Study On The Treatment Of Regenerate Papermaking Wastewater With Enhanced Coagulation-Air Floating And Submerged Membrane Bioreaetor Techology

With the development of economy and people’s life improvment,yield of the paper and paperboard is increasing at the velocity of 11.76%per year. Papermaking industry not only wastes water,but pollutes water,to save the water resources,so papermaking industry with wastepaper gets more and more important.The treatment of wastewater from regenerate papermaking industry are also increasingly been paid attention. Now,the main treatment measure is coagulation-dissolved air flotation method,it is a new task to look for good process parameters to improve wastewater treatment efficiency and lower costs.Moreover, to meet the discharge standard of "Disharge standard of water pollutants for paper industry",sometimes it is necessary to advanced treatment the regenerate papermaking wastewater. Compared with aluminum sulfate and ferric chloride,A series of experiments were carried out to study the chemical and hydraulic effect factors of inorganic polymer flocculant(PAC、PAFC) on treating wastewater from some regenerate papermaking mill by enhanced coagulation-dissolved air flotation process. The optimum chemical and hydraulic effect factors scopes were determined.And also the treatment effect of regenerate papermaking wastewater with membrane bioreactor has been investigated.The results showed that the optimum operational conditions of enhanced coagulation-dissolved air flotation were:(1) The optimum dose scopes of PAC were 140-300mg/L and that of PAFC were 160-300mg/L.(2) The optimum pH scopes of PAC were 3-6 and that of PAFC were 3-8.(3)The optimum hydraulic conditions:the optimum coagulation mixing velocity scopes were 100-250r/min (as PAC)、 50-250r/min (as PAFC),the optimum coagulation mixing time scopes were 30-90s(as PAC)、30-120s(as PAFC),the optimum flocculation mixing velocity scopes were 20-60r/min (as PAC)、20-80r/min (as PAFC),the optimum flocculation mixing time scopes were 7-9min (as PAC、5-9min(as PAFC).(4)The optimum recycle ratio were 30%(as PAC)、10%(as PAFC). (5) The optimal surface active agent:Through the comparison of cost, the combination of capric acid and PAC could save the cost of 62.1 yuan/ton COD, higher than the four other surfactants, so the capric acid was the best surface active agent.The operating results of membrane bioreactor showed that the average removal efficiency of COD、BOD5、ammonia nitrogen was 96.4%,93.3%% 85.8%, respectively.The average COD、BOD5、 ammonia nitrogen value of effluent was 27mg/L、11.2 mg/L and 1.65mg/L respectively; The removal efficiency of total nitrogen and total phosphorus are not ideal; the removal efficiency of Chroma and SS could maintain at 100%. The discharging water from membrane bioreactor can reach or exceed the requirements of Table 2 in"Dicharge standard of water pollutants for paper industry"(GB3544-2008).