constructed wetlands 2
TRANSCRIPT
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.