AWWA WQTC69434

The distribution system exerts an influence on treated water quality. This paper focuses on the behavior of C, N, P, Si and S. These parameters are major nutrients for microbiological growth. Some of them are monitored as a check on the amounts of chemical addition in water treatment. The paper also compares the results before and after ozone is used for primary disinfection. The Massachusetts Water Resources Authority (MWRA) has investigated previously the effect of ozone in the absence of biofiltration. Weekly monitoring of TOC and TIC show that BDOC increased due to ozone. But there was no negative impact on water quality in terms of microbiological growth. This could be due to the increase in chloramine target. Weekly monitoring of ammonia, nitrite and nitrate show that there is increased conversion of ammonia to nitrate. But there were no negative impacts from nitrification. TOC is negatively correlated with combined nitrite and nitrate levels. The increase in nitrite and nitrate is also negatively correlated with the level of ozone byproducts (aldehydes), as well as chlorine byproducts (haloacetic acids). There were changes in the silica and sulfur levels between finished water and distribution samples. This can be explained by changes in pH and surface adsorption due to pipe materials (cement lining). And it was observed that prior treatment with zinc orthophosphate at a community has lingering impacts on zinc and phosphorus levels even though the treatment ceased for about 10 years. Includes 4 references, figures.