What is a Root Zone Waste Water Treatment?


Author: Saudamini Sharma

The sight of filthy sewage flowing unrestricted into our rivers is not new. Our governments spend humungous public funds on treating sewage water before it is discharged into rivers. However, the sad state of our rivers indicates that a lot is left to be desired.

High maintenance cost is the main deterrent for people from having a sewage treatment plant installed in their industry or residential area. So, they completely depend on state-managed and operated Sewage Treatment Plants (STPs), which often malfunction due to overload.

While every large city in India has large-scale conventional STPs, they usually fall into disuse due to their high operating costs, equipment corrosion and lack of skilled operating personnel. If sewage is treated at each industry and residential colony, a major portion of the problem can be mitigated.

Approximately 70% of domestic water is released as wastewater, most of which can be recovered if it is properly treated. Hence, wastewater should be seen as a resource rather than waste. Wastewater can be mainly classified into two categories:

  • Grey water – wastewater generated from kitchens, laundry, bathrooms, etc.
  • Black water – wastewater from toilets containing faecal matter and urine, which is also called as “sewage”

Both grey water and black water can be suitably treated by root zone wastewater treatment and reused for non-potable applications such as toilet flushing and kitchen gardening. Among the many types of STPs, Root Zone Wastewater Treatment (RZWT) is the most innovative and eco-friendly system. The Root Zone Waste Water Treatment system is a low cost, virtually zero energy and maintenance-free plant. What’s more, it is pretty good looking too!!!

Root Zone Waste Water Treatment Spot the STP here
Root Zone Waste Water Spot the STP here!

What exactly is Root Zone Wastewater Treatment?

‘Root Zone’ is a scientific term used to cover all the biological activity among different types of microbes, the roots of plants, water soil and the sun. It consists planted filter-beds containing gravel, sand and soil. The RZWT system utilises nature’s way of biologically processing domestic & industrial effluents. This effective technology called Decentralised Wastewater Systems (DEWATS) was developed in 1970s in Germany and has been successfully implemented in different countries mainly in Europe and America.

The root zone waste water treatment system makes use of both the biological and physical-treatment processes to remove pollutants from wastewater. Due to its natural process, there is no need to add any input such as chemicals, mechanical pumps or external energy. This reduces both the maintenance and energy costs.

To accomplish this, the root zone wastewater treatment undertakes the following steps:

  1. Pre-treatment done in a Settler – a device that separates the liquid from the solid
  2. First treatment takes place in a Anaerobic Baffled Reactor – a device with several identical chambers through which the effluent moves from top to bottom.
  3. Second treatment happens in an Anaerobic Filter – a device filled with a filter material (cinder), through which the effluent moves from top to bottom.
  4. Third treatment takes place in a Planted Gravel Filter – a structure filled with gravel material and planted with water-resistant reed plants, which provide oxygen to the passing effluent.
biological wastewater treatment
Main DEWATS modules for physical and biological wastewater treatment

1. Settler | 2. Anaerobic Baffled Reactor | 3. Anaerobic Filter | 4. Planted Gravel Filter
Source: BORDA Germany

The Root Zone Waste Water Treatment system takes into account the natural slope of the ground, so that water flows from one device to another without any external energy input such as motor pump. Once the reed plants create an established stand, usually after the first growing season, the reed bed requires little or no maintenance. The plant foliage will soon blend naturally into the landscape, ever changing with the seasons and creating a pleasing sight as well!

Conventional Water Treatment PlantRoot Zone Treatment Plant
A lot of sewage aeration tanks powered with mechanical energy do not work because of power cuts, technical problems and poor maintenanceBy its treatment and construction features DEWATS is designed to limit operation and maintenance requirements and in the same to ensure high treatment standards even for shock loads
Requires lot of external energyMinimal need for external energy
Pumps neededUsing gravity instead of pumps, avoiding valves
Regular maintenance requiredZero maintenance
High operating costsLow operating costs

Rootzone waste water
RZWT system at Aravind Eye Hospital

In India, this project was first executed by Bremen Overseas Research and Development Association (BORDA) in the Auroville global community. Since the last 15 years, Auroville located in South India near Pondicherry has been experimenting with such natural wastewater recycling systems. Auroville has now become a pioneer in the Root Zone Wastewater Treatment System and has enabled many such plants across India. Another such treatment plant has now been implemented in Aravind Eye Hospital, Pondicherry by Ascenso Management & Consulting Services.

Ecoideaz is hell bent on proving that sensible green ideas do emerge from India. It is eager to build a comprehensive portfolio of all eco-friendly ideas developed in India and create a repository for innovative green ideas both from the investor and consumer perspective.


  1. Hi
    I am a consultant promoting eco friendly treatment options for waste water in south india more specifically in Tamil Nadu.
    I am very interested in your Rot Zone Treatment Process
    Kindly let me know how we can work together to save environment.

  2. Hi, i am vinod patil from Maharashtra i have working last five year in wastewater treatment and i am interested for your treatment process .please can we work together in our region.inform me .

  3. Hi. This is a very good article and I find it a brilliant idea. But sadly, that’s all it is sir. An idea. We hear about it happening in auroville but I want to start it in my own property. And encourage others to do the same. But how do I know where to get the equipment from? What specifics like size etc… to use when designing it? which plants exactly. Some more specific details would indeed be very helpful and practical to make this planet a lot greener. There are many of us who want to be green but don’t know how.

    • Hi Ninoschka,
      Its not just an idea. It is a viable option that we have ourselves implemented. The first photograph in this article is of our project that we have done for a resort. All designing aspects like size etc depends on the area of project and amount of waste water generated etc. Commonly Canna plant is used as you can see in the photo. We would advise to get the plant designed and erected by an agency which does it and then handle the maintenance yourself, as for maintenance only a mali is required!!! There are no machinery or power required for this project. Send us an email on saudamini@amcgroup.co.in, so that we can take it further if you wish to install this plant. Regards

  4. We run a residential school with 400 students. Hitherto, both grey water and black water was being sent to septic tank. We are now separating grey water allowing it to flow into the lake adjoining our premises. We are planning to set up a system to treat grey water before it enters lake. Hence, we request assistance to deploy root zone treatment. Can you help us?

  5. Hi sir, I’m student of microbiology & i think this article really innovative, helpful to all microbiology student.thank u

  6. Hello sir/mam
    I am student of civil engineering from university of pune. Currently in final year, My area of interest is water purification and disposal of sewage .I am working on RZTS as project point of view. I studied whole RZTS technology. And interested in using plants or species surviving in low sunlight for RZT indoor system.
    So kindly tell me list of plants which can be used for indoor RZTS .
    Thanking you

    • Dear Vishal,
      RZTS uses natural slope for flow of water, hence mostly we have made such systems outdoor. At present, we have not installed any indoor RZTS, but surely its an interesting idea. I would try to get some information on the types of indoor plants for such project and update you.

      Thanks and regards

  7. Great blog. It has explained a lot regarding the aspects of water treatment solutions. Thanks a lot and thanks for explaining the things regarding the different kind of waste water solutions.

  8. can this method be used in case of apartment complexes? can common areas/ recreational areas be used?

    • Hi Shilpa,
      yes, rootzone method can be used for apartments as well, provided you have enough space for small ponds in recreational areas

  9. Hello Sir/ Madam
    What about treating waste water generated from an automobile service station using RZTS? The available option of electrocoagulation etc is not affordable for these small unit holders. So it will be highly useful for this section so that they can recycle and reuse a part water. I imagine a plant setup with a series of sintex tanks. Kindly advice.

    • Hi Raghu,
      No, using Rootzone alone will not help you to treat oil-based waste water, since plants cannot absorb chemicals. for that you need to utilise the Bioremediation technique to remove oil waste first. check our article on that

    • Hi Priyan,
      there is no pond in the RZWT system! the settling tank is a completely covered cement structure and the rest is all plant bed

  10. Saudamini,
    What is the potential of implementing your system in the Arizona desert for a home that would be seasonally habitated. I presume the plants would die due to lack of water. So then would they come back once use of the system resumes?
    Curious what options I would have using this system, I do want to be self sustained and eco-friendly.
    Thank You
    Raul Ramirez

  11. Hi Sir
    I m working in environment field last 15 year in chemical units. I want to know for this system, what is limit of TDS of Effluent. Can we implement this in Dye Unit ? Do reduce TDS ?

    • Hi Sunil,
      Thanks for your specific query. TDS limits are different for different water types. are you talking about TDS drinking water? i think TDS in a chemical dye unit will be very high for bioremediation and rootzone. if you tell me your current TDS level after effluent treatment, i can guide you

      • dear lawrenece,

        my current TDS after effluent treatment is 10,000 to 12,000. Please advise me to further reduce it. And also I want to know that can we work with high TDS effluent of around 40,000 TDS.

  12. An accommodation premises generating effluent of around 3000 kld on daily basis, Then how much area required to built this root zone sewage treatment plant.

  13. Greetings.
    1. Really impressed with your RZTP. I think it is same/similar to DEWATS.
    2. What is the potential of implementing your system in the farm house near Hosur, Tamilnadu. The area required, cost of construction (2000sq ft house with about 4-6 people living).
    3. I do want the house to be self sustained and eco-friendly in treatment of both grey & black water.
    4. The lead time before the treatment plant gets operational ?
    5. How can it be ensured that rain water ingress & black flow is avoided from the plant bed, which is open.
    6. What is the frequency of cleaning & maintenance to ensure proper functioning. How often will it require desilting & removal of sludge from tanks

    Thank You

    • Hi Mukesh,
      since you are asking too many queries with elaborate details, i will mail them to you

      • Greetings,
        I have the same doubts as well.
        Also what should be the climatic conditions ?
        And what is its cost of construction including the baffled reactor, the settler and the reed bed gravel filter ??
        Please reply as soon as possible.

        Thank you

  14. I am a low cost housing consultant implementing Auroville technologies in my projects.waste water treatment is also a part of my activity.
    I am creating awareness among voluntary agencies in the above topic.
    I will come to you when in need.
    Thanks for the article.

  15. Greetings !

    I am an consultant for plumbing services, is this system is compatible for treating kitchen waste water as well as sewage water?
    My project is centralised kitchen with a small toilet block. Per day there is discharge of 20,000 ltr of waste water from kitchen out of which 10% is of black water.
    What is the maximum area you require for construction of tanks and the root beds?

    • Hi Alyson,
      as you can see the example of a hospital, this system can treat waste water from a few hundred people. but i must admit such natural ways of cleaning water will be much slower than chemical or mechanical ones

  16. Hi,
    I am MEP Engineer in working with a Builder, I am Interested to know More about the system,

  17. Hi
    A nice article explaining the system quite simply. I would like to get this system implemented in the home that we are building in Kadugodi. We are doing the following:
    1. We expect to have about 300lit a day of sullage, including kitchen waste water and possibly a similar quantity of black water, in two separate streams. These are in 2 separate streams
    2. We plan to treat the sullage using plants and recycle this stream to our flush tanks, thereafter going intot the black water stream.
    3. We do not expect to have much oil in our system, since we consume vegetarian, non-pfat food in the place.
    4. We have a 3000+sqft house on a 2400 sqft plot and are leeaving the open space that we have for sullage treatment and sewage treatment using as many passive processes as possible.
    5. The usable open space is probably 500+sqft.
    6. I have a civil contractor on site, as well as plumbing & electrical contractors available, doing work now at site.
    Could you provide me consultancy/advise, or help with implementation in any way.
    Should I travel to your location for the discussions, to get it started?
    I look forward to youyr reply
    Thanks ……….. sincerely ………. Varadu Seshamani

    • Hi Varadu,
      thank you very much for your interest in this water treatment. i will ask our expert to reply to you on your email id

  18. Hello please for a project of a 3star hotel and resort what specification and what ways will you apply this?

  19. Dear Levine Lawrence,
    Just a gentle reminder. Still awaiting mail from you. In a little bit of a hurry to finalize the house and the systems prior to commencement of construction. Would be grateful if you could reply at the earliest.

    • Hi Dhiraj,
      any swamp water plant will be suitable. Common reed plant, Giant reed, broadleaf cattail, canna lily plants are the common ones

  20. Hi,
    can we do this method in coastal areas. Actually the sewage from nearby hospital is allowed to enter into sea and the toxic sewage is creating a huge problem at present in my locality near Kozhikode beach,kerala. I hope this method is most suitable. Particularly we want to know about the approximate cost of installing this system. Please do reply it’s very urgent.

  21. Hello 🙂
    Really this is one amazing technique and I am an Architecture student and I wish to include this treatment in my Thesis , My topic is a “CONSERVATION AND RESEARCH CENTER FOR BIRDS” ,the SITE is situated near MANGROVES along the thane creek in Navi Mumbai ,my only question to you is then I can implement this treatment for my Center?? No issues if it is adjacent Mangroves??

    • Hi Kajol,
      Thanks for your heartwarming compliments. actually this is a wetland water treatment idea, so it should work with mangroves as well. in fact mangroves themselves are water absorbing trees so they will surely compliment.

      • Okay thanks for responding , how should I calculate how much area will be needed for this treatment? And what are the tank sizes needed?

  22. Hello!
    Thank you very much for this article! I am an interior architecture student from Stockholm and we are working with RZWT in a project right now. I have two special questions:

    1. How deep should the root zone go into the ground? (how deep does the whole have to be)
    2. Our root zone has the measurements 4m x 1,4m and I wonder if the 4 parts all need the same amount of space? So that each “station” is one meter long?

    I would be really thankful for answers!
    Best regards,

    • Hi Frida,
      Great to hear about your RZWT activity so far away in Stockholm! Ideally your pit should be 6-8 feet deep so that it is deep enough to settle the sediment but not harming the ground water by seepage. the four parts need to be equal but not exactly.

  23. Dear Levine Lawrence,

    Very impressed by the technology. I would like to know whether the treatment plant can be suggested for a school in Hyderabad where my niece is studying.
    The school is interested in green technology.

    Looking forward to your reply,

    Best regards,


    • Dear Ramaswamy,
      Thank you very much for your interest in using the rootzone technology. yes, it is very much suitable to any school provided they have large space for grey water storage and disposal.

  24. hello,
    I am Jay, student of architecture from gujarat, I read your article. Currently I am working on my final year thesis project in which i am proposing the root zone treatment plant for that How I can calculate the required area to install this system, My site is in the cuddalore, tamil nadu, nearer from the pondicherry.

    • Hi Jay, the best way is to visit an existing rootzone facility nearby and get a guesstimate on the spot. your site is close by to Aravind eye hospital in Pondicherry, so you can visit and see for yourself

      • I am from gujarat, I can’t visit now. can you please help me about required area to install this system, according to my calculation the effluent water flow rate is approximately 3,94,000 L.

  25. Hi I live in western rajasthan and have been studying older systems of rainwater harvesting like tankas, etc. In a bid to also minimize our water consumption, i wanna reuse the water from the baths, laundry, and even toilets (if it does not smell), but do not know if it will be feasible and manageable in a residential complex such as mine. I also need assistance in how to plan it and what equipments to use. Please get back to me asap

  26. Hello

    We are very much interested to know about this RZWL technology and would like to introduce in small towns of Himachal Pradesh.

    Please let us know how we can associate with you.

    • Hi Aditya, great to see your interest in this RZWT technology. I will send you details by mail


Please enter your comment!
Please enter your name here