Nutrient Uptake and Microbial Utilization in

Nutrient-Deficient Treatment Wetlands

Scott Wallace, NWC

Clodagh Murphy, ARM

David Cooper, ARM

Prerequisites of Biological Wastewater Treatment

• Adequate food supply (BOD)

• Adequate detention time (surface area for

attached-growth systems)

• Appropriate environmental conditions (DO, redox

potential)

• Adequate nutrients (N, P, K) for cell synthesis and

metabolism

• Lack of toxins

Constructed Treatment Wetlands

• Adequate food supply: Yes

• Adequate surface area: Yes

• Environmental conditions: Yes, with appropriate design

• Adequate nutrients: Maybe?

• Lack of toxins: Usually

Nutrient Requirements for Bacterial Growth

Nutrient g/kg of Biomass Produced

Nitrogen 85

Phosphorus 17

Potassium 10

Calcium 10

Magnesium 7

Sulfur 6

Sodium 3

Chloride 3

Iron 2

Bacterial Response to

New Food InputB

iom

ass

Death:Declining

Population

Stationary Growth:(Stable)

Log-Growth:(Rapid)

Time

Microbial Yield

Fraction of influent COD converted to microbial biomass

Activated sludge: 1.2 – 0.7 (large amounts of waste sludge)

What about Constructed Wetlands?

Difficult to measure, especially for subsurface flow wetlands

Weigh biomass?

Nitrogen utilization? (what about nitrfication/denitrification?)

Phosphorus utilization? (what about adsorption?)

Constructed Wetlands (stationary growth phase)

0.068 for tidal flow (Austin et al, 2006) – biomass weight

Constructed Wetlands (log growth phase)

> 0.3 Buffalo Airport (Wallace & Liner 2010) – prevention of slime

0.70 (median) Heathrow Airport (this study) – phosphorus utilization

0.55 (mean) Heathrow Airport (this study) – phosphorus utilization

Implications for Treatment

• Biological systems need a continuous supply of

nutrients to maintain treatment in steady-state

conditions

Domestic wastewater wetlands

• Nutrient demands will be highest when there is a

sudden increase in influent loadings

Event-driven wetlands

Industrial treatment wetlandsDeicing Treatment Wetlands

How Wetlands are Affected by

Nutrient Limitations

• Lack of bacteria growth

• No treatment or limited treatment

• Stressed bacterial communities

• Slime formation

• Foaming

• Stressed vegetation

• Limited development

• Nutrient deficiencies

Buffalo, New York

Buffalo

Buffalo Niagara International Airport

Buffalo Niagara International Airport

• Heavy snow loads in winter

• Airfield operations are heavily dependent on effective

deicing operations

Deicing Wetlands are Event Driven Systems

Equalization Treatment

Co

nce

ntr

atio

n

Co

nce

ntr

atio

n

Equalization vs. Treatment

Treatability Testing

• Measure glycol degradation in both warm and cold temperatures

• With and without aeration

Aerated rate coefficients, low temperature runs

Run

Average CBOD5 (mg/L)

k2TIS(d-1)InfluentEffluent

A 648.8 26.5 4.81

B 679.3 21.0 5.72

C 325.0 10.3 5.63

D 694.0 23.5 5.41

Average 5.39

BOD removal without aeration…

Run

Average CBOD5 (mg/L)

k4TIS(d-1)Influent Effluent

A 542.3 212.3 0.68

B 257.0 119.0 0.27

C 177.0 29.0 0.73

D 129.5 33.5 0.51

Average 0.55

Comparing BOD Treatment Effectiveness

•Aerated rate coefficient: 5.30 d-1

•Non-aerate rate coefficient: 0.55 d-1

•An aerated wetland is 10X more effective

in removing glycol-derived BOD!

Buffalo Nutrient Requirements

• 4,500 kg/d of COD would generate 1,350 kg/d of biomass

in a start-up “log growth” phase of biomass development

(at a yield ratio of 0.3)

• 1,350 kg/d of biomass would require:

115 kg/d of nitrogen (N)

23 kg/d of phosphorus (P)

Additional micronutrients

Buffalo Start-Up vs. Steady-State Operation

• Start-Up (yield ratio 0.3)

Nitrogen: 115 kg/d

Phosphorus: 23 kg/d

• Steady-State (yield ratio 0.068)

Nitrogen: 26 kg/d

Phosphorus: 5.3 kg/d

Drain LineAir Line

Mulch Layer Influent Line

Buffalo Bed Configuration

Water Level

Buffalo – Completed Treatment System

Lack of Nutrients:Foaming in Subsurface Flow Wetland Bed

Polysaccharide Slime Formation in Subsurface Flow Wetland Bed

High Viscosity Wetland Effluent

Result of 2009-2010 Nutrient Addition

• After two months, system reached full performance

• Average influent temperature 5 deg C

• During heavy loading, effluent temperature was 15 deg C

• Influent BOD 2,400 mg/L; effluent BOD 42 mg/L

0

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29/10/2010 18/11/2010 08/12/2010 28/12/2010 17/01/2011 06/02/2011 26/02/2011 18/03/2011 07/04/2011 27/04/2011

Cal

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ted

CB

OD

5 (m

g/L

)Buffalo Airport Deicing Fluid Treatment 2010-2011

Influent

Effluent

Influent CBOD5/TOC: 2.25Effluent CBOD5/TOC: 0.45Based on Calibration of TOC Meters Report (6/4/2010)

Overview of pollution control at London Heathrow

Spout Lane Lagoon

Mayfield Farm main reservoir

Causeway Nature Reserve – part of Eastern Balancing Reservoirs

Clockhouse Lane Pit – Cable 1 part of Princes ski club

The Case for Upgrading Mayfield Farm

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Aircraft Pavement

• Relatively mild winters post original construction (change in design basis)• More stringent consent limits

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Aeration Plow – London Heathrow

Air Lines After Installation – London Heathrow

Heathrow Bubble Pattern

BOD Removal and Biomass Production

(2012 – 2013)

Conclusions

• Industrial wastewaters are often deficient in one or more

nutrients. This will affect the performance of biological

systems, including treatment wetlands

• Nutrient demands will be greatest during sudden

increases in the influent loading

• Nutrient balancing is an important part of the design of

treatment wetlands; nutrient imbalances will create

performance and operational problems

• Microbial yield in treatment wetlands is still a work in

progress; the reported range (0.068 to 0.70) appears to

bracket the 2012-2013 performance data at Heathrow

Airport

Thank You!