Recovery of Ammonium Nitrogen and Phosphate from the Piggery Wastewater as Struvite and Its Assessment for the Reduction of Water Pollution Through the Field Test

Abstract

Excess N and P from the livestock manure applied to farm-lands, have entered the water systems and poses a serious threat to the natural environment. Consequently, there has been recent awareness towards the management of live-stock manure and its related fields. In this study, piggery wastewater was collected from a piggery in Pohang city, Korea. At 800℃, thermal decomposition of a natural stone, magnesite (MgCO 3 ), yielded powered MgO with particle sizes ranging between 10 to 100 µm. Furthermore, NH 4+ -N and PO 43– -P were recovered as struvite precipitates from the piggery wastewater, by adjusting the pH with MgO and H 3 PO 4 . At pH 10, the recovery efficiencies of NH 4+ -N and PO 43– -P were found to be 86.1% and 94.1%, respectively. Using an X-ray Diffractometer (XRD), the struvite in the precipitate was confirmed to be consistent with standard pure struvite. Further, the purity of the stru-vite precipitate was analyzed using an energy dispersive X-ray (EDX) and thermal gravimetry-differential thermal analysis (TG-DTA), and found to be between 79.2% and 93.0%. Additionally, struvite-containing piggery waste-water and sawdust were mixed in a weight ratio of 2.5:1 and processed into a mature compost. The newly manufactured compost passed all quality standards required for first-class graded livestock composts. Moreover, this compost was sprayed directly onto the soil at the test site, and various parameters of the soil’s effluent, such as total organic carbon (TOC), total nitrogen (T-N), total phosphorus (T-P), and dissolved oxygen (DO), were analyzed and measured. Based on these results, it is determined that the newly manufactured compost can more significantly reduce water pollution than commercial compost.