Heavy metals are common contaminants of some industrial wastewater. They find their way to municipal wastewaters due to industrial discharges into the sewerage system or through household chemicals. The most common heavy metals found in wastewaters are lead, copper, nickel, cadmium, zinc, mercury, arsenic, and chromium. Such metals are toxic and pose serious threats to the environment and public health. In recent years, the ion exchange process has been increasingly used for the removal of heavy metals or the recovery of precious metals. It is a versatile separation process with the potential for broad applications in the water and wastewater treatment field. This article summarizes the results obtained from a laboratory study on the removal of heavy metals from municipal wastewater sludges obtained from Ardhiya plant in Kuwait. Data on heavy metal content of the wastewater and sludge samples collected from the plant are presented. The results obtained from laboratory experiments using a commercially available ion exchange resin to remove heavy metals from sludge were discussed. A technique was developed to solubilize such heavy metals from the sludge for subsequent treatment by the ion exchange process. The results showed high efficiency of extraction, almost 99.9%, of heavy metals in the concentration range bound in wastewater effluents and sludges. Selective removal of heavy metals from a contaminated wastewater/sludge combines the benefits of being economically prudent and providing the possibility of reuse/recycle of the treated wastewater effluents and sludges.
Municipal wastewater may contain heavy metals, which are hazardous to the environment and humans. With stringent regulations concerning water reuse and sludge utilization in agriculture, there is a great need to determine levels of heavy metals in liquid wastes, sludges and agricultural crops. The state of Kuwait has programs to utilize waste sludge produced at wastewater treatment plants as soil conditioner and fertilizer for greenery and agricultural development projects and to reuse treated wastewater effluents in irrigation. The common metals found in Kuwait's raw wastewater and sludge are Cd, Cr, Cu, Hg, Ni, Pb, and Zn. The effects of accumulation of heavy metals in soil are long lasting and even permanent. In this study, the variations in the concentration levels of heavy metals were measured in wastewater and sludge produced at Ardiya municipal wastewater treatment plant in Kuwait. A relationship was observed between the concentrations of heavy metals in treated wastewater and sludge used for agriculture and the level of accumulated heavy metals found in residual tissues of some crops.
A B S T R AC TPerformance evaluation is presented for fl ue gas desulfurization (FGD), humidifi cation and dehumidifi cation desalination (HDD) of fl ue gases emitted from power plants. The proposed system is based on use of seawater for SO 2 absorption and removal from the fl ue gases. The FGD and HDD processes are separated in order to achieve the highest possible effi ciency. This is because FGD requires low temperatures to achieve high rates of absorption and removal of SO 2 . On the other hand, HDD requires higher temperatures to provide suffi cient temperature difference and driving force for humidifi cation and dehumidifi cation. Analysis of both systems is applied to the emission rate data of power plants in Kuwait. The design results of the seawater SO 2 absorption column showed variations in the column height between 8.1-12.6 m as the power plant capacity was increased from 244-4173 MW. Analysis of the HDD system show that it might not be the optimum desalination alternative because of its limited production capacity. However, the process layout is simple and can be formed of two packed columns for humidifi cation and dehumidifi cation, which requires a small capital when compared to conventional thermal or membrane desalination.
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