Sustainability of dairy and soy processing: A review on wastewater recycling

Abstract

Dairy and soy products are two of the most common sources of protein in the human diet. Both industries produce large volumes of wastewater (up to 10 L L⁻¹raw material), high treatment costs as high as 130 and 3374 US$/meter cubic of effluent treated for soy and dairy, respectively. The biological oxygen demand reaches 6.8 and 48 g L⁻¹, while the chemical oxygen demand reaches 12 and 95 g L⁻¹ for soy and dairy, respectively. Governments are encouraging research on circular economy. The goal is to minimize water loss and upcycle by-products by recycling wastewater. We deemed as important a review comparing recent technologies for circular economy of dairy and soy wastewater. Purification treatments range from physicochemical (flotation and coagulation) to biological (anaerobic, sludge and membrane). Treatments range from ultrafiltration, coagulation-flocculation and foam fractionation (physicochemical) to sludge and filters (biological). While irrigation with dairy wastewater increases eutrophication of soil and water, soy products wastewater can be a valuable source of protein, oligosaccharides, phytochemicals and minerals. In addition, soy wastewater has potential as texturiser (foaming agent, emulsifier and thickener) and food ingredient in new beverage development.