| With the improvement of urban infrastructure in our country, the sewage treatment rate of urban sewage treatment plant has been significantly improved, and the amount of residual sludge generated in the two biochemical process has also increased significantly. It is the key to realize the sustainable operation of the sewage treatment plant in the future for the anaerobic digestion of sludge and the conversion of organic matter into energy substance. But due to the influence of the cell wall in the process of anaerobic fermentation of sludge by extracellular and cell wall structure to hydrolysis, resulting in sludge hydrolysis and fermentation process is slow,in a certain period of time the gas production efficiency is low, the organic matter utilization rate is low, not only restricts the promotion of the implementation of sludge anaerobic digestion technology, also affect the final the disposal of sludge digestion. Through the extracellular sludge pretreatment technology for destruction of surplus sludge, accelerate the hydrolysis of cell wall, effectively improve the performance of anaerobic digestion of sewage sludge.This subject adopts alkali and heat low temperature hydrolysis pretreatment technology,based on the effects of temperature on sludge properties, obtain the optimal parameters of thermal sludge alkali pretreatment of low temperature, saving energy consumption in pretreatment and accelerated cell wall hydrolysis; The BMP (Biochemical Mathane Potential)experiment was carried out to study the feasibility and the feasibility of the application of alkali heat low temperature pretreatment to enhance the efficiency of anaerobic digestion of sludge.The results obtained are as follows:1.Through orthogonal experiment, the optimum operation parameters of alkali heat pretreatment were determined. The sludge in different water temperature (70?, 80?and 90?),different hydrothermal time (7h, 8h, 9h),different doses of alkali (0.025,0.05,0.075g/gTSNaOH) under the condition of pretreatment, orthogonal experiment, minimum consumption conditions in chemical and thermal energy, protein, carbohydrate, rate the supernatant of the maximum dissolution of SCOD, obtained the alkali and heat pretreatment under the optimum operating conditions of hot water temperature is 70, NaOH dosage of 0.025 g/gTS, hydrothermal time is 8h; the sludge thermal hydrolysis, VSS/TS from an average of 57.5%, fell to 45.9%, the removal rate of VSS is about 12%, settling performance the best is 55.3% SV sludge.2.The temperature of hot water has a significant effect on the degree of sludge disintegration. With the increase of hydrothermal temperature (increased from 50? to 100?),the degree of fragmentation of sludge floc and cells increased significantly, SCOD, protein and carbohydrate dissolution and release amount increased by 6.5 times, 4.5 times and 36.9 times,and at about 70?, the dissolution and release rate significantly the increase of molecular weight; release substances were gradually decreased with the increase of temperature, and the temperature was 70 degrees above, the low molecular weight substances of pyrolysis of sludge,which contributes to the subsequent anaerobic digestion reaction of.Under the condition of hydrothermal temperature of 60 ? and hydrothermal time of 6h, the sludge was pretreated with different doses (0, 0.025, 0.05, 0.075, 0.1g/gTS). The experimental results show that with the increasing dosage of alkali content, dissolution of SCOD from sludge, protein, carbohydrate and total phosphorus increased; when the dose of NaOH is greater than 0.05g/gTS, the content of protein and total phosphorus increased sharply, indicating that most of cell wall broken,make a large number of cellular material released, and when the dose of NaOH in 0-0.05g/gTS,only the sludge floc outside of the cell and a small number of cells and the disintegration of discrete crack.3 The efficiency of anaerobic digestion of sludge and supernatant after alkali heat pretreatment was greatly improved. Sludge by alkali heat treatment and anaerobic digestion(15d), sludge and supernatant VSS removal rates were 31% and 37% respectively, 15% higher than the original sludge and 21%; methane yield were 154.29mLCH4/gVSS and 55.14mLCH4/gVSS,than the original sludge increased 6.6 times and 1.7 times. |
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