改性活性污泥处理含铬废水的研究

【作者】 刘恢；

【导师】 柴立元；

【作者基本信息】 中南大学 ， 有色金属冶金， 2004， 硕士

【摘要】 含铬废水来源广泛、毒性大，严重危害了自然环境和人类健康。目前，处理含铬废水主要是物理化学法，例如吸附法，离子交换法，化学沉淀法，但这些方法存在二次污染严重，成本高等不足。近年来，人们开始研究采用新方法来处理含铬废水，利用硫酸盐还原菌（SRB）处理含铬废水即是当前研究的热点之一。目前SRB处理含铬废水的工艺研究仅限于纯种微生物法，尽管这种方法在实验室和中试取得了良好的效果，但纯种法存在着操作条件苛刻，菌种流失大等问题，亟待改进。 活性污泥作为一种良好的载体，能为微生物提供一个相对稳定的环境，有利于减少微生物的流失及抵抗外界水质的变化。传统上认为SRB是种严格的厌氧细菌，只能采用来源极为有限的厌氧污泥作为接种污泥，并很少见于含铬废水的处理。针对这些问题，本文对好氧活性污泥进行厌氧改性培养，考察了改性活性污泥中SRB的生长数量与硫酸根去除率之间的关系以及SRB的最佳培养条件，研究了改性厌氧污泥处理含铬废水的工艺过程及动力学，分析了厌氧污泥中铬的存在形态和分布状况，并讨论了改性污泥体系去除铬的有关机制。 通过好氧活性污泥的厌氧改性培养，成功获得了富含SRB的改性活性污泥。研究了硫酸根去除率与SRB生长之间的关系，结果表明体系中硫酸根去除率能有效地反映出SRB的生长情况，可以利用硫酸根去除率作为污泥活性的判断标准。由间歇试验获得了厌氧污泥体系中SRB培养的最佳条件：乳酸钠为碳源，pH为7，3g／LSO₄^2-，COD／硫酸根比为1.45，通入N₂。并在此条件下，进行了半连续试验。反应器中厌氧污泥培养5天后，即可以在8h内使3 g／LSO₄^2-的去除率达到90％以上，从而达到了在低COD／硫酸根比的条件下，快速起动反应器和处理高浓度硫酸根废水的目的。 在连续进料的方式下，考察了不同铬（Ⅵ）浓度、硫酸根浓度、COD浓度、水力滞留时间和多种重金属共存对污泥体系处理含铬废水的影响。结果表明，当硫酸根浓度Ig／L，COD浓度为2g／L，水力滞留时间为16h，体系能有效处理200mg／L铬（Ⅵ）的废水达标，同时出水中硫酸根浓度也能达标。在Fe，Cu，Zn，Ni四种重金属离子浓度小于20mg／L时，对体系处理含铬废水影响不大，且这些重金属也同时可以去除。通过分析可知，体系对铬（Ⅵ）的处理过程是多种细菌共同作用的结果，其中SRB的还原作用占主导地位。针对厌氧污泥体系处理含铬废水的硕士学位论文摘要过程，建立了基质降解与硫酸根还原之间的动力学方程，其式如下:m二里上玉些里丝兰型圣燮 2 Se 本研究选用逐级提取法对处理含铬废水的污泥进行研究，考察了硫酸根浓度，Cr（Vl）浓度以及多种重金属共存时对铬迁移的影响。结果表明，硫酸根浓度，Cr（Vl）浓度能影响体系的铬还原率，从而进一步影响到铬在污泥中的化学形态和分布。铬(VD的分布受条件影响比较大，没有明显的规律。铬（III）主要以残渣态存在，占总量的99%以上，这表明污泥中铬（1II）相当稳定，不易迁移。当浓度低于smg/l时，Fe、Cu、Ni、 Zn对铬的处理和迁移没有明显影响。铬（VI）的还原既可以发生在细胞外也可以发生在细胞内。体系中铬（Vl）主要是被HZS还原成铬（lII）。通过对污泥XRD的分析，可以初步推断铬在水体中发生了如下反应: 35’一+CrlO子一+14H‘。ZCr’‘+35+7厅20 Cr’‘+HZO分Cr（OH）。+3H‘改性污泥对铬(VD的吸附作用相对较小。铬（111）可向细胞内迁移，同时细胞分泌出的胞外聚合物也可吸附部分铬（III），但这两种作用都相对较弱。体系中pH范围为7一8，此时绝大部分铬（lII）以沉淀的形式从水中去除。更多还原

【Abstract】 Hexavalent chromium-containing wastewater(HCCWW), which was harmful to natural environment and human being health, has widespread sources and great toxicity. At present, physicochemical methods are the major ones to treat this wastewater, such as adsorption, ion exchange, and chemical precipitation. However, these methods will produce secondary pollution and own the shortcoming of high cost. In recent years, people started to adopt new methods to deal with HCCWW. Sulfate-reducing bacteria (SRB) available to treat wastewater were a highlight in this field. SRB can reduce sulfate to hydrogen sulfide, which would produce insoluble metal sulfides with heavy metals. So the heavy metals in the HCCWW will be drastically cleared by this characteristic. Technical research of HCCWW by SRB limits pure bacteria. Although good results can be obtained at lab and pilot scales, this method should be modified because there were some problems need to be resolved such as exacting operation terms, large loss of bacteria, and so on.Activated sludge, as a good carrier, was able to provide a stable environment for bacteria growth and benefit for decreasing the loss of bacteria and resisting the change of HCCWW. It’s traditionally known that SRB was a strict anaerobic bacterium, so only anaerobic sludge with finite sources can be used as inocula, which seldom were used to treat HCCWW. Some researches in recent years revealed that SRB could survive with oxygen and even use oxygen to grow. In order to solve these problems, activated sludge should be anaerobically modified. The Relation of quantities of SRB and rate of sulfate removal, best conditions of SRB growth, efficiency of chromium removal by sludge, occurrence and distribution of chromium in sludge, technical process and dynamics of Cr(VI) removal were investigated based on the successfully modification of activated sludge. Finally the mechanism of chromium removal by sludge was discussed.Anaerobic sludge containing high concentration SRB was obtained by anaerboically modification of activated sludge. The study on the relation of rate of sulfate removal and growth of SRB in sludge proved that the rate of sulfate reduction can act as an index to assess the conditions of SRB growth.In batch experiments, the ability of sulfate reduction of the modified sludge was researched by monitoring rateof sulfate reduction. Best conditions of SRB culture were yielded as follows: i.e. 3 g/Lsulfate, COD/sulfate ratio of 1.45, ferrous ion free, blasting N2 at pH of 7, with addition of sodium lactate. Under the conditions mentioned above, the semi-continuous experiment was carried out with the result that reactor can get more than 90% rate of 3 g/L sulfate removal after only 5 days culture. Therefore the modified sludge can be activated quickly for removing high concentration of sulfate at low COD/sulfate ratio.Effects of concentration of hexavalent chromium, sulfate and COD, hydraulic retention time and occurrence of other heavy metals on ability of sludge of chromium removal were investigated in the continuous experiments. The results indicated that the sludge can effectively remove 200mg/L Cr(VI) in wastewater at the conditions of 1g/L sulfate, 2g/LCOD and 16h HRT, and that at same time the sulfate concentration in the effluent was superior to National standard, and that below 20mg/L, other metals, i.e. Fe, Cu, Zn, Ni, had no great effect on the Cr removal and also can be effectively removed by sludge. The process of chromium removal by sludge was due to the cooperation of various microbes, out of which SRB played the most important role. Dynamical equation of degradation of substances and sulfate removal was built for the process of Cr removal by anaerobic sludge. The equation as follow:The sludge that treated HCCWW was investigated by sequential extraction method in order to understand the effect of concentration of sulfate and Cr (VI) and occurrence of other metals on the transportation of chromium in the reactor. The results revealed that the concentration of sulfate and Cr (VI) c更多还原