Rincón Guillermo J, La Motta Enrique J
Department of Civil and Environmental Engineering, University of New Orleans, 2045 Lakeshore Dr., Room 110, New Orleans, LA 70122, USA.
Department of Civil and Environmental Engineering, University of New Orleans, 2045 Lakeshore Dr., Room 102, New Orleans, LA 70122, USA.
J Environ Manage. 2014 Nov 1;144:42-50. doi: 10.1016/j.jenvman.2014.05.004. Epub 2014 Jun 6.
US and international regulations pertaining to the control of bilge water discharges from ships have concentrated their attention to the levels of oil and grease rather than to the heavy metal concentrations. The consensus is that any discharge of bilge water (and oily water emulsion within 12 nautical miles from the nearest land cannot exceed 15 parts per million (ppm). Since there is no specific regulation for metal pollutants under the bilge water section, reference standards regulating heavy metal concentrations are taken from the ambient water quality criteria to protect aquatic life. The research herein presented discusses electro-coagulation (EC) as a method to treat bilge water, with a focus on oily emulsions and heavy metals (copper, nickel and zinc) removal efficiency. Experiments were run using a continuous flow reactor, manufactured by Ecolotron, Inc., and a synthetic emulsion as artificial bilge water. The synthetic emulsion contained 5000 mg/L of oil and grease, 5 mg/L of copper, 1.5 mg/L of nickel, and 2.5 mg/l of zinc. The experimental results demonstrate that EC is very efficient in removing oil and grease. For oil and grease removal, the best treatment and cost efficiency was obtained when using a combination of carbon steel and aluminum electrodes, at a detention time less than one minute, a flow rate of 1 L/min and 0.6 A/cm(2) of current density. The final effluent oil and grease concentration, before filtration, was always less than 10 mg/L. For heavy metal removal, the combination of aluminum and carbon steel electrodes, flow rate of 1 L/min, effluent recycling, and 7.5 amps produced 99% zinc removal efficiency. Copper and nickel are harder to remove, and a removal efficiency of 70% was achieved.
美国及国际上有关控制船舶舱底水排放的法规主要关注的是油和油脂的含量，而非重金属浓度。目前的共识是，任何舱底水排放（以及距最近陆地12海里内的含油污水乳化物）的含油量不得超过百万分之十五（ppm）。由于舱底水部分没有针对金属污染物的具体规定，因此用于保护水生生物的重金属浓度参考标准取自环境水质标准。本文所介绍的研究探讨了电凝聚（EC）作为一种处理舱底水的方法，重点关注其对含油乳化物和重金属（铜、镍和锌）的去除效率。实验使用了由Ecolotron公司制造的连续流反应器以及一种合成乳化物作为人工舱底水。该合成乳化物含有5000毫克/升的油和油脂、5毫克/升的铜、1.5毫克/升的镍以及2.5毫克/升的锌。实验结果表明，电凝聚在去除油和油脂方面非常有效。对于油和油脂的去除，当使用碳钢和铝电极组合、停留时间少于一分钟、流速为1升/分钟且电流密度为0.6安/平方厘米时，可获得最佳的处理效果和成本效益。过滤前的最终出水油和油脂浓度始终低于10毫克/升。对于重金属的去除，铝和碳钢电极组合、流速为1升/分钟、出水循环以及7.5安培的电流可实现锌99%的去除效率。铜和镍更难去除，去除效率为70%。
