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Biofilms on pipe walls in water distribution systems are of interest since they can lead tochlorine demand, coliform growth, pipe corrosion and water taste and odor problems.This study is part of an AWWA Research Foundation and Tampa Bay Water tailoredcollaboration project to determine the effect of blending different source waters ondistribution systems water quality. This project is based on 18 independent pilotdistribution systems (PDS), each being fed by a different water blend (7 finished watersblended in different proportions). The source waters being compared includegroundwater, surface water and brackish water. These are treated in a variety of pilotdistribution systems including reverse osmosis (RO) (desalination), both membrane andchemical softening and ozonation - biological activated carbon (BAC for a total of 7different finished waters. The observations from this study have consistentlydemonstrated that unlined ductile iron was more heavily colonized by biomass thangalvanized steel, lined ductile iron and PVC (in that order) and that fixed biomassaccumulation was more influenced by the nature of the supporting material than by thewater quality (including secondary residual levels). However, bulk liquid water cultivablebacterial counts (i.e. heterotrophic plate counts or HPCs) did not increase with greaterbiofilm accumulation, but results to date suggest high HPCs correspond with lowdisinfectant residual more than high biofilm inventory. Temperature affected biofilmsalso, and assimilable organic carbon (AOC) was important when residual was between 0.6 and 2.0 mg Cl2/l. Anadditional aspect of the work is that the potential of exoproteolytic activity (PEPA)technique was used along with a traditional so-called destructive technique in which thebiofilm was scraped off from the coupons' surface, resuspended, and cultivated on R2Aagar. Both techniques gave similar trends and relative comparisons among PDSs butculturable biofilm values were several orders of magnitude lower than PEPA values. Includes 16 references, figures.

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Edition: Vol. - No. Published: 06/15/2003 Number of Pages: 11File Size: 1 file , 330 KB