Recently, I ran a simulation study to evaluate increase aeration for a treatment system with high ammonia waste. In this case, ammonia was the criteria pollutant for surcharges at a downstream POTW. The existing system had very low DO even with all blowers functioning. Back-of-envelope calculations revealed that there should be more than enough D.O. for the ammonia loading to the system. What was wrong?
This is a case where TKN is evolving through chemical and biological processes into ammonia. In many wastewater systems proteins, amines and other nitrogenous compounds will eventually evolve into ammonia nitrogen - either as free ammonia (NH3-N) or ammonium (NH4-N). This process accelerates with warm water temperatures and with good microbial activity. So the oxygen depletion and lack of ammonia removal was actually caused by the TKN being higher than the influent ammonia. The biological processes were working, but ammonia formed from TKN conversion was outpacing the ability to oxidize ammonia into nitrite/nitrate.
So, when presented with ammonia removal questions in wastewater, it is necessary to also evaluate TKN (total nitrogen), Total Organic Nitrogen, and Ammonia when evaluating the system.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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