Nutrient removal from wastewater by wetland systems

For past so many years wetlands have served functions like providing habitat for aquatic and terrestrial plants and animals, for recreational activities and for treatment of polluted water. Both natural and constructed wetlands gave been used for treatment for wastewater from sewage, septic tanks, agricultural activities, industries, landfills and highways, etc. Treatment of wastewater in a wetland includes process like sedimentation, filtration, removal of BOD and COD and removal of nutrients. The removal of nutrient includes removal of nitrogen and phosphorus. Removal of nitrogen takes place by the process of nitrification and denitrification, which results in removal of nitrogen in the form of N2 gas. Phosphorus is removed by process of adsorption to the ions of metals like Fe, Al, Mg, etc. The removal of nutrients in wetlands is effected by factors like inflow rate, outflow rate, pollutant loading rate, hydraulic retention time (HRT), hydraulic loading rate, climatic conditions, temperature, pH, oxygen availability, wetland design components – substrate, vegetation and living organisms. Case studies presented in the paper provide an insight on the efficiency of contracted wetlands to remove the nutrients and changes in the efficiency of nutrient removal by the change in the factors affecting it.