Enhancing The Treatment Of Petrochemical Wastewater Using Novel Redox Mediator Suspended Biofilm Carriers

The treatment efficiency of petrochemical wastewater via the traditional activated sludge process is generally unsatisfactory due to the complex and toxic features of petroleum compounds.Redox mediator(RM)can improve the biodegradation of organic contaminants by participating in the microbial extracellular electron transfer process.However,the continuous dosing of the soluble redox mediator would lead to secondary pollution and rise operation cost.In this study,an insoluble and economical redox mediator material(biochar)was introduced into high-density polyethylene(HDPE)to prepare novel suspended biofilm carriers(RM-modified carriers),and applied in anaerobic/oxic(A/O)reactors.(1)The results of XPS analysis of biochar showed that the relative contents of carbonyl(C=O)obtained by pyrolysis and oxidation modification at 300?,500? and 700? were12.3%,10.2%and 9.9%respectively.The biochar that pyrolyzed at 300? and modified by HNO3 oxidation had the highest relative content of carbonyl(C=O).With the temperature increased,the microcellular inside the biochar material increased,the content of oxygen-containing functional groups decreased.(2)The reactor filled with novel RM-modified carriers(R3)showed the removal efficiency of COD and phenol in the anaerobic zone were 34.6%and 43.0%respectively at organic loading rates(OLRs)of 22.2 kg COD/(m~3·d)and influent phenol concentration:844.08±80 mg/L,which increased by 6.8%and 8.3%respectively compared with that of the reactor filled with HDPE carriers(R2).Microbial analysis proved that the relative abundance of Bacteroides that participated in electron transfer of R3 improved by approximately 6.3%compared with that of R2.These findings demonstrated that novel RM-modified carriers improved the abundance of relevant functional bacteria and enhanced the degradation efficiency of the contaminants in petrochemical wastewater.(3)About 45 kinds of contaminants were detected in real petrochemical wastewater by GC-MS analysis,of which 11 kinds accounted for more than 2%.The contaminants of petrochemical wastewater mainly included benzene,alkanes,heterocycles,esters,ketones,acids,nitriles,organic amines and other contaminants,of which long-chain alkanes and nitrogen-containing heterocyclic compounds were the majority.The COD removal efficiency of R1,R2 and R3 reactors were 22.2%,25.9%and 29.7%under the same hydraulic retention time.The results indicated that the removal efficiency of COD in the reactor filled with RM-modified carriers was better for the treatment of petrochemical wastewater.