The effluent from the mixing tank is taken to aeration tank-1 and aeration tank-2 in which membrane diffused aeration system with two air blowers are provided. The biological treatment comprises if activated sludge having a variable process modification system is provided to degrade the organic matter with the help of oxygen to carbon dioxide and water. The overflow of the aeration tank-1 and 2 flow into the clarifier. Here the settled biomass is either recycled back into the aeration tank or the excess biomass can be taken in the sludge drying bed. The overflow from the clarifier is taken to the pertly treated water sump. The partly treated effluent is pumped to pressure sand filter and activated carbon filter for removal of color and suspended particles. Then treated effluent is collected in the final treated water sump. The treated effluent is used for irrigation and gardening purpose in factory premises.