Influencing Factors on Odor Value and Protein Extraction from Surplus Sludge by Calcium Oxide-heating Method
Various influencing factors such as temperature,pH,reaction time and water content are studied to explore their influence on the protein extraction rate and odor value of the remaining sludge.Taken the surplus sludge of the sewage treatment plant as the raw material and calcium oxides as the agent,the protein is extracted from surplus sludge by combined heating.The effect of the pH,reaction temperature,reaction time and material moisture content of the reaction system on the protein production and smell during the surplus sludge disposed is analyzed by using single factor and orthogonal experimental methods.In the process of extracting excess sludge protein by calcium oxide-heating method,the influencing factors are in a descending order as follows:pH,reaction time,temperature,and moisture content.And the influencing factors on the odor value,in a descending order:temperature,pH,moisture content,and reaction time.The optimal process condition for extracting protein from the remaining sludge is pH 13,reaction time 4h,reaction temperature 100 ℃,and water content 90％.Under the optimal process condition the protein extraction rate is 63.47％and the odor value is 6.It is conducive to the sludge hydrolysis reaction which uses calcium oxide-heating method.However,under alkaline conditions the excessively high temperature aggravates the Maillard reaction and releases more malodorous substances to increase the odor value,which is not conducive to the extraction of excess sludge protein.
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