Biofilms on pipe walls in water distribution systems are of interest since they can lead to
chlorine demand, coliform growth, pipe corrosion and water taste and odor problems.
This study is part of an AWWA Research Foundation and Tampa Bay Water tailored
collaboration project to determine the effect of blending different source waters on
distribution systems water quality. This project is based on 18 independent pilot
distribution systems (PDS), each being fed by a different water blend (7 finished waters
blended in different proportions). The source waters being compared include
groundwater, surface water and brackish water. These are treated in a variety of pilot
distribution systems including reverse osmosis (RO) (desalination), both membrane and
chemical softening and ozonation - biological activated carbon (BAC for a total of 7
different finished waters. The observations from this study have consistently
demonstrated that unlined ductile iron was more heavily colonized by biomass than
galvanized steel, lined ductile iron and PVC (in that order) and that fixed biomass
accumulation was more influenced by the nature of the supporting material than by the
water quality (including secondary residual levels). However, bulk liquid water cultivable
bacterial counts (i.e. heterotrophic plate counts or HPCs) did not increase with greater
biofilm accumulation, but results to date suggest high HPCs correspond with low
disinfectant residual more than high biofilm inventory. Temperature affected biofilms
also, and assimilable organic carbon (AOC) was important when residual was between 0.6 and 2.0 mg Cl2/l. An
additional 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 the
biofilm was scraped off from the coupons' surface, resuspended, and cultivated on R2A
agar. Both techniques gave similar trends and relative comparisons among PDSs but
culturable biofilm values were several orders of magnitude lower than PEPA values. Includes 16 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 330 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 11 |
| Published : | 06/15/2003 |
