Soap water treatment and reuse for watering the garden and washing the car

I have made a reed bed for treating bath,wash basin and washing machine water. The aim was to reuse the water for gardening without doing major changes in the plumbing of existing houses. 

  • The reed bed  is planted with canna(kardaL in marathi) of the volume of approximately 3 times the input volume which gives 48 hours retention time. the reed bed is 2' deep, filled with gravel and sand. My output values are
  • cod: 50mg/l
  • bod3: 13.2mg/l
  • phosphate:8.53mg/l
I would like to know what values are expected for
  • watering the garden
  • car wash where the water will be sprayed
What are the critical parameters for using soap water? I have presently only considered phosphate.
Would the leaves of the garden plants turn yellow with excessive soap input?

The Central pollution control board of India specifies a BOD3 of 30mg/l , cod of  250mg/l and phosphates of 15mg/l  respectively for irrigation purposes. The laboratories in my city also generally only carry out the bod3 test. However the DEWATS book which I am using as a reference considers BOd5 values. 

  • I would like to know if the BOD 5 value will always be lesser than BOD3.My conjecture was that with more time of treatment the oxygen demand at the 5th day should be lesser than that on the 3rd day . Hence if my bod 3 value is satisfying the norms, my bod 5 value will automatically be much lesser and within the specified bracket. Please enlighten me on this.
  • Are the CPCB norms made assuming water for irrigation where there is always a base flow for running water and input of fresh water ? in my case there is no fresh water addition and the water is being directly used for the garden.
  •  Can someone give a guide on calculating retention time for kitchen water which is to be held in a grease trap, the values of which are

bod3: 72mg/l
cod: 180mg/l

  • The water would then be directly led into the reed bed and it should not be smelling.
  • This water which does not have any organic input,  is mainly soap water.  kitchen water has not been taken. Hence should the plants actually be given a soil base or should they be just on sand and gravel?

The above were two projects done in pune, a city where there is no scarcity, but high inequity of water. The water would thus be put to best use/reuse.

Many thanks in advance.


Pooja Joshi

095035 22444

18 September 2010