The ability of our project to treat the sewage treatment plant (STP) water by using slow sand filter (SSF) to remove the fine suspended particles, microbes, minerals and flocs present in effluents. So the generation and disposal of STP effluent is high. It will damage the environment in the case of presence fine minerals and create bad odour to the environment. Therefore, treatment of effluent is essential. Somewhere it is a better and substitute technique for the removal of microbes, minerals in water by means of lively coagulant mediators as polystyrene and to take away the ruthless aroma via a eucalyptus greenery. In this process we enhance grinded eucalyptus paste and well detached polystyrene in directive to attain our results in respectable. SSF have been exposed to efficiently advance the water superiority. Through pleasing multiple sum of testes from engaged sample it displays that the water is polluted and not proper for irrigation resolves. So directed simple physical and chemical parameters of pH, Turbidity, Conductivity, COD, BOD, DO Tests. In the SSF technique the polystyrene is in one layer which is acts as a filter media. In this education was carried out SSF filter as a main research work and we achieved the Turbidity, TSS, BOD, Oil & Grease and COD as15.5 NTU, 97.85%, 84.67%, 98.8% and 97.65% correspondingly. It is originating that SSF with polystyrene process the finest near of water quality was better-quality and its well suitable for irrigation purposes.