Trends in the recovery of phosphorus in bioavailable forms from wastewater

Abstract

Addressing food security issues arising from phosphorus (P) scarcity is described as one of the greatest global challenges of the 21st Century. Dependence on inorganic phosphate fertilisers derived from limited geological sources of P creates an urgent need to recover P from wastes and treated waters, in safe forms that are also effective agriculturally - the established process of P removal by chemical precipitation using Fe or Al salts, is effective for P removal but leads to residues with limited bioavailability and contamination concerns. One of the greatest opportunities for P recovery is at wastewater treatment plants (WWTPs) where the crystallisation of struvite and Ca-P from enhanced biological P removal (EBPR) sludge is well developed and already shown to be economically and operationally feasible in some WWTPs. However, recovery through this approach can be limited to <25% efficiency unless chemical extraction is applied. Thermochemical treatment of sludge ash produces detoxified residues that are currently utilised by the fertiliser industry; wet chemical extraction can be economically feasible in recovering P and other by-products. The bioavailability of recovered P depends on soil pH as well as the P-rich material in question. Struvite is a superior recovered P product in terms of plant availability, while use of Ca-P and thermochemically treated sewage sludge ash is limited to acidic soils. These technologies, in addition to others less developed, will be commercially pushed forward by revised fertiliser legislation and foreseeable legislative limits for WWTPs to achieve discharges of <1 mg P/L.

Anthropogenic global shifts in biospheric N and P concentrations and ratios and their impacts on biodiversity, ecosystem productivity, food security, and human health

“…The consensus indicates that “increasing the use and cycling efficiencies of P” will be the most effective approaches to prevent P scarcity for food production and reduce environmental problems involving P (Hanserud, Brod, Ogaard, Müller, & Brattebo, ; Melia, Cundy, Sohi, Hooda, & Busquets, ; Rahman et al, ; Suh & Yee, ; Weikard, ; Withers, Rodrigues, et al, ). The direct recovery of P from all types of waste may yield large proportions of previously used P, reducing the need to exploit and release novel sources of bioactive P into the P cycle (Withers, Doody, et al, ), where secondary fertilizers are produced using recovered P (Hanserud et al, ; Jedelhauser & Binder, ; Talboys et al, ; Weikard, ).…”

“…The recovery of P from human urine and feces may meet 22% of the total P demand (Mihelcic, Fry, & Shaw, ), but its success may be hindered by technological and politicoeconomic constraints. Precipitation with iron and aluminum salts is the simplest method to recover P from waste and water, but the resulting product has limited bioavailability and is a pollutant (Melia et al, ). The precipitation of P from wastewater as struvite is more promising (Melia et al, ), because the bioavailability of P in struvite as a fertilizer is high (Talboys et al, ), and transport costs between treatment plants and farmers is low (Jedelhauser & Binder, ).…”

“…Precipitation with iron and aluminum salts is the simplest method to recover P from waste and water, but the resulting product has limited bioavailability and is a pollutant (Melia et al, ). The precipitation of P from wastewater as struvite is more promising (Melia et al, ), because the bioavailability of P in struvite as a fertilizer is high (Talboys et al, ), and transport costs between treatment plants and farmers is low (Jedelhauser & Binder, ). Recovery capacity, however, is limited (approximately 25%) unless expensive chemical methods of extraction are applied (Melia et al, ).…”

Options for Improved Phosphorus Cycling and Use in Agriculture at the Field and Regional Scales

“…These obstacles may be addressed by subjecting wastes to biological, chemical, thermal, or physical processes that isolate relatively pure P‐rich compounds, destroy pathogens, and/or reduce bulk. A number of P recovery techniques have been described and evaluated in the literature (Yuan et al, 2012; Schoumans et al, 2015; Egle et al, 2016; Cieślik and Konieczka, 2017; Melia et al, 2017; Roy, 2017; Amann et al, 2018; Peng et al, 2018; Weissengruber et al, 2018; Muhmood et al, 2019; Walling et al, 2019). In assessing the relative value of various approaches to P recovery, factors deserving consideration include the proportion of P that is recoverable, the presence of contaminants in recovered products, energy requirements, environmental impact of the process, value of the recovered products as fertilizer, and cost—recognizing that trade‐offs between desirable characteristics may be necessary (Egle et al, 2016; Cieślik and Konieczka, 2017; Roy, 2017; Amann et al, 2018;).…”

Analysis of Bakery Sewage Treatment Process Options Based on COD Fraction Changes

“…The research on trends in the recovery of phosphorus in the bioavailable forms from wastewater has proven that other than in municipal WWTPs, struvite (a superior recovered P product in terms of plant availability) precipitation has recently been investigated in a broad variety of wastewater streams from the bakery production [Uysal et al 2014;Melia et al 2017].…”