Estimation of the Quantity of Biodegradable Volatile Solids in Waste Mixture in Khulna Applying a Three-Stage Composting Process

Abstract

In many developing countries, a large proportion of municipal wastes especially organic solid wastes and Faecal Sludge are not properly disposed of. Composting of Faecal Sludge (FS) and Organic Solid Waste (OSW) can contribute as an efficient waste management tool and allows recycling of nutrients into agriculture, thereby closing the nutrient circle. In this study, the temperature variation of the composting process and estimation of Initial Biodegradable Volatile Solids in three stages were investigated. Four sets of the initial waste mixture were prepared using Faecal sludge (FS) and organic solid wastes (OSW). FS and OSW were mixed at four different ratios for four sets namely 90:10, 85:15, 80:20, and 75:25 (FS:OSW). Organic solid waste was prepared according to waste proportion; vegetable wastes: food wastes: waste paper: sawdust as 40:35:10:15. Then composting tests were done using a series of reactors for four sets, according to a planned experimental program. Composting tests were achieved in three stages of 15–30 days duration each. Temperatures at each set and stage were continuously monitored. The mean maximum temperature of the first stage and the second stage tests was 61 and 57 °C, respectively. The range of BVS reduction in different first phase tests was 32–45% of the initial estimated BVS after 30 days duration. The total biodegradable volatile solids reduction was 83–89% after 63 days. The range of reduction is very narrow with a standard deviation of 2.78. Therefore, it can be concluded that all four sets of waste contain almost the same percentage of BVS depending on their VS content.