Application of the Membrane Bioreactor Process in Upgrading a Norfloxacin Pharmaceutical Wastewater Treatment System

A norfloxacin pharmaceutical factory in Henan Province, China, uses a metal-based electrochemical redox pretreatment step followed by anaerobic hydrolytic acidification and the anoxic/oxic (A/O) process for biological treatment. The effluent chemical oxygen demand (COD) does not meet the limit of 120 mg L-1 in the national "Discharge Standards of Water Pollutants for Pharmaceutical Industry Chemical Synthesis Products Category" (GB21904-2008, in Chinese) and therefore needs to be improved. In this study, influent from the hydrolytic acidification tank and a built-in membrane bioreactor are used to determine the effects of operating parameters such as the sludge load (Ns), sludge concentration (mixed liquor suspended solids, MLSS), dissolved oxygen (DO) and sludge age (sludge retention time, SRT) on the effluent COD and NH3-N. The results show that the optimal operating ranges of each parameter are as follows: MLSS, 8,000 similar to 12,000 mg L-1; Ns, 0.14 similar to 0.33 kg COD/ kg MLSS d; DO, 2.0 similar to 3.0 mg L-1; and SRT, 15 similar to 50 d. The actual operational results after optimization of each parameter show that effluent COD is between 60 and 130 mg L-1, effluent NH3-N is less than 5 mg L-1, and 90% and 100% of the effluent COD and NH3-N measurements, respectively, meet the discharge standard. Through kinetic analysis of the reactor, the kinetic parameters of sludge degradation are found to be V-max = 0.32 d(-1) and K-s = 270.36 mg L-1.