AWWA ACE63061

Population-growth-driven increased water demands and prolonged droughtconditions along with source water contamination by upstream wastewatertreatment plants (WWTPs) is prompting many water purveyors to rethink currentand future water management practices. Water purveyors are now, more thanever, faced with the challenges of a dwindling water supply, and a greaterfraction of treated wastewater is now finding its way to drinking water supplies.Many wastewater facilities are now practicing or exploring various technologies(e.g., advanced biological treatment, membranes, soil aquifer treatment) as partof reclamation, recharge, recycling, and reuse (i.e., direct use) programs.Attention has focused on pharmaceuticals and endocrine disruptors, but WWTPsare also sources of disinfection byproducts (DBPs), if chlorine disinfection ispracticed, and DBP precursors. Operational conditions, treated wastewater quality, fate-and-transportphenomenon in the receiving body, and the relative flow of the WWTP dischargeto that of the receiving stream will determine the overall impact of wastewater-derivedDBPs on drinking water supplies. Moreover, very little is known abouthow best to invest public money between WWTPs and DWTPs in order tomaximize societal benefits while minimizing the health risks posed bywastewater-derived DBPs.To understand these important issues, a comprehensive study was undertaken.More than 20 WWTPs and DWTPs from various geographical locations in theU.S. participated in a study sponsored by the Awwa Research Foundation(AwwaRF) and U.S. Environmental Protection Agency (USEPA). A cost benefitanalyses (CBA) was performed as part of this study. This paper discusses, step bystep, the approach to CBA in predicting finishedwater DBPs level at DWTPs whose source water is impacted by treatedwastewater. The approach included a detailed characterization of the wastewater effluent by treatment type, followed by fate-and-transport (anddilution) in the receiving body prior to its treatment at the DWTP, and ultimatelyassessing the amount of DBPs to form at the DWTP and in the distributionsystem.To predict DBP precursor levels in receiving bodies after wastewater treatment,several fate-and-transport models were developed and used. These modelspredicted the impact of biodegradation on DBP precursor levels in a river. Thepredicted influent water quality to the DWTP was then used with the USEPA'sWater Treatment Plant (WTP) model to predict finished water concentrations forregulated DBPs (i.e., trihalomethanes [THMs] and haloacetic acids [HAAs]) in theplant effluent and in the distribution system. Cost curves were also developed forboth DWTPs and WWTPs in ascribing the costs associated with differenttreatment types. The cost of improved treatment at the WWTP versus at theDWTP or a combination of the two in order to ensure compliance at the DWTPwith the drinking water maximum contaminant levels (MCLs) with variousupstream WWTP scenarios was evaluated. A CBA was performed that includedthe control of both halogenated DBPs (i.e., THMs, HAAs) as well a nonhalogenatedDBP (i.e., N-nitrosodimethylamine [NDMA]). The CBA model was developed to address the following issues:level of wastewater treatment and its impact on the effluent water quality(i.e., effluent organic matter [EfOM]) of the WWTP;conveyance of DBP precursors from the WWTP to the DWTP (i.e.,discharge into a receiving body and its dilution factor) and the impact offate and transport (e.g., biodegradation) on the DBP precursors; type of treatment used at the DWTP (e.g., conventional or advancedtreatment) and its effectiveness in removing DBP precursor (i.e., totalorganic carbon [TOC], ultraviolet absorbance [UVA], dissolved organicnitrogen [DON]) prior to disinfection at the DWTP; and, disinfection practices at the DWTP (i.e., chlorine and/or alternativedisinfectants) and its impact on the type and quantity of DBPs formed atthe DWTP and in th

Product Details

Edition:

Vol. - No.

Published:

06/01/2006

Number of Pages:

9

File Size:

1 file , 290 KB