Physiologic impact of 2-chlorophenol on denitrification process in mixture with different electron sources

Abstract

The aim of this study was to evaluate the physiologic behavior of sludge in the absence and presence of 2-chlorophenol (2-CP) with different electron donors (phenol, glucose, and acetate) during denitrification process. In batch assays with phenol in the presence of 2-CP, a significant decrease of phenol consumption efficiencies (E_phenol) up to 99% was observed regarding the cultures without 2-CP. However, in most of the cases, nitrate consumption efficiencies ($E_{{{\text{NO}}_{ 3}^{ - } }}$), and yields of nitrogen gas ($Y_{{{\text{N}}_{ 2} }}$) and bicarbonate ($Y_{{{\text{HCO}}_{ 3}^{ - } }}$) were high, showing that the denitrifying respiratory process successfully occurred with phenol and 2-CP. The specific consumption rates of nitrate ($q_{{{\text{NO}}_{ 3}^{ - } }}$) and phenol (q_phenol) decreased up to 6.0 and 32.3 times, respectively. In assays with glucose in the presence of 2-CP, the denitrifying performance was not significantly altered in terms of efficiencies and product yields; however, $q_{{{\text{NO}}_{ 3}^{ - } }}$ was up to 1.6 times smaller than that obtained without 2-CP whereas q_glucose was increased up to 1.17 times. In assays with acetate plus 2-CP, the $E_{{{\text{NO}}_{ 3}^{ - } }}$, E_acetate, and $Y_{{{\text{N}}_{ 2} }}$ values remained high but 2-CP caused a decrease in $Y_{{{\text{HCO}}_{ 3}^{ - } }}$. Moreover, $q_{{{\text{NO}}_{ 3}^{ - } }}$ and q_acetate increased up to 1.4 and 2.0 times, respectively. These results show that the negative or positive effects of 2-CP on denitrification process depend on the type and concentration of electron source. The obtained physiologic and kinetic information might be useful to define strategies to maintain successful denitrification processes in wastewater treatment bioreactors fed with 2-CP.