Physicochemical Characterization and Spatial Variability of Leachate and Its Environmental Implications at Aluu Municipal Dumpsite, Port Harcourt, Nigeria

Abstract

Background: Leachate from open, unlined landfills, particularly in tropical regions like the Niger Delta, contains high levels of toxic and poorly biodegradable contaminants. Its infiltration into soil and water systems poses serious environmental and public health risks. Aim: This study aimed to characterize the physicochemical composition of leachate, determine its spatial variability, and evaluate its environmental implications at the Aluu municipal dumpsite, Port Harcourt, Nigeria. Study Design:  This study employed a field-based sampling and laboratory analytical design combined with geospatial and statistical analysis. Place and Duration of Study: The study was conducted at the Aluu municipal dumpsite, Obio/Akpor Local Government Area, Rivers State, Nigeria. Sampling and laboratory analyses were carried out over a period of three months. Methodology: Leachate samples were collected as grab samples from four spatial locations within the dumpsite corresponding to the cardinal directions (North, South, East, and West). Samples were analyzed for pH, total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD₅), and chemical oxygen demand (COD) following Standard Methods (APHA, 2017). COD/BOD₅ ratios were computed to assess leachate biodegradability. Spatial distribution patterns were evaluated using Golden Surfer software (version 20), and descriptive statistics including coefficient of variation (CV%) were calculated to quantify spatial variability. Results: Results revealed significant spatial variation in leachate quality across the dumpsite. TDS ranged from 747 to 1,579 mg/L, with values at L1 and L4 exceeding FAO irrigation water quality thresholds. BOD₅ values ranged from 7.45 to 18.6 mg/L, and COD ranged from 90 to 2,156 mg/L, all exceeding NESREA effluent discharge limits. pH (7.50–8.15) and TSS (0.001–2.1 mg/L) remained within acceptable limits. COD/BOD₅ ratios (12.1–265.5) confirmed the leachate as intermediate to stabilized and predominantly non-biodegradable. Spatial analysis identified the eastern and northern sections as primary contamination hotspots, with COD exhibiting the highest spatial variability (CV = 105.4%). Conclusion: The leachate from the Aluu dumpsite poses significant environmental risks due to elevated organic and chemical loads, particularly in the eastern and northern zones. Given the high COD/BOD₅ ratios indicating poor biodegradability, physicochemical treatment approaches including coagulation-flocculation, Fenton oxidation, and membrane bioreactors are recommended, with estimated treatment costs ranging from USD 0.50 to 8.00/m³ depending on the technology applied. Multi-seasonal sampling incorporating ammonia, nitrate, and heavy metal analyses is recommended for future studies.