Adverse Water Quality

Water intended for human consumption shall not contain disease-causing organisms or unsafe concentrations of toxic chemicals or radioactive substances. Water should also be aesthetic acceptable. Taste, odour, turbidity and colour are parameters that when controlled, result in water which is clear, colourless and without objectionable or unpleasant taste and odour.

Terminology

Maximum Acceptable Concentration (MAC)

The MAC is a health-related standard established parameters which when present above a certain concentration, have known or suspected adverse health effects. The length of time the MAC can be exceeded without injury or health will depend on the nature and concentration of the parameter.

Interim Maximum Acceptable Concentration (IMAC) The IMAC is a health-related standard established for parameters either when there are insufficient toxicological data to establish a MAC with reasonable certainty, or when it is not feasible, for practical reasons, to establish a MAC at the desired level.

Aesthetic Objective (AO)

AO's are established for parameters that may impair the taste, odour or colour of water or which may interfere with good water quality control practices. For certain parameters, both aesthetic objectives and health-related MACs have been derived.

Operational Guidelines (OG)

OGs are established for parameters that need to be controlled to ensure efficient and effective treatment and distribution of the water.

Water Quality Characteristics (health -related)

Microbiological

The microbiological quality of drinking water is the most important aspect of drinking water quality because of its association with waterborne diseases. Typhoid fever, cholera, enteroviral disease, bacillary and amoebic dysenteries and many varieties of gastrointestinal diseases, can all be transmitted by water. The introduction of a well managed water treatment system with effective chemical-assisted filtration and disinfection, an adequately maintained chlorine residual in the distribution system and the implementation of bacteriological surveillance programs to ensure the delivery of safe drinking water are measures that have demonstrated their effectiveness in eliminating water-related illnesses.

Chemical

Certain chemicals are potentially toxic and may adversely affect human health. It is desirable to control the intake of these potentially toxic chemicals from drinking water because the intake from other sources such as milk, food or air may be difficult to avoid.

Inorganic parameters may be present in water naturally or as a result of industrial, urban, or agricultural activities or other discharges.

Organic parameters are present to some degree in all municipal water supplies. Industrial and municipal waste, urban and agricultural run-off, and the natural decomposition of biological matter all contribute to the organic content. Some organic chemicals occur in water naturally as a result of organic decomposition. Synthetic organic chemicals can also be present in drinking water as a result of certain water treatment practices and/or direct contamination of the raw water.

Drinking water should be free of pesticides, and every effort should be made to prevent pesticides from entering raw water sources.

Physical

Includes colour, odour, taste, temperature and turbidity. Although these are primarily aesthetic parameters, they can have indirect effects on health through interrelationships with health related parameters.

Radioactive

There are more than 200 radionuclides. Some occur naturally while others are products from human activities such as mining and nuclear energy production. Ingestion of radionuclides in drinking water may cause cancer in individuals exposed and heritable genetic changes in their children. In Ontario, MACs have been set for radionuclide concentrations to protect consumers of drinking water from unacceptable risks.

Indicators of Adverse Water Quality, Notification Procedure and Corrective Actions

1. Escherichia coli (E.coli) or fecal colilform is detected in any required sample other than a raw water sample.

CORRECTIVE ACTION: Increase chlorine dose and flush the mains to ensure that a total chlorine residual of at least 1.0 mg/L or a free chlorine residual of 0.2 mg/L is achieved at all points in the affected parts of the distribution system. Resample and analyze.

2. Total Coliforms detected in any required sample other than a raw water sample.

CORRECTIVE SAMPLE: Resample at the same site and analyze. If confirmed to be positive, increase the chlorine dose and flush the mains to ensure that a total chlorine residual of at least 1.0 mg/L or a free chlorine residual of 0.2 mg/L to all points in the affected parts of the distribution system.

3. Samples containing more than 500 colonies per mL on a hetertrophic plant count.

CORRECTIVE ACTION: Resample and analyze.

4. Samples containing more than 200 background colonies on a total coliform membrane filter analysis.

CORRECTIVE ACTION: Resample and analyze.

5. Aeromonas spp. When Pseudomonas aeruginosa, Staphylococcus aureus, Clostridium spp or fecal streptococci are detected in samples.

CORRECTIVE ACTION: Resample and analyze.

Resampling

Should consist of a minimum of three samples to be collected for each positive sampling site: one sample at the affected site and one at each adjacent location on the same distribution line.

LOCATION ADVERSE QUALITY ACTION TAKEN RESULTS

None