Hi Pramod, For the odour ...
For the odour removal from the STP treated water, you can introduce appropriate amount Chlorine, Sodium Hypochlorite, or other disinfectants but might need a little agitation or stirring. For the algae growth, prevent sunlight from entering the pond - covering with a collapsible cover. You can also think of using above-the-ground storage tank with cover to store the treated water with the help of a pump instead of the pond.
Regards
Justin.