Effects of heavy metals on partial nitrification
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Date
2019-06
Authors
Nur Athirah Binti Azhar
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Abstract
Partial nitrification (PN) is an effective technique for treatment of high
concentrations of ammonium in wastewater by converting 50 - 57% of ammonium into
nitrite. PN is carried out by Ammonium oxidizing bacteria (AOB) is a sensitive process
because the growth rate of AOB is much lower and strongly dependent on temperature,
substrate concentration, oxygen content and pH, and the presence of heavy metals. Heavy
metals such as nickel, zinc, cadmium, and lead that enter wastewater treatment plants
through industrial discharge can give impact on nitrification performance. In this study,
the effect of heavy metals on granular biomass and floccular biomass carrying out PN
was study based on oxygen uptake rate (OUR), ammonia uptake rate (AUR) and nitrogen
uptake rate (NUR). The granular biomass and floccular biomass were exposed to Zn(II)
with concentrations at 0.3 - 1.2 mg/L and Cu(II) with concentrations at 0.1 – 0.5 mg/L.
There was significant decrease in OUR with increasing concentrations of Zn(II) and
Cu(II) in granular and floccular biomass. The AUR and NUR also decrease as
concentration of heavy metals increases in both granular and floccular biomass. Based on
OUR, the Cu(II) starts to inhibits the partial nitrification process at concentration above
0.1 mg/L while Zn(II) at concentration above 0.3 mg/L. Overall result show that the
inhibitory effects of heavy metals on floccular biomass is higher than in granular biomass.
Furthermore, the toxicity of Cu(II) is higher compared to Zn(II) in granular and floccular
biomass