Occurrence And Removal Rules Of Pharmaceutical Pollutants In The Third Wastewatertreatment Plant Of Xi’an City

Trace pharmaceutical pollutants in aquatic environment have the characteristics ofpersistence, biological accumulating and low degradability, and can bring the potentialrisk to the health of human beings and ecological environment while long term contact.Wastewater treatment plants (WWTPs) are very important component of waterenvironment system, and can purify wastewater and remove pharmaceutical pollutantssimultaneously. Therefore, it has more important significance to investigate the species,concentration variation and removal rules of the pharmaceuticals in wastewater of theWWTPs, which can be helpful to lessen the amounts of the pharmaceuticals inwastewater effectively, and to decrease the aquatic environmental impact and improvethe quality of reused water.This paper choose the third WWTP of Xi’an city as the research objective, andselect five pharmaceuticals named phenacetin, caffeine, cholesterol, diclofenac andgemfibrozil as the target objects based on the detection analysis for the influent of thethird WWTP. Different sampling sites were arranged in the units of Orbal oxidationditch treatment process that using for the wastewater treatment of the third WWTP, andthe samples were extracted and concentrated by solid phase extraction (SPE) method,and qualitative and quantitative analysis for the targets were carried out by gaschromatography-mass spectrum (GC-MS) analyzer.The experimental results showed that five pharmaceuticals, phenacetin, caffeine,cholesterol, diclofenac and gemfibrozil, had average concentrations of3.84μg/L、36.56μg/L、16.0μg/L、0.566μg/L and31.69μg/L respectively in the influent, andconcentrations of0.024~1.11μg/L in the effluent based on many time sampling detections of four seasons, which is higher than that in abroad. For Orbal oxidationditch process, the removal rates of the five pharmaceuticals were all above90%, andphenacetin, caffeine and diclofenac were mainly removed by biological degradationwith the removal efficiencies of52%,56.76%and66%separately, and gemfibrozil andcholesterol were mostly removed by physical-chemical method with the removalefficiencies of76.7%and49.56%respectively, and anaerobic removal of cholesterolwas higher than its aerobic treatment. It was also found that added flocculants in thethird treatment improved the adsorptive capacity of solid particles for thepharmaceuticals and decrease the concentrations of the pharmaceuticals in the reusedwater. Five pharmaceuticals were all checked in the floating oil of aerated grit chamberwith the concentrations of1.47~31.26μg/L. Gemfibrozil, caffeine, diclofenac andcholesterol were found in sludge phase with concentrations between0.151μg/g and3.63μg/g, but phenacetin was not detected.It indicates that Orbal oxidation ditch process has significant removal efficiencyfor five pharmaceuticals, but they still exist in the discharged effluent, floating oil andsludge, which can return to environment and cause secondary pollution. Therefore, it isnecessary to improve the wastewater treatment process further and adopt relative stepsto remove the pharmaceutical pollutants in the wastewater effectively so as to lessen thehazardous effects of the pharmaceuticals on human beings and environment.