【作者】 闫骏；

【导师】 王淑莹；

【作者基本信息】 北京工业大学 ， 环境工程， 2007， 硕士

【摘要】 水体“富营养化”问题日益突出,氮磷等营养物质过度排放是造成这一现象的重要原因。如何有效去除有机物以及深度脱氮除磷成为污水处理领域的研究热点之一。生活污水作为影响水体的重要污染源,具有C/N低的特点,严重制约了污水脱氮除磷的效果,如何在较低运行成本下达到较高的营养物去除效果成为低C/N生活污水处理的研究重点。Orbal氧化沟工艺运行管理简单,在我国广泛应用于城市污水的处理,但是其处理效果并不尽如人意。针对以上问题,提出了本课题的研究。试验采用改进的Orbal氧化沟中试模型以及静态试验,对处理低C/N实际生活污水,进行强化生物脱氮和同步生物脱氮除磷的研究,对氧化沟中的DO、pH值在线参数变化规律进行对比分析,以期为实际污水处理厂提供可靠的运行指导。Orbal氧化沟中试模型处理低C/N的实际生活污水,具有如下处理效果:出水中,CODCr浓度低于50mg/L;氨氮浓度低于5mg-N/L;总氮浓度为20～33mg-N/L,系统不具有强化生物除磷能力,为单纯脱氮系统。为了强化生物脱氮效率,提出控制系统溶解氧浓度的策略:将氧化沟外、中、内沟的溶解氧浓度分别控制为0.3mg/L、0.5mg/L和2.0mg/L。在系统中可以实现同步硝化反硝化(SND),与未采用此策略时相比,总氮去除率和SND率分别提高了13.7%和24.3%。SND的影响因素有很多,静态试验表明,新型微生物菌种作用微弱,系统中SND的主要成因为局部缺氧区和微环境所致。实际污水处理厂(尤其是北方的水厂)在运行过程中,总会面对冬夏交替、温度改变的问题,温度较低不利于污水处理效果和污泥的沉淀。控制较高的污泥龄(SRT)可以改善处理效果恶化的情况,增加前置缺氧选择器可以有效防止低温引起的污泥膨胀。水力停留时间(HRT)是反映生物反应器能力的重要指标,14.8h和17.2h的HRT对该中试系统来说,较为合理。在研究水力停留时间的过程中,发现了Orbal氧化沟工艺生物除磷的能力和亚硝酸盐积累的现象。分析研究后,提出通过改善C/N,在Orbal氧化沟工艺中实现同步脱氮除磷,并对最优化的C/N和碳源投加种类进行研究。CODCr /TN=5.0时,磷酸盐去除效果最好,磷酸盐出水浓度低于1mg-P/L;平均出水TN浓度小于15mg-N/L,可以达到GB18918-2002一级标准。研究表明,系统总氮去除效果不受碳源种类的影响;乙酸钠和葡萄糖两种碳源对除磷影响不大,淀粉对除磷的负面影响很大。投加淀粉时,放磷速率最慢,放磷量最低,这是系统除磷效果恶化的主要原因。内循环对系统脱氮效果影响显著,适当控制内循环,可以在CODCr /TN=5.0时,得到良好的同步脱氮除磷效果。当脱氮效果非常好时,除磷效果会降低,原因为二沉池污泥放磷,本文对此提出改善措施。在内循环试验过程中发现,系统中存在着反硝化聚磷菌(DNPAOs),其比吸磷速率为13.2mg P/(g VSS·h)。在氧化沟系统中实现了较高的亚硝酸盐积累。温度和氨氮负荷并不是导致亚硝酸盐积累的主要原因。亚硝酸盐积累的根本原因为:污泥龄的缩短、pH值和游离氨(FA)浓度的增加导致系统中亚硝酸盐氧化菌被部分地淘洗出系统。分析认为,通过控制SRT、DO和pH值可以在处理常温生活污水的Orbal氧化沟中试系统中实现短程脱氮。研究了Orbal氧化沟系统中,同步脱氮除磷与单纯脱氮情况下,pH的在线变化规律。同步脱氮除磷系统中,微生物放磷结束点、主要吸磷阶段和硝化反应结束点对pH值变化趋势均有影响。当曝气过量时,无论放磷在选择器中结束还是延续到外沟,也无论系统是否具有除磷能力,都会出现硝化在中沟提前结束的pH特征点,据此可判断曝气是否过量,实现节能控制。Orbal氧化沟系统中,单纯的pH在线传感控制并不完善,需要研究更多的参数来实现合理的控制。更多还原

【Abstract】 The problem of eutrophication, which is mainly caused by excessive discharges of nitrogen and phosphorus, is growing bigger and bigger. Therefore, the wastewater techniques focus on how to remove COD, nitrogen and phosphorus simultaneously. Domestic wastewater, as the mainly resource of water pollution, is of low ratio of carbon to nitrogen (C/N), which restricts the treatment quality. Thus, how to remove nutrient ideally at low cost is spotted to be the point of low C/N wastewater treatment. Orbal oxidation ditch is wildly used in China, because of its simplicity and convenienience, while its improvement is badly needed. This research defined to deal with the problems which have been just mentioned.Solo-nitrogen removal and simultaneous nitrogen and phosphorus removal was investigated using domestic wastewater with low C/N in a pilot scale Orbal oxidation ditch, assisting batch assay experiments. Analysis of dissolved oxygen (DO) and pH variation was also involved in this dissertation. All this is to provide instruction of optimized operation to wastewater treatment plant (WWTP).Using pilot scale Orbal system, we get the result as follow: CODCr in effluent lower than 50mg/L, ammonia in effluent lower than 5mg-N/L, total nitrogen(TN) in effluent around 20～33mg-N/L without enhanced bio-phosphorus removal(EBPR). Strategy of DO concentration controlled at 0.3mg/L, 0.5mg/L and 2.0mg/L in out channel, mid channel and inner channel respectively was promoted to enhance the effect of nitrogen removal. Simultaneous nitrification and denitrification (SND) was occurred in this system. Compared to non-control operation, TN removal efficiency and SND percentage was improved 13.7% and 24.3% respectively. Influence of novel microbes on SND was investigated, and approved to be of little importance. In practical, WWTP was affected by the variation of seasons and temperature.Low temperature is of negative influence on wastewater treatment and sludge settlement. Higher sludge retention time (SRT) is helpful to revise the problem, and pre-anaerobic selector can avoid sludge bulking which was caused by low temperature. Hydraulic retention time (HRT) is one of the most important parameters on bioreactor. HRT of 14.8h and 17.2h were suitable for the pilot scale Orbal system. EBPR and nitrite accumulation had been taking place in this pilot scale Orbal oxidation ditch. Thus, to achieve simultaneous nitrogen and phosphorus removal, the strategy of adjusting C/N was proposed and the best C/N and dosing carbon species were investigated. The most favored CODCr /TN is 5.0, when phosphate removal efficiency is highest, with 1mg-P/L and 15mg-N/L TN in effluent, which goes well with the first level of GB18918-2002. According to the research, carbon species is of little importance on nitrogen removal efficiency. The impact of acetate sodium and glucose on phosphate removal is quite the same, while starch is of great negative effect. The rate and amount of phosphate release is lowest while dosing starch, which is the main reason of phosphate removal deterioration. Inner recirculation was studied in this dissertation, and found to be an important factor on nutrient removal. Preferable treatment result was achieved when CODCr /TN is 5.0 at suitable recirculation rate. Phosphate removal will deteriorate while the concentration of TN in effluent is very low, because of phosphate release in clarifier. Methods were promoted to revise the situation. Denitrifying phosphate-accumulating organisms (DNPAOs), of which the specific phosphorus uptake rate is 13.2mg P/(g VSS·h), were found to be existing in the system.Nitrite accumulation with high rate was found in Orbal oxidation ditch. Temperature and ammonia load is not the main reason of this phenomenon. Shorter SRT, variation of pH and increase of free ammonia, which induced NOB washed out of the system, is the key to nitrite accumulation. Therefore, short cut nitrification in Orbal system treating domestic wastewater could be achieved by controlling SRT, DO and pH value.The variation of online pH value at situations of simultaneous nitrogen/phosphorus removal and solo-nitrogen removal in Orbal system was investigated. The end point of phosphorus release, mass phosphorus uptake period and nitrification closure point make great influence on pH value. However where the phosphorus release finishes or whether phosphorus removal happens, the peculiar pH point will appear according to nitrification ending up in mid channel, which can be a hint of excessive aeration. More parameters are needed to Orbal system control, for simple pH online control is not enough.更多还原