Physicochemical, Microbiological and Toxicological Assessment of Borehole Water in Rumuokoro, Port Harcourt, Nigeria

Abstract

Groundwater from boreholes is the primary source of drinking water for many urban communities in the Niger Delta region of Nigeria. Rapid urbanisation, industrial activities, petroleum-related operations, and poor sanitation infrastructure have increased the vulnerability of groundwater to chemical and microbial contamination. This study assessed the physicochemical quality, microbiological status, and toxicological risks of borehole water in Rumuokoro, Port Harcourt, with emphasis on human health implications for adults and children. Twenty groundwater samples were collected from ten functional boreholes during dry and wet seasons. In situ measurements of pH, temperature, electrical conductivity, total dissolved solids, and dissolved oxygen were carried out using calibrated portable multiparameter meters. Major ions were analysed using standard titrimetric and spectrophotometric methods. Heavy metals (Fe, Pb, Cd, Cr, Ni, Zn, and Cu) were determined after acid digestion using flame Atomic Absorption Spectrophotometry. Microbiological quality was assessed using membrane filtration techniques. Water quality index and human health risk indices were computed following USEPA guidelines. pH values ranged from 5.8 to 7.2, indicating slightly acidic to near-neutral conditions. Electrical conductivity varied between 214 and 682 µS/cm, while total dissolved solids ranged from 142 to 468 mg/L. Iron concentrations ranged from 0.18 to 0.92 mg/L, exceeding the 0.3 mg/L guideline in several boreholes. Lead (0.004–0.021 mg/L) and cadmium (0.001–0.006 mg/L) exceeded permissible limits in some locations. Total coliform counts ranged from 0 to 18 CFU/100 mL, faecal coliforms from 0 to 7 CFU/100 mL, and Escherichia coli from 0 to 4 CFU/100 mL. The computed water quality index value of 239 classified the borehole water as very poor. Non-carcinogenic risk assessment showed hazard quotient values exceeding unity for lead (1.58), cadmium (1.91), and nickel (1.14) in children, while adult hazard quotients remained below unity. Carcinogenic risk values for cadmium, chromium, and nickel ranged from 10-5 to 10-6 , within acceptable limits. Borehole water in Rumuokoro is unsuitable for direct consumption without treatment due to combined physicochemical, microbiological, and toxicological risks. Routine monitoring, improved borehole sanitation, effective disinfection, and targeted removal of priority metals are required to protect public health.