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As a result of progressing of industries and population growth, new chemical contaminants have entered to natural water resources that in order to protect the environment and promote hygiene, they should be purified. Acetaminophen is the most widely used chemical pharmaceutical compound. In this study has been tried to omit acetaminophen from water solutions by cyclic biologic procedures. This kind of procedures are friendly environment. The CBR process is a modification of the sequential split reactor (SBR) process. However, instead of the wastewater being injected into the reactor, the contaminant is injected into the process using a continuous drip pump, thus the possibility of shock to the reactor. The purification process is reduced. This treatment system can be used for treatment of various types of municipal and industrial wastewater. In this study synthetic sewage includes acetaminophen, in laboratory scale, has been treated. The first phase of the test involved the adaptation of acetaminophen-degrading microorganisms that lasted for 50 days. Secondary settling sludge from a pharmaceutical company was used for primary seeding. Then the effect of cycle time (6-24 hours), hydraulic retention time (10.03-27.30 hours), density of inlet contaminant (100-1000 mg/L), density of inlet COD (360-7600 mg/L), and temperature (14-30°C), on the reactor's performance was investigated. The pH value has been checking and setting on 7 at all stages. At the end of study, the performance of the two CBR and SBR reactors was compared. During the tests, the concentration of ACT was measured by UV-Vis set. The other parameters were measured based on the standard procedures. The results showed the reactor had the best performance in 18 hours' cycle. The average of removal efficiency of COD and ACT in during this period was 94.70% and 94.97%, respectively. In the phase of control of the concentration of inlet contaminant, the result showed in density of inlet acetaminophen 500 mg/L, hydraulic retention time 44.38 hours, and the 16 hours' aeration cycle, the reactor can remove more than 99% of acetaminophen and 97% of COD in the contaminants. In the same condition and concentration of inlet acetaminophen up to 1000 mg/L, removal efficiency of ACT and COD was more than 96% and 94%, respectively. Also temperature changes had a great effect on the reactor performance, so that with increasing temperature up to 30°C, COD removal efficiency decreased by 16% to 78%. Whereas with the change of temperature from 14° to 30°C the ACT mean removal was 97.8%. The results of comparing the performance of the two CBR and SBR reactors were also significant, so that, in the same condition, in the SBR, the removal efficiency of COD and ACT were decreased 15% and 10%, respectively. Since the cyclic biological reactor is injected by stepwise process, the results show foodstuffs are more rapidly absorbed by microorganisms, because microorganisms are more than foods. This feature increases the removal efficiency of organic matter in this system over continuous flow systems. Also, due to this feature, the reactor is highly resistant against of load shock. Given that all the phases, settling and discharging processes, take place in one storage, without worrying about leaving MLSS through the effluent, it can be greatly increased.

Keywords: Cyclic biological reactor, Acetaminophen, Biological treatment, Pharmaceutical compounds

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