【作者】 曹艳晓；

【导师】 龙腾锐；

【作者基本信息】 重庆大学 ， 市政工程， 2010， 博士

【摘要】 我国城市污水普遍存在的碳氮比偏低的问题逐渐成为城市污水处理达标的瓶颈;同时,作为目前生活污水处理中运用最普及的活性污泥技术,其产生的大量剩余污泥的处理与处置费用在污水厂运行成本中所占的比例也越来越大。本课题针对低碳氮比生活污水脱氮以及剩余污泥处理的问题,分别从工艺和碳源两方面入手进行研究。在工艺方面,为提高低碳氮比污水中易生物降解有机物的含量,并对现有污水处理厂进行工艺优化,设计了水解酸化/缺氧悬浮填料移动床/好氧组合工艺(简称H/AMBBR/O工艺),进行实验室中试研究,并探索该工艺应用于城市污水高效脱氮和污泥减量的可行性。在碳源方面,通过对A/O工艺的二沉池剩余污泥进行碱解发酵,提取上清液作为反硝化碳源,考察上清液的反硝化效率,利用阶段比反硝化率的概念,提出上清液回用量的确定方法,并将上清液回用到实际运行的A/O系统中,考察上清液碳源的反硝化速率及其回用对A/O系统的影响。最后,分别从处理效能和投资运行费用(预估)方面综合比较了H/AMBBR/O工艺和上清液回用的A/O工艺的最佳运行工况。试验研究的主要结论如下:①H/AMBBR/O工艺的试验结果首先,在10.9~13℃,通过反硝化预试验对比了悬浮填料两相污泥和纯缺氧污泥的反硝化性能。结果表明,悬浮填料两相污泥对COD、氨氮、硝酸盐和TN的去除率分别达到74.37%、10.48%、60.86%和21.42%,远高于纯缺氧污泥的58.89%、3.71%、41.58%和13.75%;且生物膜的活性良好。因此,在缺氧池投加悬浮填料有利于增加污泥量,改善反硝化污泥活性,减弱冬季气温的影响。其次,研究了H/AMBBR/O组合工艺的启动方式。采取接种污泥、单池分别启动的方式对水解酸化池、AMBBR和好氧池同时进行培养驯化。其中水解酸化池采用连续进出水、逐渐增大负荷的方式,在15d内启动成功;AMBBR采用好氧曝气挂膜、缺氧转换的方式,历时20d,挂膜成功。组合工艺启动后,处理效果在两周时间内达到稳定。再次,通过单因素对比试验,筛选出H/AMBBR/O工艺的最优工况。结果表明:1)水解酸化池水力停留时间以2.5h为宜,过长的停留时间会消耗更多的碳源;2)AMBBR水力停留时间越长,反硝化反应进行得越充分,试验最佳停留时间为3h;3)硝化液回流比越大对反硝化越有利,但是动力消耗也大,试验选取合适的硝化液回流比为300%;4)当平均水温高于18.0℃时,硝化和反硝化过程不受抑制,工艺处理效果较理想,当水温低于18.0℃时,硝化反应不完全,工艺处理效果明显变差,尤其是TN出水浓度远不能达到试验预期目标,建议经济条件较好的污水处理厂可以考虑在好氧池投加填料,增强低温下的硝化效果。因此,在进水流量Q=50L/h,好氧池HRT为6.0h,二沉池HRT为1.2h,且填料投配率为30%的情况下,最优工况的条件是:水解酸化池水力停留时间为2.5h,AMBBR水力停留时间为3h,硝化液回流比300%,平均水温高于20.0℃,此时,组合工艺获得最佳处理效果:COD、氨氮和TN的平均去除率分别达到90.35%、98.24%和71.92%,对应出水浓度分别为22.6mg/L、0.89mg/L和16.35mg/L。最后,对比分析了水解酸化池分别作为纯污水和污泥污水同时预处理反应器的效能,结果表明,将二沉池污泥回流至水解酸化池,既可以改善与增加碳源,为后续反硝化提供有利条件,也可以同时实现污泥的资源化和减量化,污泥减量率可达到56%以上。②剩余污泥碱解上清液的回用到A/O工艺的试验结果首先,通过试验研究了剩余污泥碱解发酵的较优条件以及碱解对污泥的减量作用。确定了碱解pH值、以及搅拌条件,并在此基础上,通过静态连续试验的指标分析、反硝化速率对比以及污泥破解后的扫描电镜照片,确定较优的SRT为9d;同时,计算得出剩余污泥在碱解过程中的污泥减量率达到56.3%。其次,分别考察了碱解上清液、乙酸钠和生活污水三种碳源的反硝化效能及其反硝化动力学,进行综合比较,确定碱解上清液可以作为反硝化脱氮的碳源。进一步的研究考察了剩余污泥碱解上清液作为反硝化碳源的反硝化速率,并据此初步确定上清液的回用量。采用不同的VFA/N比值进行批式试验,考察硝酸盐的反硝化情况,选择出试验硝酸盐浓度下的较优比值,并应用于实际生活污水中,与纯生活污水脱氮对照,考察回用的可行性,以及回用量的确定。结果显示,VFA/N比值的增加能加快反硝化反应,且比值越高,出现亚硝酸盐峰值越大,时间越滞后,硝酸盐的降解和亚硝酸盐的变化情况跟pH值能够较好地吻合;将上清液以一定比例投入生活污水,反硝化速率明显提高,平行组6h反硝化量分别达到47.02和33.95mg/L,为单纯生活污水反硝化量的2~3倍。试验进一步根据不同反应时间段的反硝化速率提出阶段比反硝化率的概念,并结合初始VFA/N比值以及反应过程中pH值的变化粗略判断出上清液的回用量,对生产实践具有一定的指导意义。最后,根据上清液回用量的确定方法进行了实际A/O工艺的回用试验研究。分别于冬季和春季不同温度条件下进行了两次上清液的回用试验。冬季试验,A/O工艺产泥量较低,上清液回用量受限,为50ml/min左右,小于理论回用量;春季试验,上清液的回用量为85ml/min左右,与理论回用量相当。分别对两次上清液回用前后系统对COD、氨氮和TN的去除效能,以及上清液回用过程中引入的氮磷对系统脱氮除磷的影响进行了分析。结果表明:1)冬季试验情况下,实际TN去除量接近42mg/L,远高于理论计算值28mg/L;2)春季试验结情况下,基于阶段比反硝化速率计算的理论TN去除量为50.4mg/L,和实际的55mg/L较为接近,TN的平均出水浓度满足GB18918-2002的一级A标准;3)两次回用过程中引入系统的总氮占原污水总氮的10.55%和21.27%,结合TN的去除情况分析,认为该比例对系统脱氮的影响不明显,可忽略;上清液回用过程中引入总磷占原污水总磷的20.86%和79.60%,对应的出水TP浓度分别为2.84和3.52mg/L,由于系统没有设置专门的除磷装置,磷在系统中的循环可能会造成累积,因此,长时间的回用可考虑在上清液中投加盐类形成磷沉淀后进行回收。③H/AMBBR/O工艺和剩余污泥碱解上清液回用的A/O工艺的最优工况对比分析两工艺最佳工况的污染物去除效能对比结果表明:1)两工艺对COD和氨氮均有较好的去除效果,COD和氨氮的出水浓度均能满足GB18918-2002的一级A排放标准;2)上清液回用的A/O工艺出水TN浓度低于15mg/L,能够满足GB18918-2002一级A排放标准,而H/AMBBR/O工艺出水TN仅能满足GB18918-2002的一级B排放标准;3)上清液回用的A/O工艺反硝化能力以及灵活性更强,而H/AMBBR/O工艺能够实现污水污泥处理以及内碳源回用的一体化,运行管理更简便。两工艺运行费用预测结果表明,费用差别产生于AMBBR中的悬浮填料和用于调节上清液pH值的酸碱试剂。其中,悬浮填料使用寿命较长(长达数十年之久),且为一次性投资材料,而酸碱试剂为日常运行材料,其消耗费用约为悬浮填料的7倍。因此,实际应用时还需综合考虑污水的处理要求和当地的经济水平。更多还原

【Abstract】 In most cities of our country, the widespread problem of domestic sewage being low carbon and nitrogen ratio gradually becomes the bottleneck of domestic sewage to attain the treatment standard. Meanwhile, as the most widely used technology in sewage wastewater treatment, activated sludge technique has produced lots of waste activated sludge (WAS), while the expenses of WAS disposal take a more larger proportion in sewage plant operation costs. This topic for denitrification of low carbon and nitrogen ratio sewage and disposal of WAS has been studied from two aspects. In process, a new combined process—hydrolysis acidification/anoxic moving bed biofilm reactor /aerobic process (H/AMBBR/O process for short) was employed to improve the content of biodegradable carbon source in sewage wastewater, and to optimize the present wastewater treatment process. Laboratory pilot study of H/AMBBR/O and its feasiblility to remove nitrogen, as well as to reduce WAS were also explored. In carbon source, WAS was digested under alkaline condition to prepare high carbon source supernatant, and which was used to remove more nitrogen. Further study was to investigate the denitrification rate of supernatant, then a new method to determine recycling dosage was proposed according to the specific stage denitrification rate. Besides, supernatant was recycled to the real A/O process to test its denitrification rate and its influent to the A/O process. Finally, the optimum operation conditions of H/AMBBR/O and A/O process with supernatant were compared in treatment efficiency and cost of investment (for estimate).①Results of H/AMBBR/O process:Firstly,denitrification performance of both suspended biofilm with two phase and pure anoxic sludge were compared through preliminary experiments under 10.9~13℃, results showed that, removal efficiency of COD, ammonia notrogen, nitrate and total nitrogen (TN) in two phase sludge system were 74.37%, 10.48%, 60.86% and 21.42%, respectively, higher than those in suspended sludge system of 58.89%, 3.71%, 41.58% and 13.75%, respectively, and the activity of biofilm was better. So adding suspended fillers to the anoxic reactor increased sludge quantity and improved sludge activity, as well as enhanced low-temperature resistance.Secondly, the start-up of the combined process was studied. Sludge inoculation and domestication by signal reactor was adopted for hydrolysis acidification reactor, AMBBR and aerobic reactor at the same time. The hydrolysis acidification reactor was started within 15 days by increasing hydrolic loading from small amount influent, while the AMBBR was better to started-up by aerobic means and operated under anoxic condition, and the biofilm grew well within 20 days. As the combined process was started-up, pollutants removal efficiency got stable in two weeks.Thirdly, through Single factor experiment, the optimum running condition of H/AMBBR/O was screened. Results showed that, 1) the best hydraulic retention time of hydrolysis acidification reactor was 2.5h, and longer HTR would consume more carbon source, 2) the longer the HRT of AMBBR, the better for the denitrification, so the optimum ratio was 3h, 3)the larger of nitrifying liquid reflux ratio the better for denitrification, while larger reflux ratio means more power consumption, and the optimum ratio was 300%, 4) while the water temperature was below 18℃, incomplete nitrification resulted in poor TN removal efficiency, so adding fillers to aerobic reactor was proposed to enhance the effect of nitrification under low temperature, especially in wastewater treatment plant with good economic conditions. So when the flow was 50L/h, HRT of aerobic reactor was 6.0h and HRT of secondary sedimentation was 1.2h, and filler packing rate was 30%, the optimum running condition for the combind process was: when the HRT of acidification reactor and AMBBR were 2.5h and 3.0h, respectively, as well as nitrifying liquid reflux ratio was 300% and T≥20.0℃, and the optimum treatment efficiency was obtained: the average removal efficiency of COD, ammonia nitrogen and TN were 90.35%、98.24% and 71.92%, respectively, and the concentrations of these parameters in the outflow were 22.6mg/L、0.89mg/L and 16.35 mg/L, respectively.Finally, comparison of pretreatment performance for hydrolysis acidification reactor between pure wastewater and the mixture of wastewater and sludge was done. And results showed that when WAS from the second sedimentation reactor was returned back to the hydrolysis acidification reactor, the carbon source can be improved and increased to provide advantage to the following denitrification, and, meanwhile, realize the resources reuse and sludge reduction, which reached 56%.②Results of alkaline hydrolysis sludge supernatant reused in A/O process as carbon source:Firstly, the optimum condition of WAS alkaline hydrolysis and sludge reduction were studied throgh experiments. pH value and mixing condition were first determined, and the optimum SRT of 9 days was determine through parameter analysis from static continuous tests, denitrification rate and electron micrograph of cracked sludge. Besides, the sludge reduction rate attained 56.3% during WAS alkaline hydrolysis.Secondly, denitrification efficiency and denitrification dynamics of three kinds of carbon source such as alkaline hydrolysis supernatant, acetic acid sodium and sewage were investigated and compared. Results showed that alkaline hydrolysis supernatant could be carbon source for denitrification.Denitrification rate of alkaline supernatant of WAS as carbon sources for denitrification were further investigated, hereby the recycling dosage was determined preliminarily. First, WAS was digested under alkaline conditions, and batch tests were conducted under different VFA/N ratio, to examine the change of nitrate concentration and choose the optimum ratio. Then the chosen ratio was applied in pure sewage wastewater compared with the pure sewage wastewater, to study its feasibility in recycle and to determine the recycling dosage. Results showed that, the denitrification rate increased obviously with the increasing VFA/N ratio, and the higher ratio the longer time needed for nitrite peak, besides, the degradation of nitrate and change of nitrite were consistent with the pH curve. Further research showed that when the supernatant was added to the sewage wastewater to certain degree, denitrification rate increased significantly, and the nitrate removal amount of two parallel tests attained 47.02 and 33.95mg/L, respectively, which was twice to triple to that of pure sewage wastewater. In addition, the definition of specific phase denitrification rate was proposed to define different reaction period, and the initial VFA/N, as well as pH value were used to judged supernertant dosage, which had instructive meanings to practical operation.Finally, the method of how to determine supernatant recycling dosage was applied to real A/O process. Two tests both in winter and spring under different temperature have been studied. During winter test, there was not so much WAS, so the recycling dosage was about 50ml/min, which is below theoretical recycling dosage, while during spring test the amount was about 85ml/min, which equal to the theoretical recycling dosage. The removal efficiency of COD, ammonia nitrogen and TN before and after recycling in both tests were analysed, as well as the influence of nitrogen and phosphrus to the system. Results showeed that: 1)during winter test, real TN removal amount was 42mg/L, 14mg/L more than the calculated value, 2) during spring test, the calculated value according to the specific phase denitrification rate was 50.4mg/L, close to the real value of 55mg/L, and the effluent TN concentration met standard A of GB18918-2002 level. 3) during the two recycling tests, the ratio between import TN and TN of raw wastewater were 10.55% and 21.27%, respectively, considering TN removal efficiency, the effect was ignored; while the import total phosphorus ratio was 20.86% and 79.60%, respectively, and the corresponding effluent concentration of TP was 2.84 and 3.52mg/L, as there was no special phosphorus removal reactor, phosphorus would accumulated to affect the normal operation, further research should try to recover phosphate through precipitation by adding metal salt.③Comparison of the best conditions between the H/AMBBR/O process and supernatant recycling A/O process Results of pollutants removal efficiency under their optimum condition show that,1) both of the two processes has good COD and ammonia nitrogen removal efficiencies, and the effluent COD and ammonia concentration met the standard A of GB18918-2002 level. 2) effluent TN concentration of supernatant recycling A/O process was below 15mg/L, which met the standard A of GB18918-2002 level, while in H/AMBBR/O process, the effluent TN concentration could only met the standard B of GB18918-2002 level. 3) the A/O process with recycling supernatant had stronger denitrifying ability and flexibility, while H/AMBBR/O process can achieve integration of wastewater and sewage sludge treatment, as well as carbon sources recycling, so its operation and management were more easily.The operational cost prediction between two processes showed that, the difference of operational costs between the two processes were suspended filler in AMBBR and acid-base reagents used to adjust pH of supenertant. The longer service life of suspended filler (more than 10 yeas) and its characteristic as one-time investment material made the filler more cheaper than that of acid-base reagents, and its cost were 15% of acid-base reagents. So in practical, both wastewater treatment requirements and local economic level should be considerd when the processes were chosen.更多还原