Bacterial dynamics in the drinking water distribution system of Brussels

Water samples and pipe coupons were collected from the Brussels's drinking water distribution system (DS). A treated surface water and various groundw aters Feed this DS. Parameters related to bacterial regrowth have been meas ured on these samples: temperature, concentrations of free residual chlorin e, concentration of biodegradable dissolved organic carbon (BDOC), abundanc e of suspended bacteria, densities of fixed bacteria and levels of bacteria l activity. Results showed that groundwaters were less susceptible to favor bacterial regrowth in the DS pipes. Treated surface water and mixed waters had the highest potential of bacterial regrowth in the DS dead ends. Resul ts also showed that the potential regrowth induced by the distribution of a treated surface water could be reduced if: (1) the BDOC levels were below 0.25 mg C/l at the outlet of the surface water treatment plant: (2) a signi ficant free chlorine residual was present within the whole DS. Second-stage biological filtration using granular activated carbon is now under constru ction at the surface water treatment plant feeding a part of this DS. This treatment implementation should reduce BDOC levels and chlorine demand of t he treated surface water and will further reduce the slight regrowth phenom ena observed in this DS. (C) 2001 Elsevier Science Ltd. All rights reserved .