Phosphorus recovery from urine and anaerobic digester filtrate: comparison of adsorption–precipitation with direct precipitation

Abstract

Hybrid anion exchange resin containing hydrous ferric oxide (HAIX-Fe) was used in column tests to remove phosphate (PO 4 ) from fresh urine, hydrolyzed urine, and anaerobic digester filtrate, and subsequently recover PO 4 as struvite IJMgNH 4 PO 4 ·6H 2 O) or potassium struvite IJMgKPO 4 ·6H 2 O) via precipitation in the spent regenerant. The recovery of PO 4 using the two-step adsorption-precipitation process was compared with direct precipitation in urine and anaerobic digester filtrate considering chemical requirements for precipitation and mineral purity. Following the saturation of HAIX-Fe resin with PO 4 from urine and anaerobic digester filtrate, up to 95% of the PO 4 was desorbed using caustic brine during the regeneration phase. The spent regenerants were more concentrated in PO 4 than the original urine and anaerobic digester filtrate due to recycling of the regeneration solution. Precipitation in the spent regenerants and original wastewaters (urine and filtrate) yielded 96.7-99.8% PO 4 recovery as struvite or potassium struvite. Direct precipitation in fresh urine and hydrolyzed urine was more efficient than precipitation in the corresponding spent regenerants based on lower chemical requirements. Precipitation in the spent regenerant from HAIX-Fe resin saturated with PO 4 from anaerobic digester filtrate produced a higher purity mineral than direct precipitation in the anaerobic digester filtrate.Environ. Sci.: Water Res. Technol. This journal is Phosphorus (P) is a pollutant, finite resource, and critical element in agriculture. As such, there is growing interest in P recovery from waste streams for beneficial use as fertilizer. The key findings of this research are new experimental data on (1) P adsorption from urine and anaerobic digester filtrate to resin under continuous-flow operation and corresponding regeneration efficiency, and (2) chemical requirements for and mineral purity of P precipitation in the spent regenerants from resin adsorption/desorption and original waste waters. The results of this research are generalizable to resource recovery from domestic and industrial waste streams, and are significant because they advance source-separated and decentralized approaches to wastewater management that aim to increase recovery of water, nutrients, and energy.

Synergistic Removal of Zinc and Copper in Greenhouse Waste Effluent by Struvite

“…Struvite (MgNH 4 PO 4 ·6H 2 O, MAP) can be recovered from nutrient-rich sources such as wastes and wastewaters to mitigate P content . The mineral product can subsequently be used as a sustainable source of phosphate fertilizer; − or disposed of if the goal is solely to reduce wastewater contamination by P. The recovery process and optimization thereof from both simulated , and actual wastes − has been assessed. However, the association of additional constituents in wastes with struvite is less well documented.…”

Ammonia recovery and fouling mitigation of hydrolyzed human urine treated by nanofiltration and reverse osmosis

“…Phosphorus adsorption to hybrid anion exchange (HAIX) resins would allow for targeted phosphorus recovery, and evaporation would produce potash, a potassium product. 20,63 Therefore, membrane treatment for ammonia recovery could be the first step in a full nutrient recovery process.…”

Development and validation of a novel modeling framework integrating ion exchange and resin regeneration for water treatment

“…Effluent samples were collected at predetermined times and analyzed for pH and PO 4 eP concentration. More information about the tests may refer to O'Neal and Boyer (2015). The parameters needed for the modeling are listed in Table 1.…”