Maize-processing wastewater, also known as nejayote, does represent a widespread residue originating from both small- and large-scale factories that produce maize-based products using the alkaline maize-cooking process (nixtamalization). Nejayote is a high-strength wastewater containing significant concentrations of soluble and insoluble organic and inorganic compounds resulting from the disintegration of maize, as well as from the substantial quantity of lime (Ca(OH)2) used in the process. In order to make nixtamalization more sustainable in terms of water usage and to mitigate the health and environmental issues related to nejayote discharges into environmental matrices and public sewage systems, appropriate and effective treatment processes must be applied either before effluent disposal or for water reuse purposes. With this problematic as the central topic, we conducted a comprehensive review of relevant literature addressing this issue spanning from the mid-1980s to the present day. This review covers three primary aspects: i) the extensive variability observed in the physicochemical composition of maize-processing wastewater, ii) the various biological and physicochemical methods developed for its treatment, and iii) the potential for organic and mineral resource recovery from this waste. Although initial efforts to treat nejayote were left behind for decades, recent years have witnessed a resurgence of research interest in these research topics mainly underpinned by the urgency to conserve water resources. Based on the comprehensive evaluation of the existing literature, we identified the existing limitations on nejayote treatment and identified prospects for developing robust and technically feasible treatment possibilities. Within this review, we propose three main approaches for wastewater treatment and water reuse: physicochemical-based technologies, bioprocess in tandem with membrane technology, and low-cost bioprocesses coupled to physicochemical methods.
Keywords: Biological treatment; Calcium precipitation; Maize-lime cooking; Nejayote; Resource recovery; Water reuse.
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