| Cassava starch is the characteristic industry of Guangxi,and it is the hot spot of research because its high concentration organic wastewater is hard to deal with.At present,there are some methods for treating the starch wastewater,such as physical method,physicochemical method,chemical oxidation method and biological treatment method and so on.Among them,the method of anaerobic aerobic process is the most widely used.In this paper,the mainly discuss the process of treating the waste water of cassava starch,and give out the main core technology through using controllable internal circulation anaerobic reactor-biological contact oxidation.The main contents are as follows:1.The startup process research about the controllable internal circulation anaerobic reactorIn the start-up phase,the fixed HRT was 24 hours,and the water temperature was controlled at 35±2℃.The forced internal circulation ratio was 5:1 and 10:1 during started running process,and after 40 days of operation,the influent CODcr concentration increases from 3000mg/L to 9000mg/L.Through studying the forced internal circulation started the effect,the statistics showed that:(1)after opening the forced internal circulation,the removal rate of CODcr increases from 90%to 95%,and the effluent pH value decreases from 7.6 to drop to 7.2-7.4;(2)during the start-up,VFA/ALK remains at a relatively stable state and the ratio was less than 0.3 with gas production increasing,but the rate of gas production was stably at more than 0.4m3/kgCODcr;(3)Once controllable sludge in circulation in the anaerobic reactor from inoculation started successfully,the particle diameter increases and the total amount of EPS increased from 7.9mg/gVSS to 12.69mg/gVSS.At the same time,coenzyme F420 increased from 0.63umol/gVSS to 1.32umol/gVSS,and the images of SEM observation showed that microorganisms were bacillus and coccus.2.Study on the operation of biological contact oxidation reactorThis passage mainly focused on the biological contact oxidation reactor start-up,operation and microbial status.The HRT was studied,the dissolved oxygen and the reflux.By comparing the variation of three parameters to the reactor,learning about the influence of removal efficiency.The results show that:(1)the biofilm was hanged by the artificiality which can start quickly biological contact oxidation reactor.After 3 days of stuffy exposure and a time of 12 hours’start-up for a week,the removal efficiency reached 80%and the packing visible light is brown biofilm.(2)when the reflux ratio of the reactor was 1:1,HRT=6h,dissolved oxygen in the condition of 2.2-2.8mg/L,the removal of CODcr,ammonia nitrogen and SS can be reached 84%,85%and 90%respectively.(3)by means of the optical microscope observation microbes in the reactor,a lot of Epistylis can be found when operation was stable and at a good effluent quality.When HRT is 6h and membrane sour of sludge,SVI,sludge concentration reached 0.29mgO2/(gMLSS-min),61mL/g,2.4g/l,meanwhile,the sludge in the reactor reached the good state.3.Study on the whole process of cassava starch wastewater treatmentAccording to the characteristics of the cassava starch wastewater,determined the overall process flow is controllable internal circulation anaerobic reactor-hydrolysis acidification pool-aerobic biological contact oxidation-coagulation sedimentation.The research results showed that(1)improving the biodegradability of the cassava starch wastewater by hydrolysis acidification pool anaerobic,the VFA stable growth was around 50%,and the BOD5/CODcr of wastewater increased from 0.07-0.25 to 0.3-0.55.(2)Since ferrous sulfate as a coagulant for phosphorus removal effect was the best,removed 46mg of dosage of coagulant through using 1g calculation of ferrous sulfate.As a result,the total phosphorus content was below 1mg/L,and the removal efficiency of the CODcr,the total nitrogen was respectively 35%and 20%;(3)the overall process of combination of the short residence time when the anaerobic retention time,hydrolysis time,aerobic time,coagulation and sedimentation time are 10h,10h,6.2h,0.5h respectively.As for other conditions,the main influent pH was around 7,and the aerobic effluent recirculation ratio was I:1.Finally the ultimate of indicators in the water can reach the direct discharge standards prescribed by the state.The content of CODcr was 80-100mg/L,and the content of BOD5 was below 10mg/L.The content of the ammonia nitrogen and the total nitrogen were 12-15mg/L,23-30mg/L respectively.The content of SS concentration was below 23mg/L,and the concentration of phosphorus was below 1mg/L. |
