ABSTRACT
This study was carried out to evaluate the effect of company treatment on Biotoxicity of Tannery Waste Water in Northern Nigeria. Sorghum (Sorghum bicolor) was used to screen for effects on growth characteristics while onion (Allium cepa) was used to test for chromosomal aberrations after exposure to company treated and untreated Tannery Waste Water. Viable seeds of S bicolor were planted in different concentrations (0, 10, 25, 40, 55, 70, 85 and 100) of treated and untreated tannery waste water and monitored for 21 days. The study was monitored for germination on the 4th, 5th, 6th, and 7th days after planting while other growth parameters were monitored on the 7th, 14th and 21st days after planting. The treated and untreated tannery waste waters were analysed for potential cytotoxicity using the Allium cepa test and their chemical characteristics were also carried out. Results of the chemical analysis on treated and untreated waste water showed that with the exception of temperature, all other parameters exceeded the permissible limits of NESREA, WHO and FAO. The cytotoxicity screening for treated waste water using A. cepa revealed the following aberrations; Sticky, fragment, bridge, multipolar and C metaphase while the untreated tannery waste water showed dispersed chromosomes and all aberrations as in treated effluent. mitotic indices reduced with increase in concentration of the waste waters (34 to 18 for treated; and 30 to 18 for untreated). Percentage chromosomal aberration in A. cepa increased with increase in concentration of both treated and untreated waste waters but more in the untreated than the treated (5.88% to 40% for treated and 15.35% to 77.75% for untreated). Allium cepa bulbs exposed to different concentrations (0, 10, 25, 40, 55, 70, 85 and100) of treated and untreated waste waters showed significant (p0.05) with increase in concentration for treated waste water while there was significant (p0.005) reduced with increase in concentration. There were also reductions in chlorophyll and carotenoid content of Sorghum bicolor with increase in concentration of the treated and untreated waste waters. This study has shown that treated and untreated tannery waste waters have cytotoxic effects on A. cepa as well as inhibitory effects on growth characteristics of Sorghum bicolor. As such, the company treated waste water falls short of treatment standards or the treatment administered is not effective.