session 2: pollutant impacts and removal mechanisms...inorganic nitrogen in media filter. phosphorus...

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ENGINEERING GROUP, INC .

Pollutant Impacts and Removal Mechanisms

FSA STORMWATER BMP SEMINAR SEPTEMBER 11, 2015

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Prevailing thoughts-Pollutant Impacts and Removal 1. Nutrient pollution impacts are best avoided by pollution prevention at the source. Well, this is actually true, but pollution prevention does not fix what impacts already exists! 2. I can achieve my goals of nutrient removal with a BMP Trains approach, or Ill use LID-I’ll just calculate my way to success and pick out what works. Just give me a permit…now!!! Fact: Session 1 lesson unfolds here-Unless we truly understand nutrient pollution characteristics and environmental transformations of these ions, compounds, and biology, we cannot understand mechanisms and design a BMP that will work!

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Today’s Agenda Overview of Session 2 goals and objectives Challenges of meeting nutrient Impairments –the (303(d) list The classic “presumptive” stormwater treatment design process Fundamentals of stormwater treatment processes Treatment modes vs. treatment processes Contemporary treatment processes that work for various water quality conditions LID vs. standard practice-What process really works? The stormwater treatment “consumers guide” Failing treatment system-It didn’t work-call 911? Yes there will be a group test!

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Overview of session goals and objectives Review the traditional methods of presumptive treatment as this relates to design Learn the basics of new trends on BMP treatment Understand realistic limitations of treatment processes How does conservation of mass influence removal? Learn how operations and maintenance impact the performance of any treatment system

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Challenges of meeting nutrient Impairments-the (303(d) list There are 2,776 reference lines of water bodies in the cumulative FDEP 303(d) list! 67 of those are in Tampa Bay Common impairments are nutrients, DO and fecal coliforms Undeveloped projects pose more challenges to meet 303(d) impairments Nitrogen can be particularly difficult to treat in undeveloped coastal environments Engineers are faced with how to balance treatment challenges with a practical cost effective solution Once a BMP is selected, design, and installed, who maintains it?

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The classic “presumptive” stormwater treatment design process Florida was a national leader in developing classic stormwater treatment design guidelines: Stormwater Retention-Infiltration of

stormwater will reduce nutrients by 80% or greater.

Stormwater detention-Wet pond treatment in littoral zone will reduce nutrients by 80%

New source developments must treat ½ inch of the basin’s storm event by retention (or infiltration) or 1 inch for wet systems

The presumptions of 80% are not accurate yet we all continue to follow the WMD requirements!!!

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Fundamentals of stormwater treatment processes Basic concepts of traditional stormwater treatment- a low maintenance and passive system Solids Settling

Physical filtration

Nutrient assimilation (biological uptake)

Nutrient dissimilation (nitrification/denitrification)

Chemical transformation

PHYSICAL PROCESS

BIOLOGICAL PROCESS

CHEMICAL PROCESS

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Fundamentals of stormwater treatment processes Physical Process of Filtration is quite simple A filter’s primary function in to

physically block solids-it is designed to block and will clog!

Traditional vertical high rate filters have capability of backwash cleaning, or reversing flow-not so in storm systems

The accumulation of sediments also forms the Schmustic layer-a biological clog

FILTER MEDIA BED IS TRADITIONALLY 2 FT

FDOT SAND

UNTREATED STORMWATER

CLEAN FILTRATE

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Fundamentals of stormwater treatment processes Physical Process of Filtration is quite simple A filter’s primary function in to

physically block solids-it is designed to block and will clog!

Traditional vertical high rate filters have capability of backwash cleaning, or reversing flow-not so in storm systems

The accumulation of sediments also forms the Schmustic layer-a biological clog

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Treatment modes vs. treatment processes Biological Treatment Processes Nitrogen removal relies on

certain bacteria that have their own needs to grow and prosper.

Nitrification is based on group of organisms know as Nitrosomas sp. These are aerobic heterotrophs

Needs minimal aerobic conditions

Needs alkalinity-this is the carbon source for bacteriological growth

Electron microscope image courtesy University of Wisconsin, Madison

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Treatment modes vs. treatment processes Chemical Treatment Processes Alum-forms polymers that settle

a large fraction of particulate matter-including algae

Synthetic polymers-polyacrylic polymers that have been custom made for various waters

Chitosan-a natural product derived from shellfish

Chemicals rely on water chemistry to work properly!

Photo courtesy of Environmental Research and Design, Inc.

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Treatment modes vs. treatment processes How does nitrification and denitrification really work?

NH4 >>>>> NH3 >>>>>>>>>>>>> NO2>>>>>>NO3 Nitrosomas and Nitrobacter do the work in Aerobic Environment The process requires Oxygen-Lots of it Nitrification Consumes Alkalinity and low alkalinity can limit effectiveness

Denitrification is Conversion of Nitrate to Nitrogen Gas 2 NO3

− + 10 e− + 12 H+ → N2 + 6 H2O Facultative Bacteria Reduce Nitrate-Acceptance of Electrons Facultative Bacteria need to Eat Carbon is food, or Alternative Electron Donar is Needed Needs Low DO to convert to Anoxic Reactions

Annamox NH4

+ + NO2− → N2 + 2 H2O

Nitrosomas and Nitrobacter do the work in Aerobic Environment

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Treatment modes vs. treatment processes

Treatment modes describe flow paths, frequency of treatment and discharge. Dry Retention: It rains, runoff is diverted to a

treatment area where it is entirely infiltrated-there is no discharge.

Wet Detention: It rains, runoff is diverted to a treatment area where it fills, and eventually discharges

Wet and dry treatment modes can be on-line or offline.

Storm-event Treatment: Rainfall runoff is diverted to a treatment area where it is retained over the inter-storm event period

Inter-event Treatment: Rainfall diverted to a treatment area where it undergoes continuous treatment.

Photo of Briarwoods Stormwater Treatment Facility

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Treatment modes vs. treatment processes Advanced and/or Hybrid Treatment Processes. Dry Retention with media infiltration:

Selective media that enhance sorption. Nitrification/denitrification may remove inorganic nitrogen in media filter. Phosphorus removal is largely sorption and biological growth-It does not evaporate!!!

Wet detention with media filtration: Detention pond discharges through a biologically active media filter

Flow-way systems: Can be conventional or inter-event. May incorporate hybrid treatment systems (i.e. media)

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Contemporary treatment processes that work for various water quality conditions Contemporary treatment processes may involve: Adsorption/Absorption Oxygenation/air stripping Harvesting and reuse Nitrification/denitrification

filters Wetland system/flow-way

optimization Chemical treatment-i.e. alum

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Contemporary treatment processes that work for various water quality conditions Adsorption/Absorption- What’s the difference? Adsorption can be described as

“sticky” removal Relies on attractive charge to

attract and hold ions (i.e. NH3 or NO4, or PO4)

Adsorption uses science tested media such as Leica, cationic media, wood chips, tire crumb, etc. (usually selective for ions).

Adsorption ultimately “saturates” sites

Electron microscope images courtesy of University

of Central Florida

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Contemporary treatment processes that work for various water quality conditions

Tire Crumb Tire Chips Limestone Crushed Shells Wood Fiber/Chips/ Compost Coconut husk Expanded Clay Florida Peat Sandy/Loamy/ Clayey soils Sawdust (untreated wood) Paper/Newspaper Palm Tree Frauds

UCF has studied many possible sources of media for adsorption or absorption

Photo Courtesy of University of Central Florida

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Contemporary treatment processes that work for various water quality conditions Biological Treatment: Flow-ways are engineered wetland systems Biological treatment relies mostly

on microbial removal-this is dissimilatory processes of nitrification and denitrification

Treatment effectiveness largely based on residence time

Design should encourage anoxic and anaerobic conditions

Kadlec-Knight equation most widely accepted model

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Contemporary treatment processes that work for various water quality conditions How does media work? Media based treatment requires

understanding of certain operational concepts:

The media will continue to work for some specified time period based on isotherms (breakthrough curves)

The media will not get excessively fouled during treatment

The media cannot completely dry out if biologically active

Surface attachments will become biologically active (for nitrogen) to “regenerate” sorptive sites

Courtesy of University of Central Florida

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LID vs. standard practice-What works where? LID practice is a treatment system to capitalize on nature Many municipalities encourage

LID with published guidelines! LID manuals have been developed

(i.e. Sarasota Co.) Little or no “permit credit”

advantage of bioswales, filter-strips, rain gardens, etc. for new projects. LID processes do work-but they

work best on retrofit situations!

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A. GENERAL SITE CONSIDERATIONS

A.1-THE PROJECT IS PLANNED TO BE CONSTRUCTED ON UNDEVELOPED

LAND WITH FLEXIBLE LOCATIONS FOR STORMWATER MANAGEMENT.

A.2-THE PROJECT IS A REDEVELOPMENT AREA OR RETROFIT PROJECT

WHERE NO STORMWATER PONDS EXIST.

A.3-THE PROJECT IS A PROPOSED LINEAR PROJECT (I.E. NEW

ROADWAY).

A.4-THE PROJECT IS COMPRISED OF A LARGE MIXED USE OR PLANNED

DEVELOPEMENT (RESIDENTIAL/COMMERCIAL DEVELOPMENT)

A.5-THE SITE IS PLANNED FOR A COMMERCIAL LARGE "BIG BOX".

BUILDINGS AND LARGE PARKING AREAS.

A.6-THE PROJECT IS PLANNED AS A CLUSTERED, HIGH INTENSITY MULTI-

FAMILY RESIDENTIAL OR "NEW URBANISM" PROJECT.

B. ENVIRONMENTAL SITE CONSIDERATIONS

B.1-THE SEASONAL HIGH GROUNDWATER TABLE IS LESS THAN 1.5 FEET

BELOW LAND SURFACE.

B.2-THE SOILS ON THE SITE ARE POORLY DRAINED WITH LESS THAN 2

INCHES/HR INFILTRATION (I.E. SCS TYPE B/D OR D).

B.3-THE SITE LIES WITHIN THE 100 YEAR FLOODPLAIN.

B.4-THE PROJECT AREA INCLUDES SPECIAL HABITATS OF CONCERN OR

REQUIRES SPEICIAL PROTECTION MEASURES.

B.5-THE PROJECT IMPACTS WETLANDS OR THERE ARE EXISTING

IMPACTED WETLANDS THAT MAY BENEFIT FROM STORMWATER.

B.6-THE SITE REQUIRES FILL MATERIALS FOR DEVELOPMENT

B.7-THERE ARE OPPORTUNITIES TO PRESERVE FORESTED AREAS FOR

NON-PRESUMPTIVE STORMWATER TREATMENT BENEFITS.

B.8-THE PROJECT SITE HAS NO POSITIVE OUTFALL

C. SPECIAL WATERSHED SITE CONSIDERATIONS

C.1 THE PROJECT LIES WITHIN A WATERSHED OF SPECIAL CONCERN

(I.E. WITHIN A PEAK SENSITIVE OR VOLUME SENSITIVE AREA).

C.2 THE WATERSHED RECEIVING STREAM IS AN OUTSTANDING FLORIDA

WATER (OFW).

C.3 THE WATERSHED LIES WITHIN AN IMPAIRED WATER BODY AND MAY

HAVE SPECIFIC TMDL'S INDENTIFIED FOR NUTRIENTS.

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LOW IMPACT DEVELOPMENT ALTERNATIVES

AVAILABLE TO MEET STORMWATER

MANAGEMENT SITE NEEDS IN SARASOTA

COUNTY

LOW IMPACT DEVELOPMENT PLANNING

CONSIDERATIONS

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LID vs. standard practice-What works where? LID practice may offer good alternatives for retrofits Filter strips provide

bioretention possibilities This practice can replace

concentrated discharges with overland flow

Infiltration through select media, maintained vegetative strip (mowing and bagging) Increased evapotranspiration

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The stormwater treatment “consumers guide” Large mass solids removal can be very effective but requires frequent servicing: Large solids can contain large masses

of nutrients If large organic solids are left alone

then decay begins

Decay releases complex organics (amides, proteins, etc.) and ammonia gas.

Courtesy of University of Bandalong

Systems

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The stormwater treatment “consumers guide” Solids removal can be very effective: Source controls are important (pollution prevention and erosion controls)

Inorganic solids-mineral weathering is source of phosphorus

Solids may also be organic (algae, dead vegetation)

Dissolved inorganic nutrients are tougher to treat: Interconnected systems may more likely have higher reacted organic sources

Stored organics may decompose with complex dissolved forms and ammonia is released

Dissolved organic nutrients are very tough to treat Long retention times, or long interconnected flow paths can create high levels

of dissolved nutrients

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The stormwater treatment “consumers guide” Dissolved inorganic nutrients are tougher to treat: Interconnected systems may more

likely have higher reacted organic sources

These nutrients mainly include ammonia, nitrate and Orthophosphate

Treatment can be by biological means, or sorption, or both Turf Grass with mowing maintenance

Wet pond littoral shelf

Upflow filter

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The stormwater treatment “consumers guide” Inorganic source control opportunities in order of effectiveness; No. 1-Infiltration No. 2-Solids settling device (baffle box) No. 3-Harvesting and reuse-from wet

ponds No. 4-Wet pond with aeration No. 4-Filtration-sand or upflow

discharge from ponds

No. 5-Sorption media (a prescription media)

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Failing treatment system-It didn’t work-call 911? Engineers should avoid panic-look for warning signs during design of any treatment system Outfall path is offsite and sheet flows across neighboring

property Tailwater conditions may raise warning signs-stain lines are

higher than survey-may be flood or tidal influence? Geotech report says “seasonal high groundwater ranges from 1-3

FT below grade”. OK, sounds like they are not sure! You are designing a dry pond when site next door has full pond. Outfall discharge looks questionable

Be careful with things like liners to isolate groundwater

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Failing treatment system-It didn’t work-call 911? Some obvious symptoms of Failed Treatment Systems Dry pond has thriving wetland

system

Wet pond normal pool is too low

Owner complains he can’t maintain the pond

Wet pond is pea green

Dead fish

A letter from the water management district

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Failing treatment system-It didn’t work-call 911? I have a mile long treatment train but I’m not achieving 80% TN Removal-Help!!!! If you are consistently achieving

40% or greater with wet pond system-you are doing pretty good. Review the predominant N

species. Understand your water quality

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Failing treatment system-It didn’t work-call 911? What is pH and Why is it Important? pH is Measure of H+ Concentration.

Important in Ammonia/Ammonium Ion balance

Important in Nitrification/Denitrification Function

What is DO and How does it Fluctuate? DO is Consumed by Algae (Photorespiration) and

Bacteria

DO is Produced by Algae (Super saturation Possible)

Why measure Turbidity? Measures Attenuation of Light

Correlates with TSS (and Algal Concentration)

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Failing treatment system-It didn’t work-call 911? What is ReDox Potential? ReDox is measure of Electron Activity

(Ability to gain or lose electrons)

Aerobic and Anaerobic Respiration has transfer of electrons (Krebs Cycle Stuff)

High ReDox Good for Aerobic Bacterial Growth

Negative ReDox Good for Anaerobic Bacterial Growth -100 is pretty good for anaerobic Conditions

What is the Difference Between the Terms Anaerobic and Anoxic? -Anoxic means “without oxygen; Anaerobic

means no oxygen

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Failing treatment system-It didn’t work-call 911? Review factors that affect nitrogen removal Shortened or excessive

residence time in wet systems Shallow water depth allows for

organic conversion

pH too low affects nitrification Temperature Alkalinity (remember rainfall has

very low alkalinity)

TOC-total organic carbon is needed for denitrification

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Yes there will be a group test! Question 1: The answer is C. Depending on the depth of the pond and limiting nutrient balance, the pond could have very high levels of algal biomass as organic nitrogen and dissolved organic nitrogen. This latter condition is much more difficult to achieve high removal rates. Most likely 45% is a more realistic removal goal for a good pond.

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Yes there will be a group test! Question 2: A golf course has potentially high ammonia and nitrate discharges to a wet stormwater pond. If you are asked to design a stormwater pond and you are considering a process that relies largely on nitrification and denitrification, which treatment system would you consider:

A. Traditional sand filtration through side bank filter B. Media upflow filter C. Flow-way wetland system D. B, and C

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Yes there will be a group test! Question 2: The correct answer is D. Nitrification and denitrification can be achieved with either process. Studies have demonstrated effective ammonia removal for media filters. By the way, it might be wise to consider a fountain as well. The aeration will strip ammonia.

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Yes there will be a group test! Question 3: I have a failed dry pond with side bank filter that does not perc at an active commercial site. The site is fully developed with asphalt parking. There is not enough treatment volume and there is no room to expand the pond. What corrective action may be considered reasonable to restore treatment effectiveness? A. Fix the filter by replacement in kind. B. Convert the dry pond to wet pond with

littoral shelf C. Add 5 tree filters D. Add infiltrative treatment with upflow filter E. Either A or D.

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Yes there will be a group test! Question 3: The correct answer is answer is E. Wet pond conversion requires more treatment volume. The existing filters could be replaced in kind-however the costs must be considered in tearing up landscape and/or parking areas. Any filter needs cleaning occasionally. I recommend an upflow-this is one that can be maintained easily!

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Yes there will be a group test! Question 4: The fictional City of Nitrosomas wishes to install a new phosphorous removal device, as manufactured by Phoskill systems, USA to remove 150 lbs of organically bound phosphorus per year with their unit-using an inter-event pumped treatment system. It claims to be entirely biological and use no chemicals. The manufacture has specified that the unit is 3 ft by 3 ft by 2 ft deep and filled with special “Phoskilled” media, which has a total weight of 150 lbs, which will remove 80% of total phosphorus for 30 years. Should I as the City engineer recommend purchase?

A. Don’t ask any questions, I want that system and install it tomorrow! B. Yeah, right. I’m smarter than that-no system can perform miracles. C. If I have accurate data, tell me what I need to do to get those results!

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Yes there will be a group test! Question 4: The most correct answer is answer is C. If we consider mass balance and that phosphorus does not “evaporate”, the total mass into the filter would be 4,500 lbs of organic phosphorus over 30 years. If the equivalent ortho phosphorus levels were only 0.2% of the total weight of organics, only 9 pounds of P would be captured-this is reasonable. But what about the remaining 4,491 lbs. How often does this filter need cleaning? By the way, Total P includes organic plus inorganic forms!!! Where does the PO4 go???

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Yes there will be a group test! Question 5: This picture is a illustrative example of:

A. Mass imbalance B. Mass balance C. Two great civil

engineering programs that teach stormwater BMP’s D. B and C E. A and C

UNIVERSITY

OF

CENTRAL

FLORIDA

5,000 ENGINEERING

STUDENTS

2,500 ENGINEERING

STUDENTS

1,500 LOST STUDENTS

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Yes there will be a group test! Question 5: The correct answer is E. It is not a mass balance. And both schools, as well as all other Florida schools, have great engineering programs that teach BMP practices! In fact Florida still remains considered as a leader in stormwater treatment BMP’s.

session 2: pollutant impacts and removal mechanisms...inorganic nitrogen in media filter. phosphorus...

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