Raw sewage is widely used on agricultural soils in urban areas of developing countries to meet water shortages. Although it is a good source of plant nutrients, such sewage also increases the heavy metal load to soils...Raw sewage is widely used on agricultural soils in urban areas of developing countries to meet water shortages. Although it is a good source of plant nutrients, such sewage also increases the heavy metal load to soils, which may impact the food chain. Management options for sewage contaminated soils includes addition of nontoxic compounds such as lime, calcium sulfate and organic matter, which form insoluble metal complexes, thus reducing metal phytoavailability to plants. In this paper we review the variation in irrigation quality of sewage at different sites and its impact on the quality of soils and vegetables. Although quality of sewage was highly variable at source, yet the effluent from food industries was relatively safe for irrigation. In comparison effluent samples collected from textile, dyeing, calendaring, steel industry, hospitals and clinical laboratories, foundries and tanneries were hazardous with respect to soluble salts, sodium adsorption ratio and heavy metals like zinc, copper, iron, manganese, nickel, cobalt and cadmium. The sewage quality in main drains was better than that at the industry outlet, but was still not safe for irrigation. In general, higher accumulation of metals in fruits and vegetable roots was recorded compared to that in plant leaves, Edible parts of vegetables （fruits and/or leaves） accumulated metals more than the permissible limits despite the soils contained ammonium bicarbonate diethylenetriaminepentaacetie acid extractable metals within a safe range. In either case further scientific investigations are needed to ensure safe management strategies. Cadmium appeared to be the most threatening metal especially in leafy vegetables. It is advisable to avoid leafy vegetables cultivation in sewage irrigated areas everywhere to restrict its entry into food chain.展开更多
For meeting the increased demand of electrical power,distributed generation(DG)based on renewable energy resources(RERs),has become a potential alternative to large plants based on fossil fuels.The power from environm...For meeting the increased demand of electrical power,distributed generation(DG)based on renewable energy resources(RERs),has become a potential alternative to large plants based on fossil fuels.The power from environmentally friendly RERs is available at a competitive price due to technological advancements in recent times.Moreover,optimal allocation of DG at the distribution network(DN)level may result in power loss reduction,improvement in voltage profile and the network’s overall reliability.However,integration of DG may increase the short circuit(SC)level beyond the capacity of the protection gear,conductors,transformers and other components of a DN.The high short circuit currents(SCCs)may be reduced by application of a fault current limiter(FCL).However,most of the existing literature proposes optimization of FCLs size by considering only normal configurations of a DN.This approach is inappropriate as it may fail to produce the desired reduction in SCCs in different N−1 contingency scenarios.In this paper,a new strategy is presented that considers both normal as well as various contingency situations for optimal allocation of FCLs in a DN with DG connection.The strategy is implemented in the IEEE 30-bus system in a MATLAB environment using a genetic algorithm(GA).The simulation results prove that the proposed strategy is effective in determining the optimal FCLs size that restricts the SCCs to a safe level in different operating conditions including N−1 contingencies and thus,improves network safety and reliability.The strategy described in the paper can play an important role in DN planning involving optimal application of DG and FCLs.展开更多
文摘Raw sewage is widely used on agricultural soils in urban areas of developing countries to meet water shortages. Although it is a good source of plant nutrients, such sewage also increases the heavy metal load to soils, which may impact the food chain. Management options for sewage contaminated soils includes addition of nontoxic compounds such as lime, calcium sulfate and organic matter, which form insoluble metal complexes, thus reducing metal phytoavailability to plants. In this paper we review the variation in irrigation quality of sewage at different sites and its impact on the quality of soils and vegetables. Although quality of sewage was highly variable at source, yet the effluent from food industries was relatively safe for irrigation. In comparison effluent samples collected from textile, dyeing, calendaring, steel industry, hospitals and clinical laboratories, foundries and tanneries were hazardous with respect to soluble salts, sodium adsorption ratio and heavy metals like zinc, copper, iron, manganese, nickel, cobalt and cadmium. The sewage quality in main drains was better than that at the industry outlet, but was still not safe for irrigation. In general, higher accumulation of metals in fruits and vegetable roots was recorded compared to that in plant leaves, Edible parts of vegetables （fruits and/or leaves） accumulated metals more than the permissible limits despite the soils contained ammonium bicarbonate diethylenetriaminepentaacetie acid extractable metals within a safe range. In either case further scientific investigations are needed to ensure safe management strategies. Cadmium appeared to be the most threatening metal especially in leafy vegetables. It is advisable to avoid leafy vegetables cultivation in sewage irrigated areas everywhere to restrict its entry into food chain.
文摘For meeting the increased demand of electrical power,distributed generation(DG)based on renewable energy resources(RERs),has become a potential alternative to large plants based on fossil fuels.The power from environmentally friendly RERs is available at a competitive price due to technological advancements in recent times.Moreover,optimal allocation of DG at the distribution network(DN)level may result in power loss reduction,improvement in voltage profile and the network’s overall reliability.However,integration of DG may increase the short circuit(SC)level beyond the capacity of the protection gear,conductors,transformers and other components of a DN.The high short circuit currents(SCCs)may be reduced by application of a fault current limiter(FCL).However,most of the existing literature proposes optimization of FCLs size by considering only normal configurations of a DN.This approach is inappropriate as it may fail to produce the desired reduction in SCCs in different N−1 contingency scenarios.In this paper,a new strategy is presented that considers both normal as well as various contingency situations for optimal allocation of FCLs in a DN with DG connection.The strategy is implemented in the IEEE 30-bus system in a MATLAB environment using a genetic algorithm(GA).The simulation results prove that the proposed strategy is effective in determining the optimal FCLs size that restricts the SCCs to a safe level in different operating conditions including N−1 contingencies and thus,improves network safety and reliability.The strategy described in the paper can play an important role in DN planning involving optimal application of DG and FCLs.
