Cr(VI)对活性污泥硝化活性的抑制及在污泥中的分布特点

重金属铬(Cr(VI))是废水中常见的、困扰很多污水生物处理系统运行效果的污染物.本文通过静态试验和静态冲击试验,研究了Cr(VI)在活性污泥系统中的分布特点和对硝化效率、活性等的影响,并进行了模型分析.结果表明,活性污泥对Cr的吸附很快,但吸附量有限,Cr(VI)投加浓度为1、5、10和30 mg · L^-1的溶液中,Cr的12 h-吸附量分别为0.79、1.98、3.19和5.78 mg · g^-1.Cr(VI)投加到活性污泥混合液中后形态分为溶解态、可洗脱和不可洗脱态,可洗脱的Cr能够向不可洗脱态转变.Cr(VI)对活性污泥硝化活性的抑制程度随着Cr(VI)浓度的增大而提高.静态试验中,1、3、5、10和30 mg · L^-1 Cr(VI)对氨氮平均降解速率的抑制率分别为5.25%、9.80%、10.41%、17.54%和21.38%.Cr(VI)对微生物的抑制作用大小是:氨氧化菌 >亚硝酸盐氧化菌 >异养菌.模型分析发现,Cr(VI)对氨氧化菌和异养菌比耗氧速率的抑制符合Haldane动力学模型,属于非竞争性抑制.冲击试验表明Cr对硝化等的抑制主要是不可洗脱的Cr造成的,抑制效果的出现具有滞后性.

Inhibitory effects of Cr(VI) on nitrification activity and Cr(VI) distribution in activated sludge

Chromium (Cr(VI)), frequently detected in wastewater, affects efficiencies of many biological wastewater treatment systems. In this work, the distribution of Cr(VI) in activated sludge systems, and toxic effects of Cr(VI) on nitrification efficiency and activities were investigated through static tests and static shock loading tests. Results showed that the adsorption of Cr onto activated sludge was fast, but the adsorption capacity was low. The 12 h-adsorption capacities were 0.79, 1.98, 3.19 and 5.78 mg · g^-1 under the dosages of 1, 5, 10 and 30 mg · L^-1 Cr(VI), respectively. The forms of Cr in the activated sludge included soluble, elutable and unelutable Cr. The elutable Cr can transform to unelutable Cr. Higher Cr(VI) concentration caused higher inhibitory effects on nitrification. In the static tests, the inhibition rates of 1, 3, 5, 10 and 30 mg · L^-1 Cr(VI) on ammonia nitrogen degradation rates were 5.25%, 9.80%, 10.41%, 17.54% and 21.38%, respectively. The order of the inhibitory effects of Cr(VI) on microflora was: ammonia oxidizing bacteria >nitrite oxidizing bacteria >heterotrophic bacteria. Modeling analysis showed that Haldane Model fitted well with the inhibitory effects of Cr(VI) on specific oxygen uptake rates of oxidizing bacteria and heterotrophic bacteria and thus the inhibitory effects of Cr(VI) should be noncompetitive. The shock loading tests showed that nitrification was mainly inhibited by the unelutable Cr, and the inhibitory effects lagged the addition of Cr(VI).