constructed wetlands 2

Introduction :

Land areas that are wet during part or all of the year are referred as wetlands.

Decentralized waste water treatment system.

Low operational cost important role in many

ecological sanitation concepts.

These are secondary treatment.Water reuse.

Classification of wet lands:- Typically a

constructed wetland can be classified as:

- free

water surface flow

- subsurface flow

- horizontal - vertical

Process description : Pre treatment material that are easily collected(tree, leaves) Screening pass through bar (cans ,plastic packet)Girt removal settlement of sand ,girt, stones.Primary treatment

to settle sludge and to remove oil and grease

Bio filtration periphyton(group of micro organism that

break down organic material)

Horizontal flow beds(HFB) common type of subsurface flow constructed wetland low maintenance requirements. interesting option especially in locations without energy supply and low hydraulic gradient. the wastewater flows slowly through the porous medium

under the surface of the bed in a horizontal path until it reaches the outlet zone.

At the outlet the water level in the HFB is controlled with an adjustable standpipe.

For continuous operation the submerged height of the bed should be less than one third of the total height of the filter bed to avoid anaerobic conditions in the bed.

Diagram of Horizontal Flow Beds :

Vertical flow bed(VFB)

higher treatment efficiencySafer and more effective at removing the more directly

harmful toxic trace metalsExpensive Compared to Surface Flow In VFBs wastewater is intermittently pumped onto the

surface and then drains vertically down through the filter layer towards a drainage system at the bottom.

The intermittent batch loading enhances the oxygen transfer and leads to high aerobic degradation activities.

Diagram of Vertical flow bed

Chemical process general contamination removal physical chemical and biological process specific contaminant removal nitrogen( ammonia ) Phosphorus biochemical oxygen demand removal and

chemical oxygen demand total suspended solids fish and bacteria

Nitrogen (ammonia) Removal : It form by mineralization or ammonifiacation of

organic matter Primary source for most flooded wetland soil

Ammonifiacation:NH3 + H2O (NH4+) + OH −⇌ Absorbed by plant or by electro statically on negatively

charged surface(anaerobic condition) Nitrification Bacteria responsible (nitrosomonas and nitrobacter)

Phosphorus removal

Occur naturally both in organic and in organic formSoluble reactive phosphateDissolved organic and inorganic phosphorus are generally not

biologically available until transform into soluble organic formBinding of phosphorusPrecipitation of insoluble phosphorus with ferric iron calcium

and aluminumTransient nutrient storage compartmentLuxury uptake of nutrientAquatic phosphorus (if harvested extend life of system)

Bio chemical oxygen demand

Chemical oxygen demand

Amount of oxygen consumed by micro organism during biological reaction

Different bio activity of microbes with temperature

increase turbidity and light penetration.

Total suspended solid

Graph for specific contaminant removal under hot and cold condition

nitrogen phosphorus

For bod and cod

Various Plant TypesWater Hyacinths Eichhornia crassipes

Forage Kochia Kochia spp

Poplar Trees Populus spp

Willow Trees Salix spp

Alfalfa Medicago sativa

Cattail Typha latifolia

Coontail Ceratophyllum demersvm L

Bullrush Scirpus spp

Reed Phragmites spp.

American pondweed Potamogeton nodosus

Common Arrowhead Sagittaria latifolia

Application

Though built to treat wastewater, constructed wetlands provide habitat for:Birds

Municipal wastewater treatment Treatment of household wastewater or grey waterTertiary treatment of effluents from conventional

wastewater treatment plants Sludge dewatering and mineralization of fecal sludge

or sludge from settling tanks. Storm water treatment and temporary storage Treatment of water from swimming pools without

chlorine. 

Conclusion :

Increase water quality stop pollution

think for a solutionBring out a revolution

constructed wetlands are referred as kidneys of mother land.