Study On Treatment Of Lysine Wastewater By Two-phase Anaerobic Process

Wastewater from lysine production not only contains high organic matter, but also contains large amounts of NH3-N and SO42-, the direct discharge of lysine wastewater will cause a serious impact to environment. Currently, the international economic growth becomes slow, it will bring new opportunities for lysine production enterprises to experience energy saving and cleaner production, and to change the idea from pollution control to reuse resources. With NH3-N removed lysine wastewater, the two-phase anaerobic process (two UASB reactors, upflow anaerobic sludge bed) was used to achieve the separation of acidogenic phase and methanogenic phase and to control the main reduction of sulfate in the acidogenic phase, which could avoid adverse effect of acidogenic bacteria and sulfate-reducing bacteria on menthanogenic process. Without the pretreatment of sulfate achieving effective removal of sulfate and organic matter, thereby reducing the process and processing costs, to achieve the purpose of recycling of resources, and provide technical support for the wastewater treatment. Eventually good environmental and social benefits could be achieved.The main results are as follows.(1) After the acidogenic UASB reactor was running for 60 days, it was successfully realized the start-up and the phase separation. Sulfate loading, COD/SO42- ratio, hydraulic loading and effluence wastewater stirring have different effects on acidogenic reactor operating results. When sulfate loading, COD/SO42- ratio, optimum hydraulic loading and organic loading were 8.0 kg SO42-/(m3·d),3.0,0.7 m3/(m2·h), and 25.4 kg COD/(m3·d), respectively, as well as effluence wastewater stirring, the removal rates of COD and sulfate could be kept at 47% and 87% in the acidogenic phase UASB reactor.(2) By using two-phase, high activity of methanogenic bacteria could be obtained in methanogenic phase UASB reactor within a relatively short period of time, which could adapt to acidogenic phase UASB reactor effluent. By using this way, successful start-up of methanogenic phase UASB reactor could be achieved. Hydraulic loading had obvious impacts on the removal rates of COD and SO42-, sludge concentration, the maximum specific methane production rate and methane content. When hydraulic loading was 1.3 m3/(m2·h), the highest removal rate of COD was 96%, and with hydraulic loading at 0.7 m3/(m2·h), the maximum sulfate removal rate was 95%.(3) After the successful connect of two phase reactors, the system was running effectively and steadily for 11 days, the average COD removal rate and sulfate removal rate can be kept at 97.2% and 96.3%.respectively. This illustrates that the use of the two-phase anaerobic process was feasible for the treatment of lysine wastewater.(4) In the optimal operation conditions of the acidogenic and methanogenic phase reactor at high concentration of COD and SO42- in the acidogenic phase reactor, the system was successfully started up again within 39 days with increased organic loading by shortening the hydraulic retention time. This provided a reliable experience for the second start-up of the two-phase anaerobic system in engineering practice.