Effect of continuous Cd feeding on the performance of a nitrification reactor

Abstract

The inhibitory effect of Cd on nitrification was investigated in a continuous-flow system with enriched nitrifying bacteria. The maximum specific ammonium utilization rate and the half-saturation constant were found as 671 mg NH(4)-N/g VSS day and 0.48 mg/l, respectively. In the case of continuous Cd input at 1 and 2.5 mg/l, nitrification was inhibited by 30% and 47%, respectively. Inhibition ranged from 20% to 40% and no further increase in inhibition was exhibited in new runs except at 10 mg/l influent Cd. At 10 mg/l influent Cd, specific ammonium utilization and nitrate production rates were inhibited by 90%. On the contrary, a serious nitrite accumulation was not observed during this period. When Cd feeding was stopped, recovery from inhibition was observed after 37 day which was seen by the improvement in ammonium utilization and nitrate production rates. A shift in microbial population from the initial Nitrosomonas sp. to the Cd-tolerant Nitrosospira sp. was observed in the recovery period from severe Cd inhibition. After the domination of Nitrosospira species, redosing at 10 mg/l and then at 15 mg/l did not affect the performance as before.

Inhibition of respiration and distribution of Cd, Pb, Hg, Ag and Cr species in a nitrifying sludge

“…This fact may be one of the reasons of the wide IC 50 range reported for heavy metals. Another reason is that toxicity of heavy metals has been rarely tested in a nitrification system alone [8][9][10][11], but in organic carbon removal systems having a high heterotrophic activity. Although this is the real case, in such a system the effect of heavy metals on nitrification may be influenced by the presence of organic matter which also complexes with metals.…”

Combined effect of zinc and cadmium ions on nitrification performance during the biological nitrogen removal of livestock breeding wastewater

“…Researches showed that when the concentration of cadmium ions was 1 mg/L and 2.5 mg/L, nitri cation was inhibited by 30% and 47%, respectively. When the cadmium ion concentration was 10 mg/L, nitrate production was inhibited by 90% (Semerci and Çeçen 2009). It can be seen that zinc and cadmium ions have signi cant effects on the performance of biological nitrogen removal.…”