The ICW Concept by Dr. Rory Harrington - Waterford County Council

The Integrated Constructed
Wetland (ICW) Concept:
Reanimating essential
ecosystem services
Dr. Rory Harrington, Senior Resident Engineer
Water Services
Waterford County Council
harrington.rory@gmail.com
Value of Wetlands. Joint Waterford County Council - Irish Wildlife Trust Conference.
Dunhill, Co. Waterford, 27 th September 2012

Deforestation and Grazing
REFERENCE
D
r
a
i
n
a
g
e
Ireland’s ecology is a
fundamentally altered one

State Arterial Drainage in Ireland and loss of
wetland ecosystem services
Blue – pre 1945
Red – post 1945

The increased need for food

Ireland’s grass-cattlebased
food economy
…half an hour later

Animal slurry, waste and
polluted water is both a
danger and opportunity!
Water and its constituents
can be recycled
ICW systems
produce clean
water and
provide many
additional
residual-values +
benefits

Published
December 2010
with
contributions
from:
Department of
Agriculture, Fisheries &
Food
Forest Service
Environmental Protection
Agency
Central Fisheries Board
Eastern Regional
Fisheries Board
Office of Public Works
County and City
Managers’ Association
Department of
Environment, Heritage &
Local Government
National Parks & Wildlife
Service
Éamon de Buitléar

Shallow water depth and
emergent vegetation providing:
• High hydraulic
impedance
• Stable anaerobic + O 2
zones
• High primary
productivity
Dissolved O 2 isotherms / water depth

Facilitating the biofilms active on all
supporting strata
On: Solid substrates (rock, soils, plants
and detritus)
Liquid – air (gaseous) interfaces
Soft tissue of living organisms
It’s
A 3.8 billion year long delopment
In and on vegetation, detritus
and soils
Complex microbial
relationships: commensal,
symbiotic and parasitic

Using local or in-situ soils

Biofilms and hydrogels

UNIVERSAL DESIGN MODEL
•Sustainable
•Robust
•Effective
•Fit for purpose
AESTHETIC
•Beautiful
•‘In context’

Explicit integration provides:
synergies, robustness and acceptability

Interdisciplinary
Interdisciplinary
Science is a complex business, as this map of journal cross-citations shows. Each node represents a
subdiscipline and the lines represent the strength of similarity between the nodes.
Image: Rafols, I et al., Science overlay maps

Basic ICW hydraulic model
Wetland emergent vegetation
intercepting precipitation
Wind speed, light & temperature
influencing evapo-tanspiration
(Typically 20-40%)
Precipitation
(Typically 120-200% of open pan
transpiration)
Influent
Cell 1.
C.1x10 -10 m/s
Freeboard at
each cell
delays
through-flow
Decreasing through-flow with increasing area
Cell 2.
C.1x10 -9 m/s
Cell 3
C.1 x10 -8 m/s
Impeded seepage/exfiltration (Typical for
landfills >1x10 -9 m/s)
No or occasional
surface discharge

Water management:
‣Source/s identified
‣Point or diffuse
‣Toxicity threshold (ammonium N Conc.

Landscape-fit:
‣Locality/location
‣Adjacent land use
‣Topography
‣Adjacent water related features – water courses etc.
‣Curvilinear or geometric
‣Access
‣Maintenance

Biodiversity:
‣Appropriate local species - source/s identified
‣Species appropriate to each cell
‣Configuration details – embankments and pools
‣Multi-cellular, ideally 4 cells, extra cells for pools or
seasonality
‣Adjacent topography and vegetation

Delivering additional benefits; e.g.
amenity and biodiversity - ICW systems
have good public acceptability

Anne Valley
catchment area
= 2,500ha; with
16 large (>1ha)
ICWsystems

Anne Valley catchment’s ICW systems
intercepting point and diffuse polluted
water
80% Village conurbation
40%
80%
Overland flow
Farmyard
wastewater

Typical farm ICW

Aerial views of the Anne Valley showing Dunhill Village
ICW under construction, right

Recently enlarged
Dunhill village ICW
(operational on 12 July
2012)
Old (1999) ICW
Functional treatment area =
2670m 2
Newly extended (July 2012) ICW
Functional treatment area =
9678m 2
Total functional treatment
area = 12348m 2 (a combined
flow PE capacity = c.400)

Starting construction on enlarged Dunhill village ICW : November 2011

March 2012

March 2012

August 2012

Molybdate Reactive Phosphorous (mg/l P)
12 farmyard ICW systems in the Anne Valley Catchment, Co.
Waterford, showing increasing performance with increasing area
350
300
250
n = 2955
Period covered 2001 - Mar 2009
Samples from 12 Farm wetlands
200
150
100
50
0
0 5000 10000 15000 20000 25000
Cumulative treatment area (m 2 )

Phosphorus (mg/L)
Standard Deviation
14
12
Molybdate Reactive Phosphorus
10
Total Phosphorus
8
6
4
Sustainable and consistent
removal of phosphorus
2
0
0 10 20 30 40 50 60 70 80 90 100
% Total Treatment Area
3.5
3.0
2.5
2.0
Molybdate Reactive Phosphorus
Total Phosphorus
1.5
1.0
0.5
0.0
0 10 20 30 40 50 60 70 80 90 100
% Total Treatment Area

Ammonia-N (mg/l)
140
Ammonia-N attenuation through five intensively
monitored ICW in Anne Valley, Co Waterford
between 2001 and 2006 (mean ± SEM)
120
100
80
60
40
c
Site 3 (n= 33-60)
Site 4 (n = 13 to 69)
Site 9 (n = 26-78)
Site 10 (n = 24-67)
Site 11 (n = 51-109)
20
0
0 2000 4000 6000 8000 10000 12000
Cummulative area (m 2 )

Dunhill ICW samples taken 5/9/12
Station ID Lab number Location
E coli per 100
mls
Ammonium
mg/l N
MRP mg/l P
7100 833 Pond 1 inlet 1,200,000 49 5.8
7300 834 pond 2 inlet >1,200,000 33 4.1
7400 835 pond 3 inlet

Amenity use of ICW systems

Also: Long-term carbon
sequestration (>13t/ha/yr)
A valuable resource;
Secure retention of phosphorus P
and nitrogen N

Improved biodiversity

ICW Concept provides a platform for
innovation in natural resource management
Resources:
Biomass
Biochar
Nutrient store
Hydrocarbonreplacement
New food crops
Materials
etc...........
Services:
Water supply
Nutrient capture
Carbon sequestration
Flood attenuation
Recreation and
amenity
Biodiversity

Warning!!
It’s important that the fundamental
requirements of the ‘Ecosystem Approach’
and the objectives to obtain multiple benefits
are not overtaken by formulaic engineered
approaches, thus compromising the
philosophy of the ICW concept.
(Where formulaic engineered solutions are often the
norm, opportunities to deliver on multiple benefits
are often missed due to a ‘tick-the-box’ approach to
design e.g. ‘Sustainable Drainage Systems’ (SUDS) .)

Summary
‣Integrated Constructed Wetlands (ICW) really
work
‣They improve our surface-waters and
landscapes
‣Deliver diverse benefits to many people in an
inherently sustainable, consistent and low
cost/maintenance way.

Dunhill Primary School students