【作者】 李晓玲；

【导师】 彭永臻；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2010， 硕士

【摘要】 面对城市污水处理厂低C/N比生活污水由于碳源缺乏而导致脱氮除磷效率较低的现状,开发利用污泥内碳源为BNR(Biological Nutrients Removal)系统进行碳源补给成已为目前污水处理领域的研究热点。污泥在厌氧条件下发酵可产出大量可溶性有机质,尤其是小分子挥发酸类物质是极易被微生物利用的有利基质。本研究着眼于在厌氧条件下对初沉污泥和二沉污泥两种性质不同的污泥进行发酵研究,探索pH和发酵时间对发酵溶出各有机物如SCOD、碳水化合物、蛋白质、各种挥发酸等和发酵副产物如氨和磷的影响。在此基础上提出针对不同污泥进行发酵产酸的较优工作参数;并设计运行发酵反应器,考察反应器内有机物的溶出过程,发酵混合液的分离及有机底物的转移,转化效率。旨在为碳源缺乏的BNR系统最大限度的提供连续,稳定,有效的碳源补给的工程实现提供技术参考。首先,通过序批试验研究初沉污泥和二沉污泥在不同pH值和发酵时间内各物质的溶出规律,结果表明:碱性条件明显有利于SCOD和VFAs的溶出,且SCOD在发酵前期迅速溶出,初沉污泥在SRT=2d时达最高,二沉泥SRT=4d达最高;较长的SRT有利于VFAs的产生,初沉污泥在SRT=7.5~9.5 d时VFAs产量较大,二沉污泥在SRT=7.5 d时产量较大;结合SCOD和VFAs两者的溶出规律,本研究中得出的初沉污泥最佳的发酵条件为pH=9,SRT=9.5d,二沉污泥的最佳发酵条件为pH=10,SRT=7.5d。其次,通过对两种污泥发酵的对比研究得出:初沉污泥不仅能在较短时间内产生大量的SCOD和VFAs,而且氨磷的释放较少,因此在初沉污泥足量的条件下单一利用初沉污泥发酵是最有效的方式。稳定后虽二沉污泥的氨磷释放率远高于初沉污泥(分别高出58.7%,73.1%)但单位二沉污泥发酵溶出SCOD的量高于初沉污泥单位溶出量(高出25.4%),结合大多数污水厂对两种污泥进行混合处理的现实,提出适当配比下混合污泥在pH=10,SRT=8d条件下进行发酵也能在溶出大量的SCOD,VFAs的同时减轻对后续处理单元的影响。再次,通过以二沉污泥为底泥的连续流碱性发酵反应器的运行研究表明:进入稳定期后,主体区内的VSS、SCOD及VFAs的产量较稳定分别为4079 mg/L、3063 mgCOD/L、1252 mgCOD/L。VFAs中乙酸占了主要部分(41.12%),其次是丙酸(23.57%),异戊酸(15.38%);发酵液液相中的氨含量(66.15mg/L)与生活污水中含量接近,因此可以忽略对后续处理系统的影响,但值得注意的是发酵液中磷的含量较高(201.4mg/L),因此有必要单独针对磷进行化学除磷的前处理。最后,通过元素平衡分析了污泥在发酵过程中的物质转移转化规律,得出C、N和P从污泥固相经发酵转移到液相中的转移效率分别为3.2%、16.8%和17.3%。可见污泥中的C还有较大的开发空间。针对发酵混合泥水分离困难的问题,采用淘洗技术,SCOD的一次淘洗效率为68%,为提高效率可采用多次淘洗技术。在淘洗过程中,三种元素的总量基本能保持平衡。C元素在淘洗过程中能够较有效的从淘洗前混合泥液相中转移到静沉区上清液中,淘洗效率为86%。更多还原

【Abstract】 As we all known, in many cities of our China, the influent water contains insufficient carbon source in some wastewater treatment plant, particularly in urban wastewater treatment plant. Accordingly, it becomes necessary to add extra carbon source to such wastewater to achieve satisfying BNR performance. Recently, production of SCOD, especially short-chain fatty acids (SCFAs) by fermentation of sludge generated in municipal wastewater treatment plants (MWTP) has attracted much attention, because it can not only take advantage of organic wastes for reclamation but also improve the SCOD concentration of influent.Primary sludge (PS) and waste activated sludge (WAS) are the two different wastes generated in MWTP. This thesis focused on the anaerobic fermentation of the two types of sludge, discussed the effect of pH and fermentation time on the products such as SCOD, carbohydrate, protein, etc as well as by-products like ammonia and phosphate, finally proposed optimal parameters for different sludge fermentation. On that basis, sludge fermentation reactor was designed and we investigated the dissolving process of organic matter, the separation of mixed fermentation liquid, transfer efficiency of organic substrate and so on. Finally results provide reference for actual project which aimed to provide maximum, continuous, stable and efficient carbon source for BNR system with insufficient carbon source.Firstly, sequencing batch method used in this experiment was to examine the different processes of fermentation of primary sludge and activated sludge, under different pH conditions and fermentation time. The results show: alkaline conditions are obviously benefit to the dissolution of SCOD and VFAs. SCOD dissolved rapidly in the initial stage, for primary sludge the maximum rate achieved at 2d, while for activated sludge was at 4d; Relatively long fermentation time was benefit to the production of VFAs. Primary sludge achieved maximum output at 7.5to 9.5d, while activated was at 7.5d; Combined with SCOD and VFAs two factors the optimum fermentation conditions of primary sludge is pH at 9 and fermentation time in 9.5 days, while for activated sludge is pH at 10 and the fermentation time in 7.5 days.Secondly, comparation of the two sludge fermentation shows: primary sludge can produce a large number of VFAs in a relatively short time with low ammonia and phosphate load, therefore, fermentation of sole primary sludge is the most effective and efficient manner as additional carbon source for BNR system; Though the amount of SCOD dissolved by activated sludge is much higher than primary sludge (about 25.4%) after stabilization under pH at 10, the phosphorus and ammonia release are also higher than primary sludge (about 58.7%, 73.1%, respectively). As we all know great deal of ammonia and phosphorus release undoubtedly aggravated the waste water processing load of the follow-up system, in order to ease this negative impact, fermentation of mixed sludge as the carbon sources is proposed in this paper, meanwhile, suggested that the optimum conditions is pH at 10 and fermentation time in 8 days, under the combination of the fermentation characteristics of the two types of sludge.Thirdly, the research of continuous flow of alkaline fermentation reactor for activated sludge shows: the biomass of the sludge fermentation area was stable (SS 6890mg/L, VSS 4079 mg/L) and the production of SCOD and VFAs was also steady (3063 mg COD/L, 1252 mg COD/L, respectively); The main VFAs was acetic acid (41.12%), followed by propionic acid (23.57%) and isovaleric acid (15.38%); ammonia content was relatively low (66.15mg/L) and approach to sewage waste water, therefore, the effect to follow-up system can be ignored. However, the amount of phosphorus was relatively high (201.4mg/L), necessary pretreatment was needed to lower phosphorus load before utilization, such as chemical precipitation.Finally, the element-balance analysis of which C、N and P from the solid phase of sludge before fermentation to liquid phase after fermentation, shows that: the transfer efficiency was 3.2%、16.8% and 17.3%, respectively. Lower C transfer efficiency manifests larger sludge development space for ever exploit. The difficult problem of separation the fermentation mixture can be solved efficiently by elutriation technology, and the efficiency was 68%, which can be improved by continuous elutriation. The content of C、N、P keep equilibrium in the process of fermentation. C can effectively transfer from fermentation mixture before elutriation to the liquid phase of Static sink tank, where the elutriation efficiency was 86%.更多还原