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 Brief Description of Root Zone Treatment Systems:

The Root Zone Treatment system (RZTS) also known as the reed bed system or constructed wetland system is a sealed filter bed consisting of a sand / gravel/ soil system, occasionally with a cohesive element, planted with vegetation that can grow in wetlands.  After removal of coarse and floating material, the wastewater passes through the filter bed where biodegradation of the wastewater takes place.  The functional mechanisms in the soil matrix that are responsible for the mineralization of biodegradable matter are characterized by complex physical, chemical and biological processes, which result from the combined effects of the filter bed material, wetland plants, micro-organisms and wastewater.

            The treatment processes are based essentially on the activity of microorganisms present in the soil.  The oxygen for microbial mineralization of organic substances is supplied through the roots of the plants, atmospheric diffusion and in case of intermittent wastewater feeding through suction into soil by the out-flowing wastewater. RZTS contain aerobic, anoxic and anaerobic zones.  This causes the presence of a large number of different strains of microorganisms and consequently a large variety of biochemical pathways are formed.  This explains the high efficiency of biodegradation of substances that are difficult to treat.

            Conversion of nitrogen compounds (nitrification / De-nitrification) occurs due to planned flow of wastewater through anaerobic and aerobic zones.  Reduction of phosphorous depends on the availability of acceptors like iron compounds and the redox potential in the soil.  The filtration by percolation through the bed material is the reason for the very efficient reduction of pathogens, depending on the size of grain of the bed material and thickness of filter, thus making the treated effluent suitable for reuse.  It should be noted that no other treatment system, without the use of additional chemicals or physical processes, can ensure the extensive elimination of pathogenic germs.

Root Zone Treatment systems have the following salient features:

  • Require simple construction methods,

  • No machinery (pumps, aerators, etc.) and no inputs of energy    or   chemicals are required for the treatment process,

  • In the rootzone treatment process no sludge is generated,  therefore the sludge handling and disposal problem is   restricted   only to   primary sludge-this is a unique and remarkable feature of RZTSs, 

  • Can accommodate significant variations in hydraulic and pollution     loads without significant loss of efficiency

  • Can handle a large variety of pollutants,

  • Does not require skilled personnel for operation maintenance,

  • Low operation and maintenance costs; typically in rootzone systems   these are less than 1% of the cost of the system per year,

  • Can be built to suit both decentralized and centralized sewage            treatment systems; in decentralized situations considerable        drainage   costs may be saved

  • Can be easily and cost-effectively expanded to accommodate         increased loads,  

  • High efficiency in removal of pathogens; no other treatment system,   without the use of additional chemicals or physical processes,can    ensure the extensive elimination of pathogenic germs,

  • Allows re-cycling and safe re-use of waste water,

  • Conversion of wastes into re-usable high quality plant biomass (reeds),

  • Capital costs comparable to other similar wastewater treatment           systems

  • Long life span of systems,

Large re-use of materials when system is decommissioned.

Approaches/methods used for people's participation.

 Thus rootzone systems are not only eco-friendly but have low operational costs, producing high water quality (up to bathing water standards) suitable for re-use.  These features make RZT systems low-cost, environment-friendly, and reliable in both the short and long term.

From past experiences in tropical conditions it has been established that a horizontal filter bed area of about 2m2 /PE (it should be noted that while the horizontal filter bed area is used as a common and convenient parameter for the dimensioning of RZTS, this is not the only parameter to be considered) is sufficient for the complete secondary and tertiary treatment of wastewater including the removal of pathogenic germs.


The Taj Garden Retreat, a Taj Group of Hotels located at Thekkady, Kerala State generate about 400 KL of sewage per day.  After pretreatment, the sewage passes through the filter bed over which reeds are grown. Following are the salient details of this treatment system:

a)   TDS of sewage entering into REED Bed    
              TDA of treated sewage 

1202 ppm
          914 ppm

b)   Inflow BOD
              BOD of treated effluent 

324 ppm
         29 ppm

c)   Inflow COD
              COD of treated effluent

433 ppm
          52 ppm 

d)   Capital cost

Rs. 15.00 Lacs 

e)   O & M Cost

Rs. 250/- per         day 

f)   Treatment Capacity

40 KL/da

For further details, the contact address of above Hotel is Given below:

Mr. Nagendra Singh Hada 
        Taj garden Retreat,
        Amalambika road,
        Thekkady 685 536. 

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