AWWA WQTC62498

The Santa Clara Valley Water District owns and operates three treatment plants and twodistribution pipelines. The District installed intra-basin baffles in two of its treated waterclearwells, one in 2002 and another in 2004. While baffling improves circulation andtheoretically should improve water quality, side effects of baffling cannot be ignored.With more surface area for microbial attachment, and under prime water qualityconditions, the baffles can become a magnet for biofilms. In addition, the districtboosted its chloramine residual from 1.4 mg/L to 2.3 mg/L in 2003 as a preventativemeasure against nitrification. As a result of these changes, the District began seeing arise in heterotrophic plate count (HPC) in one of its distribution pipelines despite maintaining ahealthy chloramine residual of 2.0 mg/L throughout the pipeline. Various causes of thehigh HPC occurrence were investigated, one of which was the assimilable organiccarbon (AOC) level in the treated water. Each treatment plant chose a different location toboost its in-plant chlorine dose in order to achieve the higher chloramine residual in thedistribution system. It was discovered that depending on the chlorine applicationscheme employed at the treatment plant, AOC levels varied accordingly. One of theplants modified its chlorine application scheme and subsequently lowered AOC in itstreated water. This paper presents the District's experience, data, and variousobservations made correlating several water quality parameters to the microbiologicalquality of its treated waters. Includes 5 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2005

Number of Pages:

14

File Size:

1 file , 1.2 MB