| In recent years, a lot of research have made in the sludge treatment and disposal technology, they are mainly through the use of physical, chemical and biological pretreatment methods to achieve stabilization, reduction and recycling. Sludge anaerobic digestion is a surplus sludge treatment, which have in-depth study and widely used. Sludge hydrolysis is a limiting step during anaerobic digestion, the low efficiency of hydrolysis will make digestive prolonged, eventually lead to reduce of the process load, poor stability of operation and cost increases. Therefore, the research and development of technology to improve the efficiency of sludge hydrolysis is important. This paper introduces several main technology of sludge hydrolysis at home and abrosd, such as ultrasonic technology, alkali-hydro pretreatment technology, efficient antioxidant processing technology, heat-loving enzyme or enzyme treatment technology, surfactant processing technology and complexing agent processing technology. The article mainly aims at explaining the influence of complexing agent sodium citrate (SC) to exocellular enzyme hydrolysis sludge by preliminary studied and discussed.The effects of complexing agent and enzyme on the promotion of excess sludge hydrolysis were investigated, the results showed that SC can strengthen the enzyme hydrolyze sludge through the contrast analysis of sludge SCOD/TCOD. The dosing quantity of SC is0.294g/gDS, the SCOD/TCOD value can achive37.4%at50℃, which is only18%in the blank group, SC has greatly improved the efficiency of sludge hydrolysis. When the dosing quantity of enzyme is60mg/gDS,0.294g/gDS SC joint three enzymes respectively, the sludge SCOD/TCOD value is improved14.86%,15.52%and20.31%than single enzyme processing, the results showed that the efficiency of sludge hydrolysis could be greatly improved by complexing agent-Sodium Citrate (SC) and composite enzyme, and confirmed that the best dosing quantity of SC is0.294g/gDS, the best dosing quantity of enzyme is60mg/gDS, the best of reaction temperature is50℃.From the variations of protein, soluble sugar and ammonia nitrogen during sludge anaerobic hydrolysis at three different processing mode, we can conclud that the content changes of protein, soluble sugar and ammonia nitrogen conformed the overall change trend of SCOD/TCOD value. When the dosing quantity of SC is0.294g/gDS, the value of each material was549,98.4,59.7mg/L higher than the blank group respectively. Protein and soluble sugar can dissloute constantly from the sludge solid-phase during sludge hydrolysis, which will further hydrolysis to create all kinds of small molecular organic matter and minerals, such as amino acids, simple sugars, ammonia, carbon dioxide and water etc, ammonia nitrogen concentration increasing. The content of soluble protein and sugar is the balanced results of dissolved out and consumption.Through the analysis of sludge pH value and enzyme activity, we are further understanding the mechanism of SC strengthening enzyme hydrolyze the sewage sludge. When SC treatment, sludge pH value slightly increase with the increase of dosing quantity of SC at50℃, but the pH change in7.3～7.46, which still accord with the optimal pH requirements of protease and amylase. It explain that SC don’t influence the enzymatic reaction rate by changing the pH of sludge system. The complexation performance of the SC can damage sludge network structure, reduce the embedding probability of enzyme and sludge which indirect reduced losses of enzyme activity, meanwhile, SC can promote hydrolysis bacteria to release hydrolysis enzyme at a certain extent, increase concentration of enzyme, and improve the efficiency of the sludge hydrolysis. |
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