AWWA WQTC60732

This research provides fundamental information on the feasibilityand development of a new biological treatment process for the destruction of trihalomethanes (THMs) formed indrinking water treatment plants.The treatment process is based on THM cometabolism by nitrifying bacteria growing onammonia (NH₃) in multimedia filters. Cometabolism can be defined as the fortuitousbiodegradation of a target chemical (i.e., the cometabolite) through reactions catalyzed by one ormore non-specific microbial enzymes. This research is unique in that almost no work has beendone on biological treatment processes for THMs. The process may be especially useful forutilities that prechlorinate for some period prior to ammonia addition to form chloramines. Bycombining the reactive surface properties of granular activated carbon (GAC) for chloraminedestruction with nitrifying bacteria that grow in biofilters without the addition of organic carbonto the water, an innovative treatment process will be developed that allows for upstreamdisinfection, while at the same time protecting bacteria in the downstream process (i.e., filtration)from the disinfectant. With this protection, bacteria will be able to biodegrade THMs formedwithin the treatment plant, thereby resulting in a lower concentration of THMs entering thedistribution system.The basic premise for this THM cometabolism treatment process derives from research notspecifically directed toward drinking water treatment (i.e., soil and aquifer remediation research).Therefore, much basic research is needed to document process performance under drinking watertreatment conditions and to assess the feasibility of the proposed process. The key question is whether nitrifying bacteria growing in granular media beds can reliably cometabolize THMs at asufficient rate to make this process attractive to utilities that practice (or want to practice)prechlorination, especially those practicing prechlorination with subsequent chloramination.Previous batch kinetic experiments demonstrated that all four THMs could be degraded by both apure culture, Nitrosomonas europaea, and mixed culture nitrifiers (Wahman et al. 2003). Basedon these results, biofilter experiments were conducted with columns seeded with mixed culturenitrifiers from Lake Austin, Texas, receiving nutrient water in the feed. Includes 3 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/15/2004

Number of Pages:

20

File Size:

1 file , 1.2 MB