Study Of Influence Of Changes In Hydraulic Conditions On Biofilm Stability In Water Distribution Network

Hydraulic conditions are very complicated in water distribution network. Biofilms attached on the inner-pipe surfaces may alter drinking water quality, if they are detached from the pipe due to changes in hydraulic conditions. At present, the research at home and abroad is mainly focused on the influence of the changes in hydraculic conditions on lab-grown biofilms stability. However, there is few systematically research on the influence of the biofilms stability under different hydraulic conditions in actual water distribution network. Research progress of the hydraulic stability of pipe biofilms is systematically summarized at home and abroad in this paper, and the main work of this paper is below:(1)5 groups of actual water supply metal pipes above 5 years ages were collected from a southern city and flushing experiments were carried out under 3 kinds of dynamic hydraulic regimes based on the actual conditions in water distribution network.(2)Physico-chemical indicators and cultivable bacteria in water samples were measured before and after flushing, and the influence of changes in hydrological regimes on water samples in different pipes was obtained.(3)The flushing experiments for 5 metal pipes on the same hydraulic condition were carried out. Biomass detachment from stainless steel pipe was compared with biomass detachment from galvanized pipe with the same diameter and age,and biomass detachment from one grey iron pipe was compared with biomass detachment from the other grey iron pipe with the same diameter and different age. Moreover, the amount of biomass detachment of nodular cast iron pipe has been analyzed.(4)After flushings in 5 metal pipes were done on 3 hydraulic conditions, the analysis on the change of bacterial community structure in phyla, class and genus level was carried out. The change of bacterial community in galvanized pipe was compared with the change of bacterial community in stainless steel pipe, and the change of bacterial community in one grey iron pipe was compared with the change of bacterial community in the other grey iron pipe with the same diameter and different age. Moreover, the change of bacterial community structure in nodular cast iron pipe after flushing was analyzed.