COMPARATIVE ASSESSMENT OF THE EFFECTS OF CHROMIUM

This study was carried out to comparatively assess the effects of chromium (Cr) and lead (Pb), on the growth of two freshwater microalgae (Chlamydomonas reinhardtii and Scenedesmus cronies). The test algae were grown in seven concentrations (0, 1, 2, 4, 6, 8, and 10 mg/L) which were set up in triplicates. Growth response of the test microalgae was monitored at twoday intervals for 14 days using a visible spectrophotometer (Model No. HV-721. The growth rate, percentage inhibition, and analysis of variance (ANOVA) were computed using Microsoft Excel software. Physicochemical parameters such as hydrogen ion concentration (pH), electrical conductivity total dissolved solid (TDS) were also determined. The results revealed
that growth of both microalgae decreased progressively with increasing concentration with chromium exhibiting greater toxicity than lead. Growth rate analysis favoured Chlamydomonas reinhardtii in both heavy metal treatments. Statistical analysis using ANOVA showed that it was significant (p < 0.05) in growth response among the various concentrations for both species. Conversely, Lead showed negligible inhibitory effects, with final biomass statistically similar to the control across all concentrations. Results of the physico-chemical parameters showed a concentration dependent relationship. pH was noticed to increase in lead-treated cultures but remaining neutral in high-chromium cultures. Despite differential toxicity, both
species showed high biosorption capacity: C. reinhardtii was exceptionally efficient, removing nearly 100% of lead. Based on the findings of this study it can be concluded that Chromium is acutely toxic at the tested range, while Lead is comparatively benign, and that both microalgae, particularly C. reinhardtii for lead, is more suited for the bioremediation of wastewater polluted with lead.