Abstract

A living consortium of green algae (Ankistrodesmus) and cyanobacteria (Nostoc and Anabaena) was tested for the removal of heavy metal ions (Fe (II), Cu (II), Pb (II), Cr (VI) and Zn (II)) from dumpsite leachate under natural climatic conditions. Metal removal experiment was performed at 5 and 10 mg L⁻¹ initial metal concentration in leachate and 0.8 and 1.6 g L⁻¹ of biomass doses. Metal removal was in the order of Pb > Cu > Zn > Fe > Cr. Among all the metals algae and cyanobacteria removed the highest amount of Pb (7.03 ± 0.6 mgg⁻¹) at 10 mgL⁻¹ initial metal concentration and algal dose of 0.8 gL⁻¹ and, the lowest amount of Cr metal (0.98 ± 0.6 mgg⁻¹) was taken up at 5 mgL⁻¹ initial metal concentration and 1.8 gL⁻¹ of biomass dose. Metal removal by unit biomass mass (mgg⁻¹) increases with an increase in initial metal concentration in leachate and decrease in biomass concentration however, the removal rates (percent removal per unit time) of metal ions has positive relationship with the initial biomass concentration. With an increase in initial metal concentration, the chances of collision between metal ions and available cations at the cell surface of biomass increases, resulting in increased metal uptake until the equilibrium is achieved after which the metal uptake remains constant. At small initial doses relatively a large number of adsorption sites at cell walls of algae and cyanobacteria are exposed, shifting the sorption equilibrium toward the biomass side resulting in rapid saturation of binding sites and increased bio sorption capacity of algae and cyanobacteria. This study reveals that living consortium of algae and cyanobacteria can be used as potential organisms for heavy metal removal from dumpsite leachate under natural climatic conditions.

摘要

测试了绿藻 ( Ankistrodesmus)和蓝细菌 ( Nostoc和Anabaena ) 的活菌群去除重金属离子 (Fe (II)、Cu (II)、Pb (II)、Cr (VI) 和 Zn (II) ) 在自然气候条件下从垃圾场渗滤液中提取。^{在渗滤液中的初始金属浓度为 5 和 10 mg L -1}以及生物质剂量为0.8 和 1.6 g L ^-1时进行金属去除实验。金属去除的顺序是 Pb > Cu > Zn > Fe > Cr。在所有金属中，在 10 mgL ^-1初始金属浓度和 0.8 gL ^-1藻类剂量下，藻类和蓝细菌去除的 Pb 量最高（7.03 ± 0.6 mgg ^{-1 ）}并且，在 5 mgL ^-1初始金属浓度和 1.8 gL ^-1生物质剂量下吸收了最低量的 Cr 金属 (0.98 ± 0.6 mgg ^{-1 )。}单位生物质质量的金属去除量 (mgg ^-1）随着渗滤液中初始金属浓度的增加和生物质浓度的降低而增加，但是，金属离子的去除率（每单位时间的去除百分比）与初始生物质浓度呈正相关。随着初始金属浓度的增加，金属离子与生物质细胞表面可用阳离子之间的碰撞机会增加，导致金属吸收增加，直到达到平衡，之后金属吸收保持恒定。在较小的初始剂量下，藻类和蓝藻细胞壁上的大量吸附位点暴露出来，使吸附平衡向生物质侧移动，导致结合位点快速饱和并增加藻类和蓝藻的生物吸附能力。