عنوان مقاله [English]
Hospital waste contains pathogens and dangerous chemicals. Considering the problems encountered in wastewater treatment, investigation of treatment methods and pesticide residue content of hospital wastewater and sewage outlet is utmost importance. The aim of this study was to evaluate the performance of activated sludge with extended aeration system in treatment plants, for removal of Lambda-cyhalothrin in hospital wastewater and provide recommendations for improving the system. In this study six sewage outlet samples were taken before pesticide treatment and after first and second treatments from a hospital with extended aeration activated sludge system. Three samples from each sampling session were transferred into a container containing 0.5g activated carbon, to assess its effect on reduction of Lambda-cyhalothrin in wastewater. Lambda-cyhalothrin was extracted using QuEChERS method and analyzed using gas chromatography with mass spectrometry (GC/ MS). Finally, by employing SPSS software and using t-test and analysis of variance, at 95% significant level (P≤ 0.05), data were statistically analyzed. The results showed that concentrations of Lambda-cyhalothrin in hospital wastewater, before application, was below the limit of the detection and after two consecutive application, level of Lambda-cyhalothrin increased to 27.49 ± 0.086 and 37.56 ± 0.07 ppm, respectively. Using activated carbon treatment, the Lambda-cyhalothrin concentration decreased to 2.22 ± 0.05 and 1.54 ± 0.01 ppm, respectively. Comparing the results with standard levels recommended for pesticides, for drinking water (0.0001ppm) and sewage (0.031 ppm), all samples even after carbon active treatment, had significantly higher levels of Lambda-cyhalothrin at 95% confidence level. This reflects the fact that the extended aeration activated sludge system alone is not a sufficient technique for the removal and reduction of Lambda-cyhalothrin in hospital wastewater and to improve the current sewage treatment system, activated carbon can also be one of the options in reducing pesticide concentrations.