Potentials of Sludge from Drinking Water Treatment Plant for Use as Source of Soil Nutrients for Reclamation of Degraded Land

Abstract

The residuals from Gubi drinking water treatment plant are usually discharged directly into the nearby streams without any form of treatment. The decomposition of the organic materials contained in the untreated sludge has caused the production of malodorous gases and unsightly condition in the area. The disposal of this sludge in an environmentally friendly manner is therefore not only desirable but necessary. The aim of this investigation was to assess the feasibility of utilizing the residuals from Gubi water treatment plant as a source of nutrients for reclamation of degraded lands especially those arising from mining activities. The study was carried out at Gubi water treatment plant located in the vicinity of Gubi Dam water reservoir.Ten sludge samples were collected from each of the three clerifiers. Important sludge properties that are known to aid nutrients status of soil were analyzed using standard laboratory procedures. The means of various soil quality parameters recorded in the WTRs were 6.8, 20.06g/kg, 34.90g/kg, 1.65g/kg, 2.30g/kg, 13.45mg/kg, 2.50Cmol/kg, 2.10Cmol/kg and 28Cmol/kg for pH, Organic C, Organic Matter, K, Total N, Olsen P, Ca, Mg and CEC respectively. The means of all the parameters analysed falls within the ranges considered good for vegetation growth. The heavy metals concentrations recorded in the residual were 1.8mg/kg, 0.1mg/kg, 2mg/kg, 29mg/kg, 66mg/kg, 15mg/kg, 8.7mg/kg, 6.2mg/kg and 0.03mg/kg for As, Cd, Pb, Cu, Zn, Ni, Co, Cr and Hg respectively. The concentrations of all the metals did not exceed the acceptable threshold limits recommended by regulatory authorities. Considering the enormous amount of plant nutrients and absence of excessive toxic metals in Gubi WTRs, it is safe to conclude that the residual can be use as a source of soil nutrients for reclamation of degraded land.

Key words: Sludge, Soil Nutrients, Degraded Land, Reclamation