Vegetated Treatment Systems for Removing Contaminants Associated with Surface Water Toxicity in Agriculture and Urban Runoff

Summary

This article summarizes the design attributes and the effectiveness of treatment systems that treat urban stormwater and agriculture irrigation runoff to remove pesticides and other contaminants associated with aquatic toxicity.

Abstract

Urban stormwater and agriculture irrigation runoff contain a complex mixture of contaminants that are often toxic to adjacent receiving waters. Runoff may be treated with simple systems designed to promote sorption of contaminants to vegetation and soils and promote infiltration. Two example systems are described: a bioswale treatment system for urban stormwater treatment, and a vegetated drainage ditch for treating agriculture irrigation runoff. Both have similar attributes that reduce contaminant loading in runoff: vegetation that results in sorption of the contaminants to the soil and plant surfaces, and water infiltration. These systems may also include the integration of granulated activated carbon as a polishing step to remove residual contaminants. Implementation of these systems in agriculture and urban watersheds requires system monitoring to verify treatment efficacy. This includes chemical monitoring for specific contaminants responsible for toxicity. The current paper emphasizes monitoring of current use pesticides since these are responsible for surface water toxicity to aquatic invertebrates.

Introduction

Surface water toxicity is prevalent in California watersheds and decades of monitoring have shown that toxicity is often due to pesticides and other contaminants¹. The primary sources of surface water contamination are stormwater and irrigation runoff from urban and agriculture sources. As waterbodies are listed as degraded due to contaminants and the toxicity is identified from urban and agricultural sources, water quality regulators partner with state and federal funding sources to implement practices to reduce contaminant loading. Green infrastructure is being promoted in California urban watersheds to reduce flooding and increase the recove....

Protocol

1. Urban Bioswale Efficacy Monitoring

1. Storm Water Sampling
   1. Sample 4 L of pre-treatment stormwater leaving the parking lot as it enters the bioswale inlet, and then 4 L of post-treatment stormwater as it leaves the bioswale through the 4" outlet drain.
   2. Using local weather predictions, collect samples at the beginning, middle, and end of the storm's hydrograph. Composite the samples to characterize runoff variability during the storm event.
   3. Collect 1.3 L samples by hand and composite them in a 4 L amber bottle. Collect inlet samples at several curb openings where storm water flows into the bioswale.<....

Results

Urban Bioswale Efficacy

During the 18.5 h of the storm, 1.52" of rain was recorded by the rain gauge, and this resulted in 50,490 gallons of water flowing from the parking lots into the bioswale. Of this total volume, 5,248 gallons were recorded by the outlet flow meter, resulting in a total infiltration of 90% of the stormwater that flowed into the bioswale. The bioswale reduced all of the chemicals monitored. Total suspended soli.......

Discussion

The practices described in this protocol are intended as final steps in an overall strategy to remove pollutants in agriculture irrigation and stormwater runoff. Use of bioswales and other urban green-infrastructure LID practices are intended as a final piece of the puzzle to remove contaminants in runoff before they reach adjacent receiving waters. This protocol emphasizes methods to monitor urban bioswales to determine treatment efficacy for removing toxicity associated with urban contaminants, with emphasis on current.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
HOBO tipping-bucket digital logger rain gauge	Onset Computer Co., Bourne MA, USA)	Onset RG3	Rain gauge
Mechanical geared pulse flow meter	Seametrics Inc., Kent WA	Seametrics MJ-R	Flow meter for measuring bioswale outlet flow
Filtrexx SafteySoxx	Filtrexx Co. - info@filtrexx.com	SafetySoxx	perforated synthetic cloth for granulated activated carbon and compost
Granulated activated carbon	Evoqua - Siemens Corp., Oakland CA	AC380	GAC for agriculture irrigation water treatment
Digital flow meters	Seametrics Inc. Kent WA	Ag2000; WMP101	Flow meters for agriculture irrigation treatment system monitoring
Data Loggers	Campbell Scientific Inc., Logan, UT	CR1000	Data loggers for recording flow data
Peristaltic pumps for composite sampling	Omega Engineering Inc. Stamford CT	Omegaflex FPU-122-12VDC	Pumps for composite sampling