Recycling MWW in cooling

Coagulation by a metallic salt is also advantageous in that it precipitates the residual phosphorus that could otherwise promote bacterial development. 

The presence of ammonium can raise the potential problem of biological nitrification in the cooling rower depending on the NH4 concentration in the water, its alkalinity and above all the conditioning of the system. 

Usual concentrations of NH4 after biological purification at high load are about 15 to 20 mg-l of N.NH4. This may involve production of 68 to 98 mgT of HNO3 (5.3 to 7.1 F) in cooling towers. 

Though nitrification does not occur with chromate-zinc conditioning, it may become a problem with phosphate-zinc conditioning at pH values of 6.6 to 6.8. It will certainly be a problem with conditioning carried out at what is termed an uncontrolled pH . Two things can then be done  

This is how power stations have been able to suspend softening treatments on their river water (40 mg4 N.NH4), leaving it up to nitrifying bacterial, momentarily, to vaccinate the water in the system (Table 33). 

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