Regulation Technology And Mechanism Of Double Cycle Anaerobic Reactor For Treating Traditional Chinese Medicine Wastewater

In recent years,with the rapid development of Chinese traditional medicine?TCM?pharmaceutical industry,the amount of TCM wastewater is also increasing.However,the treatment of TCM wastewater has not kept up with the pace of development.Many TCM processing enterprises have low efficiencies in wastewater treatment,and some enterprises even discharge wastewater beyond the standard.TCM wastewater generally has the characteristics of high concentration of organic pollutants and large fluctuation,and contains a large number of refractory and toxic substances.Anaerobic biological treatment technology can combine wastewater treatment with energy recovery,and it is the most ideal treatment technology for high concentration organic wastewater.Although anaerobic treatment technology has been successfully applied to the treatment of degradable industrial wastewater,the efficiency of anaerobic treatment technology is still low for high concentration of refractory or toxic industrial wastewater,and there are also some shortcomings such as poor impact resistance and difficult start-up.Therefore,it is necessary to develop an efficient anaerobic treatment technology for high concentration TCM wastewater.In this paper,the characteristics of water quality and toxicity of TCM wastewater were investigated.The treatment strategy of TCM wastewater was discussed.According to the characteristics of TCM wastewater,an efficient controllable double cycle?CDC?anaerobic reactor was developed.The efficiency of the CDC anaerobic reactor based on upflow rate control in treating TCM wastewater was studied.The hydraulic and biological mechanisms of efficient operation of the CDC anaerobic reactor was analyzed by investigating the hydraulic characteristics and microbial community distribution of the CDC anaerobic reactor.The performance of the CDC anaerobic reactor was regulated by quorum sensing?QS?based on acyl homoserine lactones?AHLs?signal molecules.The anaerobic control technology based on AHLs secreting bacteria was established,and the mechanism by adding AHLs to optimize the performance of anaerobic granular sludge under stress conditions was discussed.In this study,the water quality of TCM wastewater fluctuated greatly,the suspended solid concentration was high,the organic pollutant concentration was high,the COD concentration was more than 10000 mg/L,and the biodegradability was poor.Aromatic compounds and carboxylic acids were the main pollutants in the TCM wastewater.There were a large number of medicine residues and volatile fatty acids?VFAs?in the TCM wastewater.Acute toxicities of the four medicine components were higher than those of the four VFAs.The toxicity order was:protocatechuic aldehyde?PA?>salvianolic acid B?SAB?>rosmarinic acid?RA?>salvianic acid A sodium?SAAS?>propionic acid>valeric acid>butyric acid>acetic acid.Medicine components contributed more to the overall toxicity of TCM wastewater than VFAs.The order of toxicity contribution was:SAB>SAAS>RA>PA>propionic acid>acetic acid>valeric acid>butyric acid.The acute toxicity of TCM wastewater could be predicted by two conventional indicators:UV₂₅₄ and VFAs.However,the prediction model could be established according to the specific water quality.It was concluded that the separation of acid-producing phase and methane-producing phase in a single-phase anaerobic reactor would be an effective way to solve the problem of the treatment of TCM wastewater.The CDC anaerobic reactor was successfully started up after 115 days under the condition of inoculating flocculent sludge.After successful start-up,the sludge concentration in the first reactor area of the CDC anaerobic reactor was much higher than that in the second reactor area,and the sludge in the first reactor area was in granular form,while the sludge in the second reactor zone was in the coexistence state of granular sludge and flocculent sludge.Increasing the internal and external circulation strength of the CDC anaerobic reactor could increase the upflow rate,enhance the mass transfer effect of granular sludge and wastewater,reduce the dead zone ratio,and ultimately improve the treatment efficiency of the CDC anaerobic reactor.The CDC anaerobic reactor had the best effect on treating TCM wastewater under the conditions of 3.03 m/h of upflow rate in the first reaction area(V_up1)and 0.79 m/h of upflow rate in the second reaction area(V_up2).The removal rate of COD was 94.2%,the methane yield was 0.33 m³ CH₄/kg COD,and the concentration of VFAs in the effluent was 65 mg/L.The design of vertical two reaction areas and the adjustable internal and external circulation system could make the bacterial and archaeological community compositions in the two reaction areas of CDC anaerobic reactor different.A large number of VFAs accumulated in the first reaction area,which tended to be acidogenic phase.The second reaction area had higher methanogenic activity and tended to produce methane phase.Acidogenic phase and methanogenic phase could be separated to a certain extent in the CDC anaerobic reactor,which strengthened the metabolic performance of acid-producing nd methanogenic bacteria.Enhanced"phase separation"improved the overall toxicity tolerance of the CDC anaerobic reactor and ensured the overall removal efficiency of the reactor.Five kinds of AHLs signal molecules were found in CDC anaerobic reactor:C4-HSL,C6-HSL,C8-HSL,3OC6-HSL and 3OC8-HSL.Under the three stress conditions?shock loading,poor nutrition and performance recovery?,adding four dominant AHLs signaling molecules?C4-HSL,C6-HSL,C8-HSL and 3OC8-HSL?could promote the removal of organic matter,enhance methanogenesis activity,increase the concentration of extracellular polysaccharides and proteins in anaerobic granular sludge,and optimize the community structures of bacteria and methanogens.Adding 1/10 volume of AHLs secretory bacteria?Pseudomonas aeruginosa and Pseudomonas fluorescens?could improve the impact load resistance and shorten the secondary start-up time of the CDC anaerobic reactor.At the same time,the addition of AHLs secretory bacterial liquid could enhance the detoxification effect in the impact load and secondary start-up periods.Under stress conditions,exogenous AHLs could optimize the microbial community structure by repairing the shelter of microorganisms?extracellular polymers substances?,thereby improving the metabolic performance of anaerobic granular sludge.The CDC anaerobic reactor was used to treat TCM wastewater of high concentration by up-flow rate and signal molecule regulation.The treatment efficiency of the reactor was improved,the impact load resistance of the reactor was strengthened,and the secondary start-up time of the reactor was shortened.In this paper,only a typical TCM wastewater was studied.The results of this study provide a technical reference for other TCM wastewater,and also provide a research idea for other refractory organic wastewater of high concentration.