Development of Predictive Models for Disinfection by-products and Filtration Technology Assessment in Small Community Water Supply Systems
In the province of Newfoundland and Labrador, chlorine is the most commonly used form of disinfection. Out of 536 public water supply systems, 459 utilities use chlorine. Chlorine is considered to be the most effective disinfectant to kill microorganisms in drinking water, but in the presence of natural organic matters (NOMs), residual chlorine reacts with NOMs and forms disinfection by-products (DBPS) in the water supply system, some of which are harmful to health and have shown to be carcinogenic in animal studies. There are hundreds of different types of known DBPs associated with different forms of disinfection and it is difficult to monitor all of them. The recent focus has been on two groups of DBPs: trihalomethanes (THMs) and haloacetic acids (HAAs), since these two groups have been identified as the largest class of DBPs detected in chlorinated drinking water.
The main objective of this study was to conduct an in-depth investigation on the formation of DBPs in the drinking water supply systems in small communities near St. Johns, NL. This was accomplished by taking water samples from the intake and from different points in the water supply system after chlorination (e.g., storage tanks, main transmission lines and residential taps). For this, the communities of Torbay and Pouch Cove were selected following a detailed investigation. The detailed analysis on the level of THMs and HAAs was conducted for these two communities with and without filtration. The levels of DBPs in these communities were found to be much higher than the Canadian guidelines.
Another objective of this study was to design a cost-effective filtration system to reduce THMs and HAAs in the drinking water systems. To reduce the concentration of THMs and HAAs, a series of experiments were conducted on tap water from Pouch Cove using an inexpensive absorbent. The results show more than 95% removal of THMs and a 35% of HAAs in the Pouch Cove drinking water using activated carbon. The preliminary analysis shows a great potential to develop an affordable filtration technology for small communities in the province.