Understanding　salt　effects　on　activated　Sludge　systems　and　treatment　performance　is　essential　in　order　to　design　and　operate　a　full　scale　treatment　plant　processing　saline　sewage.　For　this　purpose,　a　bench　scale　modified　University　of　Cape　Town　(MUCT)　process　for　treating　saline　sewage　was　used　to　provide　information　with　regard　to　microbial　population　shift　and　treatment　performance.　Various　salt　levels　(5,　8,　10　and　15　g/L)　Were　studied.　Experimental　results　indicated　that　the　salt　concentration　in　sewage　significantly　affected　phosphorous　removal,　while　salt　inhibition　of　ammonium　degradation　was　slight,　even　in　a　15　g/L　salt　solution.　Outstanding　nitrite　accumulation　in　aerobic　tanks　occurred　in　the　MUCT　treating　8　g/L　saline　sewage,　which　resulted　in　denitrifying　nitrite　by　phosphorous　accumulating　organisms　(PAOs)　in　the　anoxic　tank.　Population　size　of　physiological　groups　(aerobic-heterotrophic,　nitrifying　and　denitrifying　microbial　group)　was　also　investigated　at　different　salt　levels.　The　investigation　of　changes　in　the　dynamics　of　the　activated　sludge　microbial　Structure　gave　an　insight　into　the　nature　and　the　magnitude　of　salt　effects　on　the　microbial　community.