Modelling salinity inhibition effects during biodegradation of perchlorate

Abstract

Aims: To determine the mathematical kinetic rates and mechanisms of acclimated perchlorate (ClO)‐reducing microbial cultures by incorporating a term to relate the inhibitory effect of high salinity during biological reduction of concentrated perchlorate solutions. Methods and Results: Salt toxicity associated with the biodegradation of concentrated perchlorate (200, 500, 1100, 1700 and 2400 mg l−1 as ClO) was investigated using two microbial cultures isolated from a domestic wastewater treatment plant [return activated sludge (RAS) and anaerobic digester sludge (ADS)]. Experiments were performed in wastewaters containing various sodium chloride concentrations, ranging from 0% to 4·0% (w/v) NaCl (ionic strength: 0·14–0·82 mol l−1, total dissolved solids: 5·3–42·6 g l−1) at near‐neutral values of pH (6·7–7·8). Perchlorate biodegradation was stimulated through stepwise acclimation to high salinity. The ADS culture was capable of reducing perchlorate at salinities up to 4% NaCl, while the RAS culture exhibited complete inhibition of perchlorate degradation at 4% NaCl, probably resulting from either a toxic effect or enzyme inactivation of the perchlorate‐reducing microbes. Further, a kinetic growth model was developed based on experimental data in order to express an inhibition function to relate specific growth rate and salinity. Conclusions: Biological reduction of concentrated perchlorate wastewaters using either acclimated RAS or ADS cultures is feasible up to 3% or 4% NaCl, respectively. In addition, the kinetic model including a salinity inhibition term should be effective in many practical applications such as improving reactor design and management, furthering the understanding of high salinity inhibition, and enhancing bioremediation under high salinity loading conditions. Significance and Impact of the Study: Applications of these findings in water treatment practice where ion exchange or membrane technologies are used to remove perchlorate from water can have the potential to increase the overall attractiveness of these processes by eliminating the need to dispose of a concentrated perchlorate solution.

Biological reduction of nitrate and perchlorate in brine water using up-flow packed bed reactors

“…Using a nonlinear curve-fit, the values of the kinetic model parameters (K s and K i ) under different salinity conditions were 268 and 531 (3% NaCl), 830 and 205 (5% NaCl), and 975 and 160 (10% NaCl), respectively. Among these, the values for 3% NaCl conditions were similar to the 295 (K s ) and 575 (K i ) values obtained byPark and Marchand [53]. …”

“…This decrease in perchlorate reduction rate resulted from NaCl toxicity to the perchlorate-reducing microorganisms, implying that its overall growth and enzyme stability were adversely affected. [53] Park and Marchand [53] reported that the inhibitory effects of salinity on perchlorate reduction were significantly different depending on the microbial culture. Anaerobic digester sludge (ADS) cultures are capable of reducing perchlorate at salinities of up to 4% NaCl, while return activated sludge (RAS) cultures were completely inhibited at 4% NaCl.…”

Molecular assessment of salt-tolerant, perchlorate- and nitrate-reducing microbial cultures

“…Gingras & Batista (2002) found that a culture enriched from activated sludge yielded only insignificant perchlorate reduction after 550 hours of incubation in 1.5% NaCl. Park & Marchand (2006) were able to acclimate a culture to completely degrade perchlorate in up to 4% NaCl in a stepwise manner and developed a model that included a salinity inhibition term.…”

Greenhouse gases from membrane bioreactors: Mathematical modelling, sensitivity and uncertainty analysis

“…Eq. (4) is valid in the range of 0-4% NaCl as indicated by Park and Marchland (2006). Therefore, under 0% NaCl condition I s is equal to zero.…”

“…Mampaey et al (2015). The biological model includes the influence of the influent salinity both for the autotrophic and heterotrophic biomass (Park and Marchland, 2006). More precisely, the maximum growth rate of both autotrophic and heterotrophic biomass is modelled considering a reduction coefficient (i.e., I s coefficient), assessed as:…”