Hi Mamta You appear to have ...

Hi Mamta

You appear to have a natural watercourse which is receiving inflows of domestic sewage (not industrial or trade waste) from five separate areas. The first task is to draw up a diagram of the relevant collection area with the main channel and the laterals which are contributing. You should then look at each of the laterals and calculate the amount of sewage which each contributes based on the connection rate and the population. This can be tested by measurements of the BOD and SS from each branch and in the main channel. This should give you a clear understanding of what is going on and then you can look into the options for remediation. A first test of options would be to do a comparison of the capital and operating costs of treating the main outfall, against putting treatment on each of the individual branches - or even a new, separate collection system. You should be looking for some form of natural treatment such a lagoons or constructed wetlands in the first instance. If you have to go to primary and secondary treatment then costs will spiral.