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Effects Of These Waste Water• Decaying organic matter and debris can useup the dissolved oxygen.• In a lake so fish and other aquatic biotacannot survive excessive nutrients, such asphosphorus and nitrogen (includingammonia), can cause eutrophication.• Bacteria, viruses and disease-causingpathogens can pollute beaches andcontaminate shellfish populations.• Leading to, cadmium, chromium and arseniccan have acute and chronic toxic effects onspecies.
What is Wet Land?• A constructed wetland or wetpark is an artificialwetland, marsh or swamp createdas a new or restored habitat fornative and migratory wildlife, foranthropogenic discharge such as• Wastewater• Storm water runoff• Sewage treatment• Land reclamation aftermining, refineries,
Classification of Wet LandsConstructed wetlands are classified according to the waterflow regime• Free water surface flow (FWS CWs) or• Subsurface flow CWs.Based on the flow of water in the SF CWs. They are again classified into• Horizontal Flow Beds (HFB)• Vertical Flow Beds (VFB)
Horizontal Flow Bed Inlet Outlet HFB HFB near Portugal
Design Specifications• The depth of filter beds is normally around 60 cm with anadditional 15 cm freeboard for water accumulation.• The required specific surface area is about3-10 m²/p.e. depending on temperature and other factors.• The organic loading per surface area should not exceed4-10 g BOD/ (m²) in cold climates16 g COD/ (m²) in warm climates.• The hydraulic loading should be 60-80 mm/d for greywater and 40 mm/d for wastewater.
Vertical Flow Bed Inlet Outlet Vertical Flow Beds
Design Specifications• The depth of the sand filter beds should be atleast 50 cm, with an additional 20 cm of gravel atthe base to cover the drainage pipes.• The required specific surface area is usually3-4 m²/p.e. in cold regions.• The organic loading per surface area should belimited to 20 gCOD / (m²·d) in cold climates).
Pre TreatmentPre-treatment removes materials that can be easilycollected from the raw waste water before theydamage or clog the pumps.• Screening• Grit Removal
Primary Treatment:• In the primary sedimentation stage, sewage flows through large tanks,commonly called "pre-settling basins", "primary sedimentation tanks" or"primary clarifiers”.• The dimensions of the tank should be designed to effect removal of ahigh percentage of the floatables and sludge.• A typical sedimentation tank may remove from 50 to 70 percent ofsuspended solids.• 30 to 35 percent of biochemicaloxygen demand (BOD) from thesewage.
Bio Filtration• Vegetation in a wetland provides a substrate(roots, stems, and leaves) upon which micro organisms cangrow as they break down organic materials.• This community of microorganisms is known asthe periphyton. The periphyton and natural chemical processesare responsible for approximately 90 percentof pollutant removal and waste breakdown.
Plants Chosen:• MacropytesThey produce oxygen, and act as food for some fish andwildlife.• Although the majority of constructed wetland designershave long relied principally on Typhas and Phragmites. Eichhornia crassipes
General Contaminants Removal:• Physical, chemical, and biological processes combine in wetlands toremove contaminants from wastewater.• Theoretically, wastewater treatment within a constructed wetlandoccurs as it passes through the wetland medium and the plant’srhizosphere.• Rhizosphere is a thin film around each root hair is aerobic due to theleakage of oxygen from the rhizomes, roots, and rootlets.
Specific Contaminants Removal:• Nitrogen Removal :The biological transformation of organically combined nitrogen toammonium nitrogen during organic matter degradation byammonifaction process.• Ammonia removal :The formation of ammonia (NH3) occurs via the mineralization orammonification of organic matter under either anaerobic oraerobic conditions.This ion forms when ammonia combines with water as follows:Ammonifiaction:NH3 + H2O ⇌ (NH4+) + OH −
The Nitrite is oxidized to nitrate (NO). The overall nitrificationreactions are as follows:Nitrification:(1) 2(NH4+) + 3O2 ⇌ 4H+ + 2H2O + 2NO(2) 2NO + O2 ⇌ 2NO
Phosphorus Removal:It occurs naturally in both organic and inorganic forms.1. The binding of phosphorus in organic matter as a result ofincorporation into living biomass,2. Precipitation of insoluble phosphates with ferric iron, calcium, andaluminum found in wetland soils.
BOD and COD removal:• Bio Oxygen Demand (96.2 % removal)• Chemical Oxygen Demand (93.8% removal)
Applications:1. Municipal wastewater treatment2. Treatment of household wastewater or grey water3. Tertiary treatment of effluents from conventional wastewatertreatment plants4. Industrial wastewater treatment such as landfillleachate, petroleum refinery wastes, acid minedrainage, agricultural wastes, effluent from pulp and papermills, textile mills.5. Sludge dewatering and mineralization of fecal sludge or sludgefrom settling tanks.6. Storm water treatment and temporary storage7. Treatment of water from swimming pools without chlorine.