Disinfection in the final effluent of wastewater, lead to high Ecoli

Good day,

 

Am having a problem with the final effluent of one the biggest water treatment works of 16,5ml/d. The WWTWs disinfect with chlorine gas. The free chlorine and Total chlorine also monitored on shift basis, and it shows that chlorine is present in the effluent.  And both free and total are above 2.20 mg/l, on shift basis. My questions was:

I hope i will receive good responds from the forum.

 

Thank you,

 

Mr Mangena P