Kinetics of hydrogen‐dependent denitrification under varying pH and temperature conditions

Abstract

It is important to determine the effect of changing environmental conditions on the microbial kinetics for design and modeling of biological treatment processes. In this research, the kinetics of nitrate and nitrite reduction by autotrophic hydrogen-dependent denitrifying bacteria and the possible role of acetogens were studied in two sequencing batch reactors (SBR) under varying pH and temperature conditions. A zero order kinetic model was proposed for nitrate and nitrite reduction and kinetic coefficients were obtained at two temperatures (25 +/- 1 and 12 +/- 1 degrees C), and pH ranging from 7 to 9.5. Nitrate and nitrite reduction was inhibited at pH of 7 at both temperatures of 12 +/- 1 and 25 +/- 1 degrees C. The optimum pH conditions for nitrate and nitrite reduction were 9.5 at 25 +/- 1 degrees C and 8.5 at 12 +/- 1 degrees C. Nitrate and nitrite reduction rates were compared, when they were used separately as the sole electron acceptor. It was shown that nitrite reduction rates consistently exceeded nitrate reduction rates, regardless of temperature and pH. The observed transitional accumulation of nitrite, when nitrate was used as an electron acceptor, indicated that nitrite reduction was slowed down by the presence of nitrate. No activity of acetogenic bacteria was observed in the hydrogenotrophic biomass and no residual acetate was detected, verifying that the kinetic parameters obtained were not influenced by heterotrophic denitrification and accurately represented autotrophic activity.

Kinetics of microbial bromate reduction in a hydrogen‐oxidizing, denitrifying biofilm reactor

“…Our K value of 1.3 mg BrO À 3 /L is the first reported K value for bromate reduction. For hydrogen oxidizing, autotrophic denitrifying bacteria, previous studies showed a q max ¼ 0.38-0.74 (Rezania et al, 2005) and K ¼ 0.18-0.16 mg N/L (Kurt et al 1987). For hydrogen oxidizing, autotrophic perchlorate-reducing bacteria, the parameters were q max ¼ 3.1 mg ClO (Nerenberg et al, 2006).…”

Chemolithotrophic denitrification in biofilm reactors

“…Carrier materials used in these systems have an extremely high specific surface area which allows high biomass concentrations and, thus, the treatment of high nitrate loadings. Several studies report higher denitrification rates in biofilm systems such as fixed-bed or fluidized-bed reactors compared to suspended growth reactors [12][13][14][15].…”

Experimental and modelling study of drinking water hydrogenotrophic denitrification in packed-bed reactors

“…Although there are several studies on hydrogenotrophic denitrification reported in the literature, only few of them use biological kinetic data to facilitate the design and operation of biological nitrogen removal plants [10,[13][14][15] and even less study the kinetics of the biofilm process in a hydrogenotrophic denitrifying reactor [16]. However, modelling of denitrifying biofilm reactors has been carried out by several authors in heterotrophic [17,18] and sulphur autotrophic [19,20] denitrification.…”