A systematic framework to assess the feasibility and effectiveness of carbohydrate-rich wastewater treatment with bioresource exploitation alternatives in small- and medium-sized enterprises

A conceptual design framework for wastewater treatment with advanced bioresource exploitation is developed. Using the framework, a process that minimizes chemical oxygen demand (COD) of the treated wastewater is designed, considering factory-specific conditions while satisfying a constraint on treatment budget allowance (TBA). A food processing factory can now assess the initial investment, economic payback period, and environmental impacts associated with designs generated for various TBA constraints. For a specific factory in Taiwan producing 4900 kg day–1of tofu, a baseline 1.9 million New Taiwan dollars investment is proposed, which is paid back in 5.5 years mainly by the avoided pollution fee rather than recovered heat and electricity. Two anaerobic digestion reactors (73.9 and 70.7 m3) and a 5 kW biogas combined heat and power unit will reduce wastewater COD (from 14793 to 100 mg L−1) and achieve a potential reduction of 72 kg–CO2–eq. day−1 of greenhouse gas emissions.