Mass Balance Model for Sustainable Phosphorus Recovery in a US Wastewater Treatment Plant

Abstract

In response to limited phosphorus (P) reserves worldwide, several countries have demonstrated the prospect of recovering significant amounts of P from wastewater treatment plants (WWTPs). This technique uses enhanced biological P removal (EBPR) to concentrate P in sludge followed by chemical precipitation of P as struvite, a usable phosphate mineral. The present study models the feasibility of this enhanced removal and recovery technique in a WWTP in Arizona with design parameters typical of infrastructure in the United States. A mass balance was performed for existing treatment processes and modifications proposed to estimate the quantity of P that could be recovered under current and future flow conditions. Modeling results show that about 71 to 96% of the P being lost potentially could be recovered as struvite. About 491 ± 64 t yr of struvite may be recovered after process modification, which corresponds to $150,000 ± $20,000 yr in P sales to fertilizer industries. The process was projected to be economically feasible, with a payback period of 45 ± 30 yr in the studied WWTP and a much shorter duration of 3 ± 1 yr for WWTPs already using an EBPR process. Furthermore, modeling results suggest that P recovery can improve the quality of biosolids by favorably reducing the P:N ratio. Implementation of this strategy at US WWTPs may increase national security by reducing dependence of limited P resources. Considering all aspects of the recovery process with respect to environmental, economic, and social implications, the examined technique is concluded to represent a cost-attractive and sustainable method for P management in US WWTPs.

Mass fluxes of nitrogen and phosphorus through water reclamation facilities: Case study of biological nutrient removal, aerobic sludge digestion, and sidestream recycle

“…Similar mass balance studies at wastewater treatment plants have been conducted previously for applications such as calibrating process simulation models (Nowak, Franz, Svardal, Müller, & Kühn, 1999), estimating the potential for phosphorus recovery (Venkatesan, Hamdan, Chavez, Brown, & Halden, 2016), and determining the fate of heavy metals (Karvelas, Katsoyiannis, & Samara, 2003) or fluorochemicals (Schultz et al, 2006). The current effort described herein has been undertaken through a University-Utility Partnership between the University of South Florida and Hillsborough County Public Utilities, as described elsewhere (WEF/WRF/LIFT, 2017).…”

Soil in the City: Sustainably Improving Urban Soils

“…The amount of P recovered from this WWTP could fertilize about 2000 ha of agricultural land. The study conducted by Venkatesan et al (2016) shows that there is a potential of recovering between 20 and 50% of excreted P in the form of struvite; the process was projected to be economically feasible for WWTPs with a payback period of ∼3 yr. Furthermore, for every 1 t struvite production, approximately 10 t CO 2 equivalent emissions would be offset compared with conventional fertilizer production.…”

“…These technologies offer sustainable option for reducing P-loading in receiving waters as well producing biosolids with relatively favorable P/N ratio. In their study, Venkatesan et al (2016) modeled the feasibility of P recovery from a typical WWTP serving a population of 160,000 in Arizona. Modeling results showed that about 71 to 96% of the P being lost in effluent discharge could be recovered, resulting 491 ± 64 t yr −1 of struvite fertilizer.…”

Modeling the pH-mediated extraction of ionizable organic contaminants to improve the quality of municipal sewage sludge destined for land application

“…Incineration of MSS, on the other hand, involves high operational costs and concerns over toxic flue gas emissions (Lundin et al, 2004). Recent efforts in using MSS as a resource for energy production and nutrient recovery have increased the beneficial value of MSS (Rulkens, 2007; Venkatesan et al, 2015; Wang et al, 2008). Beneficial use of MSS already is applied to over half of the total U.S. sewage sludge mass and this trend is expected to increase in future.…”