Optimization of Struvite Batch Crystallization Reactor for Recovery Process from Urea Fertilizer Plant Wastewater

Abstract

The present paper reports removal of ammonium nitrogen concentration from a urea fertilizer plant wastewater through struvite crystal (NH4MgPO4.6H2O) formation. The aim of this research was to obtain the optimum conditions of mole ratio, pH value, and crystallization time in NH4+–N recovery by producing slow release fertilizer material (struvite crystal). In this work, a source of Mg and P was magnesium chloride (MgCl2) and potassium dihydrogen phosphate (KH2PO4) solution, respectively. Experiment was designed in a batch crystallizer-reactor at different mole ratio of Mg2+, NH4+ , and PO43−. The reactor volume was 500 ml equipped with an agitator. The study was conducted at a room temperature. The effect of Mg2+:NH4+ :PO43− mole ratio was studied, it was found that at a molar ratio of Mg2+:NH4+ :PO43− (1:1:1) and pH of 9, the ammonium removal was obtained around of 90.48%. Recovery for NH4+ increased with increasing Mg2+ concentration. The removal achieved around 93.66% at the ratio Mg2+:NH4+ :PO43− of 1.2:1:1. Moreover, the obtained struvite crystals were analyzed using a SEM to indicate that the shape and the size of struvite crystal.