Reclaimed phosphorus commodity reserve from water resource recovery facilities—A strategic regional concept towards phosphorus recovery

Abstract

Despite all the right reasons for phosphorus (P) recovery, many water resource recovery facilities (WRRFs), especially for small WRRFs, cannot afford to implement P recovery technologies. This work systematically evaluated cost impacts of recovering P into fertilizer form from 80 major WRRFs in the Chicagoland area. Using a 20-year present worth analysis, results indicate that it would cost US$21 billion for all 80 major WRRFs to recover P into struvite fertilizer form. Based on unit cost analysis ($ per kg P recovered), P recovery from biosolids is cost-prohibitive due to high energy demand. P recovery from sludge liquor is economically viable but only up to 30% of the influent P load can be recovered. P recovery from sludge ashes is comparable with P recovery from sludge liquor or de-facto P recovery by biosolids land application from a cost perspective but it has the highest P recovery potential (up to 90% of the influent P loads) and lessens the increasing concern of transferring emerging contaminants from biosolids to crops through land application. This leads to a novel approach of a centralized, regional P recovery facility where WRRFs of all sizes can “dispose” of their biosolids for incineration and that P can be recovered as calcium phosphate from the sludge ashes and stored in a monofill as a commodity reserve for future use. This paper proved that the concept of building a commodity P reserve through a centralized P recovery facility is economically justifiable for all WRRFs within the region.