We are operating cooling tower with circulation rate of about 10,000 m3/hr. Recently a case of oil ingress occurred through one of the coolers in a process unit. This oil ingress resulted in increasing the cooling water supply temperature from 29 degC to about 36 degC. Although oil content in the cooling tower has been reduced to below 10 ppm by appropriate chemical dosing the problem of high CWS temperature still persists. Cooling tower fans and CW distribution through fills have been checked and found to be working fine. Can anyone suggest some measures for reducing this CW supply temperature back to normal?