Integrating chemical precipitation and membrane separation for phosphorus and ammonia recovery from anaerobic digestate

Abstract

This study focuses on developing and demonstrating feasibility of an integrated chemical precipitation and membrane filtration method for recovering phosphorus (P) and ammonia (NH 3 -N) in two separate streams from anaerobic digestate generated from municipal wastewater. Nutrient recovery from waste streams creates alternative raw material sources of fertilizers and offers opportunities for reduced energy usage and CO 2 emissions compared with their conventional production processes.Using both synthetic and real anaerobic digestates, the effects of ferrous dosage and precipitation pH on P recovery through vivianite precipitation was examined. Fe/P molar ratio 2.1 at circumneutral pH was found as an optimal condition for ~100% P recovery. The P-free digestate was further treated with polyelectrolyte-modified nanofiltration (NF) membranes to separate NH 3 -N and the organic constituents as a means of N recovery. The surface-modified membranes demonstrated ~2X NH 3 -N/ organic carbon selectivity versus commercial NF membranes. This integrated Fe-enabled chemical precipitation and membrane-based process demonstrates a unique approach to sustainably recover critical nutrients from wastewater.

Carbon Emission Calculations and Reductions in Membrane Water Treatment: A Review

“…Piash et al successfully recovered the nutrients phosphorus (P) and ammonia (NH 3 –N) from the anaerobic digestion solution produced by municipal wastewater by using a comprehensive method of chemical precipitation and membrane filtration . Studies have shown that the anaerobic membrane bioreactor (AnMBR)-biochar adsorption-RO process can achieve a 0.503 kWh/m 3 energy offset through biological carbon adsorption to recover ammonia, which is equivalent to reducing 498 g CO 2 /m 3 carbon emissions .…”

“…Piash et al successfully recovered the nutrients phosphorus (P) and ammonia (NH 3 −N) from the anaerobic digestion solution produced by municipal wastewater by using a comprehensive method of chemical precipitation and membrane filtration. 93 Studies have shown that the anaerobic membrane bioreactor (AnMBR)-biochar adsorption-RO process can achieve a 0.503 kWh/m 3 energy offset through biological carbon adsorption to recover ammonia, which is equivalent to reducing 498 g CO 2 / m 3 carbon emissions. 94 Shin et al used a fluidized anaerobic membrane bioreactor (AF-MBR) to ammoniate domestic wastewater to produce ammonium-rich effluent, which was then concentrated by the RO process, and finally, concentrated NH 4+ was efficiently recovered by stripping ammonia.…”