Occurrence And Removal Of Pharmaceuticals And Personal Care Products In Sewage Treatment Plants

In recent years, pharmaceuticals and personal care products (PPCPs) as a kind of emerging environmental pollutants, have attracted widespread concerns due to the frequent detection in various environmental media and the potential risk to human health and ecological environment. The study of emerging contaminants in our country is gradually rise. At this stage, the pollutant emissions standards and quality control standards about this kind of pollutants are absent. Sewage treatment plants identified as the main point source of PPCPs into the environment, is also an important way for removing this type of pollutants. Most studies on the occurrence of PPCPs in our country have been evaluated by investigating the concentration of PPCPs in the sewage treatment plants, and few specific to the laboratory mechanism analysis. The object of these studies is mostly for antibiotic.In this reseach, using GC/MS and HPLC detection means, we study the occurrence and environmental risks of PPCPs belonging to different therapeutic classes in full-scale sewage treatment plants, and the removal mechanism of to the typical PPCPs by activated sludge in the laboratory.The concentrations of eleven kinds of target PPCPs in the three sewage treatment plants in Guangdong were monitored over the course of three years, to gain an insight into the occurrence and environmental risks. The results showed that the detection rates of the target PPCPs in the three sewage treatment plants were very high, and the concentration levels were lower than those in the other countries and similar with the other domestic reports. The main source of PPCPs in the water environment was identified as domestic wastewater. The influent concentrations of PPCPs were mainly associated with the human use and the rainy season. The concentrations of PPCPs in sewage treatment units and effluent were restricted to feed concentrations and determined by the removal effects of the sewage treatment units. The maximum concentrations mainly occured in January, while the minimum in July. Biological treatment process played a main role in the total removal efficiencies. Anaerobic tank and aerobic tank were beneficial to remove of PPCPs, and anoxic tank often appeared negative removal rates. Risk assessment showed that diclofenac could pose a high risk to aquatic organisms in the effluent of sewage treatment plant STP1, and salicylic acid and mefenamic acid could pose a medium risk to aquatic organisms. In sewage treatment plant STP3, clofibrate and diclofenac could pose a medium risk to aquatic organisms. Triclosan could pose a high risk to aquatic organisms in the three sewage treatment plants.This study investigated the degradation characteristics of three acidic pharmaceuticals (naproxen, benzafibrate and ibuprofen) and roxithromycin in the presence of activated sludge under aerobic and anoxic conditions. Experimental results indicated that roxithromycin was significantly adsorbed by activated sludge, and the effective biodegradation of benzafibrate and naproxen was observed both under aerobic and anoxic conditions. The concentration of roxithromycin leading to acute toxicity on activated sludge was higher than that of ibuprofen. The degradation of naproxen and benzafibrate could be described by pseudo first-order kinetic model, while the adsorption data could be well interpreted by pseudo second-order kinetic model. The spiked concentrations of the two-target compounds were negatively correlated with degradation and adsorption rate constant. The adsorption of pharmaceuticals by activated sludge was rapid, and the relative adsorbabilties of the two-target compounds based on their log Kow and pKa values. The adsorption process of naproxen in activated sludge was suitable for the Freundlich adsorption isotherm. Desorption effect of naproxen was not obvious, therefore naproxen was not easy to cause secondary pollution to the environment in the excess sludge treatment and disposal process.Using454high-throughput sequencing technology, we realized the coupling relationship between the microbial community structure and the capacity of decontamination in activated sludge system. The bacterium group achieved advantage degradation of naproxen were mainly classified as Betaproteobacteria. There are considerable differences of the microbial community structure between different pH conditions in the domestication system. Under the acid condition, the system could better remove naproxen, but poor stability. The high levels of naproxen removal from the high concentration wastewater only containing naproxen was achieved by the domestication system under neutral condition, and the system had complexity and diversity of microbial ecology.