Bioconversion of coir ETP sludge: An eco-friendly path to circular economy

The accumulation of sludge from Effluent Treatment Plants (ETPs) in coir industries has become a serious concern, raising critical questions about the eco-friendly management of large volumes of coir industry ETP sludge in coir-producing countries like India. This study aimed to explore a viable solution for bioprocessing the sludge and assess its potential as a soil amendment. Based on the C: N ratio and the initial characteristics of the ETP sludge, cow dung, and poultry manure were identified as potential amendments for sustainable bioconversion. The mixture was inoculated with TNAU Biomineralizer, a specialized culture that aids in decomposition. The bioconversion experiment used six treatment combinations (T1 to T6) to monitor nutrient transformations. Compost from treatment T6 (50% Sludge + 25% Poultry Manure + 25% Cow Dung + TNAU Biomineralizer) exhibited a significant improvement in nutrient content. The efficacy of the composted sludge was further assessed through a pot culture experiment using the Amaranthus variety CO 6, where different proportions of the composted sludge were applied alongside recommended agricultural practices. The results revealed that treatment T8 (100% Composted Sludge + Silica Solubilizing Bacteria) and the recommended package of practices combined with 100% Composted sludge significantly enhanced growth parameters, including root length, shoot length, and the number of leaves, outperforming other treatments. This study highlights that the bioconversion of coir industry ETP sludge with organic amendments and TNAU Biomineralizer offers a sustainable and eco-friendly solution, presenting a promising approach to advancing the circular economy.