Root Zone System
Root Zone Systems are artificially prepared wetlands comprising of clay or plastic lined excavation and emergent vegetation growing on gravel/sand mixtures and is also known as constructed wetland. This method combines mechanical filtration, chemical precipitation and biological degradation in one step for the treatment of wastewater. A number of factors like low operating cost, less energy requirement and ease of maintenance attribute to making root zone system an attractive alternative for wastewater management.
The process in a root zone system to treat the sewage begins with passing the raw effluent (after removing grit or floating material) horizontally or vertically through a bed of soil having impervious bottom. The effluent percolates through the bed that has all the roots of the wetland plants spread very thickly, nearly 2,500 types of bacteria and 10,000 types of Fungi, which harbor around roots get oxygen form the weak membranes of the roots and aerobically oxidize the organic matter of the effluent. The characteristics of plants of absorbing oxygen through their leaves and passing it down to roots through their stems which are hollow, is utilized as a bio-pump. Away from the roots, anaerobic digestion also takes place. The filtering action of the soil bed, the action with fungi etc. and chemical action with certain existing or added inorganic chemicals help in finally obtaining very clear and clean water. The system of plants regenerates itself as the old plants die and form useful humus. Hence, the system becomes maintenance free and can run up to 50 to 60 years without any loss of efficiency.
• With no use of machinery and associated maintenance, the root zone system provides for low maintenance cost and negligible attendance for operation and monitoring
• It enhances the landscape and gives the site a green appeal
• It provides natural habitat for birds and after a few years gives an appearance of a Bird’s sanctuary
• It is a green zone, it does not have mosquitoes problem.
• Salinity may not be a problem for a survival or operations of reed beds
• It is recommended to combine vertical flow and then horizontal flow of sewage with a soil having impervious bottom
• In the horizontal flow system, the sewage percolates through bed and that has all roots of the wetland plants spread very thickly nearly with 2500 types of bacteria and 10,000 types of fungi and aerobically oxidized organic matter of the effluent.
• Root zone system gives a very good performance of removing 90% BOD and 63% Nitrogen.
• Phragmites australis has been found more efficient in nitrogen removal compared to Typha latifolia.