Treatment of UrbanTreatment of Urban WaterWater RunoffRunoff

Biofiltration using a Biofiltration using a BioswaleBioswale

Robert Ryan Robert Ryan UC Santa BarbaraUC Santa Barbara

11/30/0411/30/04

BioswalesBioswales

What is a Bioswale and why use one?What is a Bioswale and why use one?

How a Bioswale WorksHow a Bioswale Works

Results of Bioswale usageResults of Bioswale usage

Benefits of Bioswale use and the Benefits of Bioswale use and the AlternativesAlternatives

What is a Bioswale?What is a Bioswale?

Figure 1.1 [bren study]

Why Use a Bioswale?Why Use a Bioswale?

Ecologically sound treatment of Ecologically sound treatment of runoff. Includes:runoff. Includes:

HydrocarbonsHydrocarbonsHeavy MetalsHeavy MetalsSedimentSedimentNutrientsNutrientsAnd many more possibilitiesAnd many more possibilities

Would otherwise pollute Would otherwise pollute downstream water ecosystemsdownstream water ecosystems

Figure 1.2 [bren study]

How a Bioswale OperatesHow a Bioswale Operates

Channels runoff from Channels runoff from assigned watershedassigned watershed

Dimensions critical to Dimensions critical to efficient operationefficient operation

Heavy volume flow is Heavy volume flow is diverteddiverted

Figure 1.3 [bren study]

Water enters forebay Water enters forebay of Bioswale of Bioswale

Water enters backbayWater enters backbay

Sediments settleSediments settle

Phytoremediation Phytoremediation occursoccurs

Output exits outlet Output exits outlet pipe into natural or pipe into natural or constructed waterway constructed waterway

Figure 1.4 [bren study]

How a Bioswale Operates, continuedHow a Bioswale Operates, continued

PhytoremediationPhytoremediation

Breakdown in soil, or Breakdown in soil, or accumulation in shoots accumulation in shoots and leaves and leaves

Certain plants for certain Certain plants for certain contaminantscontaminants

Broad application (TNT)Broad application (TNT) Figure 1.5 [soil.edu]

Using plants to remove, transfer, or stabilize, Using plants to remove, transfer, or stabilize, contaminants in soil, sediment, and groundwater.contaminants in soil, sediment, and groundwater.

Results of Bioswale UseResults of Bioswale Use

Dramatic reduction of sediments Dramatic reduction of sediments Lower flow velocitiesLower flow velocities

Reduction of hydrocarbons, nutrients, and metals Reduction of hydrocarbons, nutrients, and metals EPA studies of Superfund sites: 30-70% decreases EPA studies of Superfund sites: 30-70% decreases

Mature plants more efficient at removalMature plants more efficient at removal

Efficiency increases with size of BioswaleEfficiency increases with size of Bioswale

High volume flow decreases efficiencyHigh volume flow decreases efficiency

Additional Benefits and AlternativesAdditional Benefits and Alternatives

Benefits:Benefits: Ecological PreservationEcological Preservation Flood controlFlood control Aesthetic ValueAesthetic Value Inexpensive in comparisonInexpensive in comparison

AlternativesAlternatives Stormceptor (Costly)Stormceptor (Costly) FossilFilter (high maintenance) FossilFilter (high maintenance)

ConclusionConclusion

Bioswales meet increasing demand for Bioswales meet increasing demand for mitigation measures to stop pollution from mitigation measures to stop pollution from urban environmentsurban environments

Bioswales Bioswales workwork SedimentationSedimentation PhytoremediationPhytoremediation