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Design Queries : Septic Tank for a Kayaking Center - Uttarakhand

We (my husband, my daughter and I) are living in a village named Shivanandi in Rudraprayag District in Uttarakhand.  We are building a kayaking center close to the banks fo the Alaknanda River.

In the long run. we're expecting to have around 30 people occupying this place (for around 6 months of the year).  We are going to separate our gray water from the sweage.   The gray water will be purified through a wetland and reused for our ornamental garden.

Treatment of sewage will be done with a septic system.  The system will include a separation chamber from which a pipe will conduct the water into a perforated septic pit.

we are located about 15 meters above the river water level (these days... much closer in the monsoon).

I have a few questions

1.  will 15 meters of very sandy soil (i.e. river bank sand) be a large enough filter in order to prevent contamination of the river?  after 15 meters the water will reach the river bank level and will continue filtering until it leaks into the river.  The river is our life, we would not want to harm it.

2.  If the answer to 1 is positive, what size should we build?  As I understand, 48 hours of retention time is good enough in the seperation chamber.  Assuming 50 liters per person per day, we need a 3 cubic meter seperation chamber (50x30x2=3).  We have a much larger area for the chamber (around 12 cubic meters).  Is a longer retnetion time a hazard or a blessing for the system?

3.  How big a pit should we dig for the septic pit?  Should it be empty with a perforated brick wall to hold it or should we fill it with rocks?

 Thank you very much, Alice Shalabh and little Maya.



1. Design Query

Dear Alice Shalabh and little Maya,

The suggestions are as given below:

    * In the long run. We’re expecting to have around 30 people occupying this place (for around 6 months of the year).

Black water -- from toilets will be 30x 20 lit == 600 lit

Grey water form house will be 30 x 100 lit == 3000 lit

Both together will be 3600 lit i.e 4000 lit per day, will be design capacity of tanks, chambers etc.

    * Only wet land will not do, you will take care to use organic soaps/ detergent etc.

The gwt chambers with filters, wet-lands with plants and a retention tank of say 1 day capacity will have to give you cumulatively 6 to 8 days retention. This will be required, more it is better it will be. Can you make an open pond- this will give bio-remediation, UV, and can have rain-water also stored in it? Aquatics will upgrade the aesthetics, if fish is introduced this will also bio-clean and join in your gwt.

    * Can provide a design for an improved septic tank, retention in tank called baffled reactor- retention 2 days and next to have chamber called baffled filter reactor with gravel retention 4 days, then have it sent to wetlands it is called planted filter- retention 3 days, storage in sump or open- pond retention 2 days.

The retention given is bare minimum. If you increase, it will be advantageous.  

Also please see this ppt sent to get some idea, access here: Vigyan Vijay PPT

Be in touch for more details.

With well wishes,

Er. Ajit Seshadri
Secretary and Head- Environment & Energy
The Vigyan Vijay Foundation
New Delhi

2. Dear Alice,  If you still

Dear Alice, 

If you still require help with this project I may be in your area in the coming months and would be able to come and have a look and maybe offer some ideas. 

I may also be able to assist you in constructing a micro hydro or wind power scheme.

If you are in a fog rich area you could harvest water from the fog too.

Please feel free to contact me on

Best of luck with the project, 


Tarun Nanda

Principal Engineer

Nanda Bouma

Civil & Environmental Engineers

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