The Promotion Of UASB For The Treatment Of Phenolic Wastewater With Addition Of Humic Acid Containing Support Materials

In recent years,the petrochemical and coal chemical industries produce large quantities of phenolic wastewater.The phenolic wastewater has a wide spread of pollution and toxicity,which is the focal point of industrial wastewater treatment.UASB process has a good application prospect because of the suitable occupation area,high volumetric loading and secondary energy production.The start-up and operation of UASB process are greatly affected by the performance of granular sludge.Rapid formation of granular sludge to accelerate the start-up of reactor and optimization of microbial system to promote the transformation of pollutants are the key to realize efficient treatment of phenolic wastewater in UASB.Humic acid is a kind of redox mediator widely exists in nature.It can accelerate the transfer of electron and promote the conversion of pollutants.Therefore,this study aims to add natural/immobilized support materials containing humic acid into UASB to improve phenolic wastewater treatment performance.In this research,lignite and peat soil as natural humic acid containing support materials were selected.The feasibility of these support materials to promote UASB performance for the treatment of phenolic wastewater were investigated.The results showed that both support materials can accelerate the start-up of reactor and improve the resistance of impact load.During the stable period,the average COD and phenolic removal efficiency in the reactor with peat soil reached to 86.26% and 91.37%,increased by 3.15% and 2.32% compared with the control reactor,and the average methane production rate was 1.07 L/d·kg COD.The GC-MS analysis showed that the addition of the two support materials promoted the biodegradation of phenolic substances.The reactor added peat soil showed the fastest degradation speed of phenol,o-cresol and p-cresol.From the analysis of microbial community,the addition of lignite and peat soil enhanced the microbial diversity.The proportion of Methanosaeta,Methanolinea and other methanogens increased,and the phenolic-degrading bacteria Syntrophorhabdus was the dominant genus.Based on the above results,the effects of humic acid immobilized material and humic acid embedding material on UASB treatment of phenolic wastewater were also investigated.The materials were prepared by immobilized humic acid on natural zeolite and embedded in sodium alginate.The results showed that the embedded humic acid material can promote the degradation of phenolic wastewater when the concentration of phenolic substances fluctuated greatly.The average removal rate of COD was 85.61%.Methane productivity of sludge was also improved,and the average production of methane was 1.37 L/d·kg COD.The reactors domesticated more species of methanogens and phenol-degrading bacteria.The dominant genus is Methanosaeta,Methanolinea,and Syntrophorhabdus.However,the immobilized humic acid support material did not promote the treatment of phenolic wastewater in the reactor,but inhibited the degradation of phenolic substances,which may be related to the immobilization method.According to the functional mechanism of humic acid materials,it proved that the content of humic acid is the main factor affected the performance of UASB treating phenolic wastewater.In addition,good promotion effect could be achieved only by addition of immobilized humic acid materials in the reactor.The optimal immobilization method and suitable dosage of humic acid still need to be further studied.