Balancing Hydraulic Control and Phosphorus Removal in Bioretention Media Amended with Drinking Water Treatment Residuals

Abstract

Green stormwater infrastructure such as bioretention can reduce stormwater runoff volumes and trap sediments and pollutants. However, bioretention soil media can have limited capacity to retain phosphorus (P) or even be a P source, necessitating addition of P-sorbing materials. We investigated the potential trade-off between P removal by drinking water treatment residuals (DWTRs) and hydraulic conductivity to inform the design of bioretention media. Batch isotherm and flow-through column experiments showed that P removal varied greatly among three DWTRs and across methodologies, which has implications for design requirements. We also conducted a large column experiment to determine the hydraulic and P removal effects of amending bioretention media with solid and mixed layers of DWTRs. When DWTRs were applied to bioretention media, their impact on hydraulic conductivity and P removal depended on the layering strategy. Although DWTR addition in solid and mixed layer designs improved P removal, the solid layer restricted water flow and exhibited incomplete P removal, while the mixed layer had no effect on flow and removed nearly 100% of P inputs. We recommend that DWTRs be mixed with sand in bioretention media to simultaneously achieve stormwater drainage and P reduction goals.

Stormwater subsurface gravel wetland hydraulics, phosphorus retention, and chloride dynamics in cold climates

“…For example, aluminium-based drinking water treatment residuals have been shown to enhance the P sorption capacity of bioretention media. 55 Therefore, these materials or others with high P sorption capacity should be investigated as an ingredient in SGW soil mixtures to reduce PSR M3 , increase capacity to sorb dissolved P loaded directly or released from plant litter via mineralization, and in turn reduce the risk of dissolved P export long-term.…”

Field Application of Spent Lime Water Treatment Residual for the Removal of Phosphorus and other Pollutants in Urban Stormwater Runoff

“…Contact time is an important design parameter for P removal structures because it affects treatment efficiency and the chemical properties of treated stormwater [18,36]. The contact time (t c ) between stormwater and spent lime DWTR at a given 10-min time interval (i) was calculated using (Equation ( 1)):…”

“…Hydraulic conductivity may be further reduced as precipitants and amorphous minerals reduce the effective porosity, potentially causing clogging [65]. Thus, the physiochemical properties of the filter media are key to performance in stormwater BMPs, with the ideal media having coarse particle sizes, high hydraulic conductivity, and high particle surface area [36].…”

“…A third key design consideration is the fact that most P removal structures are required to operate under variable flow and P loading conditions (i.e., low to very high). This fact is important because many laboratory studies of P sorption use high P concentrations and long contact times, which are not representative of field conditions [36].…”

Nitrogen removal performance in roadside stormwater bioretention cells amended with drinking water treatment residuals

“…DWTRs are promising amendments for bioretention media due to their high concentrations of metal (hydr)oxides and associated P sorption capacity (Marvin et al., 2020). A growing body of research exists investigating DWTRs as a means for enhancing P sorption in bioretention and other soil systems (Agyin‐Birikorang et al., 2007; Ament et al., 2021; Babatunde et al., 2009; Liu & Davis, 2014; Makris et al., 2004; Shrestha et al., 2019). However, to our best knowledge, there are currently no studies that explicitly investigate the effects of DWTR amendment on N removal performance in field‐scale bioretention systems.…”