Characterization of grit generated at Lubigi Waste Water and Faecal sludge treatment plant for resource recovery potential.

Abstract

Grit, a wastewater and faecal sludge treatment by product, is normally disposed of at landfills, and when reused, the aim is usually to reduce disposal fees. The characterization of grit provides an opportunity to determine its appropriate reuse options, thereby providing a viable source of income and a reduction in disposal fees incurred. Therefore, this study focused on quantifying and determining the physical, chemical and microbiological characteristics of grit generated at Lubigi wastewater and faecal sludge treatment plant. We, distinctively, sampled grit that is brought in by the sewer system, grit brought by vacuum trucks and grit collected using manual FS collection systems to investigate if there was any variation in the characteristics due to the collection system used. Additionally, we sampled grit in both wet and dry season to further investigate the implication of seasonal variation on the characteristics of grit. The physical parameters considered were density, moisture content and particle size distribution. The chemical characteristics measured included pH, electrical conductivity, organic matter, nutrients, cation exchange capacity, and heavy metals while the microbiological parameters evaluated were faecal coliforms and helminths eggs. The results indicated that the variation of grit characteristics greatly depended on the collection system used (p<0.05) but was not significant (p>0.05) for all, when we considered the seasonal variation. Irrespective of the collection system used, grit had a high percentage of organic matter, cation exchange capacity and nutrients, and these will prove beneficial in the different reuse options selected. The potential risk of toxicity of heavy metals in grit was also evaluated. Faecal coliform counts were significant;1.1 ×104±4909.73 CFU/100ml grit from the sewer system, 1.2 ×104±6102.504 CFU/100ml grit brought by vacuum trucks, 8.5 ×103±2506.458 CFU/100ml grit collected using manual FS collection systems. Therefore, grit must undergo prior treatment before use.