Transformation of technogenic waste based on water treatment sludge into granulated fertilizer

Abstract

Low-temperature transformation of technogenic waste, and water treatment sludge and fly ash of thermal power plants in particular, into long-acting fertilizers is a promising way to reduce their negative impact on the environment. We developed technology of waste utilization that includes determining the composition of the raw material mixture, mixing, granulation and drying of the fertilizer granules. It was stated that the components of the fertilizer should be mixed in the following ratio (wt.%): fly ash 4–6; CaO 20–25; zeolite clinoptiolite 15–20; sludge of water treatment of municipal sewage 50–55; and urea – the remainder. During the mixing of the components and their granulation some physical and chemical processes take place and heat releases; therefore to ensure the required moisture of the granules, they were dried at the temperature of 30–400C. The obtained porous granules of fertilizer contain (wt.%): total nitrogen 5.1–5.2; total potassium 0.34–0.35; total calcium 21.7; and ammonium nitrogen 0.6–0.7. Zeolite as an adsorbent promotes the gradual release of ammonium from fertilizer into the soil. The results of fertilizer testing showed that sunflower biomass was increased by 7–10% in case of using the fertilizer as compared with the soil without it.