Water Reuse: Technologies for Industrial and Municipal Applications
Stormwater Treatment - Neil Alongi, Maul Foster Alongi
1. ELEC WASHINGTON STORMWATER CONFERENCE
STORMWATER TREATMENT
AND TECHNOLOGY
Neil Alongi, P.E. – Maul Foster & Alongi
February 7, 2011
2. DISCUSSION OVERVIEW
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
3. BMP HIERARCHY APPROACH
Treatment BMPs = Capital
+ Operational Costs
e.g. Active Treatment
Structural BMPs = Capital
costs
e.g. materials isolation
Operational BMPs
e.g. Pavement sweeping
5. TREATMENT BMPs – SITE SIZE
Large site = High volumes and flow rates
Flow
attenuation a critical factor
Complexity of contaminants challenging
6. SMALL SITE STORMWATER
CHALLENGES
Site space limitation usually results in
additional costs to manage & treat
May force facilities underground
Operations personnel may be limited
7. QUANTITY CONTROL
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
9. CHARACTERIZE FIRST
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
10. TYPICAL CONTAMINATION
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)
16. Filtration – Cartridge Filters
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
17. Adsorptive Filtration
Reactive media with targeted
contaminant removal
May first need pretreatment for
pH or to remove larger particles
Media for metals, coliform,
nutrients
18. Adsorptive Filtration
Dual media gravity filtration
Adsorptive filtration for metals
Multi-stage treatment available
e.g. StormwateRx
20. ELECTROCOAGULATION
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
22. MULTIPLE STAGE TREATMENT
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
23. MULTIPLE STAGE TREATMENT
Example of advanced treatment
system designs includes
Pre-settling
pH adjustment
Electrocoagulation
Settling
Pressure Sand Filtration
Micron-level cartridge filtration
25. DISPOSAL OPTIONS
Receiving Water Bodies
Direct
discharge
Diffuser
outfall for
enhanced
dilution
26. DISPOSAL OPTIONS
Municipal Storm Sewer –
potential dilution
Municipal Sanitary Sewer –
potential higher limits
Infiltration – potential for no
monitoring except bypass
27. TRENDS FOR THE FUTURE
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”
