Prof. Abdul A Rahman
 
Prof. Abdul A Rahman


Project development

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Project development

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SEWAGE

Development of root zone treatment Technology for sewage

     Reeds, Phragmites australis is considered to be the best plant because of its roots form horizontal rhizome that guarantee a perfect root zone filter bed.

The process in a root zone system to treat the sewage is very simple to explain yet complex in nature. Raw effluent (after removing grit or floating material is passed 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 a 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 upto 50 to 60 years without any loss of efficiency as has been described.

Reed bed is one of the natural and attractive methods of treating domestic, industrial and agricultural wastes. A reed bed is an engineered method of purifying polluted water as it passes through artificially constructed wetland area, usually containing common reeds. Reed bed is considered as an effective and reliable secondary and tertiary treatment method where land area is not a major constraint. Generally reed bed is made in shallow pits, installed with a drain pipe in a bed of pieces of lime stones and filled up with pebbles, iron filings and graded sand. In this sandy body, reed plants (with hollow root which bring oxygen into the filter bed) are planted

It is advantageous to treat the sewage by root zone system. It achieves the standard for tertiary level treatment standard with no operating cost. There is no chemical used for pH adjustment or for flocculation. Low electricity is consumed for pumping treated water from the collection tank to the reed bed. From the reed bed the treated water is collected and used for irrigation by gradient flow.

The root zone system has low maintenance cost since it involves no machinery and its associated maintenance. It requires negligible attendance for operation and monitoring. It has no sludge handling problem such as scraping of slurry from the sludge drying beds and its disposal twice in a week.

The sludge gets mineralized in the vertical zone of the reed bed .The sludge mineralizing beds needs to be disposed once in 10 or 15 years.

  • 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 though an effluent treatment plant, it does not have odour problem and though
  • It is a green zone, it does not have mosquitoes problem.
  • The reeds are not grazed by ruminants.
  • 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.

However, compared to the conventional treatment processes such as activated sludge, aerated lagoons, waste stabilization pond etc the performance of the root zone treatment system is good with regard to the removal or reduction of BOD,COD,TOC and Total coliforms(Fig. 1 & 2).

Hotel Oriental Towers Thanjauvr, Tamilnadu, wastewater treatment plant (Kitchen, Laundry and Bathroom waste), Separate treatment process Kitchen ­ Biological treated removing the oil and grease separately, Laundry and Bathroom waste water treated chemically( Fig. 3).

    sewage    sewage    sewage               Root zone treatment system                         Laundry and Bathroom waste
                                                                                   water treatment



                sewage


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