Biodegradation of bisphenol a and ibuprofen by ammonia oxidizing bacteria



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Texas A&M University


Bisphenol A (BPA) is a compound that is commonly used in the manufacture of epoxy resins and plastics. Because of large scale production and widespread usages, BPA is released into the atmosphere through air, land, and water. BPA is weakly estrogenic in animals and has acute aquatic toxicity even at low concentrations of 1- 10????g/L. Ibuprofen is a widely used analgesic and antipyretic. Ibuprofen and its metabolites are mainly released into the environment by human urinary excretion. Ibuprofen has been detected at low concentrations in surface and waste waters. The environmental and health effects at such concentrations are unclear. The high removal of BPA and ibuprofen in the wastewater treatment plants (WWTPs), suggest that biodegradation might be responsible for the removal of these compounds. Several bacterial strains, isolated from waste water, are known to degrade BPA and ibuprofen. No studies, however, have reported using ammonia oxidizing bacteria for this purpose. Ammonia oxidizing bacteria (AOB) are an important group of microorganisms in nitrifying activated sludge of WWTPs. AOB are known to express ammonia monooxygenase (AMO) to degrade many different aromatic and aliphatic organics via cometobolic degradation (non beneficial mechanism). Nitrosomonas europaea is a widely studied AOB found to degrade synthetic estrogen by a study. This study aims to characterize the biodegradation of BPA and ibuprofen by AOB. The biodegradation ability of N.europaea with respect to BPA and ibuprofen was examined. Experiments were conducted in the presence/absence of the AMO inhibitor (allylthiourea), an external reducing energy source (sodium formate) and different primary substrate (ammonia) concentrations. The second part of the study comprises of biodegradation tests on BPA and ibuprofen using activated sludge from two WWTPs, one with one-sludge activated sludge system and the other one with two-sludge nitrification system. From the experiments conducted BPA at a concentration of 1.6 mg/L was degraded to 0.12 mg/L by N.europaea. BPA at concentrations of 1.0 mg/L and 0.75 mg/L was completely degraded by the cells. Resting cells of N.europaea were, however, unable to degrade BPA. Also ibuprofen of two concentrations, 0.42 mg/L and 0.8 mg/L, were not degraded by the culture. BPA at a concentration of 1 mg/L was degraded to 0.2 mg/L and ibuprofen at 0.5 mg/L was completely degraded by the activated sludge from the combined reactor. The activated sludge from the nitrification tank degraded BPA of concentration 1 mg/L and ibuprofen of concentration 0.5 mg/L completely. Hence, it can be summarized that Bisphenol A was degraded by N.europaea and also by the activated sludge obtained from the WWTPs. Ibuprofen was found incapable of inhibiting ammonia oxidizing bacteria in the case of the pure culture while it was successfully degraded by the mixed culture.