Aerated Lagoon

  Hi everyone I have a municipal wastewater treatment plant with aerated lagoon process with capacity 1500 cm/d and with:pretreatment part (screening and aerated grit removal tank) aerated lagoon ( 2900 m2) with 4 aerators with unit capacity 25 kg/hfacultative lagoon (2800 m2) with 2 aerators  with unit capacity 25 kg/hClarifier (490 m2)This plant built since 1991 receive now 2500 m3/d.The main problem is the bad quality of treated water (SS > 120 mg/l and whitish look) and the sludge fails to settleHow to do ?