Changes to microbial community due to long term exposure of Cetylpyridinium chloride, increasing antimicrobial resistance
Chua, Kiat Leong
Date of Issue2017-05-17
School of Civil and Environmental Engineering
Nanyang Environment and Water Research Institute
Emerging contaminants (ECs) in wastewater and natural water bodies have gained much attention in the recent years. This is due to their potential adverse effects on both ecological and human health even at very low concentrations. These ECs are released to the environment from the discharge of municipal wastewater effluents. Cetylpyridinium chloride (CPC) is a cationic surfactant, belonging to the group of quaternary ammonium compound. CPC is found in oral products, nasal sprays, and other personal care products. It is one of the most common cationic surfactants used for disinfection. There is rising concern about surfactant accumulation in the sludge treatment. High concentrations of surfactants can inhibit certain bacteria and disrupt the fragile biological balance of activated sludge. However, little is known about its fate (degradation, transformation and sorption) and their impact on the activated sludge microbes during wastewater treatment process. The fate and effects of CPC on antimicrobial resistance and microbial community structure were investigated on aerobic microbial communities exposed to CPC. The aerobic bioreactor was seeded with activated sludge originating form Jurong Water Reclamation Plant. Microbial communities were enriched with two different concentrations of CPC (50 and 500 µg/L) under aerobic conditions. After 10 weeks of exposure to CPC, the microbial community was found to be less susceptible to CPC. Microbial community continued to grow despite constant addition of CPC feed every 3.5 days. Further tests were done on six different antibiotics and the CPC exposed community showed increased resistance to four of the antibiotics namely, Ampicillin, Streptomycin, Vancomycin and Tetracycline, which resistance to Ampicillin was the strongest. Removal efficiencies of CPC were found to be high, where the routes of removal were found to be dominated by degradation and adsorption. The results of this project will have important implications in propelling further studies on how the exposure of CPC to a microbial community strengthened the antimicrobial resistance as this could affect both environmental and human health. Sustainable engineering strategies (e.g. bioaugmentation) and removal methods of CPC can be explored to effectively reduce the potential toxicity of CPC in the environment.
Final Year Project (FYP)
Nanyang Technological University