Abstract
This study examined the impact of the antibiotic tetracycline at environmentally relevant concentrations (1μg/L and 10μg/L) on the composition and function of the microbial community that are responsible for the secondary treatment step in a municipal wastewater treatment plant (MWTP). Specifically, this study examined whether nitrification is inhibited by the presence of tetracycline under high and low nutrient replacement conditions. Aerated semi-batch reactors were set up containing activated sludge samples from a MWTP. Reactors were replenished with a synthetic wastewater media at two constant replacement rates for a period of 4 weeks. Parameters such as ammonia, nitrate/nitrite and total Kjeldahl nitrogen concentrations were monitored to evaluate the nitrogen removal efficiency. Under a low nutrient replacement rate, tetracycline was observed to have a positive impact on ammonia removal and nitrification than at the higher one. However, total Kjeldahl nitrogen concentrations increased in low nutrient replacement reactors under the presence of tetracycline which suggested a potential inhibitory effect on denitrification. At high nutrient replacement rates, tetracycline did not demonstrate an inhibitory effect on both nitrification and denitrification processes. Overall, it appears that both antibiotic presence and nutrient replacement rates can influence the community composition and function of microbial communities found in a MWTP.
Highlights
First and foremost I would like to thank my supervisor Dr Kimberley Gilbride for believing in me enough to provide me with an opportunity that opened the door to the world of research for me
It is observed that 30-90 % of pharmaceutical products ingested by humans are excreted in the urine or feces (Robinson et al, 2007). These compounds can take on a “pseudopersistent” quality because of the continuous influx of pharmaceuticals that arrive from various waste streams such as hospital wastewaters and municipal wastewaters (Daughton, 2004)
This study has suggested that tetracycline does have an impact on the nitrification and denitrification processes that occur in the secondary treatment of wastewater
Summary
Wastewater is defined as the water after use from residential, industrial and institutional sources. Microorganisms are important in the secondary treatment step of wastewater that is known as the biological treatment step Their wide array of abilities to degrade organic and inorganic compounds allows for the removal of nutrients such as carbon, nitrogen and phosphorus. Nitrification is often regarded as the “Achilles heel” of wastewater treatment because if nitrifiers are inhibited and removed from a system, reestablishment of nitrification is often a lengthy and expensive mission (Wagner and Loy, 2002) The importance of these nitrifiers and their biotechnological application in wastewater remediation highlights the need to understand the impact of long-term exposure of pharmaceuticals on the ecology and physiology of biological treatment microbial communities. The objective of this study was to assess the impact of tetracycline on the microbial community involved in the secondary treatment of municipal waste water using a semi-batch wastewater reactor system. The effect of high and low nutrient replacement rates under tetracycline pressure was assessed
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