Commissioning And Experimental Study On Pilot System For Treatment Of High Concentration Washing Wastewater Based On SMAD-BBR Combined Process

Since entering the 21 st century,the mature system of the global fine chemical industry has been basically completed,and most of the traditional chemical companies in various countries have completed the arduous task of transforming into the fine-grained direction of “fine” and “diversified”.The development of the fine chemical industry not only lays a solid foundation for the advancement of national science and technology,but also produces fine chemicals that are inseparable from the improvement of human life quality.While the fine chemical industry creates huge economic benefits for the country,the waste generated in its production process also creates problems for environmental protection.In terms of equipment washing wastewater,it contains not only a large amount of surfactants and phosphates,but also raw materials and waste materials left after the processing of the equipment.This leads to the complex composition of the wastewater,the variety of organic matter,the difficulty of degradation,and the high COD content.Some of the wastewater also contain highly toxic aromatic and polycyclic aromatic hydrocarbon compounds.If this type of wastewater cannot be effectively degraded,it will cause irreparable damage to the ecological environment and human beings.Therefore,it is of great practical significance to find a safe,efficient and energysaving way to treat such wastewater.In this study,the equipment cleaning wastewater of a fine chemical company in Qingdao was used as the experimental object.On the basis of consulting a large number of related literatures and laboratory tests in the early stage,and after comprehensive research,it was decided to adopt two new sewage treatment technologies,Self-Mixing Anaerobic Digester(SMAD)and Baffled Bioreactor(BBR),as the main process of this pilot study.The operation efficiency of SMAD-BBR combined system in washing wastewater treatment was investigated,and the impact of water quality and operation conditions on the combined system was further discussed.The research results are as follows:(1)Analysis of the water quality data during the commissioning operation of the SMAD shows that the acidity of the SMAD tends to be due to the lower p H of the influent water at the initial stage of commissioning.After adjusting the influent p H value of about 6.0,the activity of microbial bacteria in the SMAD gradually recovered,and the COD removal rate also increased gradually.The COD of the SMAD effluent remained stable at the 89 th day after the start,and the average removal rate reached 73.39%.In addition,the study found that SMAD has a low removal rate of NH3-N and TP.(2)For the analysis of water quality data during the commissioning and operation of BBR,it can be seen that the BBR effluent at the 69 th day after the start reaches the discharge standard stably.During the stable operation,the concentrations of COD,NH3-N and TP in BBR effluent are 279 mg/L,7.39 mg/L and 4.31 mg/L,respectively.The average MLSS in the aeration zone between 107 and 129 d was maintained at 6830 mg/L.The sludge structure was good and the color was healthy during the microscopic examination.A large number of protozoa were also found.(3)Influencing factors of SMAD results show that when the SMAD is in stable operation conditions,the increase of influent COD and NH3-N concentration does not affect the anaerobic system.However,when the temperature dropped from 35.0 °C to 27.3 °C,the microbial activity decreased due to the decline of intracellular enzyme synthesis rate,and finally the COD removal rate decreased from 69.90% to 36.35%.(4)Influencing factors of BBR showed that when the average concentration of NH3-N jumped to 271.64 mg/L,the removal rate of COD by BBR was 93.96%.When the DO concentration is maintained at 3-4 mg/L,the removal efficiency of BBR for COD is up to 96.35%;When the volumetric load Nv is increased from 0.4 kg/(m~3·d)to 0.75 kg/(m~3·d),the COD removal efficiency of BBR is still greater than 94%.The comprehensive research results show that the combined system of SMAD-BBR has obvious degradation effect on high-concentration washing wastewater.In actual operation,the removal rates of COD,NH3-N and TP in the combined system are 99.18%,90.85% and 85.89%,respectively.The effluent meets the requirements of Class B in Table 1 of the “Wastewater quality standards for discharge to municipal sewers”(GB/T 31962-2015).