Effect of household pipe materials on formation and chlorine resistance of the early-stage biofilm: various interspecific interactions exhibited by the same microbial biofilm in different pipe materials.

Microbial community biofilm exists in the household drinking water system and would pose threat to water quality. This paper explored biofilm formation and chlorination resistance of ten dual-species biofilms in three typical household pipes (stainless steel (SS), polypropylene random (PPR), and copper), and investigated the role of interspecific interaction. Biofilm biomass was lowest in copper pipes and highest in PPR pipes. A synergistic or neutralistic relationship between bacteria was evident in most biofilms formed in SS pipes, whereas four groups displayed a competitive relationship in biofilms formed in copper pipe. Chlorine resistance of biofilms was better in SS pipes and worse in copper pipes. It may be helped by interspecific relationships, but was more dependent on bacteria and resistance mechanisms such as more stable extracellular polymeric substance. The corrosion sites may also protect bacteria from chlorination. The findings provide useful insights for microbial control strategies in household drinking water systems.

Microbial community analysis in a combined anaerobic and aerobic digestion system for treatment of cellulosic ethanol production wastewater.

This study investigated the microbial diversity established in a combined system composed of a continuous stirred tank reactor (CSTR), expanded granular sludge bed (EGSB) reactor, and sequencing batch reactor (SBR) for treatment of cellulosic ethanol production wastewater. Excellent wastewater treatment performance was obtained in the combined system, which showed a high chemical oxygen demand removal efficiency of 95.8% and completely eliminated most complex organics revealed by gas chromatography-mass spectrometry (GC-MS). Denaturing gradient gel electrophoresis (DGGE) analysis revealed differences in the microbial community structures of the three reactors. Further identification of the microbial populations suggested that the presence of Lactobacillus and Prevotella in CSTR played an active role in the production of volatile fatty acids (VFAs). The most diverse microorganisms with analogous distribution patterns of different layers were observed in the EGSB reactor, and bacteria affiliated with Firmicutes, Synergistetes, and Thermotogae were associated with production of acetate and carbon dioxide/hydrogen, while all acetoclastic methanogens identified belonged to Methanosaetaceae. Overall, microorganisms associated with the ability to degrade cellulose, hemicellulose, and other biomass-derived organic carbons were observed in the combined system. The results presented herein will facilitate the development of an improved cellulosic ethanol production wastewater treatment system.

Effects of pipe materials on chlorine-resistant biofilm formation under long-term high chlorine level.

Drinking water distribution systems are composed of various pipe materials and may harbor biofilms even in the continuous presence of disinfectants. Biofilms formation on five pipe materials (copper (Cu), polyethylene (PE), stainless steel (STS), cast iron (CI), and concrete-coated polycarbonate (CP)) within drinking water containing 1.20 mg/L free chlorine, was investigated by flow cytometry, heterotrophic plate counts, and denaturing gradient gel electrophoresis analysis. Results showed that the biofilms formation varied in pipe materials. The biofilm formed on CP initially emerged the highest biomass in 12 days, but CI presented the significantly highest biomass after 28 days, and Cu showed the lowest bacterial numbers before 120 days, while STS expressed the lowest bacterial numbers after 159 days. In the biofilm community structure, Moraxella osloensis and Sphingomonas sp. were observed in all the pipe materials while Bacillus sp. was detected except in the CP pipe and Stenotrophomonas maltophila was found from three pipe materials (Cu, PE, and STS). Other bacteria were only found from one or two pipe materials. It is noteworthy that there are 11 opportunistic pathogens in the 17 classified bacterial strains. This research has afforded crucial information regarding the influence of pipe materials on chlorine-resistant biofilm formation.