Study of struvite crystallization from fertilizer industry wastewater by using fluidized bed reactor

The fertilizer industry produces wastewater containing 9815 mg/L of phosphates and 2558 mg/L of ammonium, which may cause eutrophication if untreated. Wastewater that contains a large amount of phosphate can become a potential source of phosphate which is depleting on a global scale. Fluidized bed reactors are an effective method of phosphate recovery by producing struvite crystals. This study evaluates the effects of the upflow velocity on the performance of the fluidized bed and analyzes the struvite that is recovered. The experiment was conducted in laboratory scale at room temperature. Fertilizer industry wastewater and MgCl2 were added into fluidized bed reactors at 0.014, 0.019, and 0.0024 m/s upflow velocity. The operating pH was 8.5±0.2. Inside the reactors was sand No. 30/60 that worked as a seed material. The result showed that fluidized bed reactors could recover phosphate up to 73% and ammonium up to 57% at 0.014 m/s upflow velocity. Increasing the upflow velocity at intervals of 0.005 m/s could decrease the phosphate recovery by 1-2% and ammonium by 3-4%. SEM-EDX analysis showed that products were attached to the seed material, which contained N, P, Mg, O, Ca, F, and Si as the main constituent elements. The recovered products contain 60.2% of struvite, which mainly works as a slow released fertilizer.