Botswana International University of Science and Technology, Department of Civil and Environmental Engineering, Private Bag 16, Palapye, Botswana.
Botswana International University of Science and Technology, Department of Earth and Environmental Sciences, Private Bag 16, Palapye, Botswana.
J Environ Manage. 2021 Mar 15;282:111909. doi: 10.1016/j.jenvman.2020.111909. Epub 2021 Jan 16.
Water treatment sludge have shown promising results as adsorbent for phosphorus and sulphate removal from real wastewater. The study was conducted through batch kinetics and equilibrium isotherm modes. The chemical composition reveal that aluminium compounds were dominant in the fresh sludge and aluminium phosphates were also observed in the used sludge. The results reveal that Manganese was leached from the material at all pH values investigated with the highest level observed at pH 2 and all concentrations higher than the national standard of discharge into the relevant environment. The point of zero charge of the adsorbent was pH 8.04 and high adsorption capacities for both sulphate and phosphate ions were observed at pH values lower than this point. Batch kinetic results revealed 96.0 ± 3.0% sulphates removal in the first 30 min whereas the highest phosphates removal was 88.0 ± 4.0% attained at 300 min of the experiment. Pseudo - second order reaction fitted the data better than Pseudo-first order reaction. The percentage removal of sulphates was observed decreasing with increasing adsorbent dose after 2.4 g dose but removal increased with increasing media dosage for phosphorus. The equilibrium data was better described by Freundlich isotherm with constants relating to adsorption capacities being 6.76 and 6.2 L g respectively, for sulphates and phosphates adsorption. The adsorption capacity of phosphates was observed decreasing with increasing temperature, but the results were not conclusive in the case of sulphates. The results reveal that copper, nickel, and zinc have affinity for sulphates. The water treatment sludge can be used for phosphate and sulphate removal from wastewater though the leachability of manganese is a concern. Further investigations through fixed bed columns will need to be investigated before field trials. In conclusion, the sludge can be used as adsorbent for phosphorus and sulphates removal from wastewater through filtration and onsite treatment methods such as vertical or horizontal flow wetland systems. The success of the adsorbent will reduce the costs associated with its disposal which can also lead to leachability of metals into the environment with time.
水处理污泥作为一种从实际废水中去除磷和硫酸盐的吸附剂，已显示出良好的效果。该研究通过批动力学和平衡等温线模式进行。化学成分表明，新鲜污泥中主要含有铝化合物，而使用后的污泥中还观察到铝磷酸盐。结果表明，在所有研究的 pH 值下，锰都从材料中浸出，在 pH 值为 2 和所有浓度都高于国家排放标准的情况下，浸出量最高。吸附剂的零电荷点为 pH8.04，在低于该点的 pH 值下，对硫酸盐和磷酸盐离子都表现出高吸附容量。批动力学结果表明，在前 30 分钟内，硫酸盐的去除率为 96.0±3.0%，而在实验的 300 分钟时，磷酸盐的去除率最高为 88.0±4.0%。拟二级反应比拟一级反应更能拟合数据。在 2.4g 剂量后，随着吸附剂剂量的增加，硫酸盐的去除率观察到逐渐下降，但对于磷，随着介质剂量的增加，去除率增加。平衡数据更符合 Freundlich 等温线，与吸附容量相关的常数分别为 6.76 和 6.2Lg，分别用于硫酸盐和磷酸盐的吸附。随着温度的升高，磷酸盐的吸附容量下降，但硫酸盐的结果并不确定。结果表明，铜、镍和锌对硫酸盐有亲和力。水处理污泥可用于从废水中去除磷酸盐和硫酸盐，但锰的浸出是一个问题。在进行现场试验之前，需要通过固定床柱进一步进行研究。总之，该污泥可作为从废水中去除磷和硫酸盐的吸附剂，通过过滤和现场处理方法，如垂直或水平流湿地系统。该吸附剂的成功应用将降低与其处置相关的成本，随着时间的推移，这也可能导致金属浸出到环境中。
