【作者】 樊杰；

【导师】 沈韫芬； 陶涛；

【作者基本信息】 华中科技大学 ， 市政工程， 2010， 博士

【摘要】 我国已建或在建的污水处理厂80%采用了活性污泥法,A2／O工艺因其是最简单的同步脱氮除磷活性污泥法而得到了广泛应用,但A2／O工艺存在释磷与脱氮争夺碳源、硝酸盐氮干扰释磷等固有缺陷。本文中的A2／O工艺是一种改良工艺,改良体现在预缺氧选择池的设置、分点进水以及阶式曝气池的应用。以改良型A2／O工艺处理中国南方典型的低浓度污水为研究对象,进行了实验室和现场研究,研究表明：(1)预缺氧选择池能有效去除回流污泥中的硝酸盐氮和亚硝酸盐氮,且去除硝酸盐氮的效果更稳定。预缺氧选择池的设置,使厌氧池内几乎不发生脱氮作用,脱氮主要发生在选择池和缺氧池,改善了厌氧池的释磷条件。(2)低浓度污水处理中,生物池MLSS浓度应根据F／M=0.10-0.12以及进水BOD确定,MLSS达到某一定值后出现提升困难,过度提升MLSS浓度对提高运行效果无益。水质波动不大时,可采取定MLSS控制策略,在维持生物池内MLSS的同时应及时适当排泥。排泥可以提高COD、NH3-N、TP、SS去除率。不排泥不仅会使除磷效果恶化,还会引起污泥活性降低、出水SS剧烈波动,脱氮率也降低。无脱氮要求时,混合液回流比的选择应综合考虑运行成本与除磷要求,因为混合液回流比低,回流污泥中的NO3-N增多,影响除磷率的提高。(3)阶式曝气池有如下典型特征：阶式曝气池单池设计成方形(L=1.58B)时,流态介于推流与全混流之间,更接近推流,且随着串联级数的增加越来越接近推流,此种池型比廊道式曝气池更简单。阶式曝气池内有机物、氨氮降解以一级反应为主,对污染物的降解进行模拟时宜采用分段拟合。阶式曝气池的MLSS逐级浓度分布与是否排泥、排泥量以及曝气池的混合状态有关。单池内流态为CSTR时,阶式曝气池比单级曝气池的推动力更高、体积大幅减小。设计中采用等体积CSTR曝气池串联可保证总体积最小。曝气池改造中,增加隔墙即可改造成阶式曝气池,污染物去除率提高。(4)进水受到偏碱性冲击时,对除磷无不利影响,TN去除率提高,氨氮去除率不变；进水受到低磷冲击时,除磷率提高了15.9%,但低磷时需要更长的硝化时间。(5)进水中氨氮浓度低时、好氧段DO控制不当时易出现过量曝气,过量曝气会导致除磷效果恶化,聚磷菌受抑制后反硝化菌夺得更多碳源,脱氮率提高。过量曝气不会导致出水SS增加,但污泥的SVI上升、颗粒粒径变小。氨氮降解速率提高,彻底硝化所需的时间缩短,过量曝气时应缩短曝气时间,避免混合液回流时携带过多的溶解氧进入缺氧池。(6)安庆市城东污水厂的ASM实测化学计量系数和动力学参数如下,可以为低浓度污水厂的运行模拟提供参考。水质参数：Ss占总COD的比例平均为4.8%,xs占总COD的比例平均为10.5%,SI占总COD的比例平均为21.5%,XI占总COD的比例平均为62.7%。氨氮占TN的71%；硝态氮占TN的11%；SND占TN的7%；XND占TN的11%。污泥参数(10℃时)：异养菌产率系数0.71 g(COD)／g(COD),异养菌衰减系数0.40d-1,异养菌最大比增长速率系数2.0g(Xs)／g(XH).d。更多还原

【Abstract】 80% of the existing wastewater treatment plants adopt activated sludge system. A2/O process which is the most simple simultaneous nutrient removal process is widely used in wastewater treatment plants. But there are some challenges troubled with A2/O process, such as carbon competition between phosphorus-accumulating organisms and denitrifier, effect of nitrate on phosphorus removal, sludge retention time conflict between autotrophic bacteria and heterotrophic bacteria. A modified A2/O process was presented in this thesis, and its modified configuration included (1) an anoxic selector at the head of A2/O process. (2) step-feed in anoxic selector and anaerobic tank. (3) stage aeration tank in aerobic zone. The thesis focused on characteristics and control of modified A2/O process treating South China wastewater tipical of low strength. The main conclusions are drawn as follows.(1) Anoxic selector could remove 35% of nitrate and 30% of nitrite in return sludge when 10% of influent entering selector. The removal of nitrate was more stable than nitrite. Denitrification mainly completed in selector and anoxic tank other than anaerobic tank, so selector improved conditions for phosphorus release in anaerobic tank.(2) MLSS should be determined according to F/M=0.10-0.12, and excess MLSS was not suitable for treating low strength wastewater. Excess sludge discharge could improve removal of COD, NH3-N, TP and SS. Without excess sludge discharge, effluent SS fluctuated badly and denitrification was also affected. If influent TN was very low, selection of mixed liquid recycle ratio should based on co-consideration of run cost and phosphorus removal. Because low mixed liquid recycle ratio could result in more nitrate in return sludge disturbing phosphorus release.(3) Characteristics of stage aeration tank were as follows.The mixed condition of single tank (L=1.58B) of stage aeration tank was closer to plug flow. Its configuration was simpler compared to channel aeration tank.The degradation of COD and NH3-N in stage aeration tank was afford to first order reaction. Simulation of stage aeration tank should base on multi-stage mode other than considering stage aeration tank as a whole.MLSS in stage aeration tank is uneven. This was attributed to excess sludge discharge amount and different mixed condition in each tank.If the mixed condition in single tank was CSTR, after adopting staging strategy, reaction rates could be improved and volume of biomass tank could be reduced. And the volume could be minimun when volume of each was the same. It is convenient to modify conventional aeration tank to stage aeration tank, and this modification could get higher removal rate.(4) When influent was fluctuated with weak alkaline(pH8.0-8.5), it did not have a negative effect on system performance, phosphorus and NH3-N removal maintained, TN removal improved. When influent phosphorus was very low, phosphorus removal improved 15.9%, but time for completed nitrification was extended.(5) Excess aeration resulted in deterioration of phosphorus removal and improved TN removal. SS in surface effluent was increased and also SVI of sludge. NH3-N removal rate was improved due to high DO concentration, so aeration time should be shortened in order to maintain less DO owing to mixed liquid recycle from anerobic tank to anoxic tank.(6) ASM stoichiometric coefficients and kinetic parameters of AnQing wastewater treatment plant were as follows.Water quality parameters:ratio of Ss, Xs, SI, XI to COD was respecially 4.8%,10.5%, 21.5%,62.7%.Ratio of NH3-N, NOX-N, SND, XND to TN was respecially 71%,11%,7%, 11%.Sludge parameters:YH, bH,μH was respecially 0.71 g(COD)/g(COD),0.40 d-1,2.0 g(Xs)/g(XH).d更多还原