[论文解读] Efficient and Sustainable Treatment of Tannery Wastewater by a Sequential Electrocoagulation-UV Photolytic Process

Sameh Jallouli, Ahmed Wali+5 more|arXiv (Cornell University)|Oct 7, 2020

Dye analysis and toxicity被引用 6

一句话总结

本研究提出一种先电凝（EC）后紫外光解的连续处理工艺，以高效且可持续地处理高浓度制革废水。该组合工艺实现了94.1%的化学需氧量（COD）去除率，将COD降至428.7 mg/L，远低于1000 mg/L的排放限值，同时降低了植物毒性，并展现出中等能耗下的良好可扩展性（314.28 kWh/m³）。

ABSTRACT

Tannery wastewater contains large amounts of pollutants that, if directly discharged into ecosystems, can generate an environmental hazard. The present investigation has focused the attention to the remediation of wastewater originated from tanned leather in Tunisia. The analysis revealed wastewater with a high level of chemical oxygen demand (COD) of 7376 mgO2/L. The performance in reduction of COD, via electrocoagulation (EC) or UV photolysis or, finally, operating electrocoagulation and photolysis in sequence was examined. The effect of voltage and reaction time on COD reduction, as well as the phytotoxicity were determined. Treated effluents were analysed by UV spectroscopy, extracting the organic components with solvents differing in polarity. A sequential EC and UV treatment of the tannery wastewater has been proven effective in the reduction of COD. These treatments combined afforded 94.1 % of COD reduction, whereas the single EC and UV treatments afforded respectively 85.7 and 55.9 %. The final COD value of 428.7 mg/L was found largely below the limit of 1000 mg/L for admission of wastewater in public sewerage network. Germination tests of Hordeum Vulgare seeds indicated reduced toxicity for the remediated water. Energy consumptions of 33.33 kWh/m3 and 314.28 kWh/m3 were determined for the EC process and for the same followed by UV treatment. Both those technologies are yet available and ready for scale-up.

研究动机与目标

• 解决含有高化学需氧量（COD）的高浓度制革废水带来的环境危害。
• 评估电凝（EC）、紫外光解及其连续组合工艺在降低COD方面的有效性。
• 通过黑麦草（Hordeum vulgare）发芽试验评估处理后出水的植物毒性。
• 确定连续EC-紫外光解工艺的能耗及可扩展性潜力。
• 利用紫外光谱法和极性溶剂萃取法识别处理后废水中有机组分。

提出的方法

• 采用铝电极在不同电压和反应时间下进行电凝（EC）处理，以破坏胶体和溶解性污染物的稳定性。
• 在EC处理后进行紫外光解（254 nm），以降解难降解有机物并进一步提高COD去除率。
• 利用紫外-可见光谱法表征处理前后有机物组成的改变。
• 使用不同极性的溶剂（如正己烷、乙酸乙酯、甲醇）萃取有机组分，评估污染物的转化情况。
• 测量EC及EC-紫外光解组合工艺的COD去除效率和能耗（kWh/m³）。
• 通过黑麦草（Hordeum vulgare）种子发芽试验评估处理后出水的植物毒性。

实验结果

研究问题

• RQ1 电凝（EC）、紫外光解及其连续组合工艺对制革废水的COD去除效率如何？
• RQ2 连续EC-紫外光解工艺如何影响处理后出水的植物毒性？
• RQ3 EC及EC-紫外光解工艺的能耗是多少？该系统是否具备可扩展性？
• RQ4 废水中的有机组分在处理后其组成和极性如何变化？
• RQ5 连续EC-紫外光解工艺能否使COD水平低于排入公共污水管网的1000 mg/L阈值？

主要发现

• 连续EC-紫外光解工艺实现了94.1%的COD去除率，将浓度从7376 mgO2/L降低至428.7 mgO2/L。
• 单独EC处理使COD降低了85.7%，而单独紫外光解则实现了55.9%的去除率。
• 最终COD值428.7 mgO2/L远低于排入公共污水管网的1000 mg/L限值。
• 植物毒性测试显示，EC-紫外光解处理后的出水毒性降低，表现为黑麦草种子发芽率提高。
• 能耗分别为EC工艺33.33 kWh/m³，EC-紫外光解组合工艺314.28 kWh/m³，表明能耗适中。
• 紫外光谱法和溶剂萃取结果表明，有机污染物发生了显著转化，特别是复杂高分子量化合物的分解。