Impact of Abattoir Wastewater Discharge on Physicochemical, Microbial and Human Health Risks of Chokocho River, Rivers State, Nigeria

Abattoir operations in many developing regions discharge untreated wastewater into surface waters, causing severe environmental pollution and public health risks. The Chokocho River in Etche Local Government Area, Rivers State, Nigeria, receives such effluent from abattoirs, yet data on its impacts remain limited. This study assessed the physicochemical, microbial, ecological, and human health implications of abattoir wastewater discharge on the river. Water samples were collected from four sites: the raw effluent discharge point, 50 m downstream (ST1), 100 m downstream (ST2), and a control site at Elelenwo River. Parameters included physicochemical indicators, heavy metals, and microbial counts, with risks evaluated via the Potential Ecological Risk Index (RI) and health models. Results revealed extreme pollution at the discharge point. Turbidity hit 1228 NTU (WHO guideline: 5 NTU), and BOD reached 37.84 mg/L, reflecting high organic loads from blood, fats, and fecal matter. Levels declined downstream (ST1 BOD: 10.55 mg/L; ST2: 6.49 mg/L) but stayed elevated, while the control site showed 12.99 mg/L BOD, hinting at other upstream sources. Heavy metals often exceeded WHO limits: Pb peaked at 0.589 mg/L in effluent (~59× the 0.01 mg/L guideline), with As (0.015 mg/L) and Cr (0.019 mg/L downstream) also elevated; Zn was higher at the control (0.089 mg/L), suggesting non-abattoir contributions. Ecological assessment showed very high risk, with RI = 2985.17 at the effluent site (lead ErF = 2945 dominating). Human health risks were alarming: non-carcinogenic effects were pronounced in children (Pb HQ = 98.25; combined HI = 101.7) versus adults (HI = 43.5). Chromium posed carcinogenic risk (ILCR = 5.43 × 10⁻⁴, above USEPA's 1 × 10⁻⁴ threshold). Microbial contamination was severe, with Total Coliform and Heterotrophic Bacteria exceeding WHO's 0 CFU/100 mL at impacted sites, yielding near-100% infection probability upon exposure. Untreated abattoir effluent has heavily degraded the Chokocho River, threatening ecosystems and communities. Urgent actions, wastewater treatment, stricter regulations, routine monitoring, and health education is critical to safeguarding the river and public health.