Constructed wetland management

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CONSTRUCTED WETLAND MANAGEMENT

RISHABH RATHOR

B110229CE

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CONTENTS

• What is a wetland?• Economic benefits• Types of wetlands• Components of wetlands• Working mechanism

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WHAT IS A WETLAND?

• A wetland is an area that is regularly saturated by surface water or groundwater and is characterized by a prevalence of vegetation that is adapted for life in saturated soil conditions (e.g., swamps, bogs, fens, marshes and estuaries).”

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CONSTRUCTED WETLAND

• Natural wastewater treatment systems• Used for secondary or tertiary treatment• Treatment processes

– Filtration – Sedimentation– Biological degradation

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BENEFITS

• Improvement of drinking water quality• Flood control• Cleaning the water• Fisheries• Recreation• Wildlife habitat• Other benifits

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TYPES OF WETLANDS

• Surface flow or free water surface constructed wetland

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TYPES OF WETLANDS

• Subsurface horizontal flow constructed wetland

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TYPES OF WETLANDS

• Vertical flow constructed wetland

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COMPONENTS OF WETLAND

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• Waterproof basin– To avoid groundwater and soil contamination– To prevent infiltration of groundwater into the

wetland bed

– Layer of compacted clay – Plastic liners

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• Filter media– Gravel (12-20mm)– 20-40mm at ends

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COMPONENTS OF WETLANDWetland plants

• Helicona • Common reed

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COMPONETS OF WETLAND

• Inlet and outlet structures

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WORKING MECHANISM

• Organic matter– Aerobic microbial degradation– Anaerobic microbial degradation

• Suspended solids – Sedimentation– filtration

• Pathogens– Sedimentation – Filtration – Natural die-off– Predation

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WORKING MECHANISM

• Nitrogen– Ammonification followed by microbial

nitrification (Nitrosomonas and Nitrobacter)– Denitrification(anaerobic bacteria)

– Plant uptake– Matrix adsorption

• Phosphorus – Matrix sorption– Plant uptake

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WORKING MECHANISM

• Removal efficiency

Wastewater constituent Removal efficiency

Organic matter 80-90% (high)

Suspended solids 80-90% (high)

Phosphorus Approx 20% (low)

Nitrogen 20-40% (low)

Coliforms 1-3 log units (medium)

Helminth eggs Upto 3 log units (high)

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CONSTRUCTION

• Site selection– Position and topography of land– Hydrograph preparation and data interpretation– Sub-grade soil properties– Plantation in the given area

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CONSTRUCTION

• Land survey– Elevation survey– Contour survey (1’ accuracy)– Potential area with most acreage of shallow water– Depth of water should be less than 3 feet

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CONSTRUCTION

• Levee construction– To impound and manipulate water– Compaction tests should be done – Height < 4 -5 feet– Freeboard – 1-2 feet– Side slope- 3:1 to 10:1– Highest points near water control structures

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CONSTRUCTION

• Water sources– Rainfall runoff– Wells – Pumps– Upstream storage lakes

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CONSTRUCTION

• Water control devices– To regulate water impounded by leeves– Not flood control fixures– Types

• Flashboard risers• Screw gates • Flap gates

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CONSTRUCTION

• Flashboard risers

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CONSTRUCTION

• Screw gates

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CONSTRUCTION

• Flap gates

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THANK YOU

Engineering

Constructed wetland management