Year of Publication: 1996
Abstract:
The World Health Organization (WHO, 1993) states that:
"Water is essential to sustain life and a satisfactory supply must be made to achieve a drinking water quality as high as practicable"
The primary purpose of drinking water treatment is the protection of public health. The quantity of drinking water and the efficiency of treatment can be assessed through comparison to guidelines. In Canada, the applicable document is the Guidelines for Canadian Drinking Water Quality (1993) which has been adopted as minimum drinking water quality for licensed facilities in the province of Alberta. Most other developed countries have similar guidelines or regulations. The World Health Organization has also developed "Guidelines for Drinking Water Quality" (WHO, 1993) with a primary aim of protecting public health.
To assess drinking water quality in the Northern River Basin Study area results obtained from existing information and that obtained during this study were compared to both sets of guidelines discussed above. Of the sites investigated many were licensed facilities by Alberta Environmental Protection (AEP) and are required to meet as a minimum the Guidelines for Canadian Drinking Water. Other sites although not licensed by AEP still supply water to consumers, who tend to assure the water is of potable quality. As stated in the guidelines for Canadian Drinking Water:
"The guidelines and recommendations listed herein are intended to apply to all drinking water supplies, public and private. ... Judicious use of the guidelines will result in the provision of drinking water which is both wholesome and protective of public health."
As a result both licensed and unlicensed facilities were assessed based on comparison to guidelines.
Based on site visits to 38 facilities, water quality analyses completed for the site visit and analysis of existing water quality information a number of conclusions can be made on the drinking water quality in the Northern River Basin Study area.
1. Small facilities in the study area tend to produce poorer water quality than larger facilities. This was found to be the case in terms of microbiological quality, turbidity (a good overall measure o f treatment performance), and historical THM data.
2. As stated by the World Health Organization (1993):
"Infectious diseases caused by pathogenic bacteria, viruses and protozoa or by parasites are the most common and wide spread health risk associated with drinking water."
As it is not possible or feasible to test for all pathogenic organisms, microbiological quality of drinking water is assessed based on indicator organisms. If these indicator organisms are present in the finished drinking water it then must be assumed that pathogens could also be present. The most common microbiological indicator used in drinking water is the coliform group of organisms. Due to difficulties in sampling, transporting and analysis a single coliform positive sample may not truly reflect the microbial quality of the drinking water. As a result the Guidelines for Canadian Drinking Water Quality (GCDWQ,1993) state that not more than 10% of samples taken should be coliform positive. The WHO (1993) uses a more stringent guideline of not more than 5% be coliform positive. As the number of samples in small facilities are not great the 10% value was used in this study to assess microbial water quality to avoid unwarranted concerns to be raised for a facility based on a couple of bad samples. Analysis of a large database obtained from AEP of coliform results from communities in the Northern River Basin Study area was completed. This database consisted ofroughly 270,00 total and 270,000 fecal coliform analyzes taken over the last seven years. O f the smallest facilities, watering points, 30% o f them exceeded the 10% coliform positive guideline. If one includes samples which are considered poor by the GCDWQ (1993) this increases to 45%. Of particular concern was the finding that a number of facilities had high coliform positive percentages for all of the seven years the data was analyzed.
The occurrence of fecal streptococci, another indicator of fecal contamination, in 6 of the 28 surface water sites visited adds additional concern on the microbiological quality of water in many communities in the NRBS area.
3. It was also found that small facilities in the study area tended to have higher turbidity than larger communities. Although turbidity is only a measure of the clarity of water, high turbidity has been shown to negatively impact the performance of disinfection. In addition the most effective method of removal of protozoan cysts such as Giardia and Cryptospordium is through physical-chemical treatment processes for which there performance can be related to turbidity removal. The importance of turbidity as a parameter to indicate microbial quality is evident in the USEPA using turbidity to
justify pathogen removal credits in their most recent standard. In these standards, maximum credits are earned with turbidity of < 0.5 NTU 95% of the time.
Results from existing data indicated that surface water facilities serving populations less than 500 have a significantly higher turbidity than facilities serving populations greater than 500. Because these samples were obtained from the distribution system and the small number of samples collected, compliance with guidelines could not be assessed.
During the site visits 6 of the 38 sites had turbidity greater than 1 NTU, which in included the two watering points visited. These grab samples cannot be compared to standards which specify the maximum average turbidity 95% of the time must be below 1 NTU but they indicate that there may be problems at these sites.
4. Chemical parameters associated with raw water quality were found to be below guideline values based both on existing data and site visit data. However, for disinfection by-products (THMs) which are produced during treatment, the site visit data found, that 60% (12 Of21) ofthe surface water sites exceeded the guideline value of lOOug/L for THM. Analysis of existing data for THMs was complicated by the fact that most samples taken occurred under the old value of 350ug/L. The analysis did show however, if levels remained unchanged, 20 of the 62 sites analyzed by AEP would have difficulty meeting the lower standard value that is now in place.
5. Observation from site visits tended to indicate that much of the difficulties associated with small facilities may be related to operation of the facilities. Generally this can be related to the allotted time the operator is given to operate the facility, with smaller facilities having less time than larger facilities. The attitude of the people in decision making positions related to water treatment may also be an important factor. Operation performance may also be related to training as in larger facilities the majority or sole duty ofthe operator is to run the facility. As a result the opportunity for these operators to receive training is much greater. In small facilities, the operation of the treatment facility may be one of numerous tasks the operator may have to do. As many other tasks may be part of their daily routine the opportunity and incentive for these operators for training tends to be less.
6. Based on results of this study, remedial action is required in many small communities in the Northern River Basin Study area to bring the drinking water into compliance with current standards which are based on the protection of public health. Many communities are currently drinking water that may not meet Guidelines for Canadian Drinking Water Quality. Areas of concern are both the microbiological quality of the water and high levels of disinfection by-products. Of these the microbiological quality of the drinking water is by far of greatest concern. Many of the small communities showed higher than acceptable levels of indicator organisms as well as high turbidity. The occurrence of both would indicate that if pathogenic organisms are present in the raw water source they probably will not be removed by the treatment system.
In the time needed for remedial actions to rectify the problems it is of utmost importance that consumers of water be notified immediately as to the status of their drinking water with respect to standards along with recommendations of prudent courses of action available to them. In the case of microbiological problems that are not rectified consumers should be advised to boil their drinking water as recommended in Guidelines for Canadian Drinking W ater Quality (1993) and W orld Health Organization (1993).
