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Modeling Simultaneous Effect of Initial Biomass, Copper, and Zinc Concentrations on Ammonia Oxidation

Modeling Simultaneous Effect of Initial Biomass, Copper, and Zinc Concentrations on Ammonia Oxidation
Yang, Wang
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Biological nitrification is an important process in domestic and industrial wastewaters for removal of total nitrogen and/or ammonia. In general, two steps are involved in nitrification: the oxidation of ammonia into nitrite called nitritation carried out by Ammonia Oxidizing Bacteria (AOB) and subsequent oxidation of nitrite into nitrate called nitratation carried out by Nitrite Oxidizing Bacteria (NOB). AOB are generally considered to be the most sensitive microbes in the nitrification process. It can readily inhibited by various environmental factors and heavy metals including copper and zinc found in wastewater or contaminated sites. Although there are some studies focusing on the combined effect of environmental factors on microbial activity and structure, information about simultaneous effect of initial biomass and inhibitors concentration is limited. The simultaneous effect of initial AOB, copper and zinc concentration on nitrification with respect to lag period and ammonia oxidation rate was studied using response surface analysis. In addition, the effect of these three independent variables on AOB community population and diversity was also investigated by RSA. Following conclusions could be deduced based on the results from this research. 1) Copper and zinc were toxic to nitrification and they could extend the lag period and decrease the AOR. However, maintaining a high concentration of initial AOB was able to neutralize the negative effect of copper and zinc. 2) Lag period and AOR could be calculated based on the quadratic equations from RSA. It provides significant support for process control in WWTPs against inhibitory materials (copper and zinc). 3) Two species, Ntrosomonas eutropha and Nitrosospira multiformis were confirmed in seed using DGGE. 4) Population change of NSS was not affected by initial AOB, copper and zinc concentration significantly. Population change of NSMeur was mostly affected by initial AOB concentration.
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