Integrated Assessment of Water Quality and Public Health Risks in the Ossah River, Southeastern Nigeria: Implications For Sustainable Water Resource Management

) for most metals. Figure 2: Heavy Metal Concentrations (Iron and Manganese) 3.3. Microbiological Contamination Microbiological analysis revealed widespread and severe fecal contamination throughout the river system (Table 4). Total coliform counts ranged from 240 to 5,800 MPN/100mL (mean 2,450±1,280 MPN/100mL), vastly exceeding WHO guideline of <10 MPN/100mL for drinking water. Fecal coliform ranged from 85 to 2,400 MPN/100mL (mean 850±520 MPN/100mL), also greatly exceeding WHO guideline of <1 MPN/100mL. E. coli, a specific indicator of fecal contamination, ranged from 28 to 1,650 MPN/100mL (mean 580±340 MPN/100mL), with 100% of samples exceeding WHO guideline of 0 CFU/100mL for drinking water. Spatial patterns showed progressive contamination increase from upstream to downstream. Reference station S1 showed lowest (though still elevated) counts (total coliform: 240±85 MPN/100mL, E. coli: 28±15 MPN/100mL), while downstream station S6 exhibited extreme contamination (total coliform: 5,800±1,250 MPN/100mL, E. coli: 1,650±380 MPN/100mL), representing 24-fold and 59-fold increases respectively. Seasonal analysis revealed higher microbial counts during dry season, likely due to reduced dilution and potentially increased contamination loading as water levels decrease. Strong correlations were observed between microbial indicators and physicochemical parameters, particularly BOD (r=0.84 for total coliform, r=0.88 for E. coli; p<0.001), COD (r=0.79, r=0.82; p<0.001), and inverse correlation with DO (r=-0.75, r=-0.80; p<0.001). These relationships confirm organic pollution sources driving both oxygen depletion and microbial contamination. The pervasive fecal contamination indicates inadequate sanitation infrastructure, with untreated domestic wastewater and possibly agricultural runoff contributing substantial pathogen loads. IIARD International Journal of Geography & Environmental Management Table 2: Microbial Population Densities in Ossah River Water Sample Point Total Coliform (cfu/mL) Total Heterotrophic Bacteria (cfu/mL) Total Heterotrophic Fungi (cfu/mL) Point A (Upstream) 1.80 × 106 ± 0.05 × 106 2.94 × 107 ± 0.08 × 107 1.25 × 104 ± 0.03 × 104 Point B (Midstream) 1.70 × 106 ± 0.04 × 106 2.84 × 107 ± 0.07 × 107 1.30 × 104 ± 0.04 × 104 Point C (Downstream) 1.75 × 106 ± 0.06 × 106 2.85 × 107 ± 0.06 × 107 1.40 × 104 ± 0.05 × 104 WHO Standard (Drinking) 1.0 × 102 1.0 × 102 Not specified WHO Standard (Recreation) 5.0 × 102 1.0 × 103 Not specified Figure 3: Microbial Contamination Levels 3.4. Water Quality Indices and Health Risk Assessment Water Quality Index values varied spatially from 52 to 78 across stations, with mean WQI of 64.5±8.2 (Figure 1). Upstream reference station S1 showed 'good' water quality (WQI=52), while stations S2-S4 fell in 'poor' category (WQI=58-68). Downstream stations S5 and S6 approached 'very poor' classification (WQI=72, 78 respectively). Seasonal analysis revealed mean dry season WQI (68.8±7.5) significantly higher (worse quality) than wet season (60.2±8.1) (t-test: t=3.85, p<0.01), primarily due to reduced dilution effects. The WQI results confirmed progressive water quality deterioration along the river course, with particular concern IIARD International Journal of Geography & Environmental Management for downstream areas. Heavy Metal Pollution Index ranged from 42 (S1) to 95 (S6), with overall mean of 68.5±16.8, indicating moderate to high pollution levels. Stations S5 and S6 approached the critical threshold of 100, beyond which water is considered highly polluted and unsuitable for consumption. Lead and cadmium contributed disproportionately to HPI scores due to their high toxicity weights and substantial exceedance of standards. Spatial gradient analysis showed HPI increasing linearly downstream (R2=0.89), suggesting cumulative pollution accumulation. Health risk assessment revealed concerning findings (Table 5). Non-carcinogenic hazard quotients (HQ) for adults ranged from 0.18-0.85 for individual metals, with hazard index (HI = ΣHQ) of 2.45, exceeding the acceptable threshold of 1.0. For children, HQs ranged from 0.78- 3.68, with HI of 10.6, indicating substantial non-carcinogenic risk. Lead contributed highest risk for both adults (HQ=0.85) and children (HQ=3.68), followed by cadmium (adults: HQ=0.68, children: HQ=2.95). The dramatically elevated risks for children reflect their lower body weights, higher water consumption rates relative to body weight, and greater sensitivity to toxic effects. Carcinogenic risk assessment for cadmium and chromium revealed lifetime excess cancer risks of 2.8×10−4 and 1.2×10−5 respectively. Cadmium risk substantially exceeded the acceptable upper threshold of 10−4, indicating unacceptable cancer risk over a lifetime of water consumption. When considering microbial contamination, acute health risks from waterborne diseases are immediate and substantial, particularly for immunocompromised individuals, children, and elderly populations. The combination of chemical and microbial risks presents a serious public health challenge requiring urgent intervention. 4. Discussion 4.1. Physicochemical Water Quality and Pollution Sources The physicochemical characteristics of Ossah River water reflect multiple pollution pressures typical of rivers in rapidly developing regions of sub-Saharan Africa. Dissolved oxygen depletion (mean 4.2 mg/L, minimum 1.8 mg/L) indicates significant organic pollution, as decomposition of organic matter consumes dissolved oxygen. The WHO guideline for aquatic ecosystem health (>5 mg/L) was violated at 68% of sampling events, particularly at downstream stations during dry season. This hypoxic stress threatens fish populations and benthic organisms while potentially releasing metals from sediments under reducing conditions (Schwarzenbach et al., 2010). Elevated BOD (mean 8.5 mg/L) and COD (mean 24.3 mg/L) confirm substantial organic loading, likely from multiple sources including domestic wastewater, agricultural runoff carrying crop residues and animal waste, and possibly food processing waste from small-scale commercial activities along the river corridor. The spatial gradient increasing downstream clearly indicates cumulative pollution loading. Comparison with other Nigerian rivers reveals similar or worse conditions: Ogun River BOD 6.5-12.8 mg/L (Edokpayi et al., 2015), Aba River BOD 9.2-18.5 mg/L (Akpan & Offem, 2016), confirming widespread organic pollution challenges. Turbidity levels (mean 58 NTU, maximum 158 NTU) substantially exceeded WHO drinking water guideline of 5 NTU, primarily due to suspended sediments from erosion, especially during wet season. High turbidity reduces water aesthetic quality, interferes with disinfection by shielding microorganisms from treatment chemicals, and indicates potential transport of adsorbed contaminants including heavy metals and pathogens. The strong correlation between IIARD International Journal of Geography & Environmental Management turbidity and heavy metals (r=0.55-0.75) confirms this association. Erosion control measures including riparian vegetation restoration and improved land management practices are essential. 4.2. Heavy Metal Contamination: Sources, Patterns, and Concerns Lead contamination (mean 0.085 mg/L, 8.5-fold above WHO guideline) represents the most serious heavy metal concern. Potential sources include leaded gasoline residues despite official phase-out (incomplete implementation in informal sectors), battery disposal and recycling activities, paints and coatings, and mining or industrial activities in the watershed. Lead's well- established neurotoxicity, particularly impacting children's cognitive development, makes even low-level exposures unacceptable (Lanphear et al., 2005). Blood lead levels in children consuming water with Pb concentrations measured here could approach or exceed 5 μg/dL, the reference level associated with decreased IQ and behavioral problems. Cadmium exceedance (mean 0.012 mg/L, 4-fold above guideline) is particularly concerning given cadmium's classification as a Group 1 human carcinogen. Sources may include phosphate fertilizers used in agriculture, batteries, industrial processes, and atmospheric deposition. Cadmium accumulates in kidneys and liver, causing tubular dysfunction at chronic low-level exposures. The calculated excess lifetime cancer risk (2.8×10−4) translates to approximately 3 additional cancer cases per 10,000 people over a lifetime—an unacceptable burden from a single environmental source. Iron elevation (mean 1.25 mg/L, 4.2-fold above guideline), while less toxic than Pb or Cd, creates aesthetic problems (discoloration, taste) and may indicate poor water treatment effectiveness. High iron is common in tropical soils and likely reflects natural geological sources combined with erosion and sediment transport. However, iron can enhance microbial growth in distribution systems and interferes with other water quality parameters. The spatial and seasonal patterns of heavy metals—increasing downstream and showing generally higher dry-season concentrations—clearly indicate anthropogenic pollution sources rather than purely natural origins. 4.3. Microbiological Contamination and Public Health Implications The pervasive fecal contamination documented in this study—with E. coli presents in 100% of samples at concentrations 28-1,650 times the WHO guideline—indicates critical failure of sanitation infrastructure and poses immediate health threats. The strong correlation between microbial indicators and organic pollution parameters (BOD, COD) confirms sewage as a primary contamination source. In many riverside communities in southeastern Nigeria, inadequate sewage collection and treatment leads to direct discharge of untreated wastewater into rivers. Open defecation practices in some areas and poor hygiene in food markets near the river likely contribute additional fecal loading. The public health implications are severe. Waterborne diseases including cholera, typhoid fever, hepatitis A, giardiasis, and cryptosporidiosis are endemic in regions with such contamination levels. Diarrheal diseases alone cause approximately 800,000 deaths annually in sub-Saharan Africa, with children under five bearing disproportionate burden (Bain et al., 2014). Communities consuming Ossah River water without adequate treatment face substantial acute disease risk. Even non-consumption uses including bathing, food preparation, and agricultural IIARD International Journal of Geography & Environmental Management irrigation present exposure pathways. The practice of using river water for irrigating vegetables sold in local markets creates a farm-to-fork contamination pathway particularly concerning for Vibrio cholerae and Salmonella species. Seasonal patterns showing higher dry-season contamination despite expected dilution effects during wet season suggest concentration of pollution in reduced water volumes and potentially increased human contact with water during dry periods when alternative sources fail. The 59-fold gradient in E. coli from upstream to downstream (28 to 1,650 MPN/100mL) clearly demonstrates cumulative human waste inputs along the river course, highlighting the need for distributed intervention rather than single-point solutions. 4.4. Integrated Assessment and Management Implications The integrated assessment combining physicochemical, heavy metal, microbiological, and risk- based approaches provides a comprehensive understanding of Ossah River's water quality challenges. Water Quality Index classification of 'poor' to 'very poor' for most stations, combined with Heavy Metal Pollution Index indicating moderate to high pollution, confirms that the river requires substantial remediation before water can be safely used for domestic purposes. The quantitative health risk assessment demonstrated HI>1 for adults and HI=10.6 for children, along with unacceptable carcinogenic risk, provides evidence-based justification for urgent intervention. Priority management interventions should include: (1) Sewage collection and treatment infrastructure development in riverside communities, starting with the most densely populated areas contributing largest loads. (2) Public awareness campaigns educating communities about contamination risks and promoting water treatment (boiling, filtration, chemical disinfection) before consumption. (3) Riparian buffer zone restoration to reduce erosion, trap sediments and nutrients, and provide natural filtration. (4) Regulation and monitoring of pollution point sources including commercial activities discharging to the river. (5) Improved agricultural practices reducing fertilizer runoff and promoting proper livestock waste management. (6) Regular water quality monitoring program establishing baseline conditions and tracking intervention effectiveness. The study limitations include temporal snapshots rather than continuous monitoring, focusing on selected parameters rather than comprehensive contaminant screening, and lack of source apportionment using isotopic or molecular markers. Future research should employ high- resolution monitoring during rain events to characterize runoff contributions, conduct epidemiological studies linking water quality to health outcomes in exposed populations, investigate sediment contamination as a secondary pollutant source, and pilot-test low-cost water treatment interventions suitable for resource-limited communities. Despite limitations, this integrated assessment provides essential baseline data for evidence-based decision-making. 5. Conclusion Integrated assessment of the Ossah River, southeastern Nigeria reveals severe water quality degradation posing substantial public health risks. Physicochemical analysis documents significant organic pollution with dissolved oxygen depletion, elevated BOD and COD, and excessive turbidity. Heavy metal contamination exceeds WHO drinking water guidelines for lead (8.5-fold) and cadmium (4-fold), with clear spatial gradients indicating anthropogenic sources. Microbiological analysis reveals pervasive fecal contamination with E. coli exceeding guidelines at 100% of sampling locations by 28-1,650 fold. Water Quality Index values (52-78) classify IIARD International Journal of Geography & Environmental Management water quality as 'poor' to 'very poor' at most stations, while Heavy Metal Pollution Index (mean 68.5) indicates moderate to high pollution. Quantitative health risk assessment demonstrates unacceptable non-carcinogenic risks particularly for children (HI=10.6) and excess lifetime cancer risk from cadmium (2.8×10−4). The findings conclusively demonstrate that Ossah River water is unsuitable for direct human consumption without treatment and poses immediate health threats through waterborne disease transmission and chronic toxic metal exposure. Urgent interventions including sewage infrastructure development, pollution source control, community education, and regular monitoring are essential to protect public health and restore this critical water resource. This study provides baseline data supporting evidence-based water resource management and public health policy in the region.