Effluent treatment plant in a factory : Need solutions to get rid of the bad smell

Our factoryhas an ETP where canteen waste water, septic tank water and DM plant regenerated water is being treated. Its capacity is 200 T/Hr and max drain water flow is 100 KL/Hr. We are having problem of bad smell coming out of treated water. The temperature of inlet water is also at 40-45 deg generally (mostly due to canteen). Our ETP is FAB reactor type and is of reputed design installed only 5 yrs back. I need solutions to 4 problems in this regard

1. Why is the smell coming ?
2. Can I measure the smell coming and identify the root cause?
3. Is there any agency which can come to my site, study the problem in detail and help me solve it in India
4. If I can solve it myself, how to go about doing it?

Chetan G.K.