Temperature Effects on Zn(II) Toxicity to Metabolisms of Polyphosphate Accumulating Organisms in Aerobic and Anaerobic Conditions

Though enhanced biological phosphorus removal (EBPR) is a standard technology for removing phosphorus from wastewater, the responsible organisms and relevant mechanisms are complex and not well-understood. Substrate type has been identified as an important factor affecting the competition between polyphosphate accumulating organisms (PAO_s) and glycogen accumulating organisms (GAOs), which are usually dominant in a failedEBPR. In addition, temperature is also considered an important factor in practice governing the efficiency of phosphate removal in EBPR because the population competition between PAO_s and GAO _s is significantly Ref. affected by water temperature. Ref.found that the predominant microbial population changed from PAO _s to GAO _s when temperature gradually rose from 20°C to 35°C. Similarly found PAO_s were the dominant microorganisms at low temperature (10°C), regardless of the influent carbon source or pH. 

However found conflicting results. Heavy metal ions have also been reported to be able to inhibit biological reactions responsible for carbon, nitrogen and phosphate removals. Ref.found that the presence of Cd (II) significantly changed the structure of microbial population and was toxic to the bacterial community in nutrient removal sludge, especially to the bacteria in the Beta proteobacteria. Monitoring of a full-scale advanced municipal wastewater treatment plant showed the P removal efficiency decreased dramatically after tin (Sn) levels in the solids fraction of the mixed liquid suspended solids (MLSS) exceeded 4 μgSn L^-1 . A similar study by showed 2 mg L^-1 of Cd(II) took the lead in affecting biological phosphate removal. At the level of 5 mg L^-1 of Cd (II), the total nitrogen removal and nitrification efficiency substantially declined and the denitrification rate was inhibited by about 61%. At the same time, the inhibition percentages of anaerobic release, anoxic and aerobic uptake rates of phosphate were about 76, 64, and 90%, respectively Ref.Further conducted a series of batch experiments to identify the toxic effects of Pb(II), Ni(II) and Cd(II) on nitrification and denitrification for nutrient removal sludges.(Read more)