermain as required by Sections 5.1.1.2 and 5.1.1.3 of ANSI / AWWA Standard C651, based on the pipe size and the measured flow rate.. Connections equal to or less than one pipe length (Generally ≤ 6 m ) The Operating Authority shall ensure that Connections equal to or less than one pipe length (generally ≤ 6 m) are undertaken in accordance with Section 4.10.1 of ANSI / AWWA Standard C651 and that the Connection remain Isolated from the existing Drinking Water System, except while being flushed or sampled, until satisfactory results are received from one Microbiological Sample, taken by a Certified Operator or Water Quality Analyst, from water that has been directed through the Connection.. Where a section of watermain has been Isolated from a Drinking Water System and a concentration of 0.05 mg/L of free chlorine residual in a chlorinated system (or 0.25 mg/L of combined chlorine residual in a chloraminated system) was not maintained within the Isolated section ( e.g. , a valved-off stub), the Operating Authority shall develop and implement a re-commissioning plan that reflects the duration of isolation and the associated risks.. All watermain breaks shall be classified as Category 2 as per Section 2.1.2 of this procedure unless an Operator-in-Charge ( OIC ) conducts a visual inspection upon completion of the excavation to determine the nature of the watermain break and classifies it as a Category 1 as per Section 2.1.1.. Notification to the Ministry is not required for Category 2 watermain breaks however if a Water Advisory is declared or a watermain break is assessed to be a Special Case as described in sections 2.4.4 and 2.4.5, the Operating Authority shall verbally notify the Ministry as soon as reasonably possible by speaking in person or on the telephone with a person.. Special case—Sewage Contamination If there is evident or suspected sewage Contamination of a watermain, in addition to the steps in Sections 2.2 and 2.4 of this procedure, the Operating Authority shall develop and implement a plan with site-specific procedures for disinfection and sampling.. Special case—Chemical Contamination If there is evident or suspected chemical Contamination of a watermain, in addition to the steps in Sections 2.2 and 2.4 of this procedure, the Operating Authority shall develop and implement a plan with site-specific procedures for disinfection and/or decontamination and sampling.. Connections referred to in Section 1.1.4: Length of Connection; Confirmation whether sanitary construction practices were followed; Confirmation that proper disinfection was performed; Name of Certified Operator present for the installation of the Connection if required; Results of Microbiological and disinfectant residual samples if required; Reason for using the exception under s. 1.1.4.2 (if used); Disinfectant residual after watermain is flushed and put in service; and Date and time watermain was placed into service.. Acceptable Disinfectant Concentration means: a disinfectant concentration of at least 0.2 mg/L free chlorine residual in a chlorinated system or 1.0 mg/L combined chlorine residual in a chloraminated system; or, if these disinfectant concentrations cannot be achieved, a disinfectant concentration that is representative of the residual in the area, determined by testing upstream and downstream from the testing location or by using documented benchmarks for the area, as long as free chlorine concentrations are at least 0.05 mg/L in a chlorinated system and combined chlorine concentrations are at least 0.25 mg/L in a chloraminated system.

This document provides information on what to do to correct adverse microbiological test results from drinking-water samples taken from systems not currently using chlorine.

For all drinking-water systems operating under O. Reg .. The owner of the drinking-water system must ensure that the following corrective action is taken.. Use a fresh supply of chemical disinfectant Disinfect the system such that a free chlorine residual of 50 mg/L can be detected at all points in the affected part(s) of the distribution system and in the plumbing that is connected to the system for at least 12 hours Flush the water lines with water to ensure the chlorine is removed from the system Resample and test 24 to 48 hours after flushing. Use a fresh supply of chemical disinfectant Disinfect the system such that a free chlorine residual of 50 mg/L can be detected at all points in the affected part(s) of the distribution system and in the plumbing that is connected to the system for at least 12 hours Flush the water lines with water to ensure the chlorine is removed from the system Resample and test 24 to 48 hours after flushing. Use a fresh supply of chemical disinfectant Disinfect the system such that a free chlorine residual of 50 mg/L can be detected at all points in the affected part(s) of the distribution system and in the plumbing that is connected to the system for at least 12 hours Flush the water lines with water to ensure the chlorine is removed from the system Resample and test 24 to 48 hours after flushing. Use a fresh supply of chemical disinfectant Disinfect the system such that a free chlorine residual of 50 mg/L can be detected at all points in the affected part(s) of the distribution system and in the plumbing that is connected to the system for at least 12 hours Flush the water lines with water to ensure the chlorine is removed from the system Resample and test 24 to 48 hours after flushing. Use a fresh supply of chemical disinfectant Disinfect the system such that a free chlorine residual of 50 mg/L can be detected at all points in the affected part(s) of the distribution system and in the plumbing that is connected to the system for at least 12 hours Flush the water lines with water to ensure the chlorine is removed from the system Resample and test 24 to 48 hours after flushing. Use a fresh supply of chemical disinfectant Disinfect the system such that a free chlorine residual of 50 mg/L can be detected at all points in the affected part(s) of the distribution system and in the plumbing that is connected to the system for at least 12 hours Flush the water lines with water to ensure the chlorine is removed from the system Resample and test 24 to 48 hours after flushing. Chlorination can effectively disinfect a well and water system.

This document outlines procedures for disinfecting water mains as part of an addition, modification, replacement, extension, planned maintenance, or emergency repair in a municipal residential drinking water system. The procedures are required to be followed in order to satisfy conditions imposed by the Director in a drinking water works permit. Published in November 2015

1.1.1 Disinfection of New Watermains Where the operating authority is chlorinating using the tablet, continuous feed, slug, or spray chlorination methods for disinfecting newly constructed watermains as per the procedures in ANSI / AWWA Standard C651, the minimum contact times, initial chlorine concentrations, and maximum allowable decreases in chlorine concentration as listed in Table 1 shall be used.. a flow meter shall be installed to measure flow through the new watermain; a sampling point shall be installed at the end of the new watermain (additional sampling points may also be installed along the length of the watermain); and flow shall be established and samples shall be collected from the sampling point(s) at intervals that are calculated to represent the lengths of the watermain as required by ANSI / AWWA C651, based on the pipe size and the measured flow rate.. This procedure does not require that the local Medical Officer of Health be notified of Category 2 watermain break repairs unless an observation of improper disinfection has been reported as noted above; however, the local Medical Officer of Health may exercise his/her option to require such notification.. If these disinfectant concentrations cannot be achieved, Flushing shall continue until the disinfectant concentration at the point of Flushing is representative of the system residual in the break area, determined by sampling upstream of the break area and downstream at the Flushing location, or by using documented benchmarks for the area, as long as free chlorine concentrations are at least 0.05 mg/L in a chlorinated system and combined chlorine concentrations are at least 0.25 mg/L in a chloraminated system.. Microbiological samples taken (Yes/No/Not applicable) Date and location(s) of sample(s) ( e.g. Chain of custody) Date and time of return to normal service Water Advisory declared: Date and Time (Yes/No/Not Applicable) Public Agency Notification – local Ministry office (Date and Time) (Yes/No/Not Applicable) Public Agency Notification – Spills Action Centre (Date and Time) (Yes/No/Not Applicable) Public Agency Notification/Direction – local Medical Officer of Health (Date and Time)

Videos

1. Legionella Management and Guidelines
(The Water Research Foundation)
2. Disinfecting Your Household Plumbing
(Gary the Water Guy)
3. Step-by-step: How to sample your private well water for bacteria
(Ottawa Public Health)
4. How to Disinfect Your Well
(Manitoba Government)
5. How to Disinfect Your Well Water to Kill Bacteria
(Gary the Water Guy)
6. Viqua Sterilight (UV) Ultraviolet Disinfection System Review
(Gary the Water Guy)

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