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.

The Use of Nixtamalization Waste Waters Clarified by Ultrafiltration for Production of a Fraction Rich in Phenolic Compounds

“…A major type of waste water in Mexico is waste waters resulting from nixtamalization of maize (Zea mays). A production of 600 Ton maize per day produces between 1500 and 2000 m 3 of the waste water, the monthly volume generated in Mexico is about of 1.2 million m 3 [1]. The latter process is carried out as a pretreatment of the maize grain in order to make it more amenable (during its postprocessing) to preparation of flour, masa, tortillas, and other food products [2].…”

Treatment and alternative usage possibilities of a special wastewater: Nejayote

“…COD and BOD values of wastewater can be reduced using aerobic (Pedroza‐Islas & Durán de Bazúa, ; Salmerón‐Alcocer et al, ) and anaerobic reactors (Civit, Durán de Bazúa, Engelmann, González, & Hartmann, ; Durán de Bazúa, Sanchez‐Tovar, Hernandez‐Morales, & Bernal‐Gonzalez, ). It has been reported that usage of one of the anaerobic and aerobic systems will be economical for the corn industries with daily 2,500 m 3 or more wastewater.…”

Integral use of Nejayote: Characterization, New Strategies for Physicochemical Treatment and Recovery of Valuable By-Products

“…Traditional maize is lime-cooked in clay pots over a fire, followed by steeping for 8-16 h (generally overnight), the supernatant called maize wastewater or commonly known as "nejayote", derived from the Nahuatl word meaning "lime broth ashes" is discarded and then the nixtamal is hand-washed. Nixtamal is ground into a fine masa with a stone grinder called metate and then hand-molded, patted or pressed into disks, which are baked on both sides on a hot griddle [4][5][6][7][8][9][10].…”

“…Nejayote is considered an environmental pollutant because it is an alkaline wastewater, with high chemical and biological oxygen demand [2,9]. Due to the presence of lime in the process, the pH of the wastewater is very high (12)(13)(14), with a high temperature between 40 and 70°C), containing suspended solids (corn husks and broken grains) and a very high portion of dissolved material from the alkaline hydrolysis of corn components [14].…”

“…Thus, alternatives for sanitation of nejayote and utilization are needed [14]. Among the solutions that have been reported, they are from biological treatment processes [9], membrane filtration, nixtamalization methods that minimize water use and the use of nejayote as a supplement in animal feed [17].…”