Water Resources Research Act Program

Details for Project ID 2014NC187B

Microbial Quality and Risk Assessment of Type 2 NC Reclaimed Water for Non-potable and Potable Reuse

Institute: North Carolina
Year Established: 2014 Start Date: 2014-03-01 End Date: 2015-08-31
Total Federal Funds: $7,500 Total Non-Federal Funds: $22,500

Principal Investigators: Mark Sobsey

Abstract: Problem addressed. New regulations for NC type 2 reclaimed water (NCT2RW) address risks from pathogens by specifying log10 reductions and final effluent quality for bacteria, virus and protozoan parasite indicators and by specifying treatment that includes dual disinfection by UV radiation and chlorination (or substitutes). There are little to no data on whether existing NC reclaimed water facilities meet these requirements, whether microbial indicators predict treatment performance and water quality for pathogens and whether NCT2RWs from current systems pose low pathogen risks from various exposure pathways of allowed non-potable uses or as source water for potable drinking water. There is an urgent need to quantify the microbial qualities and human health risks from different exposures to NCT2RW so that such data can be used by various stakeholders to make informed decisions about non-potable and potable uses. Objectives. The overall objectives of this project are to determine the microbial quality of NC type 2 reclaimed water (NCT2RW) from existing NC facilities and do quantitative microbial risks assessments (QMRAs) on the microbial health risks of these waters based on their quality and various types of exposures resulting from different non-potable and potential potable uses. Methods. 1. Measure the microbial quality of periodic and episodic samples of NCT2RW, partially treated water and raw sewage from several NC water reclamation facilities, analyzing for indicators (E. coli bacteria, coliphage viruses and Clostridium perfringens as a protozoan parasite surrogate) as well as key pathogens (Salmonella bacteria and human enteric viruses). 2. From levels of indicators and pathogens in NCT2RW, raw sewage and partially treated sewage, determine log10 reductions and compare them to those specified in the NCT2RW regulation, addressing variability in quality by location, under different conditions and over time. 3. Use collected data for fecal indicator and pathogen levels in NCT2RW for quantitative microbial risk assessment (QMRA) from human exposures by different uses and compare to US EPA-allowed health risks from primary contact recreation use and by drinking water exposures. 4. Use collected data for fecal indicators and pathogens in NCT2RW for QMRAs of human exposures from drinking water made by blending NCT2RW with natural water in various ratios, either directly (direct reuse) or indirectly after residence times in impoundments (indirect reuse), and then treating by drinking water treatment processes for potable water production. Compare the calculated risk level estimates of waterborne health effects from various exposure scenarios to US EPA’s acceptable risk level of 1 in 10,000 (10-4) infections/person /year (US EPA, 1992). Expected outcomes. Expected outcomes are reliable data on the microbial quality of NCT2RW and quantitative assessments of microbial health risks from various water exposure scenarios when used for non-potable purposes and as potential source water for drinking water supplies.