Nitrifying Biomass Acclimation to High Ammonia Concentration

Selection, acclimation, and kinetic characterization of a nitrifying microflora chosen from natural sources and capable of degrading total ammonia nitrogen (TAN) at high concentration was performed. The inocula of animal manure and of marine sediments were selected due to their nitrate production (55.8 mg N/L⋅day) and tolerance to salinity (16 g ${\mathrm{Cl}}^{-}/L)\text{.}$ An acclimation continuous culture was made using TAN up to 1,000 mg N/L and nitrogen load rate of 250 to 1,000 mg N/L⋅day. The TAN degradation rate after acclimation reached 0.16 mg N/mg VSS⋅h (VSS=volatile suspended solids) at a feed concentration of 1,000 mg N/L; the ammonia-oxidizing population increased from 60 to 77% whereas nitrite-oxidizing bacteria decreased from 40 to 23%. The following substrate-inhibition Haldane parameters were determined: $r_{\mathrm{TAN}\text{,}\max }=0.21$ and 0.19 mg N/mg VSS⋅h; $K_s=3.0$ and 4.8 mg ${\mathrm{NH}}_3-N/L;$ $K_i=22.4$ and 35.6 mg ${\mathrm{NH}}_3-N/L$ for sludge before and after acclimation, respectively. Differences between $r_{\mathrm{TAN}\text{,}\max }$ values were not statistically significant with a confidence limit of 95%, whereas $K_s$ and $K_i$ differences were significant, showing a better tolerance to higher ammonium concentrations.