| Anaerobic digestion of sludge is widely used in the world, but it has some obviousshortcomings, for example, its reaction period is very long, and methane productionrate is not high and so on. Alkali treatment is a rapid and effective pretreatmenttechnology, but the pH of alkali pretreatment product is too high to anaerobic digestion.This experiment studied the influence of different conditions for traditional alkalinetreatment, include the pH, sludge concentration and reaction time, in order to determinethe best conditions. The results showed that the optimal conditions were pH12.5,sludge concentration20g/L and reaction time1h. In this case, SCOD was7582.8mg/L,SCOD/TCOD reached25.23%, removal rate of TS was28.79%, and VS removal rateof VS can reach36.88%.Based on the preliminary results, we improved the alkali pretreatment technology.Using the buffer ability of sludge, we invented the new technology：two-step alkalinedisintegration. The experimental results showed that the best conditions were pH13.0,the ratio of sludge and water1.75. Reaction effluent could be stable after the6th cycle,and this proved the stability of the system. Compared with traditional alkali treatment,the two-step alkaline disintegration could reduce15.0%Alkali dosage and didn’t needacid to adjust pH. What is more, VS and TS removal rate increased by26.78%and25%,respectively reached44.3%and33.5%. Besides, the moisture content decline to88.6%,and the sludge volume was reduced by78%. This proved that the two-step alkalinedisintegration has significant advantages.The effluent of two-step alkaline disintegration was used in anaerobic digestion. Weresearched into the influence of granular sludge concentration and pH to determine thebest condition. The results showed that the two-step alkaline disintegration couldreduce the HRT of anaerobic digestion from20-30d s to11.9h, and it indicatedsignificantly better advantage than the other pretreatment technology. Basides thetwo-step alkaline disintegration could make the pH of effluent less than10.0, and theeffluent could be used to produce methane directly without adjusting pH. The methaneproduction rate could reach0.26m3/kgVS. The experiment proved that the two-step alkaline disintegration-anaerobic digestion process has many advantages. For example,its reaction period is very short, and its reactor can be builded smaller. In addition, itsoperation is easy. It is has been proved that the two-step alkaline disintegration haswide application potential and value. |
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