Investigation of Amoxicillin and Ciprofloxacin Behaviours in Sequencing Batch Reactor and Their Effects on Chemical Oxygen Demand Removal Efficiencies

In this study, the behaviors of amoxicillin and ciprofloxacin were investigated in the conventional treatment systems in both theoretical and experimental manner. The doses of these pharmaceuticals which inhibit the treatment were determined. The efficiencies of amoxicillin and ciprofloxacin in response to dose increments were determined by monitorization of chemical oxidation demand parameter. Based on the results of these studies, amoxicillin doses >35 mg/L and ciprofloxacin doses >10 mg/L reduced treatment efficiency by leading changes in the structure of activated sludge. The sludge became sticky and dark due to the increase in the extracellular polymeric substance formation in the bacteria with increasing pharmaceutical concentration. The highest and lowest removal efficiencies were found as 39.8 and 14.9% for amoxicillin doses of 5 and 20 mg/L, respectively. The greatest part of the removal efficiency was achieved through adsorption in the sludge (33.8%). On the other hand, the highest and lowest removal efficiencies were found as 15.17 and 2.85% for ciprofloxacin doses of 30 and 75 mg/L, respectively. Again, the greatest part of the removal efficiency was achieved through adsorption in the sludge (11.83%). This indicates that removal mechanisms for both pharmaceuticals were sludge adsorption as amoxicillin and ciprofloxacin biodegradations were low at all doses investigated. To compare experimental data with theoretical estimations, pharmaceutical removal was calculated in Sewage Treatment Plant (STP) using EPI Suite program. According to experimental results, the total removal efficiencies were consistent with theoretical estimations calculated by Environmental Protection Agency (EPA) Draft Method. There may be inconsistency between theoretical estimations and experimental results due to differences in experimental conditions caused by microbiological behaviors in the theoretical conditions. The removal efficiencies for amoxicillin and ciprofloxacin calculated by default method were lower than those calculated by EPA draft method since biodegradability is not taken into consideration in the default method.