CFD simulation of a novel mixing and aeration system for wastewater treatment

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Water and wastewater systems are significant energy consumers with an estimated 3%-4% of total U.S. electricity consumption. Wastewater treatment using activated sludge process is generally aided by aeration, supplying the required oxygen for degradation of organic materials. Current aeration systems account for 50% to 80% of wastewater treatment plant operating budgets. With rising energy costs and a growing focus on energy conservation and carbon footprint reduction, there is increasing demand for energy-efficient aeration technologies. Ekologix Earth-Friendly Solutions Inc. (Ekologix) is currently experimentally testing its new invention, Plunge-AspiroTM Mix (PAM) that can reduce energy use by up to 60%. Using a liquid pump and multiple vertical jet streams introduced from the top of the aeration reactor, PAM concurrently mixes and aerates while supplying tiny bubbles, resulting in improved performance and energy efficiency of the reactor. Although, performance of current design of PAM is being tested in full-scale, both hydraulic and process optimizations should be conducted for further improvement in the efficiency by simulating alternating hydraulic mixing levels without sacrificing process efficiency (i.e. organics destruction and nitrification efficiency). This can be achieved by computational fluid dynamics (CFD). The objective of this project is to establish a CFD simulation model for an aeration basin fitted with a basic design of PAM to determine the mixing pattern in the tank and to identify short-circuiting, dead and recirculation zones. The validated CFD model will be coupled with kinetic models to predict the organics removal for variable water and air flow rates, suspended solids, and dissolved organics concentration. The validated CFD model along with the bio-kinetic model will be a useful tool for the design of similar activated sludge aeration basins.