Status Diagnosis Of Anaerobic Reactor Treating Typical Refractory Wastewater

Nitrobenzene(NB)and tetrachloroethylene(PCE)are widely used as industrial raw materials,typical refractory organics,which cause serious pollution to the environment due to improper management and disposal.Numerous researches have been conducted on anaerobic biodegradation of NB and PCE in recent years.However,most researchers paid attention to anaerobic biodegradability,mechanism of biodegradation and biodegradation efficiency.Biodegradation stability has not been further studied.The stability of anaerobic degradation of NB and PCE was suppressed due to their biological toxicity.An online diagnosis and control system is necessary to guarantee the stability of anaerobic treatment.The anaerobic degradation of NB and PCE was studied in two upflow anaerobic sludge blanket(UASB)reactors,respectively.Then extra toxicity load was added.Reactor parameters variation was monitored by an on-line monitoring system during the overload.The inhibition mechanism and kinetic parameters analysis were conducted by the batch experiment.Sensitive parameters were filtrated to build evaluation indexes,which can be utilized to diagnose reactor status.The stability of anaerobic treatment of refractory wastewater can be improved on the scientific basis of automatic monitoring.Firstly,two UASB reactors were utilized,whose activities was quickly restored by inoculating granular sludge in UASB reactor.The chemical oxygen demand(COD)removal rate reached more than 90%,and the methane yield reached 5 g/(L·d)after a period operation.Sucrose(5 g COD/L)was used as co-degradation substance,gradually increase the concentration of NB and PCE to acclimate the granule sludge respectively,operated under 12 h hydraulic retention time(HRT).The stable removal of 100 mg/L NB and PCE was achieved eventually,whose rate reached more than 99%.Secondly,several toxic shock experiments were summarized,found that there were commonness and characteristics of parameters change:total volatile fatty acid(TVFA)increased,acetate proportion dropped,propionate proportion raised in both reactors after shock;hydrogen partial pressure and methane content showed the same trend,the concentration of aniline(AN)increased linearly in NB treatment reactor,however hydrogen partial pressure and methane content showed the opposite trend,the concentration of PCE and TCE changed rapidly.Batch experiment result showed that NB and PCE have huge biological toxicity,the relationship between the degradation rate and concentration accords with Andrews inhibition kinetics model.Inhibition of NB and PCE on methanogens is greater than acid formation bacteria,and the toxicity of NB is greater than PCE.Finally,according to the batch experiment results and monitoring data,sensitive parameters was supposed to establish evaluation indexes,which can diagnose reactor state.M(Methane-producing activity index),A(Acid-producing activity index)and S(Stability index)were proposed,the corresponding relationship between reactor status and indexes was given.