Leachate characterization and assessment of surface and groundwater water qualities near municipal solid waste dump site at Okuvo, Delta State, Nigeria

Abstract

The paucity of standard engineered landfills in Nigeria has given rise to the proliferation of open waste dumpsites. The environment can be impacted negatively by leachates from these dumpsites if not properly managed. This study aimed at assessing the characteristics of municipal solid waste leachate and its contamination potential on surface and groundwater. Leachate, groundwater and surface water samples were collected from refuse dump site, saver pit, borehole and river in the vicinity of the Okuvo refuse dump site. Physical parameters, oxygen demanding parameters, nutrients and heavy metals were investigated using standard laboratory procedures. Results obtained were compared with standards from national regulatory agencies. The BOD/COD ratio for the leachates varied from 0.34 to 0.52, indicating high organic content.  Surrounding water bodies show low pollution from the discharged leachates as indicated by unobjectionable odour and colour, pH (6.55-7.20), DO (3.02-6.60mgl^-1), BOD (0.55-2.90mgl^-1), COD (1.98-7.45mgl^-1), phosphate (0.18-0.52mgl^-1) and nitrate (0.06-0.24mgl^-1) results. Heavy metals concentrations range from 0.011-0.028mgl^-1, 0.005-0.018mgl^-1, 0.032-0.096mgl^-1, 0.001-0.008mgl^-1, 0.001-0.003mgl^-1 and 0.010-0.018mgl^-1 for Ni, Cr, Fe, Pb, Cd and Mn. Concentrations values for Arsenic and mercury were <0.001mgl^-1. These were all within the country’s regulatory limits except few recorded concentrations of nickel where concentrations were observed to be slightly higher. These observed results may be as a result of the young age of the dumpsite. Some proactive remedial actions were suggested to curtail future environmental and health implications posed by the dumpsite. The study concludes that in spite of absence of pollution, the groundwater beneath the landfill has the tendency of being polluted in the distant future except the refuse dump site is upgraded to an engineered standard landfill with effective monitoring protocols put in place.

Keywords: Landfills, Solid waste, Contamination, Surface and Water pollution