Biostabilization of fecal sludge and tannery liming sludge: A novel approach

Fecal sludge and tannery liming sludge management is essential for humans and the environment. The emitted amount of waste from two industries is reduced in composting leading to value-added products. This research focused on the effectiveness and feasibility of co-composting fecal sludge and hair-burning liming sludge from tannery. Fecal sludge was intermittently mixed with hair-burning liming sludge which also consisted of chicken manure and sawdust. Five piles (Pile 1, Pile 2, Pil3, Pile 4, and Pile 5) indicated respectively as P#1, P#2, P#3, P#4, and P#5, contained various ratios of composting materials were mixed, piled onto a horizontal bamboo frame, and observed for 120 days. To ensure a suitable oxygen supply, the composting piles were turned on in the thermophilic stage so that pathogens could not survive. The highest temperatures in the thermophilic stage were 39.0°C, 49.2°C, 55.7°C, 41.7°C, and 51.3°C. These referred to the respective piles P#1, P#2, P#3, P#4, and P#5. The Dewar stability index confirmed the stability of each composting pile, and the maximum degradation was found for P#3. The metals chromium (Cr), zinc (Zn), lead (Pb), iron (Fe), and nickel (Ni) in the final compost were found to be 38.1, 144.7, 15.1, 450.5, and 22.7 mg/kg, respectively. TCLP results reveal only an insignificant amount of metal leaching. Fecal coliform of the compost was below the standard level; Helminth eggs and Salmonella spp. were absent. SEM micrographs reflect the decomposition of composting materials. The maximum germination index and germination capacity of compost pile P#3 for compost-soil ratio 1:0 and 1:1 were 90%-92.8% and 100%, respectively. The present approach produced nutrient-enriched compost from fecal sludge and hair-burning liming sludge from a tannery emerges as a suitable solution for reducing solid wastes.