Removal of nitrate from drinking water by a coupling of methanol-based electrochemical hydrogen and carbon dioxide generator and a packed-bed bioreactor was investigated. The major goal was to study the performance of this integrated system for simultaneous, economical, in situ, and on-demand electron donor and carbon source production for hydrogenotrophic denitrification of drinking water in actual scales. The ability of system has been evaluated for treatment of natural underground water up to 120 mg NO 3 2 /L (threefold of the drinking water limit) nitrate concentration. Removal efficiencies above 95% were achieved for more than 150 days of operation at a 2-5 h retention time. Furthermore, the system was operated only by injection of two harmless gases (produced by electrolysis of methanol) and without any chemical addition (solid or liquid). In the electrolysis process, H 2 and CO 2 (H 2 as an electron donor and CO 2 as a carbon source for denitrifier bacteria) was produced cheaply and simultaneously by applying a very low DC voltage (4-6 V) to a solution that includes an easily oxidizable organic substance (methanol) and electrolyte solution comprised water and a base. In situ and under control generation of H 2 and CO 2 by an efficient, cost-effective way showed that this process can be an acceptable and reliable system for treatment of nitrate contaminated drinking water in actual scales. Additionally, convenient process operation without need of high pressure and explosive gas cylinders and only by voltage adjustment is other advantage of the process.
Waste Stabilization Ponds (WSPs) are known for the economical treatment of wastewater, especially if low-cost land is available. In this research to overcome some common operational problems such as undesirable color changes in ponds, severe odor problems, and most importantly, deviations from the effluent standards, the performance of a novel installation of a small-scale fine bubble diffused aeration system in the inlet zone of the facultative pond has been investigated. The long-term operational data of the system in two wastewater treatment plants in the east of Iran demonstrated that this system can significantly improve the efficiency of the treatment plant in addition to eliminating the mentioned operational problems. Pre-aeration of the inlet zone of the facultative ponds (Birjand WSPs) by the aeration system consists of 250 fine bubble disk diffusers (12 inches in diameter) and one 22 kW roots blower showed that purple color and odor problem can eliminate after almost two weeks and organic matter removal efficiency increased from 58 ± 15% to about 85 ± 10% based on BOD5. Almost similar results were obtained from the WSPs of Neyshabur. Long-term experimental results showed this system can be used successfully to control the process and upgrade these natural and efficient treatment processes, especially in developing countries.
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