Multiple Pathways to Bacterial Load Reduction by Stormwater Best Management Practices: Trade-Offs in Performance, Volume, and Treated Area

Abstract

Stormwater best management practices (BMPs) are implemented to reduce microbial pollution in runoff, but their removal efficiencies differ. Enhanced BMPs, such as those with media amendments, can increase removal of fecal indicator bacteria (FIB) in runoff from 0.25-log to above 3-log; however, their implications for watershed-scale management are poorly understood. In this work, a computational model was developed to simulate watershed-scale bacteria loading and BMP performance using the Ballona Creek Watershed (Los Angeles County, CA) as a case study. Over 1400 scenarios with varying BMP performance, percent watershed area treated, BMP treatment volume, and infiltrative capabilities were simulated. Incremental improvement of BMP performance by 0.25-log, while keeping other scenario variables constant, reduces annual bacterial load at the outlet by a range of 0-29%. In addition, various simulated scenarios provide the same FIB load reduction; for example, 75% load reduction is achieved by diverting runoff from either 95% of the watershed area to 25 000 infiltrating BMPs with 0.5-log removal or 75% of the watershed area to 75 000 infiltrating BMPs with 1.5-log removal. Lastly, simulated infiltrating BMPs provide greater FIB reduction than noninfiltrating BMPs at the watershed scale. Results provide new insight on the trade-offs between BMP treatment volume, performance, and distribution.

Biochar-augmented biofilters to improve pollutant removal from stormwater – can they improve receiving water quality?

“…Watershed-scale implementation of SCMs has been investigated regarding water quantity, but fewer studies have investigated the impacts of watershed-scale installation of SCMs on water quality, 102,103 and only two studies to date have looked at watershed scale effects of biochar-augmented biofilters. 104,105 Studies have generally found that installation of biofilters results in improved water quality at the watershed scale, but these results vary in extent depending on watershed size, climate, impervious area treated, and pollutants of concern. 102,103 For example, Bedan and Clausen 106 monitored a watershed in the US state of Connecticut and found SCM installation decreased storm flows, nitrogen, Pb, and Zn loads compared to a paired control watershed without SCMs, while total P and total suspended solids loads increased relative to the control watershed.…”

“…108 Existing studies show pollutant reduction is often correlated to the hydrologic processes such as infiltration and volume reduction, and not necessarily the biogeochemical processes occurring within the filters. 102,104 Surface water quality is regulated at the watershed scale, and biofilters can be used to help reach compliance, but the extent of installation is often substantial and costly. For example, Gagrani et al 109 evaluated the efficacy of using backyard biofilters in conjunction with the existing SCM network to reach mandated pollutant load reductions of 85% for TSS and 70% for total P (in comparison to predevelopment conditions) for a watershed in the southeast United States.…”

“…For example, in the Dominguez Channel watershed (184 km 2 , 71% impervious), despite treating 90% of the watershed runoff with biofilters, Cu only reached 12.5% and Zn only reached 25% compliance. 111,112 Given the challenges in meeting water quality requirements with conventional SCMs, Wolfand et al 104 investigated how improving biofilter performance with the addition of biochar may impact water quality at the watershed scale. Implementation of biochar-augmented biofilters was examined using the Ballona Creek watershed as a case study.…”

Co-Design of Engineered Hyporheic Zones to Improve In-Stream Stormwater Treatment and Facilitate Regulatory Approval

“…Vogel et al [48] discuss geomedia mixes and BMP design modifications to target specific pollutants; Wolfand et al [49] show geomedia can improve water quality compliance for load-and concentration-based standards.…”

Pollutant Loading Analysis of Suspended Solid, Nitrogen and Phosphorus at Bertam Catchment, Cameron Highlands using MUSIC

“…The degradation of water quality and flooding problems could be mitigate by introduce a promising solution with the application of suitable stormwater Best Management Practices (BMPs) at the catchment [9]. This judgment of using Stormwater facilities/BMPs depends on not only relevant theoretical considerations but also a significant amount of practical experience and the availability of relevant data, as well [10]. Determining the nature and magnitude of a problem is a prerequisite to planning and development of cost-effective solutions [11].…”