New York Rural Water Association

In 1999 and 2000, the National Rural Water Association and the EPA co-funded a study to provide a national assessment of drinking water characteristics by collecting information on small drinking water systems serving less than 10,000 populations. Specifically, the intent was to develop a database to reflect a small systems treatment technique, disinfection practices and the existence of disinfection by-products in the finished drinking water distributed to residents.While chemical disinfection has proven to be very successful in controlling disease-causing organisms in drinking water, recent research has confirmed that disinfection can create by-products that pose health risks to drinking water users. Generally, it has been found that various disinfectants react with naturally occurring organic matter to form new pollutants, which are believed to be carcinogenic. Chlorine, a widely used disinfectant reacts with organic material in the source water to form compounds such as trihalomethanes, haloacetic acids and other potential health risk related pollutants. Bromides in source water react with ozone to create bromates also believed to be carcinogenic. Similarly chlorine dioxide produces chlorates & chlorites when combined with organic matter.In 1996, EPA published a regulation, known as the Information Collection Rule (ICR), which recognized the need and required the collection of data on source water quality and related formation on disinfection by-products. Because of monitoring costs, the ICR was limited to large systems serving greater than 10,000 populations. The intention was to collect data from large systems using various treatment technologies and disinfection practices to determine the general prevalence of the problem. In addition to costs, the ICR did not include smaller systems because generally they have smaller distribution systems that limited contact time between the disinfectant and the finished drinking water, thus reducing the likelihood of forming disinfection by-products.In 1998, EPA promulgated the Disinfectants and Disinfection By-products Rule (D/DBPR) establishing limits on the amount of D/DBP allowed in drinking water distribution systems. This Stage1 rule applies to all community water systems and non-transient, non-community water systems that add a disinfectant, and transient, non-community water systems that use chlorine dioxide. In addition to establishing limitations, the rule also imposes monitoring requirements that begin in 2003 for small systems. A Stage II rule may be published in the future which would update limits and/or monitoring requirements based on findings and compliance assessments of the Stage I rule.

Based on the promulgation of the rule, NRWA and EPA cooperatively undertook the study to determine the burden of the D/DBPR on small systems and to establish conclusions and/or recommendations relative to the future drinking water regulations. The data provides a preliminary assessment of environmental and economic impact of the rule on systems serving less than 10,000 and a national summary of small system compliance trends.

SUMMARY OF THE SMALL SYSTEM SAMPLING PROJECT

The study was based on the random selection from the EPA database of public systems serving less than 10,000 population using surface water as their source. To ensure a 90% confidence level that the results would be statistically representative of all small surface systems meeting the same criteria, the study was to include at least 112 systems. Because higher temperatures increase the interaction of disinfectants and organic matter, winter and summer samples were incorporated into the study to attempt to bracket D/DBP values in the distribution systems.In order to evaluate the potential for an actual formation of disinfection by-products, samples were collected at four locations: source water, plant effluent, the mid-point of the distribution system (average resident times) and the end of the distribution system (maximum resident times). The source water samples were analyzed for total organic carbon, bromide, uv254, ph, ammonia, alkalinity, hardness, and turbidity. Plant effluent was analyzed for the same parameters and additionally analyzed for chlorine residuals, total trihalomenthane, and haloacetic acids. Finally, the two distribution system samples were analyzed for total trihalomenthane, haloacetic acids and chlorine residuals.

All samples were collected on-site by State Rural Water Association employees in cooperation with the system officials. During the winter 1999, 117 systems and 32 Rural Water Associations participated in the sampling effort. During the summer 2000, 103 systems and 30 Rural Water Associations participated. Participates were identified by sample number and a facility ID number. Only the system, and the Rural Water Association employee knew the link between the sample number/facility ID and the system name. In New York, I took samples from 12 systems around the state. All the data collected was fed into a model, used in conjunction with sample analysis results, to determine treatment techniques, disinfection practices, and the extent of disinfection byproduct presence at the mid and end point of distribution systems.

SUMMARY AND CONCLUSIONS

Small system source water TOC results were similar to the ICR system results, but small system THM4 and HAA5 were significantly greater. Small system source water bromide levels tended to be lower than ICR systems; as much as 50% lower.In terms of regulatory compliance, the following is a summary of the results of the small systems project:

TOC Removals: Of those systems required to achieve specific treatment removal rates (systems having TOC levels equal to or greater than 2 mg/l), approximately 64% of small system treatment techniques exceeded the TOC removal standard. THM4: Approximately 30% of winter samples and approximately 60% of summer samples exceeded the THM4 limit of 80 ppb.
HAA5: Approximately 20% of winter samples and approximately 25% of summer samples exceeded the HAA5 limit of 60 ppb.

With the data obtained from this study, we can begin to develop a better understanding of how small systems compare to large systems in terms of economic, environmental and health related concerns. This will become especially useful in assessing the potential impact of future drinking water regulations on small systems. I learned a great deal while collecting these samples, and had some memorable experiences as well. I'll never forget my "close encounter" with the river otter while collecting the raw water sample out of Cayuga Lake. If anyone is interested in the complete report, feel free to contact me and I'll see that you get a copy.