| The widely use of activated sludge process in the field of sewage treatment isbound to generate a lot of excess sludge. With the increase of urban scale andwastewater flowrate, this process will generate an increasing amount of excessactivated sludge. As the amount of excess sludge is huge, the cost of it’s treatment anddisposal is very high, besides it is easy for excess sludge to produce secondary pollution.Therefore, sludge treatment and disposal has become a headache problem of sewagetreatment plant. Moreover, as entrophication becomes serious year by year, the removalof nutriment, such as nitrogen and phosphorous, has become a most important missionfor municipal sewage treatment plant. In practical operation, it was found that thenitrogen and phosphorous removal efficiency was hard to be improved due to lowsludge yield rate and influent concentration of organic matter.In this study, SBR-SO process was adopted to achieve two abjectives: the first wasto utilize the high efficiency of ozone disintegrate sludge rate while with few secondarypollution produce during sludge oxidation, and the second was to maintain the effluentwater quality by using the organic obtained from sludge disintegration as a carbonsource. Results of this study were described as follows:In the sludge oxidation unit，the sludge disintegration was effective and sludgedisintegration rate remained at33.5%~36.2%. COD，TN，TP concentration of the liquidphase increased rapidly after sludge oxidated by ozone, and TN was mainlyconstituted by Kjeldahl nitrogen and ammonia.Compared to the control process，when the sludge was returned to the anaerobicsection of SBR reactor, activated sludge SOUR reduced significantly, which means thedegradation rate of organic compounds was slowing down. However, when the sludgewas returned to the aerobic section of SBR reactor, activated sludge SOUR increasedand when the returned sludge amount accounted for65%of total excessive sludge,activated sludge SOUR got biggest increase.Although the sludge disintegration rate was only about35%, SBR-SO processobtained a good effect of sludge reduction. When the sludge was returned to theanaerobic section of SBR reactor and returned sluge amount account for50%,65%,80%of total excess sludge, sludge Yobsreduced37.9%,69.1%,79.0%; when the sludgewas returned to the aerobic section of SBR reactor and returned sluge amount account for50%,65%,80%of total excess sludge, sludge Yobsreduced48.8%,50.0%,75.6%.The greater the returned sludge flow, the better the sludge reduction would get.The removal rate of COD was less affected by returned sludge，and COD effluentconcentration was low. But, when the sludge was returned to the anaerobic section ofSBR reactor, the removal rate of TN decreased, and the greater the returned sludge flow,the worse the removal rate of TN would get. However, the removal rate of TN was lessaffected when the sludge was returned to the aerobic section of SBR reactor. Whenreturned sluge amount account for50%,65%,80%of total excess sludge, TN removalrare firstly reduced7.5%and0.7%, and then increased7.4%.Compared to the control process, the removal rate of TP decreased after sludgereturned to SBR reactor. However, when the sludge was returned to the aerobic sectionof SBR reactor, the greater the returned sludge flow,the smaller the negative impact ofthe returned sludge would have on the removal rate of TP. When returned sluge amountaccount for50%,65%,80%of total excess sludge, TP removal rate was firstly reduced29.7%and7.4%, and then increased2.5%. Besides, when the returned sludge accountedfor65%of total excess sludge, the TP removal rate of SBO-SO process was very stableand the concentration of effluent TP was low.In a word, on the conditions of the sludge was returned to the aerobic section ofSBR reactor and the returned sludge accounted for65%of total excess sludge, SBR-SOachieved a good effect of sludge reduction and effluent water quality as well. |
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