Research On Treatment Of Coal Gasification Wastewater With Anaerobic-aerobic Process

Coal gasification wastewater contains high concentrations of phenols,ammonia, polycyclic aromatic substances, refractory organics and toxicpollutants. Treatment of coal gasification wastewater is a hard problem,which has become the bottleneck for the development of coal gasificationindustries. Compared with the traditional activated sludge process,anaerobic technology has the advantages of enhancing the biodegradabilityof wastewater, high volume loading rate and low operating cost. Anaerobictechnology has gained widespread attention in the field of coal gasificationwastewater treatment in recent years. This subject aims to study thebiochemical degradation rule of organic pollutants in coal gasificationwastewater with anaerobic-aerobic batch reactor. The author investigatesthe degradation of pollutants, improvement of wastewater biodegradability,and the degree of sludge domestication, focuses on the analysis ofmetabolic fate of organic pollutants and carbon source balance inanaerobic reactor, discusses the components of phenolic compounds incoal gasification wastewater and influence factors of anaerobic metabolism,and analyses the changes of microbial population structure in anaerobicreactor.The concentration of COD, total phenol, volatile phenol and NH+4-Nrespectively is about1400,280,140,85mg/L in the coal gasificationwastewater. The removal rate of COD, total phenol, volatile phenol,NH+4-N respectively is nearly86%,85%,100%,65%by hydrolyticacidification-aerobic process. With the enrichment of preponderantbacterium, the efficiency of coal gasification wastewater treatment by anaerobic-aerobic treatment is gradually strengthened. Some substances incoal gasification wastewater cannot be removed by anaerobic-aerobicprocess.The anaerobic sequencing batch reactor was used for the study ontreatment of wastewater by hydrolytic acidification in the mediumtemperature. A stable system formed after4months’ domestication ofanaerobic granular sludge. The results indicate that when the concentrationof COD, total phenol and volatile phenol respectively is1100,220and110mg/L, the removal rate respectively is about45%,50%and99%, in thecondition of (35±1)℃,48hr for hydrolytic acidification. COD loadingrate is0.488kg COD/m3.d, sludge loading rate is0.136kg COD/kg SS.d.The bio-chemical degradation kinetics for COD, total phenol and volatilein this system fits for the characteristic model of first-order reactionkinetics. The best hydrolytic acidification period is35hr, themethane-producing rate is0.0025kg CH4/kg COD removal,77%of TOCremoval is used for sludge proliferation and the sludge-increasing rate is0.3kg SS/kg COD removal.The biodegradability of coal gasification wastewater is enhanced aftertreatment by hydrolytic acidification. The aerobic sequencing batch reactorwas used for the study on treatment of anaerobically digested effluent, inthe condition of (30±1)℃,64hr for aeration.The concentration of COD,total phenol and NH+4-N respectively is250-300,20-40,45mg/L in theeffluent from aerobic reactor, the removal rate respectively is about45%-50%,45%-60%,45%. The bio-chemical degradation kinetics forCOD, total phenol and in this system fits for the characteristic model offirst-order reaction kinetics. The best aeration period is30hr.The coal gasification wastewater contains many kinds of phenoliccompounds, such as phenol, ortho cresol, M-cresol, p-cresol, resorcinol,hydroquinone and so on. Volatile phenol content is the highest, which isthe main reduced phenolic compound in the hydrolytic acidificationprocess. Phenol is largely degraded with24hr hydrolytic acidification for coal gasification wastewater, and the others change little.The anaerobic sludge is flocculent in stable hydrolytic acidificationsystem. The zoogloea external has distribution of streptococcus, bacillus,spherical bacteria, arc shape bacteria etc. The bacteria in the system aremainly Proteobacteria, most of which are mesophiles. The typicalanaerobic bacteria, Syntrophobacter bacteria, denitrifying bacteria, andsulfate reducing bacteria, and the latest accepted anaerobic bacteriaSynergistaceae are founded in anaerobic system, as well as aerobic bacteriaAcinetobacter, playing an important role in the metabolic process together.