Ecotoxicological Composition and Potential Treatment with Orthophosphate Modified Rice Husk Activated Carbon of Wastewater Discharge from Local Chemist Shops Within Onitsha Metropolis

The study involved the preparation of orthophosphate-modified rice husk activated carbon and subsequent utilization for the treatment of pharmaceutical wastewater discharge within Onitsha Metropolis. Wastewater from five major pharmaceutical companies was treated with the rice husk activated carbon. The analysis of pharmaceutical wastewater in Onitsha metropolis indicated higher concentrations of essential elements (Mg, Fe, Zn) with an averageof 5.301 mg/L, compared to toxic metals (Pb, Cd, Co) with an average of 0.388 mg/L. Pb (0.954 mg/L) exceeded NAFDAC/NESREA and WHO limits, while Cd (0.124 mg/L) and Zn (2.451 mg/L) fell within acceptable ranges. The concentration hierarchy was Mg ˃ Fe ˃ Zn ˃ Cd ˃ Co ˃ Pb, with activated rice husk demonstrating effective adsorption, particularly for Pb (95.07%) and Fe (86.95%). The bioindicator plant, tomatoes, accumulated metals, indicating a high potential for biomagnification for Zinc (BAF = 1.014), while iron showed a BAF below one (BAF = 0.715). Hazard quotient evaluations identified significant health risks from lead (HQ = 19.00) and cadmium (HQ = 16.12), with trace metals posing minimal risks (HQ < 1).Correlations showed negative relationships between turbidity and pH (-0.66), while acidity positively correlated (0.53) with pH. The wastewater’s pH ranged from 2.01 to 7.36, with an average turbidity of 4.63 NTU.Treatment 5.68 and turbidity to 4.55 NTU, while fluoride concentrations (8.89 mg/L) were above WHO standards, showing a 95.55% removal post-treatment. However, nitrogen removal was poor (7.58% efficiency). Bacterial colonies decreased significantly post-treatment, showing effective reduction of pathogenic bacteria by orthophosphate modified rice husk activated carbon. Overall, the study underscored the efficiency of rice husk activated carbon in wastewater treatment and the ongoing risks posed by certain heavy metals.