As source water quality declines, small systems are increasingly faced with nitrogenous contaminants that negatively impact human health and/or water quality. The overarching objective of Program D of WINSSS is to biologically manage the nitrogenous contaminant grouping (i.e., ammonia, nitrite, nitrate, and nitrogenous-disinfection by-product [N-DBP] precursors) and to demonstrate that such biological processes can yield other water quality benefits related to pathogen suppression and trace organic compound (TrOC) removal. The hypotheses to be tested are as follows:
(1) a nitrification process will reduce the occurrence of potential pathogens in the drinking water distribution system;
(2) soluble microbial products (SMP) generated in a nitrification process will lead to increased TrOC removal by heterotrophic bacteria;
(3) accumulation of nitrite in a denitrification process at below-optimum temperature can be offset by micronutrient addition;
(4) nitrification or denitrification processes will not substantially change N-DBP formation after final disinfection.
Nitrification, TrOC removal, and microbial community structure will be studied in biofilters at the bench- and pilot-scale; two natural waters from different sites in the United States will be used to operate parallel bench-scale nitrifying biofilters, and a 6-month pilot-scale nitrifying biofilter study will be conducted at one of the sites. The impact of SMP on TrOC biodegradation will be studied in controlled batch experiments. Denitrification will be studied in biofilters at the bench-scale. Using effluent from the bench- and pilot-scale biofilters, the formation of N-DBPs (halonitromethanes, haloacetonitriles, haloacetamides and N-nitrosodimethylamine) will be examined. The bench-scale nitrifying and denitrifying biofilters will be run at the University of Texas; the pilot-scale nitrifying biofilter will be managed by Carollo Engineers and operated by the University of Texas. The N-DBP experiments will be conducted at the University of Massachusetts. The SMP experiments will be conducted jointly by both universities.
Program D research is expected to demonstrate that biological processes are a robust and sustainable option for small drinking water systems and that they can be used to manage nitrogenous contaminants as well as to positively impact pathogen occurrence and TrOC removal.
Presentation from WINSSS March 2016 Center Meeting