ELEC WASHINGTON STORMWATER CONFERENCE

STORMWATER TREATMENT AND

TECHNOLOGY

Neil Alongi, P.E. – Maul Foster & AlongiFebruary 7, 2011

Hierarchal approach to compliance Large and small site challenges Characterization Treatment BMPs: Selection

Considerations Cost of compliance- Reasonably

attainable? Thoughts about the future of Treatment

BMPs

DISCUSSION OVERVIEW

Treatment BMPs = Capital + Operational Costs e.g. Active Treatment

Structural BMPs = Capital costs e.g. materials isolation

Operational BMPs e.g. Pavement sweeping

BMP HIERARCHY APPROACH

STRUCTURAL BMP EXAMPLE

Large site = High volumes and flow rates Flow attenuation a critical factor Complexity of contaminants challenging

TREATMENT BMPs – SITE SIZE

Site space limitation usually results in additional costs to manage & treat

May force facilities underground Operations personnel may be limited

SMALL SITE STORMWATER CHALLENGES

Sites with little available space = underground storage + high rate treatment system Underground storage = high cost Shifts costs to high rate treatment

systems Cost balance between these two

components

QUANTITY CONTROL

UNDERGROUND STORAGE

Like any site, must first characterize contamination and understand goals Check permit parameters Check parameters that may impact

treatment, e.g. dissolved metals Internal monitoring

Diverse contamination types May mean more than one type of

treatment to meet permit benchmarks

CHARACTERIZE FIRST

Most problematic contaminant types Metals, especially dissolved metals High turbidity from colloidal

particles Chemical Oxygen Demand (COD) Biological Oxygen Demand (BOD) Nutrients (Phosphorus, Nitrate,

Nitrite)

TYPICAL CONTAMINATION

PASSIVE EXAMPLES Created wetland Bioretention filtration

ACTIVE EXAMPLES Polymer – enhanced filtration Cartridge Filtration Adsorptive Filtration Electrocoagulation Multi-stage treatment

TREATMENT TECHNOLOGIES

Treatment dependant on detention/travel Low cost option TSS, oils/grease, some metals removal Space intensive

PASSIVE - CREATED WETLAND

Treatment and infiltration Low cost option Site and soil conditions critical Preferred SW

management approach

PASSIVE - BIORETENTION FILTRATION

Treatment and discharge Biomass retention of pollutants Natural and manufactured media Adsorptive

filtrationmediaapplication

e.g., Filterra –Ecology GULD

BIORETENTION FILTRATION

Most commonly used is chitosan TSS and turbidity High treatment capacity

POLYMER-ENHANCED FILTRATION

Mixed media cartridge inside vault TSS, P, turbidity and some metal Typical Zn removal efficiency of 45%

and 38% for total and dissolved Typical Cu removal efficiency of 50%

and 40% for total and dissolved Life of cartridge highly dependent on

site conditions e.g. Bayfilter – Ecology Conditional Use

Filtration – Cartridge Filters

Reactive media with targeted contaminant removal

May first need pretreatment for pH or to remove larger particles

Media for metals, coliform, nutrients

Adsorptive Filtration

Dual media gravity filtration Adsorptive filtration for metals Multi-stage treatment available e.g. StormwateRx

Adsorptive Filtration

ADSORPTIVE MEDIA

Effective for a variety, but not all, contaminants

High capital, moderate O& M Metal removal rates around 90% Treatment train can include pH,

settling, filtration e.g. WaterTectonics, Oil Trap

ELECTROCOAGULATION

ELECTROCOAGULATION

Single-stage advanced treatment is expensive

Multiple stage treatment more so

Multi-stage approach driven by either low effluent limits or a wider variety of contaminants

MULTIPLE STAGE TREATMENT

Example of advanced treatment system designs includes Pre-settling pH adjustment Electrocoagulation Settling Pressure Sand Filtration Micron-level cartridge filtration

MULTIPLE STAGE TREATMENT

MULTIPLE STAGE TREATMENT

Receiving Water Bodies Direct discharge

Diffuser outfall for enhanced dilution

DISPOSAL OPTIONS

Municipal Storm Sewer – potential dilution

Municipal Sanitary Sewer – potential higher limits

Infiltration – potential for no monitoring except bypass

DISPOSAL OPTIONS

Implications of stormwater permit requirements starting to set in

Development of new technology driven by demand

Pacific NW - leading role in R & D Capital and O & M costs will be

closely analyzed Need for guidance on “Reasonable”

TRENDS FOR THE FUTURE

Neil Alongi, P.E.nalongi@maulfoster.com360.694.2691

Thank You