Importance of cadmium speciation in nitrification inhibition

Semerci, Neslihan; Çeçen, Ferhan

doi:10.1016/j.jhazmat.2007.01.041

Cited by 23 publications

(22 citation statements)

References 26 publications

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“…The inhibitor concentration I was expressed in terms of bulk labile Cd rather than free or biosorbed Cd since inhibition was shown to depend on labile metal concentration (Semerci and Ç eçen 2007;Semerci 2007). The continuous-flow reactor was initially filled with the same sludge as in previous batch experiments.…”

Section: Mechanism Of Heavy Metal Inhibitionmentioning

confidence: 99%

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

Semerci

Çeçen

2008

Biodegradation

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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.

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Section: Mechanism Of Heavy Metal Inhibitionmentioning

confidence: 99%

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

Semerci

Çeçen

2008

Biodegradation

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“…Studies to date have shown that heavy metals inhibition of nitrification may be attributed to the free ion, complexed ion and sorbed ion (extracellular or intracellular) rather than the total metal concentrations (Hu et al 2002;Semerci and Çeçen 2007). Some researchers reported that the free metal ions are responsible for the inhibition of nitrifying bacteria (Braam and Klapwijk 1981;Hu et al 2002) and some researchers have indicated that inhibition can be correlated to the sorbed metal ion concentration (Semerci and Çeçen 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Some researchers reported that the free metal ions are responsible for the inhibition of nitrifying bacteria (Braam and Klapwijk 1981;Hu et al 2002) and some researchers have indicated that inhibition can be correlated to the sorbed metal ion concentration (Semerci and Çeçen 2007). Several researchers have shown that adsorbed copper concentration has no direct correlation with nitrification inhibition even though the biomass has a higher sorption affinity for copper than other heavy metals (Zn, Cd, Ni;Chua et al 1999;Hu et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Inhibitory Effects of Copper on Nitrifying Bacteria in Suspended and Attached Growth Reactors

Lee

Tian

Ong

et al. 2009

Water Air Soil Pollut

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Municipal wastewaters with industrial discharges typically contain heavy metals which may inhibit the biological processes in wastewater treatment plants. In this study, copper inhibition on strict nitrifiers in a suspended growth (SG) reactor and a combined attached and suspended growth (A&SG) reactor was compared. Both reactors were subjected to a continuous copper input of 5 mg/L. When the accumulated total copper concentration in the reactor were approximately 25 mg/L (due to sorption to the biomass), a sharp decrease in nitrification (increase in inhibition) were observed in the SG reactor while nitrification remained the same for the A&SG reactor indicating that attached growth systems were more robust against copper toxicity than suspended growth systems. Using MINTEQA2, the concentrations of various chemical species were estimated and, of the different species present, adsorbed copper in the biomass and aqueous Cu(NH 3 ) 4 +2 were found to positively correlate with percent inhibition of nitrification. Based on the changes in the concentrations of the two species, Cu(NH 3 ) 4 +2 was probably the main chemical species responsible for inhibition of nitrification. This study has implications for wastewater treatment plants treating wastewaters with high ammonia and copper present.

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“…10 Also, earlier studies on Zn and Cd indicate that nitrite oxidation is not as seriously inhibited as ammonium oxidation. 11,12 It is recognized that the majority of inhibition studies has been carried out in sewage treatment systems where also complexation of metals with dissolved organic matter and heterotrophic biomass plays a role. However, this type of interference should be avoided if the main aim is to have an insight into nitrifier activity.…”

Section: Introductionmentioning

confidence: 99%