Physicochemical characterization of an artificial pond receiving leachate influx at Aba-Eku dumpsite, Ibadan, Nigeria

Abstract

El tratamiento de lixiviados debe ser adecuado para disminuir el impacto ambiental. En la localidad de Aba-Eku, Ibadan al suroeste de Nigeria, se encuentra una laguna de lixiviados donde se efectúa un tratamiento correcto. Durante enero del 2003 y setiembre del 2004 se tomaron muestras comparativas mensuales a la laguna y a las aguas subterráneas de: pH, TSS, solidos totales, conductividad y DQO. Se analizaron con métodos del Departamento de Salud Pública de los Estados Unidos. El calcio y el magnesio se determinaron por medio del plasma de acoplamiento inductivo, aniones seleccionados y el amoníaco por cromatografía iónica. Los coeficientes de prueba T y la correlación se utilizaron para el análisis de datos. Los resultados fueron los siguientes: pH: 8,21, SST: 144,94mg/l, sólidos totales: 1377,67mg/l, conductividad: 2466,00 us/cm y COD: 57,63mg/l fueron significativamente elevados (p<0,05) por encima del testigo, pH: -7,79; TSS: 42,96mg/l, sólidos totales: 119,52mg/l, conductividad: 153,09us/cm y COD: 9,80mg/l. El calcio y magnesio en lixiviados difieren significativamente del testigo. Metales en el lixiviado y el testigo no mostraron diferencias significativas con excepción del hierro (5,27; 0,82mg/l), manganeso (2,31; 0,04mg/l) y el cadmio; (0157, 0,03mg/l). Plomo, cobre, zinc, cromo y níquel no fueron significativamente diferentes del testigo. Cloruro (597,98; 5,24mg/l), nitrato (12,3; 2,35mg/l) y el sulfato - 118,86; 3,09mg/l) en el lixiviado y el testigo, sin embargo diferían significativamente y no se detectó fosfato. El amonio se correlacionó negativamente con el nitrato (-0,608) y sulfato (-0,676) p <0,05. ABSTRACT Proper leachate treatment is necessary to avoid adverse environmental impact. An artificial pond receiving leachate influx from the Aba-Eku dumpsite, Ibadan, South-Western Nigeria, was characterized to provide baseline information for appropriate treatment. Pond leachate and comparative groundwater control were sampled monthly between January 2003 and September 2004. The pH, TSS, total solids, conductivity and COD were analyzed using American Public Health methods. Calcium, magnesium and selected metals were determined using Inductively Coupled Plasma; selected anions and ammonia were determined using Ion Chromatography. T-test and correlation coefficients were used for data analysis. Results: pH: 8,21, TSS:1 44,94mg/l, total solids:1377,67mg/l, conductivity:2466,00us/cm and COD:57,63mg/l were significantly elevated (p<0,05) above control; pH: -7,79; TSS: 42,96mg/l, total solids:119,52mg/l, conductivity:153,09us/cm and COD: 9,80mg/l. Calcium and magnesium in leachate differed significantly from control. Metals in leachate and control showed no significant differences except for iron (5,27; 0,82mg/l); manganese (2,31; 0,04mg/l) and cadmium; (0,157; 0,03mg/l). Lead, copper, zinc, chromium and nickel were not significantly different from control. Chloride (597,98; 5,24mg/l), nitrate (12,3; 2,35mg/l) and sulphate – 118,86; 3,09mg/l) in leachate and control however differed significantly, phosphate was not detected. Ammonium correlated negatively with nitrate(-0,608) and sulphate(-0,676) p<0,05. Attenuation processes reduced contaminant levels. Similarities in metal content may be due to increased leachate pH which consequently reduced metal solubility. Suspended solids and chloride were parameters of concern. Nitrates and sulphates increased in the wet season probably due to ammonium oxidation reactions. There is minimal need for treatment. However, polishing of leachate effluent via physico-chemical methods may be considered.