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Fertilizer wastewater contains a high concentration of ammonium and phosphate. One method of reducing the ammonium and phosphate contents is to recover them in the form of magnesium ammonium phosphate (MAP) or struvite (MgNH4PO4.6H2O). The objective of this experiment was to obtain the optimum mixing rate, pH, and molar ratio for struvite precipitation. A mixture of wastewater containing [Mg2+]:[NH4 +]:[PO4 3-] in molar ratios of 1:1:1, 1.5:1:1, and 2:1:1 was added to a 0.5-L beaker glass. Samples were then stirred under G.t values of 0.5 × 106, 106, and 1.5 × 106 for 60 minutes and left for 30 minutes for the sedimentation process. pH was set to 7.5, 8, and 8.5. Subsequently, the experimental results were compared with thermodynamic modelling using PHREEQC v3.0. The results showed that the optimum mixing rate was 158 rpm, which is equal to a G.t of 106; the optimum pH was 8.5 ± 0.2; and the optimum molar ratio of [Mg2+]:[NH4 +]:[PO4 3-] was 1:1:1. The removal percentage was 86.14% for ammonium and 98.98% for phosphate. Experimental results displayed a pattern similar to that predicted by the model. Additionally, the morphology of struvite shown by SEM-EDX and XRD analysis also demonstrated that struvite was formed in the precipitate.

Surabaya has become one of the cities in Indonesia with the largest volume of solid waste. One way to reduce waste generation in Surabaya City is through waste banks. The number of waste banks in Surabaya is 374 units since 2012, with 0.55 ton/day or a 0.05% reduction effort against total waste. The non-organic municipal waste potential that can be utilized is 40% and the total waste reduction for non-organic waste is 0.13%. The unit price of each type of solid waste is one of the main factors in people’s willingness to sell their solid waste. The higher the price of the waste, the more revenue they will earn. This research is focused in South Surabaya where the greatest number of waste banks is located. Based on typical mass balance analysis, the total waste that can be reduced is 20% for compostable waste and 18.24% for non-compostable waste. Meanwhile, based on research, the total waste is reduced by 10.16% for compostable waste and only 0.343% for non-compostable waste. The reduction potential occurring through the waste bank activities is 0.146% of the total generation of 237,801.9 kg/day. The reduction percentage needs to be increased so that the volume of municipal waste can be suppressed. Therefore, there must be an effort to improve the performance of waste banks or to increase the number of waste bank units.

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.