I'm doing a pre-treatment using BB-DOE with 4 factors (polymer, powdered activated carbon, zeolite and mesh size) and 3 levels for each factor testing TSS, COD, Ammonia and Fecal Bacteria removal.
I realized that I have a few runs where the dose of Zeolite is zero (with variable doses of polymer, PAC and mesh size). For these runs, the level of ammonia increase (higher than Raw water level). I was wondering why that happens. I was thinking it is because I still have a high level of COD (ranged between 400 and 500 mg/L) that may affect ammonia removal. Could be that the reason why ammonia increase?
What other reasons could increase the ammonia level?