Field Scale Demonstration of Fly Ash Amended Bioretention Cells for Stormwater Phosphorus Removal: A Review of 12 Years of Work

Abstract

In 2007, ten bioretention cells were constructed in Oklahoma as part of a full-scale technology project to demonstrate stormwater phosphorus reduction. The filter media used was amended with 5%, Class C fly ash by weight to increase phosphorus and heavy metal retention. In 2014, core samples were collected from four of the cells, and three were instrumented for continuous water monitoring for the following year. This paper will review the design, construction, computer modeling of phosphorus retention, and measured phosphorus removal after seven years of operation. Total phosphorus retained in the sampled cells showed reductions in effluent water concentrations of 68 to 75%, while total effluent mass reductions of 51 to 93% were achieved. Total phosphorus accumulation in the cells measured in cores ranged from 0.33 to 0.60 kg/year, which was somewhat greater than the annual calculated effluent reduction of 0.27 to 0.41 kg/year. While good, phosphorus retention was not as high as computer modeling predicted. Other research on the cells, including hydraulics, heavy metal adsorption, and microbial transport, is summarized. Experimental challenges with phosphorus extraction from samples are also discussed. All experience and results suggest that fly ash amendments are an effective option for phosphorus removal in bioretention cells.

Comparing Vegetation and Substrate Performances on Nutrient Removal and Biomass Establishment Using a Natural Swimming Pool Experiment

“…Similarly, wollastonite, a naturally occurring mineral that is also high in iron and aluminum oxide, showed good P removal capabilities in swimming and fishpond systems (82%-96% removal) (Fondu et al 2015) and vertical upflow columns of secondary wastewater (80%-96% removal) (Brooks et al 2000). However, even with very high P removal levels, the effluent P in most studies exceeded the FLL-suggested levels of 0.01 mgÁL À1 (e.g., 0.03 mgÁL À1 with fly ash-sand bioretention media blend) (Vogel et al 2021) and 0.015 mg•L À1 with sandy loam amended with 15% air-dried water treatment residual (Qiu et al 2019). In a few cases, sand and compost bioretention media mixed with activated alumina achieved 0.01 mgÁL À1 (Ali and Pickering 2023).…”

Scientific Evidence behind the Ecosystem Services Provided by Sustainable Urban Drainage Systems

“…However, bioretention performance can fluctuate [80] and can even increase the concentrations of pollutants [81] and nutrients [53]. Operativity can improve with age [82] and some modifications [83]; fly ash amendments improved microbial removal in bioretention cells [84] and are an effective option for phosphorus removal [85], as a retrofitted upflow filter [86]. Bioretention acts as both a nitrogen source and sink (by infiltration and plant uptake mainly) [87].…”