剩余污泥厌氧酸化液VFAs为碳源驱动硝酸盐去除的研究

发布时间：2018-05-23 20:43

本文选题：剩余污泥 + 单因素法　；参考：《中国海洋大学》2015年硕士论文

【摘要】：我国城镇污水处理厂产生的剩余污泥中,含有大量的难降解有机物和氮、磷等营养元素。若只经过减量化处理后外排,会严重威胁环境安全和公众健康。目前,厌氧酸化法是能同时实现污泥无害化和资源化的途径之一。通过厌氧酸化,污泥中的大部分有机物可以转化为挥发性脂肪酸(VFAs)和乙醇等易降解物质,回用于污水处理中,既可以解决反硝化碳源不足的问题,还能进一步提高污水的脱氮除磷效率。但一般厌氧条件下污泥产生的VFAs量很少,不足以满足实际工程中反硝化菌对碳源的需要,因此需要不断调控厌氧酸化的影响因素,提高剩余污泥的水解酸化率。同时,不同条件下剩余污泥产生的VFAs组成分布不同,而VFAs中各酸含量的不同又会对反硝化速率和硝酸盐去除率产生不同的影响。因此,本论文结合国内外污泥产酸发酵的研究进展,运用单因素调控和响应面法系统地研究了不同厌氧条件对污泥产酸及其组分的影响,并人工模拟不同组成分布的VFAs作碳源,对UASB反应器中污水的反硝化速率和脱氮率进行了初步探索。首先单一调控剩余污泥的初始pH、ORP和反应的振荡速率,以污泥发酵液中的SCOD、VFAs及其组分的变化为研究重点,根据污泥水解和产酸的效果确定各因素的最佳值。结果表明,最适初始pH为6.0或8.0,此条件下污泥能快速生成340.7 mg/L和325.8 mg/L的VFAs,酸化率分别为65.90%0、63.6%。最适初始ORP为200 mV,此时厌氧过程中pH和ORP均在水解酸化菌的适宜范围内。虽然初始ORP对VFAs产量影响不大,且各组分含量在厌氧过程中基本保持不变,但较低的ORP有利于增加戊酸的含量并使乙酸长时间积累。振荡速率和发酵时间密切相关,60 r/min、反应4h和150r/min、反应12h都取得了较好的产酸效果,VFAs产量分别为318.0 mg/L和278.2 mg/L,酸化率各为65.3%、59.3%。此外,振荡速率对丙酸的形成影响较小,而高振速下出现了乙酸的累积。为研究多因素之间的相互作用,本论文采用响应面法设计污泥SS、初始ORP和振荡速率的不同组合条件,对嗜热菌处理后的剩余污泥进行厌氧酸化,通过分析响应面图和拟合方程,确定污泥发酵液中SCOD、VFAs及其组分、乙醇、蛋白质和糖类含量最大时的最适条件。实验表明,污泥SS对剩余污泥产生的VFAs总量影响不大,而初始ORP和振荡速率较低的条件则有助于VFAs的积累。这是由于初始ORP较低能使发酵过程的ORP控制在水解酸化菌适宜的范围内,振荡速率较低则能使污泥中的有机物与微生物长时间充分接触。最适条件8.0 g/L、0 和 60 r/min下VFAs产量最大为1400.8 mg/L,约是原污泥的29倍。同样,SCOD受SS影响很小,在混合状态相同时高浓度污泥并没有生成更多的可溶性有机物。预测的SCOD最大值是8331.7 mg/L,对应的最适条件为8.0 g/L、143.7 mV和60.0 r/min。此外,发酵液中乙酸和乙醇的含量与SS和振荡速率密切相关：丙酸和丁酸的含量受初始ORP的影响较大,这可能是由于初始ORP的变化容易引起剩余污泥产酸过程中发酵类型的改变,从而造成丙酸或丁酸的积累：SS和初始ORP相互影响了戊酸和蛋白质：而厌氧菌的发酵可能多以糖降解为主,使得糖类累积量很少,三因素对其作用规律仍未可知。最后研究了不同组成分布的VFAs作碳源对硝酸盐去除的影响。用不同比例的乙酸和丙酸制成混合酸后,污水的反硝化速率和脱氮率都比较高。其中乙／丙为1：2时降解最快,脱氮率最高为97.5%。硝酸盐氮的降解速率还与丙酸含量呈一定的正相关。这也证明了VFAs中丙酸比乙酸更适合作反硝化碳源。当不同体积比的乙酸、丙酸、丁酸和戊酸作反硝化碳源时,污水的反硝化速率和脱氮率差异很大。结果显示,四种酸的最佳体积比为30%：60%：5%：5%,此时各酸含量分别为482.5 mg/L、205.7 mg/L、52.3 mg/L和26.9 mg/L。该比例下虽然反硝化速率不是最快,但出水中硝酸盐氮浓度会随反应时间不断下降,达到2.0 mg/L以下,脱氮率最高为97.5%,实现了污水的深度脱氮。此外,增加丁酸和戊酸的含量对污水中硝酸盐的快速降解也能有一定的促进作用。
[Abstract]:The residual sludge produced by urban sewage treatment plants in our country contains a large number of refractory organic compounds and nutrients such as nitrogen and phosphorus. If only after reduction and treatment, the sewage sludge will seriously threaten the environmental safety and public health. At present, anaerobic acidification is one of the ways to realize the harmless and resourceful sludge at the same time. Most of the organic compounds can be converted into volatile fatty acids (VFAs) and ethanol, which can be used in sewage treatment, which can not only solve the problem of denitrifying carbon source, but also improve the efficiency of denitrification and dephosphorization of sewage. However, under the general anaerobic condition, the amount of VFAs produced by the sludge is very few, which is not enough to meet the actual project. Nitrifying bacteria need to be used for carbon source, so it is necessary to regulate the influence factors of anaerobic acidification and improve the hydrolysis acidification rate of residual sludge. At the same time, the distribution of VFAs composition in the residual sludge is different under different conditions, and the different acid content in VFAs will have different effects on the denitrification rate and nitrate removal rate. Combined with the research progress of acid fermentation at home and abroad, the effects of different anaerobic conditions on the acid and its components of sludge were systematically studied by single factor regulation and response surface method, and VFAs as a carbon source was simulated by artificial simulation, and the rate of denitrification and denitrification of sewage in UASB reactor was preliminarily explored. The initial pH, ORP and the oscillating rate of the remainder sludge are regulated by the change of SCOD, VFAs and its components in the sludge fermentation broth. The optimum value of each factor is determined according to the effect of sludge hydrolysis and acid production. The results show that the optimum initial pH is 6 or 8. Under this condition, the sludge can quickly produce 340.7 mg/L and 325.8 mg/L VFAs, acid The optimum initial ORP was 200 mV, respectively. In the anaerobic process, both pH and ORP were within the suitable range of the hydrolytic acidification bacteria. Although the initial ORP had little effect on the yield of VFAs, the content of each component remained unchanged during the anaerobic process, but the lower ORP was beneficial to increase the content of valerate and to accumulate the acetic acid for a long time. The rate is closely related to the fermentation time. 60 r/min, reaction to 4h and 150r/min, the reaction 12h has achieved good acid producing effect. The yield of VFAs is 318 mg/L and 278.2 mg/L, respectively, the acidification rate is 65.3%, 59.3%. in addition, the oscillation rate has little effect on the formation of propionic acid, and the accumulation of acetic acid appears under Gao Zhensu. In this paper, the response surface method was used to design the sludge SS, initial ORP and the different combination conditions of the oscillation rate. The anaerobic acidification of the residual sludge treated by thermophilic bacteria was carried out. By analyzing the response surface map and the fitting equation, the optimum conditions for the determination of SCOD, VFAs and its components, the maximum content of ethyl alcohol, protein and sugar in the sludge fermentation liquid were determined. The results showed that the sludge SS had little effect on the total amount of VFAs produced by the remaining sludge, while the initial ORP and low oscillation rate were helpful to the accumulation of VFAs. This was due to the low energy of initial ORP to control the ORP in the fermentation process in the suitable range of hydrolytic acidification bacteria, and the low oscillation rate could make the organic matter and microorganism in the sludge long enough for a long time. Contact. The optimum conditions 8 g/L, 0 and 60 r/min for VFAs production are 1400.8 mg/L, about 29 times of the original sludge. Similarly, SCOD is affected by SS very little. In the same mixing state, the high concentration sludge does not produce more soluble organic matter. The predicted SCOD maximum is 8331.7 mg/L, and the corresponding optimum conditions are 8 g/L, 143.7 mV and 60 r/mi. N. in addition, the content of acetic acid and ethanol in the fermentation broth is closely related to the SS and the oscillation rate: the content of propionic acid and butyric acid is greatly influenced by the initial ORP, which may be due to the change of the initial ORP, which may cause the change of the fermentation type in the process of residual sludge producing acid, resulting in the accumulation of propionic acid or butyric acid: SS and the initial ORP interact with each other. Valerate and protein: the fermentation of anaerobic bacteria may be mainly degraded by sugar, which makes the accumulation of carbohydrates less, and the three factors are still unknown. Finally, the effect of the different distribution of VFAs on the removal of nitrate is studied. The rate of denitrification and removal of sewage after mixed acid and propionic acid in different proportions is used. The nitrogen rate is high. The degradation rate is the fastest when B / C is 1:2, the highest nitrogen removal rate is 97.5%. nitrate nitrogen degradation rate and the positive correlation with propionic acid content. It is also proved that propionic acid is more suitable for denitrifying carbon source than acetic acid in VFAs. When the different volume ratio of acetic acid, propionic acid, butyric acid and valerate as denitrifying carbon sources, the wastewater is reversed. The rate of nitrification and denitrification was very different. The results showed that the optimum volume ratio of the four acids was 30%:60%:5%:5%, and the acid content of each acid was 482.5 mg/L, 205.7 mg/L, 52.3 mg/L and 26.9 mg/L., although the denitrification rate was not the fastest, but the nitrate nitrogen concentration in the effluent would decrease with the reaction time, reaching less than 2 mg/L, The maximum denitrification rate was 97.5%, which realized the deep denitrification of the sewage. In addition, the increase of butyric acid and valerate content could also promote the rapid degradation of nitrate in sewage.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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