Factors Affecting the Intensity of Color Released In Water Extract by Soil-Like Material Obtained From Mining of Old MSW Dumps

This paper presents the analysis of release of dark-colored leachate from soil-like material (SLM) mined from three old municipal solid waste dump sites of before its reuse as earth-fill. If SLM is to be re-used in earth-fill, the release of dark-colored leachate can cause coloration of the surrounding water bodies. Laboratory studies (in terms of single batch leaching) were undertaken to quantify the release of color and identify the source/cause of the phenomenon. Influence of repeated washing, heating at various temperature, and aeration of SLM on the intensity of release of color was identified. Correlation of color with total dissolved solids and volatile dissolved solids was also established. The intensity of color of water extract from SLM in platinum cobalt unit (PCU) was found to in the range of 288-712, 465-485 and 740-925 from Delhi, Kadapa and Hyderabad dumpsites respectively. In contrast, the intensity of color in water released from local soils was found to be 25-30 PCU. Organic content present in SLM was identified as the primary cause for the release of color. Results showed that large quantity of water (70-120 ml per gram of SLM) was required to cause significant reduction in the intensity of color. Heating of SLM to 500°C was observed to reduce the color very effectively but short-term aeration of SLM did not reduce color. Good correlation of volatile dissolved solids with color was observed which further confirmed the organic content as the main reason for the release of dark-colored leachate from SLM.