Center of Environmental Systems Stevens Institute of Technology, Hoboken, NJ 07030, USA.
New Jersey Department of Environmental Protection, 401 East State Street, Trenton, NJ 08625, USA.
Sci Total Environ. 2020 Jul 10;725:138351. doi: 10.1016/j.scitotenv.2020.138351. Epub 2020 Apr 3.
Discharge of treated municipal wastewater containing arsenic (As) may cause adverse effects on the environment and drinking water sources. Arsenic concentrations were measured throughout the treatment systems at two municipal wastewater plants in New Jersey, USA. The efficiency of As removal by ferric chloride and alum coagulants were evaluated. Besides, the effects of suspended solids in the mixed liquor, pH, and orthophosphate (PO) on As removal were investigated. The total recoverable As (TAs) concentrations in the influent and effluent of Plant A were in the ranges of 2.00-3.00 and 1.50-2.30 μg/L, respectively. The results indicated that <30% of the As was removed by the conventional biological wastewater treatment processes. The influent and effluent TAs concentrations at Plant B was below 1.00 μg/L. The bench-scale coagulation results demonstrated for the first time that the coagulation treatment could not effectively remove As from the municipal wastewater to <2.00 μg/L. Very high doses of the coagulants (8 and 40 mg/L of Fe(III) or Al(III)) were required to reduce the TAs from 2.84 and 8.61 μg/L in the primary clarifier effluent and arsenate-spiked effluent samples to <2.00 μg/L, respectively, which could be attributed to the high concentrations of PO and dissolved organic matters (DOM) in the wastewater. The protein DOM in wastewater may negatively impact removal efficiencies more than the DOM in natural water, which mainly consists of humic substances. Furthermore, an artificial neural network was constructed to determine the relative importance of different parameters for As removal. Under the experimental conditions, the importance followed the order: coagulant dose>dissolved PO > initial As concentration > pH. The findings of this study will help develop effective treatment processes to remove As from municipal wastewater.
处理后的含砷市政废水的排放可能对环境和饮用水源造成不良影响。在美国新泽西州的两个市政污水处理厂的整个处理系统中测量了砷浓度。评估了三氯化铁和硫酸铝混凝剂去除砷的效率。此外，还研究了混合液中的悬浮固体、pH 值和正磷酸盐 (PO) 对砷去除的影响。工厂 A 的进水和出水的总可回收砷 (TAs) 浓度分别在 2.00-3.00 和 1.50-2.30μg/L 范围内。结果表明，<30%的砷通过常规生物废水处理工艺去除。工厂 B 的进水和出水 TAs 浓度均低于 1.00μg/L。 混凝小试结果首次表明，混凝处理不能有效地将市政废水中的砷去除到<2.00μg/L 以下。需要非常高剂量的混凝剂（8 和 40mg/L 的 Fe(III)或 Al(III)），才能将初沉池出水和砷酸盐加标出水样品中的 TAs 分别从 2.84 和 8.61μg/L 降低到<2.00μg/L，这归因于废水中高浓度的 PO 和溶解有机物 (DOM)。废水中的蛋白质 DOM 可能比天然水中主要由腐殖质组成的 DOM 对去除效率的影响更大。此外，还构建了人工神经网络来确定不同参数对砷去除的相对重要性。在实验条件下，重要性的顺序为：混凝剂剂量>溶解 PO>初始砷浓度>pH 值。本研究的结果将有助于开发有效的处理工艺，从市政废水中去除砷。
