Publication Details
Abstract
This study investigates the feasibility of producing organomineral fertilizers based on Aznek phosphorite (AF) and activated sludge (AL) derived from biochemical wastewater treatment plants. The main objective was to determine the optimal component ratios and evaluate the effect of nitric acid activation on the transformation of phosphorus into plant-available forms. Laboratory experiments were carried out using AF:AL mass ratios ranging from 90:10 to 20:80 and nitric acid (55.6% HNO₃) dosages of 50–90% of the stoichiometric requirement relative to CaO content. The results showed that increasing acid dosage led to a decrease in total P₂O₅ content (from 13.16% to 10.44% at 90:10 ratio), while significantly enhancing the amount of assimilated P₂O₅ (from 6.07% to 8.51%). The relative availability of phosphorus increased up to 86.26% with increasing activated sludge content and acid dosage. A similar trend was observed for calcium, where assimilated CaO increased with acid treatment. The organic matter, including humic and fulvic acids, increased significantly with higher AL proportions, reaching up to 30.13%.