Concentration and Cytogenotoxicity of Heavy Metals and Microorganisms in Labana Rice Mills Wastewater Birnin Kebbi, Northwestern Nigeria

Authors: Yahaya TO, Aliero AA, Oladele EO, Obadiah CD, Nathaniel J, Abdullahi MZ

DOI Info: http://doi.org/10.5281/zenodo.5048285

ABSTRACT

Nigeria’s rice milling industry is undergoing expansion to diversify the nation’s economy and boost food sufficiency. However, there is a dearth of information on the safety of wastewater emanating from the industry. This study determined the physicochemical and microbiological characteristics as well as cytogenotoxicity of wastewater from a rice mill in Birnin Kebbi, Kebbi State, Nigeria. The water characteristics were determined using standard protocols, after which the wastewater was subjected to cytogenetoxicity test using Allium cepa toxicity test. Fifty Allium cepa bulbs divided equally into 5 groups were grown in beakers containing tap water (control) and 25, 50, 75, and 100 % (v/v) of the wastewater, respectively for 3 days. The root-tips of the bulbs were then examined for chromosomal aberrations. The physicochemical analysis showed that the levels of nickel (Ni), chromium (Cr), iron (Fe), pH, sulphate, and temperature were within the World Health Organization (WHO) permissible limits. However, lead (Pb), nitrate, turbidity, total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were above the permissible limits. The microbiological analysis showed normal coliform counts (< 400 CFU/ml), while bacteria and yeast colonies were above the permissible limits (> 1000 CFU/ml)). In the cytogenetic test, the exposed A. cepa showed dose-dependent sticky and vagrant chromosomes and anaphase bridges as well as significantly reduced (p < 0.05) mitotic index (MI) and root length growth. These findings suggest that the wastewaters could pose some health hazards unless treated.

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