Abstract
The reclaimed water containing high salinity, great amounts of organic matters and high nutrients can easily lead to growth of biofilms in reclaimed water distribution systems (RWDSs). The microbes colonize the cement surface and microbial metabolites can cause cement biodeterioration. To understand the effect of microbial involvement in the degradation, this study investigated the transformation characteristics of cement-mortar lining and microbial biomass in the simulated RWDS for 1 year by X-ray diffractometer (XRD), X-Ray Fluorescenc (XRF), Heterophic bacteria count (HPC) and DAPI staining. Microbial metabolites were analyzed by GC/MS. The result shows that the carbonation reaction took place in the surface of the eroded cement-mortar lining where the content of CaCO3 was continuously increasing while the content of hydrated compounds were decreasing. The depositing layer of CaSO4·2H2O, CaAl2Si2O8·4H2O and Mg4Al2(OH)14·3H2O on the lining surface were formed by minerals such as Ca, Si, Al and Mg lost from the degraded hydrated compounds. Microbial biomass in the RWDS has maintained an increasing trend during the study. The main microbial metabolites of the biofilm on the cement surface are fatty acids, amino acids, and carbohydrate.
Highlights
The utilization of reclaimed water is an effective ways to alleviate water resources shortage, reduce pollution load of urban water environment, improve the ecological environment
The ductile iron pipe with cement-mortar lining are widely used in the reclaimed water distribution systems (RWDSs) because of its cost-effective, stable mechanical property and durability
The simulated reclaimed water distribution system consists of three lm-length DN100 new cement mortar lined ductile iron pipe sections, the water tank, metering pump and flow meter connected by PVC plastic pipe (DN20) to form a recirculating pipe rig system (Figure 1)
Summary
The utilization of reclaimed water is an effective ways to alleviate water resources shortage, reduce pollution load of urban water environment, improve the ecological environment. The ductile iron pipe with cement-mortar lining are widely used in the reclaimed water distribution systems (RWDSs) because of its cost-effective, stable mechanical property and durability. High sulfate reacts with Ca(OH) in the cement-mortar lining to form gypsum (eq.3) which can cause internal expansion and softening [5,6].The microbes colonized on the concrete surface and in its pores, capillaries and micro-cracks cause damage through biodeterioration, such as sulphur bacteria, nitrifying bacteria, acid producing fungus and their microbial metabolites. Yang et al have found that reclaimed water had carbonic aggressivity to the cement-mortar liner, and the erosion products on the lining surface can not form a effective protective layer [8]. The erosion process of micro-organisms and their metabolites on cement-mortar liner in a simulated RWDS was investigated. Combined with the above results, the microbial metabolites were analyzed to reveal the chemical and microbiological erosion of cement lining in RWDS
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
