Guidance For Providing Safe Drinking Water in Areas of Federal Jurisdiction - Version 1

Part 2 - Application of The Federal Framework

4.0 Technical Standards, Benchmarks and Targets

The following technical standards, benchmarks and targets for water quality are provided to assist federal departments, water managers, designers and operators (including those in First Nations communities) to meet the Guidelines for Canadian Drinking Water Quality and drinking water-related regulations.

Guidance on how to meet these targets is provided throughout Part 2 of this document. The benchmarks noted below are current as of July 2005 and may be updated as new information becomes available.

Given the sheer number of federal drinking water supplies and the wide variety in system size, location, and site-specific concerns, the guidance in this document is designed to be flexible. In broad terms, for the purpose of this document, drinking water systems are defined as large, small, and very small, depending on the size of the population served (see Section 1.3 or the Glossary for definitions).

Drinking water sources may be surface water or ground water supplies. Surface water is defined as water open to the atmosphere and subject to surface run-off. Groundwater under the direct influence of surface water (GUDI) is defined as any water beneath the surface of the ground with (i) significant occurrence of insects or other microorganisms, algae, organic debris, or large-diameter pathogens such as Giardia lamblia or Cryptosporidium, or (ii) significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface water conditions. Groundwater sources not under the direct influence of surface water (hereafter referred to as groundwater), by default, are neither of these two cases.

4.1 Microbiological quality

The most significant parameters to be monitored relate to the microbiological quality of drinking water. The presence of pathogens can result in serious health hazards. Indeed, ensuring the microbiological quality of drinking water is the highest priority for protecting public health.

For this reason, it is important that federal water quality management systems address any existing and potential microbiological quality concerns at the site (e.g., level of treatment, historical testing results, surface and groundwater vulnerabilities, potential water quality risks, user activities and local trends), prior to establishing a routine monitoring regimen.

Microbiological parameters include the indicator organisms E.coli and total coliforms. System operators may also choose to test for heterotrophic plate count bacteria in order to better understand the overall quality of the drinking water. Turbidity and chlorine residuals should also be monitored in order to ensure the microbiological integrity of the water, even though these are not specifically microbiological parameters.

Table 4.1 provides a summary of the recommended sampling frequencies and locations for the microbiological parameters.

4.1.1 Sampling frequencies

The recommended sampling frequency for microbiological parameters depends upon the quality of the source water, the number of water sources, the past frequency of unsatisfactory samples, the adequacy of treatment and capacity of the treatment plant, the size and complexity of the distribution system, the practice of disinfection, the size of the population served, and sampling history ⁽¹⁵⁾.

For federal departments and First Nations communities that collect and treat their own drinking water, the variables listed above make it difficult to apply a universal sampling frequency formula.

Sampling frequency should be established by the appropriate department or responsible authority, at the facility or system level, with proper guidance and after due consideration of local conditions and sampling history. The following sampling frequencies are offered as a guide and do not necessarily apply to very small systems.

Generally, for all systems, a minimum of four samples per month should be taken at regular intervals throughout the month. Sampling could be scheduled to match provincial guidelines or regulations where these are more stringent. It is recommended that chlorine residuals be tested when bacteriological samples are taken.

For very small systems which serve very few individuals, and where the supply has a history of producing water of high bacteriological quality, it may be possible to reduce the number of samples analysed ⁽¹⁵⁾. In such cases, samples should be collected and analysed when the risk of contamination is highest (i.e. there is potential public health risk) (e.g., spring thaw, heavy rains or dry periods, and/or when a noticeable deterioration in water quality occurs). In addition to this, new or renovated wells should be sampled and analysed at start-up to confirm acceptable bacteriological quality.⁽¹⁸⁾

Facilities that receive municipal water should already be receiving microbiologically safe water. Nonetheless, technical support staff and drinking water monitors should adopt internal water monitoring procedures and schedules to suit local conditions.

As a general rule, these facilities should take one bacteriological sample per month. Actual sampling frequency, number of samples and range of analyses completed should be based on the sanitary survey and vulnerabilities assessment. If they demonstrate that no problems exist and the municipality is sampling at the recommended frequency (or more), fewer samples could be deemed appropriate. Conversely, if a greater degree of risk or unknowns exists, the planned sampling should be adjusted accordingly in order to gather sufficient data upon which to base corrective actions. If corrective actions are successful, sampling could ultimately be scaled back to the recommended frequency according to this document.

If the review of the municipal water quality against federal benchmarks reveals non-compliance, measures should be taken to protect public health. Measures could include maintenance (e.g., disinfection and flushing), additional treatment, or providing an alternative safe supply of drinking water.

4.1.2 Sampling locations

Samples should be taken at the point where the water enters the system (to eliminate the source water as the cause of the adverse water quality) and from representative points throughout the network, although not necessarily the same points on each occasion. For very small systems where there is little or no distribution system, samples should be taken as the water leaves the pumphouse.

If the water supply is obtained from more than one source, the location of sampling points in the distribution system should ensure that water from each source is periodically sampled. The majority of samples should be taken in potential problem areas: low-pressure zones, reservoirs, dead ends, areas at the periphery of the system farthest from the treatment plant and areas with a poor previous record. ^{(18, 51)}

Facilities that receive municipal water should collect samples at the main or point of entry to the building, in the building's plumbing system, and in other locations identified in the sanitary survey and vulnerabilities assessment.

Sampling locations within the building's plumbing system could be randomly selected at first, to find "hot spots." Over time, these "hot spots" could become regular sampling locations. Samples should occasionally be collected from other locations in the building.

4.1.3 Interpreting sampling results

4.1.3.1 Total Coliforms and E. coli bacteria

General:

Microbiological quality is measured by testing samples for total coliforms and E.coli. Samples should be analysed by an accredited laboratory or by trained personnel using an accepted portable laboratory test kit. (See Section 7.3.2.1)

The Guidelines for Canadian Drinking Water Quality state that the maximum acceptable concentration (MAC) for bacteriological quality of drinking water systems is no coliforms detectable per 100 mL. Drinking water that fulfills all the following conditions is considered to conform to this MAC:

• No sample should contain Escherichia coli (E. coli). The presence of E. coli indicates recent faecal contamination and the possible presence of enteric pathogens that may adversely affect human health. If E. coli is detected, the appropriate agencies should be notified, a boil water advisory should be issued, and corrective actions taken.
• No consecutive samples from the same sampling location within a distribution system, or not more than 10% of samples from the distribution system in a given calendar month, should show the presence of total coliform bacteria. In systems collecting fewer than 10 samples per month, no samples should contain total coliforms.

The ability of total coliforms to indicate the presence of faecal pollution is less reliable than E. coli. However, this group of bacteria is a good indicator for quality control purposes.

While the presence of total coliforms does not necessarily mean a boil water advisory must immediately be issued, re-sampling and corrective actions may need to be taken.

Very small systems with little or no distribution system:

For very small systems with little or no distribution system, the following guidance could apply:

• No sample should contain E. coli. As stated above, the presence of E. coli indicates faecal contamination and the possible presence of enteric pathogens; therefore the water is unsafe to drink. If E. coli is detected, a boil water advisory should be issued and corrective actions taken.
• No sample should contain total coliform bacteria.

The presence of total coliforms does not necessarily mean a boil water advisory must immediately be issued; however, corrective actions should be taken.

In non-disinfected well water, the presence of total coliform bacteria in the absence of E. coli indicates the well may be prone to surface water infiltration and is therefore at risk of faecal contamination. In disinfected water systems, the presence of total coliform bacteria indicates a potential failure in the disinfection process. In both disinfected and non-disinfected systems, total coliform detection may also indicate the presence of biofilm in the well or plumbing system.⁽¹⁸⁾ A biofilm is a community of micro-organisms attached to a solid surface, for example the inside wall of a pipe, in an aquatic environment.

Even though the biofilm itself is not a health concern, it could interfere with analytical testing. Also, it could eventually impede water flow, potentially leading to deterioration of aesthetic water quality and ultimately taste and odour problems.

Boil water advisories

For very small systems, boil water advisories should be issued--or an alternative safe source of drinking water used--in the following cases:

• If the water supply is not disinfected and is contaminated with either total coliforms or E.coli.
• If the water supply is disinfected and water leaving the pumphouse has no chlorine residual or is contaminated with either total coliforms or E.coli.

It is recommended that a boil water advisory be used only as a temporary measure while problems are being identified and remediated. If total coliforms are present with no E. coli present, it is likely due to the presence of biofilm. If this is the case, re-sampling and corrective action should be taken. These corrective actions could include shock chlorination (the addition of a strong solution of liquid chlorine into a drinking water system to reduce the presence of microbiological contaminants) and flushing of the well and/or distribution system.

If there is no evidence to suggest faecal contamination, a boil water advisory may not be necessary.

A recommended approach to shock chlorination of wells can be found in Health Canada's "Water Talk: What's In Your Well? - A Guide To Well Water Treatment And Maintenance", at http://www.hc-sc.gc.ca/ewh-semt/water-eau/drink-potab/well_water-eau_de_puits_e.html

For more information on issuing and rescinding boil water advisories, see Section 7.6 and Appendix 7.

4.1.3.2 Heterotrophic Plate Count

Heterotrophic plate count (HPC) bacteria and background colonies, although not a suitable indicator of the microbiological safety of water, are a useful indicator of the overall quality of the water. Testing for HPC bacteria or background colonies is optional.

Effective treatment can reduce concentrations of HPC bacteria to less than 10 colony forming units per 100mL of water. These counts can be used for quality control in water treatment plants and as a measure of quality deterioration in wells, distribution lines and reservoirs.

A sudden rise of HPC or background colonies in drinking water collected from a site that has traditionally had low counts should give rise to concern. If a sample contains greater than usual levels of HPC or background colonies, the site should be re-sampled and the disinfectant residual verified. If the repeat sample still indicates an elevated HPC, the system should be inspected to determine the cause, and if necessary, remedial action should be taken. ⁽¹⁸⁾

4.2 Turbidity

Federal facilities and facilities in First Nations communities that treat and supply their own drinking water must monitor their water for turbidity as it is a strong indicator of water quality. It is also an important indicator of treatment efficiency and filter performance in particular.⁽¹⁶⁾ Turbidity can be measured by on-line turbidity meters, a laboratory, or by using a test kit.

Turbidity in water is caused by suspended and colloidal matter such as clay, silt, fine organic and inorganic matter, and plankton and other microscopic organisms.⁽¹⁶⁾ Control of turbidity in water supplies is important for both health and aesthetic reasons. Water that has high levels of turbidity is not only unappealing to the consumer, but the substances and particles that cause turbidity can interfere with disinfection and can be a source of disease-causing organisms.

Turbidity samples must be tested immediately by a trained person using a turbidity meter that measures in Nephelometric Turbidity Units (NTU). ⁽⁴⁸⁾

The most recent Canadian guideline for turbidity (October 2003) states that waterworks systems that use a surface water or groundwater source under the direct influence of surface water (GUDI) should filter the water to reduce the level of turbidity to as low as reasonably achievable, with a treated water turbidity target of less than 0.1 NTU at all times. However, actual levels of turbidity achieved will vary from technology to technology, so for this reason, the turbidity guideline is broken down by type of technology.

For guidance regarding situations where the target of 0.1.NTU is not achievable, and for criteria that describe the circumstances when filtration is not required, see the supporting document for the turbidity guideline in the Guidelines for Canadian Drinking Water Quality.

4.2.1 Guidance for surface water or GUDI sources that use filtration

For systems that use a surface water or GUDI source and use filtration, the water that passes through each filter should be continuously monitored to make sure the filters are operating properly and to determine when backwashing is necessary. Micro-organisms concentrate on filters and a breakthrough could result in contaminated water reaching consumers.

Where continuous monitoring is not feasible, a sample of water that has not been disinfected should be taken at least once per day (for large and small systems) or once weekly (for very small systems) from a point in the system where all filtration has been completed. Frequency may be increased or decreased depending upon historical data. A turbidity sample should also be taken at each filter outlet following filter cleaning or backwashing.

4.2.2 Guidance for unfiltered systems that use a surface water or GUDI source

For unfiltered systems that use a surface water or GUDI source, turbidity should be measured at least once per calendar day at the point in the system directly before the first treatment chemical is applied. The daily source water turbidity level can be based on either a single grab sample measurement or the arithmetic average of all the source water turbidity measurements taken in one calendar day.⁽²⁾ Frequency may be increased or decreased depending upon historical data.

4.2.3 Guidance for secure groundwater sources

The health-based turbidity guideline does not apply to secure groundwater sources, i.e., those not under the direct influence of surface water. Turbidity in these cases is non-organic, should pose no health threat and should not hinder disinfection (in cases where disinfection is being done). However, for effective operation of the distribution system , it is good practice to ensure that water entering the distribution system has low turbidity levels of around 1.0 NTU.

Therefore, turbidity sampling once per day is suggested for secure groundwater supplies. However, if historical data indicates that turbidity is consistently less than 1 NTU, the frequency of routine monitoring can be reduced to 4-12 times per year depending on the number of people served.

That said, turbidity should also be monitored during events such as spring run-off, heavy rains, and seasonal start-ups.

4.3 Disinfection targets

Barring system-specific exemptions (as described below), all drinking water supplies should be disinfected⁴ to ensure the safety of the drinking water supply in the treatment plant. In addition, where disinfection is practised, a residual of an appropriate disinfectant, typically chlorine or chloramine, should be present at all times in the distribution system. (See Section 6.3 for further information on chlorine/chloramine residuals.)

The effectiveness of disinfection can be predicted based on a knowledge of the residual concentration of disinfectant, temperature, pH (for chlorine and chloramine), and the time between the moment the disinfectant is added to the water and the moment the water arrives to the first customer. This relationship is commonly referred to as the "contact time" or "CT" concept. CT is the product of C (the residual concentration of disinfectant, measured in mg/L) and T (the disinfectant contact time, measured in minutes). This calculation is used by large drinking water systems as a tool for ensuring adequate inactivation of organisms during disinfection ⁽¹⁸⁾

C-T tables can be found within each supporting document for microbiological guidelines for Canadian drinking water quality, at http://www.hc-sc.gc.ca/waterquality

Chlorine/chloramine residuals should be tested when bacteriological samples are taken, as identified above, as well as independently. Chlorine residuals can be verified by a laboratory or by using an acceptable test kit (See Section 7.3.2.1).

Additional testing of chlorine residuals could also be done to routinely monitor the integrity of the distribution system. Note that residuals are not necessary for in-home plumbing (e.g., where point-of-use treatment devices are used).

For more information on chlorine residuals, see Section 6.3.

In the case of a groundwater source not under the direct influence of surface water, disinfection may not be necessary provided an annual sanitary survey and vulnerabilities assessment (determined on a case-by-case basis), is conducted to ensure that the source is not subject to contamination and that conditions have not changed.

If a comprehensive sanitary survey is conducted following the methods outlined in Appendix K of the Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems using Surface Water Sources ⁽³⁵⁾ then the survey frequency may be reduced to once every three to five years, as appropriate. However, sufficient microbiological testing must still be done to ensure the water is potable.

Note: Even in cases where a sanitary survey or vulnerabilities assessment suggests that disinfection is not required, periodic disinfection may become necessary in situations where the microbiological quality of the water deteriorates. For this reason, disinfection equipment and supplies, or an equivalent incident response mechanism (such as an alternative source or boil water advisory), must be available to deal with potential occurrences.

4.4 Contaminant targets

The Guidelines for Canadian Drinking Water Quality lists many chemical and physical parameters of concern in Canadian drinking water supplies. Many of these, though, are only a concern in certain parts of the country due to site-specific geology or industrial or agricultural activity. For this reason, it is recommended that federal departments and, in First Nations communities, water managers and technical support staff, conduct a baseline chemical analysis of their water supplies to determine which substances should be monitored as part of the monitoring program. The baseline chemical analysis should be done for all drinking water supplies (including municipal and hauled water).

4.5 Drinking water materials

Drinking water materials are materials that come into contact with drinking water, from its intake at the source through the treatment plant and the distribution system and all the way to the consumer's tap (and beyond).

These materials fall into three general categories: treatment devices (such as filters and reverse osmosis systems and their components), treatment additives (such as alum and chlorine) and system components (such as pipes and faucets). Drinking water quality concerns from these materials are generally related to:

• Leaching of contaminants from the material into the drinking water.
• Treatment devices not meeting their manufacturer's claim of efficiency for removal of specific contaminants.

During the construction, maintenance or replacement of any component of a drinking water treatment or distribution system, only materials that meet applicable performance and health-based standards should be used.

Health Canada does not recommend specific brands of drinking water treatment devices, but it strongly recommends that consumers look for a mark or label indicating that the device has been certified by an accredited certification body as meeting the appropriate NSF International (NSF) / American National Standards Institute (ANSI) standard. These standards have been designed to safeguard drinking water by helping to ensure the material safety and performance of products that come into contact with drinking water. Certification organizations provide assurance that a product or service conforms to applicable standards and must be accredited by the Standards Council of Canada (SCC). An up-to-date list of accredited certification organizations can be obtained from the SCC ( http://www.scc.ca).

NSF standards are widely accepted in North America. They reference and incorporate other relevant standards and protocols as appropriate.

The NSF International web site ( http://www.nsf.org) has information about both health-based and performance standards related to drinking water treatment devices including a listing of certified systems. Standards exist for most drinking water treatment devices. The two key standards with respect to health effects are NSF/ANSI Standard 60: Drinking water treatment chemicals-health effects and NSF/ANSI Standard 61: Drinking water system components-health effects. NSF/ANSI Standard 61 is often referenced in many of the standards for drinking water treatment devices to ensure the devices meet minimum health effects requirements.

Plumbing systems (internal building distribution systems) within federal buildings and in First Nations communities must be designed and constructed to meet the National Plumbing Code of Canada. This may not be possible in situations such as foreign embassies in other countries. In these situations, minimum sanitary engineering practices should be met.

Other international standards do exist (e.g., British Standards International), but do not currently address the health-based issues related to materials that come into contact with drinking water and therefore should not be considered equivalent. Any chemicals and additives used in drinking water treatment processes and/or the distribution system must meet the applicable health-based standards established by NSF International.⁽¹⁴⁾

⁴ Includes bottled water