Aerobic treatment of maize-processing wastewater (nejayote) in a single-stream multi-stage bioreactor

Abstract

The manufacturing processes of tortillas, corn chips, tortilla chips, and related products yield a liquid waste called nejayote. This waste causes serious pollution problems since its chemical oxygen demand is very high, from 25000 to 30000 ppm. To reduce the pollution potential of this effluent, the use of a cascade of three continuous flow bioreactors-in-series is proposed in this work. When nejayote was supplemented with KH2PO4 and (NH4)2SO4, at COD:KH2PO4 and COD:(NH4)2SO4 ratios of 87 and 26, respectively, and the pH in the first stage was adjusted at 7.0 every 24 h, high removal efficiencies of COD (86.4%) and nitrogen (80.9%) were obtained. Although the treated water still requires a further treatment prior to its disposal, the proposed system is a potential alternative for nejayote treatment, since it allows a greater COD removal efficiency than those reported in the literature for equivalent organic loads. Key words: nejayote, biodegradation, multi-stage bioreactor, cascade.