1. Natural Wastewater Treatment Systems
Professor Nick Gray
Centre for the Environment
Trinity College
University of Dublin
© Tigroney Press

2. Natural Wastewater Treatment Systems
Learning Objectives:
To explore the key NWT systems
To understand the processes involved in such systems
To be able to design reed beds and stabilization ponds

3. Natural Treatment Systems
Biological treatment systems that require little or no energy and that have low ghg emissions.
Options:
Land treatment
Macrophyte/emergent plant-based treatment
Stabilization ponds

4. Natural Treatment Systems
Land Treatment
Surface irrigation
Sub-surface irrigation
Infiltration-percolation
Overland flow
Overland flow (170 acres)
Sewage farming c1890

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Land Treatment
Surface irrigation

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Land Treatment
Sub-surface irrigation

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Land Treatment Sub-surface irrigation

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Land Treatment
Infiltration-percolation

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Land Treatment
Infiltration-percolation
Also widely used in SUDS
Swales
Infiltration ponds
Infiltration trenches/ditches
Retention-detention ponds

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Land Treatment
Overland flow

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Wetland treatment
Natural wetlands, marshes and reed beds no longer used for treatment as it severely damages ecological balance of these delicate systems
Essex marshes
Norfolk broads

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Wetland treatment
Constructed Wetlands:
Free water (FWS) or Surface flow (SF)
Subsurface flow (SSF) either vertical or horizontal
FWS treating farm runoff
FWS wetland

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Constructed Wetlands:

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Reed Beds:

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Liners can be puddled clay, butyl rubber or rigid plastic
Reeds are planted in graded gravel, sand or soil

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Reed beds can be located almost anywhere providing flexible design options
Simple outlet with manhole section used as secondary settlement tank

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Newly planted bed
Septic tank and 9 reed bed tanks in series serving school

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Treatment of mine waters
Treatment of surface runoff from motorways

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New Forest: Reed bed treatment system within National Park
Reed beds now available as package units

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Stabilization Ponds
Anaerobic Lagoons
Oxidation ponds
Facultative pond
High-rate aerobic lagoon
Maturation ponds
River purification lakes
Aeration Lagoons

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Anaerobic lagoons

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Covered Anaerobic Lagoons
A covered anaerobic lagoon utilises a floating geomembrane cover with integrated gas collection system and can be used as a cost effective alternative to the reactor type digesters for very high strength effluents where space is not an issue.

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Typical design of Facultative pond

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Action of Facultative pond

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Fish Culture
Tilapia
Labeo rohita
Catla catala

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Tilapia Fish Ponds in Brazil

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Duckweed ponds

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Water Hyacinth

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Indoor modular treatment cells

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References
Anaerobic ponds:
Use chapter 13 in course text to expand on this brief lecture
More details in Chapter 6 Biology of wastewater Treatment.