This abstract reports the results of a trial designed to recover struvite (MgNH4PO4●6H2O) and K-struvite (MgKPO4●6H2O) simultaneously in the form of a pelletized slow release NPK fertilizer directly from a synthetic wastewater stream. The experiment was conducted using a novel bench scale fluidized bed crystallization reactor designed to obtain sparingly soluble substances in the form of agglomerates. The reactor was operated continuously for the period of 150 hours. The nutrient content in the influent wastewater was modelled after a palm oil mill effluent and contained on average 40 mg/L N-NH3, 121 mg/L P-PO4, 3038 mg/L K, 445 mg/L Mg, and had pH of 5.06. The influent was injected into the reactor together with a solution of sodium hydroxide to increase the pH and trigger crystallization. The reactor influent and effluent were periodically sampled and analyzed. The data was subsequently analyzed using the PHREEQC chemical equilibrium software to determine supersaturation ratios and develop a mathematical model of the process chemistry. The effluent concentrations showed that 83% of P-PO4 and 45% of N-NH3 were removed from the influent. The reactor was harvested every 1-2 days to remove the agglomerates formed. The recovered product is shown in Figure 1. The pellets were spherical, hard, and had the size of 1-2 mm. Chemical and XRD analyses of the pellets showed that they contained on average 52% of K-struvite and 43% of ammonia struvite with the rest 5% being impurities of cattiite (Mg3(PO4)2●22H2O) and kovdorskite (Mg2PO4(OH)●3H2O). Moreover, both struvites coexisted as a solid solution. The results prove the possibility of obtaining these types of valuable products in the form of pellets directly from wastewater streams without additional processing and open new perspectives on nutrient recovery from municipal, agricultural, and industrial wastewater streams.

Simultaneous recovery of struvite and K-struvite from a synthetic wastewater stream as a pelletized slow release fertilizer

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.