NH3 stripping: heat liquid waste or use hot air to strip?

[kiamaster]

Any practical experience with ammonia stripping? We are at the planning stage of treating a 60m3 per day of ammonia wastewater - with ammonium levels at 50 - 100ppm. We will vent the stripped NH3 to air.
NH3 stripping depends on pH and temperature. I would to know from anyone with practical experience which approach is better. To heat the liguid waste (35 - 40C) and blow air at ambient temperatures to strip or to use heated air to strip without heating the liquid (15 - 18C).

thanks for any information or insights.

 

[bimr]

Ammonia stripping is an excellent process for the removal of ammonia but most of the time the application is not practical.

The practicality of the application will depend on the water quality.

It will not be practical to heat the wastewater in order to strip the ammonia. Heating the wastewater will be quite expensive. Most of the time, you simply need to increase the pH.

If you have hardness in the water, the hardness will precipitate out of solution onto the packing media. It is impractical to clean the scaled media.

Ammonia is also considered to be an air toxic in some states. You will need to check the air regulations to see if is acceptable to release ammonia into the atmosphere.

 

[moltenmetal]

You can heat the air, but if you don't heat it enough to heat the water, it won't do any good. The Henry's constant is determined by the water temperature which determines the vapour pressure of the solute (ammonia in this case).

Yes, you may need to raise the pH, and that might be expensive depending on how well buffered the water is.

If this is a continuous process, note that you'd do the heating using a cross exchanger between inlet and outlet to do most of the work, and a heater to only provide enough heat to provide the heat of evaporation plus a little delta T across this exchanger. This can still be expensive, but less so than trying to do all the heating using a heater.

An alternative possibly worth considering is ion exchange. This will give you a smaller volume of strip solution to treat, at a higher concentration.