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  The current approaches applied for removing nitrate from drinking water, commonly uses many chemical additives that may have undesirable or unknown effects on human health and in some cases caused many by products more dangerous than nitrate in drinking water. In present there are few appropriate and economic processes in this field and because of water scarcity in many areas development a suitable technology for treatment of nitrate contaminated drinking water for application in actual scales is crucial. In this research we develop an economic process with high selectivity for nitrate removal and minimum disturbance in other drinking water quality parameters that utilizes only hydrogen and carbon dioxide, produced in a methanol based electrochemical gas generator by applying a very low DC voltage (5-10 volt). We evaluate the ability of hydrogenotrophic denitrification for removal of nitrate in a bioreactor packed by light expanded clay aggregates known as LEACA. The results showed by proper coupling of electrochemical gas generator and denitrification bioreactor only by injection of tow clean and harmless gases, hydrogen and carbon dioxide and without any other chemicals addition for common concentrations of nitrate in natural waters by hydraulic retention time of 2-5 hr, removal efficiencies greater than 95% can be achieved. Also in comparison with other conventional methods such as ion exchange, reverse osmosis, electrodialysis, and biological heterotrophic with organic carbon source this system has several advantages such as: high selectivity for nitrate ion, low biomass yields, low electrical energy consumptions, without any problems resulted from organic carbon source addition (for example: taste and odor problem, carcinogenic THM production in disinfection process and rapid clogging of biofilter), easy operation, and compatibility with health issues in drinking water treatment.

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Wastewater treatment with microalgae and its reuse is an effective step toward reducing water consumption and preserving water resources. The possibility of growing spirulina microalga on cattle effluents and the possibility of purifying effluents using microalga were investigated. Different concentrations of standard culture medium (Zaruk)-wastewater were used to measure the optimal algal growth on wastewater and to determine the concentration of effluent-Zaruk for optimal algal growth. The treatments were T1 including 100% Zaruk and no wastewater, T2 including 75% Zaruk and 25% wastewater, T3 including 50% Zaruk and 50% wastewater, T4 including 25% Zaruk and 75% effluent and T5 including 100% effluent without Zaruk. Treatments that had more Zaruk, showed more optimal growth, and those that had a higher concentration of effluent often showed a relatively lower growth of algae biomass. The results showed the high growth of algae on the concentrated effluent. T1 with 0.35 and T2 with 0.3 g/liter of dry biomass had the highest biomass of microalgae. T1, T2, T4, T3, and T5 had the highest to the lowest amount of phycocyanin pigment production in microalgae, respectively. The highest removal of nitrate belonged to T5 and T4 with 82.57% and 78.21% removal respectively, and the lowest nitrate removal belonged to T1 and T2 with 57.17% and 70.94%, respectively. The highest removal of phosphate belonged to T1 and T2 with 94% and 92.11% removal, respectively. The lowest removal of phosphate belonged to T4 with 84% removal. Findings indicated the high potential of microalga for treating cattle wastewater.