Innovative Low Cost Technology for Nutrient Removal from Soybean Wastewater by Applying Real-time Control Strategies

摘要

A new low cost technology for simultaneous carbon-nitrogen removal from soybean waste-water has been developed in this study. The technology is performed through shortcut nitrification-denitrification. The process operated under real-time control of aeration and mixing time. The shortcut nitri-fication-denitrification in sequencing batch reactor (SBR) was achieved efficiently and steadily by controlling temperature (28+-0.5°C) and using real-time control strategies. This enabled the prevention of nitrite oxidation, leading to lower operational costs. The feasibility of oxidation-reduction potential (ORP) and pH value as control parameter for shortcut nitrification-denitrification process was investigated. Results showed that the average removal efficiency of ammonium was more than 95%, and nitrosation rate (NO_2~--N/NO_x~--N) was reached to 96%. At the same time, the variation of ORP and pH value was well related to organic matter degradation and ammonium oxidation in SBR. So that judgment on the ending of nitrification and denitrification can be based on the inflection point on the varied curve of ORP and pH throughout each SBR processing cycle, and thus reducing aeration and mixing time for saving energy source. The method saves organic energy up to 40% of COD in denitrification process, which should reduce the need for an extra external source of organic carbon. Shorter hydraulic retention time should allow the volume of the reactors to diminish, and thus diminish investment costs. Lower oxygen demand of about 25% gives lower exploitation costs.