| Pig manure sewage wastewater is a kind of high concentration organic wastewater,the concentration of COD,SS and NH3-N in it is very high.The C/N ratio of the digestate wastewater is serious imbalance,and the B/C ratio of it is very low,the biodegradation is poor,which belongs to one of refractory wastewater.The effluent of the piggery digestate wastewater treated with the traditional biological process is hard to meet the discharge standard.Therefore,it has an important practical significance to develop a reasonable economic and being simple to operate process to treat the piggery digestate wastewater.Based on the existing problems in piggery digestate wastewater treatment,the article proposes the ozone aerated internal micro-electrolysis combined bio-contact oxidation process?O3/ME-BCO?to treat piggery digestate wastewater,the optimal operation conditions of the combined process are systematic studied,and its mechanism is discussed.Combined the advantages of the micro-electrolysis?ME?and O3,the two processes are coupled,and which combined with BCO process could be effective to deal with piggery digestate wastewater.The main contents and conclusions of the study are as follows:1.The effect of the single ME process treatment piggery digestate wastewater was studied,and the influence of the four factors:aeration rate,initial pH,reaction time and dosages of Fe-C particles on the ME process was investigated;the important order of influence factors and control strategies were determined through response surface method?RSM?.The results indicated that:the dosages of Fe-C particles were the most important factor affecting the treatment efficiency followed by initial pH,aeration rate and reaction time.Within the range of trial design,compared with the other two factors,the effect of aeration rate and reaction time on COD removal efficiency was weak,which had a weak positive correlation;initial pH had a negative correlation;the dosages of Fe-C particles had a positive correlation in the system.The optimum conditions fitted according to the regression equation were:aeration rate=6 L/h,initial p H=6.00,reaction time=9 h and the dosages of Fe-C particles=200 g/L,and the COD removal efficiency was 54.74%under the optimum condition.2.The effect of the single O3 process treatment piggery digestate wastewater was studied,and the influence of the four factors:air flow rate,initial pH and reaction time on the O3 process was investigated;the important order of influence factors and control strategies were determined through response surface method?RSM?.The results indicated that:the optimum conditions fitted according to the regression equation were:air flow rate=60 L/h,initial pH=7.74 and reaction time=70min,and the COD removal efficiency was 47.58%under the optimum condition.Reaction time was the most important factor affecting the treatment efficiency followed by air flow rate and initial pH,air flow rate and reaction time had weak positive correlation;and the initial pH greater than 7.00 had a weak negative correlation,while the initial pH less than 7.00 had a weak positive correlation.3.With the vaccination of some sludge,the bio-contact oxidation?BCO?reactor through almost 20 days domestication,the COD removal efficiency achieved88.86%,the NH3-N removal efficiency achieved 81.06%.After the success of membrane-hanging,the effect of the BCO reactor treatment simulated piggery digestate wastewater was studied,and the influence of the factors:gas water ratio,hydraulic retention time?HRT?and Fe3+on the BCO reactor treatment simulated piggery digestate wastewater was investigated;the optimum conditions of the reactor was achieved.The results indicated that:the optimum conditions were the temperature=27-30°C,gas water ratio=17:1 and HRT=12 h,the COD,NH3-N and TP removal efficiency was 83.97%,81.65%and 70.40%,respectively.After the reactor was stable operation,the reactor was added different concentration of Fe3+.When the concentration of Fe3+was 25,50,75 and 100 mg/L,the pollutants removal efficiency increased after slightly decreased,finally stabilized.Microbiological characteristic analysis showed that the microbial in the reactor mainly attached to the biological membrane;the result of specific oxygen uptake rate?SOUR?was 24.75mgO2/gMLVSS?h,which indicated that the speed of microbial metabolism was fast,which could be degradation of organism strongly.4.The influence of the factors:initial pH and air flow rater on the O3/ME coupled process treatment piggery digestate wastewater was investigated,and the preliminary mechanism was discussed.The optimum conditions were that the temperature was room temperature,initial pH=8.0,reaction time=70 min and air flow rate was 60 L/h.The COD and TOC removal efficiency was 75.71%and62.37%,respectively under the optimum condition.The B/C ratio was improved,and the biodegradability of the wastewater was increased.The results of preliminary mechanism showed that?1?.The synergistic effect of ME and O3,and ME process played dominant roles at the previous stage of reaction;?2?.Catalytic effect of Fe2+/Fe3+on ozone;?3?.The concentration of iron ion decreased with the increasing of the pH.5.The ozone aerated internal micro-electrolysis combined bio-contact oxidation process treatment actual piggery digestate wastewater was operated 30 days,the conditions of the combined process were that initial pH was around 8.00,the air flow rate of ozone reactor was 60 L/h,the gas water ratio and HRT of BCO reactor was17:1 and 12 h,the dosages of Fe-C particles were 200 g/L and the temperature was room temperature.The operational mode of O3/ME coupled reactor was sequencing batch inflow,continuous ozone aeration,and the operational mode of BCO reactor was continuous inflow and aeration.Then,under the above conditions,the results of the combined process treatment actual piggery digestate wastewater as follows:?1?.The average concentration of influent COD was about 1249.23 mg/L,the average concentration of effluent COD was about 109.62 mg/L.Then,the COD average removal efficiency of the combined process was 91.22%.;?2?the concentration of influent NH3-N was ranged from 680 to 730 mg/L,and the concentration of effluent NH3-N was kept below 100 mg/L,then,the NH3-N removal efficiency of the combined process was 86.49%;?3?the average concentration of influent TP was about 40 mg/L,the average concentration of effluent TP was almost kept below 8mg/L,then,the TP average removal efficiency was 84.82%. |
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