Water Science & Technology: Water Supply—WSTWS Vol 10 No 1 pp 105–112 © IWA Publishing 2010 doi:10.2166/ws.2010.734

The effect of the surface-to-volume contact ratio on the biomass production potential of the pipe products in contact with drinking water

Z. G. Tsvetanova and E. J. Hoekstra

The biomass production potential (BPP) test is a semi-static test for assessment of microbial growth promoting properties of construction products in contact with drinking water (CPDW). In 2003 the test was selected for incorporation into a scheme for acceptance of CPDW in the framework of implementation of the European Construction Product Directive and Drinking Water Directive. The pass/fail criterion for the BPP test is based on the sum of microbial growth in water and in biofilm caused by substances released from CPDW. The test is performed at a surface-to-volume contact ratio (S/V) of 0.17 cm^-1, that is quite different from the practice in buildings and domestic installations, where the usual ratios are 2.1 cm^-1 for 3/4 inches pipe, 1.6 cm^-1 for 1 inches pipe or 1.0 cm^-1 for 1.5 inches pipe. The goal of the study was to evaluate the importance of S/V ratio for performance of the BPP test and for correct assessment of the growth promoting properties of CPDW. The BPP of 10 pipe products were compared under the S/V ratios of 0.17 cm^-1 and 1.7 cm^-1. The BPP of most polymer products were higher under the S/V ratio of 1.7 cm^-1 in individual trials, but the differences were insignificant. However, the planktonic biomass concentrations were 4–14 fold higher at larger S/V ratio and this can be important from hygienic point of view. For acceptance of CPDW, besides a pass/fail criterion for the BPP, the planktonic biomass concentration could be taken as a second criterion for evaluation.

Keywords: adenosine triphosphate; biofilm; biomass production; distribution systems; drinking water; pipes

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