Advanced Treatment Of Effluent From A Secondary Process Treating Pharmaceutical Wastewater In A North Factory

Because of high chemical oxygen demand (COD) concentration, salinity, colority,poor biochemical purification ability, and biological toxicity, in the pharmaceuticalwastewater, the integrated process of pretreatment-anaerobic and aerobic treatment hasbeen developed. Along with the full implementation of "wastewater pollution emissionstandards for the pharmaceutical industry", the strict quality of pharmaceutical effluentisneeded. Consequently, the advanced treatment of pharmaceutical wastewater secondaryeffluent is imperative.A combined treatment, including coagulation sedimentation,Fenton oxidation andsand filtration process was used for the secondary effluent of a pharmaceutical factoryin northern China, based on systematic analysis of water quality characteristics andresearch achievements of pharmaceutical wastewater advanced treatment processes.COD and TP were used for determining the treatment effectiveness and the optimizingthe process parameters. The aromatic compounds were analyzed by UV-vis(Ultraviolet–visible spectroscopy) before and after wastewater treatment.Water quality characteristics analysis showed that the content of suspended solidsand colloidal material of the secondary effluent is greater than50%and the colloidalsubstances are negatively charged. At ambient temperature (20℃±1℃), four cationiccoagulant of PAC (PAC), ferric sulfate (PFS), ferric chloride (PAFC) and ferric chloride(FeCl3) were selected for coagulation experiments. The results showed that thecoagulating effect of ferric chloride was the best. The optimal dose of ferric chloridewas175mg/L and the initial pH was adjusted at7. Under these coagulating conditions,after stirred fast at150rpm for2min and stirred slowly at50rpm for20min, thensettled for20min, the removal rate of COD and TP wrer up to43.4%, and95%. Theeffluent of coagulation process was further treated by Fenton oxidation. The order of theinfluence factors effecting Fenton oxidation process is H2O2∶Fe2+(M/M), H2O2dosage,reaction temperature and reaction time. The optimized operating conditions wereH2O2∶Fe2+（M/M）of7.5∶1, c(H2O2) of10mmol/L, temperature of20℃and reactiontime of60min. Sand filtration was further adopted in order to improve the effluentquality. The particle size of quartz sand is40to70meshes, and the suitable filtrationrate of8m/h.The performance of comprehensive processing of coagulation, Fenton oxidation,and sand filtration was researched on the basis of the optimized operating conditions. The results showed that with influent COD155~190mg/L, TP6~8mg/L, and UV2541.4~1.6cm-1, the removal rates of COD, TP and UV254were achieved75~80%,90%and85~90%, respectively. The effluent COD, TP and UV254were35~40mg/L,0.1~0.3mg/L,0.15~0.20cm-1, reseparately, which meets the requirements of DischargeStandards of Water Pollutants for Pharmaceutical Industry Fermentation ProductsCategory (GB21903-2008) and wastewater reuse of pharmaceutical factory.