School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.
School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China; Shanghai Institute of Pollution Control and Ecological Security, 1239 Siping Road, Shanghai, 200092, China.
Environ Res. 2021 Apr;195:110783. doi: 10.1016/j.envres.2021.110783. Epub 2021 Jan 23.
Sewage sludge is one of the sinks for PAHs accumulation and concerns are growing regarding the environmental risk of the discharge of PAHs in waste activated sludge (WAS) as a major byproduct of sewage treatment. Here, we evaluated the effectiveness of ozone treatment to eliminate the 16 priority PAHs in WAS. The PAHs removal efficiency increased with ozone dosage and was strongly pH dependent. Even at ozone dosage of 40 mg O·g, the PAHs removal efficiency at pH 9.0 (44.5%) was significantly higher than that observed at pH 5.0 and 200 mg O·g (41.7%). The pH-dependent elimination behavior of PAHs was attributed to the varying yield of hydroxyl radicals (OH) and degree of sludge disintegration (R = 0.88-0.92). Over 96% of the PAHs were in the particulate flocs (PF) phase, while the fraction bound to the freely dissolved (FS) and dissolved and colloidal (DC) matters was negligible, indicating the need of WAS disintegration during ozonation to make PAHs more accessible to O molecules and OH to initiate oxidation reactions. Failure of the three-compartment model to describe the PAHs sorption behavior in sludge matrix during ozonation implied that oxidation reaction occurred simultaneously with the partitioning of PAHs from PS to DC/FS fraction. Lastly, the results of the intermittent ozonation experiment demonstrated the interference of soluble organic compounds during PAHs degradation, particularly proteins and humic substances, as O and OH scavengers. At ozone dosage of 120 mg O·g (pH 9.0), the PAHs removal efficiency was improved by 19.5% by intermittent ozonation, as compared to continuous ozonation under the same conditions.
污水污泥是多环芳烃（PAHs）积累的汇之一，人们越来越关注作为污水处理主要副产物的废活性污泥（WAS）中 PAHs 排放对环境的风险。在这里，我们评估了臭氧处理消除 WAS 中 16 种优先 PAHs 的效果。PAHs 的去除效率随臭氧剂量的增加而增加，且强烈依赖 pH 值。即使在臭氧剂量为 40 mg O·g 的情况下，在 pH 值为 9.0 时（44.5%）的 PAHs 去除效率也明显高于在 pH 值为 5.0 和 200 mg O·g 时（41.7%）。PAHs 的 pH 值依赖性消除行为归因于羟基自由基（OH）的产量和污泥解体程度的变化（R=0.88-0.92）。超过 96%的 PAHs 存在于颗粒絮体（PF）相中，而与自由溶解（FS）和溶解胶体（DC）物质结合的部分可以忽略不计，这表明在臭氧氧化过程中需要对 WAS 进行解体，以使 PAHs 更容易被 O 分子和 OH 接触，从而引发氧化反应。臭氧氧化过程中三组分模型不能描述 PAHs 在污泥基质中的吸附行为，这表明氧化反应与 PAHs 从 PS 分配到 DC/FS 部分同时发生。最后，间歇臭氧氧化实验的结果表明，在 PAHs 降解过程中，可溶性有机物，特别是蛋白质和腐殖质，会干扰氧化反应，充当 O 和 OH 的清除剂。在臭氧剂量为 120 mg O·g（pH 值为 9.0）的情况下，与相同条件下的连续臭氧氧化相比，间歇臭氧氧化使 PAHs 的去除效率提高了 19.5%。
