摘要
活性污泥法是目前城市污水处理厂应用最广泛的污水生物处理技术之一。但是,该工艺存在一个最大的缺点:在运行过程中产生大量的剩余污泥,由此带来污泥处理设施的基建和运行成本都非常高昂。在我国有大量的剩余污泥不经处理就直接堆放或简单填埋,对环境造成了严重的二次污染。当前的各种污泥减量技术由于成本或是一些未能解决的技术问题,尚没有一个被广泛的应用于实际中。投加化学解偶联剂法以其污泥减量效果好、运行管理方便等优点受到人们越来越多地关注,利用该技术进行污泥减量处理已成为当前研究热点。
本文采取序批式连续曝气运行的方式,通过向活性污泥系统中投加解偶联剂的方法,从几种毒性相对较小,污泥减量效果明显的解偶联剂中筛选出了最佳解偶联剂及其作用条件,研究了其在活性污泥系统中的迁移转化途径,并考察了pH值、温度、解偶联剂浓度及活性污泥浓度等因素对活性污泥系统和污泥吸附解偶联剂的影响,在此基础上探讨了代谢解偶联剂污泥减量的作用机理。
在解偶联剂筛选实验中,综合评价解偶联剂对污泥减量效果、系统基质去除率的影响及经济成本因素,研究确定2,6-二氯苯酚作为最佳的解偶联剂;在最佳作用条件筛选实验中,通过各因素对污泥减量效果及系统基质去除率的影响,得到最佳pH=5,最佳温度=25℃,最佳活性污泥浓度=2g/L～2.5g/L,最佳DCP作用浓度=20 mg/L,最佳DO值=5mg/L的结论。
在DCP的迁移转化实验中,研究发现:DCP进入活性污泥系统后即与污泥发生作用,而非完全溶解后再发生;颗粒态、粉末态、溶解态DCP加入活性污泥系统后,分别在18h、8h和2h时溶解达到最大值,而且解偶联剂的溶解只与自身理化性质有关,与外界环境无关;通过比较分析粉末态DCP和液态DCP对污泥产率、系统运行效能以及DCP出水浓度等因素的影响,得到固体投加形式为最优化的投加方式;低浓度下(小于30mg/L),DCP的非生物损失率均小于6%,说明非生物损失影响可以近似忽略,且非生物损失率随着解偶联剂投加量的增加而增大;生物活性抑制实验说明,在活性污泥系统中不存在微生物的降解转化作用。综上可知,在短期时间内,活性污泥与DCP之间主要进行了生物吸附作用。超过75%的解偶联剂被活性污泥吸附,一小部分解偶联剂残留出水中,二者之和占总投加量的92%以上。
在活性污泥吸附解偶联剂的影响因素实验中,研究发现:随着pH值的增大,解偶联剂在出水中的浓度不断升高,污泥吸附量则不断下降;温度实验证明活性污泥吸附DCP的反应是放热反应;DCP的吸附量随初始浓度的增加而增加,但增加幅度逐渐变小;DCP出水浓度与污泥吸附量均随着活性污泥浓度的增加而下降;
活性污泥吸附解偶联剂是解偶联剂在活性污泥系统中的主要去除途径,为下一步深入研究污泥吸附解偶联剂机理提供了理论基础。
Today, the activated sludge process is one of the most far-ranging biology treatment technology in municipal wastewater treatment plant. But there will be a mass of excess sludge in the process, which is the maximal disadvantage of the activated sludge process. The construction capital and operating cost of the excess sludge treatment and disposal facilities are all very highly. The mass of excess sludge was directly piled up or simply buried without treated, which will be serious secondary pollution to the environment. Currently, due to cost or numerous of unresolved technical issues, the sludge reduction technologies were not widely used in practice. With the advantages of effectiveness and convenient operation and management, addition of chemical uncoupler has been more and more concerned, with which to reduce sludge production has become the hotspot.
In this paper, taking sequencing batch style with continuous aeration, through inputing metabolic uncoupler to the activated sludge system, the best chemical uncoupler and operation conditions were selected. The transfer and transformation of DCP in the activated sludge were studied. Meanwhile, the effect of pH, temperature, DCP concentration and MLSS on the activated sludge system and adsorption behavior of DCP were also studied. On the basis of preliminary studies, the mechanism of metabolic uncoupler to reduce sludge production was discussed.
In the experiment of metabolic uncoupler screening, comprehensive evaluating the effect of metabolic uncoupler on sludge reduction, substrate removal efficiency and economic costs, 2,6-dichlorophenol was chosen as the best uncoupler. In the experiment of best operation condition screening, we made the conclusion that the best pH=5,temperature=25,activated sludge concentration =2g/L~2.5g/L,DCPconcentration=20mg/L,DOconcentration=5mg/L.
By studying the transfer and transformation of DCP in the activated sludge, some conclusions were made: DCP had immediate interaction with the sluge rather than happened after completely dissolved. when joined in the activated sludge, the granule, powder and dissolved DCP reached their maximum dissolution in 18h, 8h and 2h. The dissolution of uncoupler was only concerned with their own physical and chemical properties and had nothing to do with the environment. By comparing the effect of powder and dissolved DCP on activated sludge yield, substrate removal efficiency and effluent, the most optimal dosage was powder form. In the low concentration(less than 30mg/L), the abiotic loss of DCP was below 6% and increased with DCP concentration, which means the impact of abiotic loss could be ignored. The experiment of inhibition of biological activity showed there was no biodegradation in the sludge. From above, more than 75% of DCP was biosorbed by the activated sludge, little was residued in the water, and this two parts accounted for more than 92% of the total dosage.
The impact of various factors on the biosorption of DCP was as follows: The DCP concentration in the effluent increased with the pH while the biosorption capacity decreased. The temperature experiment proved that the biosorption reaction was exothermic. The biosorption capacity increased with DCP concentration while increased gradually. The DCP concentration in the effluent and the biosorption capacity decreased with the increase of sludge concentration.
Biosorption of DCP was the main removal way, which provide the theoretical basis for studying the mechanism of biosorption .
引文
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