【作者】 罗琨；

【导师】 杨麒； 李小明；

【作者基本信息】 湖南大学 ， 环境工程， 2010， 硕士

【摘要】 活性污泥法是目前世界上应用最为广泛的污水生物处理技术,但是它存在一个很大的弊端,就是会产生大量的剩余污泥。其生成的剩余污泥量一般是污水处理量的0.3%-0.5%(以含水率97%计)。目前我国污泥产生量约为2500万t/a(按含水率80%计算),若不及时进行妥善的处理与处置,将会对环境造成直接或潜在的污染。污泥处理方面的投资可占整个污水处理厂总运行费用的25%-40%,甚至高达60%。从根本上减少污泥的污泥减量技术逐渐成为国际学术界共同关心的热点领域。水解是污泥消化的限速步骤,因此强化水解是污泥减量化的重要前提和基础。相对于物理法、化学法、生物法等污泥处理方法,外加酶水解污泥技术不但可以缩短消化时间,改善污泥消化性能,而且经济高效,易控制,其产物对环境也无污染副作用。结合后续工艺不仅可以实现污泥的“零排放”,还可以同时实现废水的高效生物降解和沼气产能的增加,应用前景良好。所谓污泥减量技术,是指在保证污水处理效果的前提下,通过利用物理、化学、生化的手段减少整个污水处理系统向外排放的生物固体量。本文综合介绍了国内外几种常见的污泥减量技术：降低细菌合成量的解偶联技术、增强微生物利用二次基质进行隐性生长的各种溶胞技术、利用食物链作用强化微型动物对细菌捕食的技术和胞外酶强化污泥水解技术。本文主要针对胞外酶强化污泥水解,实现污泥减量化作了深入的探讨。本研究采用向污泥中外加酶(a-淀粉酶和中性蛋白酶)强化污泥水解的处理方式,考察了单一酶作用时(投加量分别为0、30、60、120、180mg酶／gTS,水解时间分别为4、8、12h),酶投加量和水解时间对城市污水处理厂剩余污泥破解及减量化的影响。结果表明,外加酶可以促进污泥中悬浮固体的溶解和大分子有机物的降解。在厌氧条件下,外加酶水解反应在4 h内基本完成,a-淀粉酶和中性蛋白酶的最佳投加量均为60mg酶／gTS。当酶投加量为60mg酶／gTS时,淀粉酶比蛋白酶的水解效果好,SCOD/TCOD分别提高到22.3%和18.5%,VSS去除率分别达54.24%和39.70%。复合酶(a-淀粉酶和中性蛋白酶按一定配比混合)的水解效果比单一酶的效果好,当水解温度为50℃,蛋白酶和淀粉酶的配比为1：3时,水解效果最佳,VSS去除率达68.43%,还原糖和NH4+-N浓度分别提高了377%和201%。本研究对外加酶水解污泥过程的机理和动力学进行了分析探讨。酶催化污泥水解反应在4 h内基本完成,在此过程中,反应迅速,此后水解速率缓慢。污泥在酶水解处理的前4 h,VSS溶解反应遵循一级反应动力学方程。蛋白酶,淀粉酶和复合酶溶解速率常数Kh的大小分别为：0.12 h1、0.20 h-1、0.24 h-1,分别是空白对照组的5,8,10倍。温度和反应速率的关系符合阿仑尼乌斯方程,回归方程为(R=0.964),活化能为Ea=20.19 kJ/mol,指前因子A=263 L/(mg.min)。本研究还考察了在外加酶水解污泥过程中a-淀粉酶和中性蛋白酶酶活力的变化。结果表明,在水解过程中蛋白酶和淀粉酶的活力均呈先上升,后下降趋势,4 h左右两种酶活力均达到最高值,分别为2.57 U／mL和4.64 U／mL。酶活力的变化情况解释了酶水解反应过程中动力学曲线的变化情况。更多还原

【Abstract】 Activated sludge method is used widely in biological wastewater treatment, but it will produce large amounts of excess sludge. It almost takes up 0.3%-0.5% of the amount of wastewater treatment. Annual sludge production is about 25 million tons in China presently (calculated by 80% of water content), which will pose a significant threat to the ecology system if it is not properly disposed. Costs for traditional treatment and disposal of excess sludge are quite expensive and it accounts for up to 60% of the total operation costs of a wastewater treatment plant. Sludge hydrolysis is a hot topic in the area of sludge reduction, and hydrolysis is the rate limiting step of sludge digestion. Therefore, enhancing sludge hydrolysis is important premise and base to reduce sludge. Compared with other sludge hydrolysis technology, such as physical, chemical and biological treatment, enhanced hydrolysis by additional enzyme can not only cut down digesting time, improve sludge digestibility, and reduce disposal costs, but also can be easily controlled, and its products are harmless to environment. Combined with the following process,it can realize sludge "zero discharge", and simultaneously realize high effective wastewater biodegradation or enhancement of biogas production.The technology of sludge reduction is the minimum of sludge biomass through physical, chemical, biological and chemical methods to meet the government effluent standard. The possible approaches for sludge reduction based on following aspects:uncoupling metabolism, cryptic growth enhanced through cell lysis and microfauna pry, sludge hydrolylsis by enzymes. Characteristics of each technology were compared, and the sludge reduction based on additional enzyme was discussed particularly in relevant research.In this investigation, the effects of commercial enzyme preparation containing alpha amylase and neutral protease on hydrolysis of excess sludge were evaluated. Protease and a-amylase were added singly, the dosage of enzyme and the hydrolysis time are 0,30,60,120, 180 mg enzyme/gTS and 4,8,12 h, respectively. The results indicated that additonal enzymes can enhance sludge hydrolysis. The hydrolysis basically completed within 4 h under anaerobic digestion, and the optimal dosage of enzyme is 60 mg enzyme/gTS. a-amylase had higher efficiency than protease, SCOD/TCOD rose to 22.3% and 18.5%, respectively.VSS reduction achieved respectively 54.24% and 39.70% at the optimal dosage of 60 mg enzyme/g TS. The hydrolysis rate of sludge improved with temperature increasing from 40 to 50℃, which could be well described by the amended Arrhenius equation. Mixed-enzymes (enzyme preparation containing alpha amylase and neutral protease) had great impact on sludge hydrolysis than single enzyme. The mixture of the two enzymes (protease: amylase=1:3) resulted in optimum hydrolysis efficiency, the efficiency of solids hydrolysis increased from 10%(control test) to 68.43% at the temperature of 50℃. Correspondingly, the concentration of reducing sugar and NH4+-N improved about 377% and 201%, respectively.According to the mechanism and kinetic analysis of enzymatic hydrolysis process, VSS solubilisation process within prior 4 h followed first-order kinetics, dring which the rate of the reaction is fast firstly, and then it slows down.The hydrolysis rate constants Kh for protease, amylase, mixed-enzyme treatment were 0.12,0.20 and 0.24 h-1, which were 5,8,10 times that of the blank, respectively. Obviously, the first-order hydrolysis rate constants obtained in this study followed an Arrhenius type of behavior R=0.964).The relationship between reaction rate constant and temperature was in accordance with Arrhenius equation, with activation energy 20.19 kJ/mol and preexponential factor 263 L/(mg.min).The variation of enzyme activity during sludge hydrolysis (protease and a-amylase) was also investigated. It was found that enzyme activity were both rose firstly, and reduced thereafter. The maximum enzyme activity were obtained at around 4h after hydrolysis,2.57 U/mL and 4.64 U/mL respectively for protease and a-amylase, which could well explain the curve of enzymztic reaction dynamics.更多还原