Study On Two-phase Anaerobic Pretreatment Process Of Trimethylolpropane Plant Wastewater

According to the characteristics of wastewater from trimethylolpropane?TMP?plant,this paper mainly analyzed the water quality characteristics and biological treatment toxicity of the wastewater,and the inhibition degree of the wastewater to anaerobic microorganisms.The hydrolytic acidification-metamorphic pretreatment process of TMP wastewater was further studied and the process operation parameters were optimized.On this basis,the removal effect of two-phase anaerobic pretreatment on characteristic organics was discussed.The main conclusions are as follows:The main characteristic organics in TMP wastewater include 2-ethylhexanol,trimethyl-propane,2-ethylhexyl aldehyde,iso-octanoic acid,butyl isothiocyanate and decyl butyrate,etc.,which are important sources of wastewater toxicity.The results of TMP wastewater toxicity showed that anaerobic acidogenic bacteria had higher resistance to toxic substances than mechanistic bacteria,and their anaerobic acidogenic and mechanistic toxicity test semi-inhibitory effect concentrations(EC₅₀)were 342.25mg COD/?g·VSS?and 205.29mg COD/?g·VSS?,respectively.In the start-up stage of a two-phase anaerobic process,the reactor continued to operate for 90d,the inlet water at the first end of the reactor was neutral,the HRT and reflux ratios of the two reactors were 24h and 3:1 respectively,and the organic load of the inlet water at the first end was gradually increased.After the organic load of the reactor increased from 1.5kg COD/?m³·d?to 6.5kg COD/?m³·d?,the COD removal rate of the hydrolytic acidizing phase was stable at about 33.4%,and that of the methylene producing phase was stable at about 61.6%.By analyzing EPS components of microbial secretions,EPS three-dimensional fluorescence spectra and sludge characteristics,the microorganisms in the two reactors were in good condition.In the stage of operation parameter regulation of two-phase anaerobic process,through a series of experimental analysis,the final optimization parameters of the hydrolytic acidification reactor HRT were 18h,pH was 6.0 and reflux ratio was 3:1.The optimization parameters of methane-producing reactor HRT were 24h and the reflux ratio was 3:1.The COD removal rate of hydrolytic acidizing phase remained stable at about24.8%,and the average COD removal rate of methane-producing phase was 81.1%.After the two reactors stabilized under optimal operating conditions,it was found that the characteristic organic compounds in the hydrolytic acidizing water were decomposed effectively,and the contents of acetic acid,prophetic acid and butyric acid has increased,which improved the acidification degree and reduced the toxicity of methane-producing biological treatment.After the hydrolyzed acidified effluent was treated by the methanogenesis reactor,the amounts of characteristic organics in the original wastewater were reduced from 30 to 9 and the higher content of 2-ethylhexanol and trimethylolpropane were not detected.