Advanced Treatment Of Petrochemical Wastewater Treatment Plant Secondary Effluent By Pre-ozonation And Biofiltartion

The petrochemical industry is an energy-intensive industry, which also has thecharacteristics of heavy environmental pollution. The treatment of petrochemicalwastewater is a focus in the filed of environmental protection. The secondaryeffluent of petrochemical wastewater treatment plant can be used as a goodpotential water source due to its large quantity. It will relieve the crisis of waterresource if make advanced treatment of the secondary effluent.In this research, ozone-biological aerated filter (O3/BAF) was used to treat thesecondary effluent of a petrochemical wastewater treatment plant. The waterquality of the secondary effluent was analyzed and the performance of O3/BAFtreating the secondary effluent was investigaed. In addition, the factors that affectthe treatment efficiency was also analyzed systematically.The COD of the secondary effluent is among60-120mg/L and the TOC isamong20.5-43.6mg/L. The organic matters with molecular weight lower than1KDa is the dominant fraction of the secondary effluent, which approximatelyaccounts for54%~62%of the total TOC. Soluble microbial products (SMP)contribute great to the COD of the raw water. The3-D fluorescence analysis resultsindicated that protein and Humic acid are the main matters of the organics. TheGC/MS analysis results indicated that the organic matters with ring-like structurehave the proportion of56.8%and alkanes with the proportion of17.8%.It alsocontain other matters like ketone and alkenes.The pre-ozonation of the secondary effluent showed that the removals ofCOD, UV254were18.8%and19.6%, respectively, when the ozone dose of10mg/L and the contact time of4min. At the same time, the ozonation changed thepercentage of organic matters with MW<1K Da decreased from58%to67%. Thebiodegradability of secondary effluentincreased after pre-ozonation. The removaleffect of organic matters was better in alkaline condition than in acid condition.The results of O3/BAF combined processshowed that COD, UV254, turbidityof effluent are48.9mg/L,0.456,4NTU, respectively, when the ozone dose of10mg/L and the contact time of4min.The operation conditions of the BAF were:water inflow1L/h, gas towater ratio3:1, HRT3h. GC/MS analysis results showed that the species of the organic matters detected in the treated effluent decreasedmore than150than in the raw secondary effluent.The research results showed that the O3/BAF combined process is a goodadvanced technology for the treatment of petrochemical secondary effluent. It hasvery broad application prospects.