Co-vermicomposting of Wastewater Treatment Plant Sludge and Yard Waste: Investigation of Operation Parameters

Abstract

Million tons of domestic wastewater treatment plant sludge is produced in each year. Since it increases the volume of the landfill area, the treatment of sludge with vermicomposting is an attractive approach. Vermicomposting of domestic wastewater treatment plant sludge with yard waste was carried out using Eisenia Fetida for 60 days. The effects of Bio-One™ (liquid microbial fertilizer), additives (different mature vermicomposts), recirculation and ventilation on decomposition rate of composting were investigated for composting mixtures. Temperature, moisture content (MC), organic matter (OM), pH, electrical conductivity (EC), total carbon (TOC) and total kjeldahl nitrogen (TKN) were monitored during the composting process. In addition, phototoxicity level and worm number changes of the mixtures were determined. C/N and OM value decreases ranged between 27.56–63.77% and 15.15–43.12%, respectively. It was concluded that vermicomposting process was faster than traditional composting process in terms of decomposition of organic matter. The result C/N ratio was more suitable to use it as soil remedial material in vermicomposting process. It has been shown that Bio-One™ addition has a positive effect on the acceleration of the process. It has been found that the process of recirculation some of the leachate formed during the vermicomposting process is an advantageous. It has been determined that mature vermicompost addition is an effective method. The final worm numbers were higher (except ventilation conditions) than the initial. The positive results of the plant growth tests on the final products in all cases may indicate that the products will not cause any toxic effect in the use as soil conditioning material.