Biodegradation of organic pollutants in saline wastewater by halophilic microorganisms: a review

Abstract

Agro-food, petroleum, textile, and leather industries generate saline wastewater with a high content of organic pollutants such as aromatic hydrocarbons, phenols, nitroaromatics, and azo dyes. Halophilic microorganisms are of increasing interest in industrial waste treatment, due to their ability to degrade hazardous substances efficiently under high salt conditions. However, their full potential remains unexplored. The isolation and identification of halophilic and halotolerant microorganisms from geographically unrelated and geologically diverse hypersaline sites supports their application in bioremediation processes. Past investigations in this field have mainly focused on the elimination of polycyclic aromatic hydrocarbons and phenols, whereas few studies have investigated N-aromatic compounds, such as nitro-substituted compounds, amines, and azo dyes, in saline wastewater. Information regarding the growth conditions and degradation mechanisms of halophilic microorganisms is also limited. In this review, we discuss recent research on the removal of organic pollutants such as organic matter, in terms of chemical oxygen demand (COD), dyes, hydrocarbons, N-aliphatic and N-aromatic compounds, and phenols, in conditions of high salinity. In addition, some proposal pathways for the degradation of aromatic compounds are presented.

Linkage of microbial kinetics and bacterial community structure of MBR and hybrid MBBR–MBR systems to treat salinity‐amended urban wastewater

“…An efficient utilization of microbes for wastewater treatment can be difficult due to characteristics of wastewater, such as salinity. It has been found that salinity affects microbial communities in wastewater treatment bioreactors in different ways, such as increasing mortality rate due to differential osmotic pressure across cell membranes, inhibition of biodegradation of toxic metabolic intermediate compounds, and reduction of bioavailability of substrates, among others . Urban wastewater usually has a salinity level between the 0.7 and 3.0 mS cm −1 measured as electric conductivity .…”

“…It has been found that salinity affects microbial communities in wastewater treatment bioreactors in different ways, such as increasing mortality rate due to differential osmotic pressure across cell membranes, inhibition of biodegradation of toxic metabolic intermediate compounds, and reduction of bioavailability of substrates, among others. 1,2 Urban wastewater usually has a salinity level between the 0.7 and 3.0 mS cm 21 measured as electric conductivity. 3 Nevertheless, there are many industrial processes and human activities that produce wastewater of higher salinity, such as seafood processing, utilization of seawater for toilet flushing, snow-melting strategies in human settlements, or legal or illegal disposal of flowback from gas drilling procedures.…”

Effect of variable salinity wastewater on performance and kinetics of membrane‐based bioreactors

“…It has been reported that salinity decreases the microbial activity of microorganisms, but however this limitation can be overcome by adaptation . Treatment of high‐salinity wastewater showed that ammonium was predominantly removed by ammonium oxidizing archaea (AOA) and ammonium oxidizing bacteria (AOB), with a clear domination of archaea over bacteria in terms of total 16S rRNA gene copy number .…”

“…36 It has been reported that salinity decreases the microbial activity of microorganisms, but however this limitation can be overcome by adaptation. 37 Treatment of high-salinity wastewater showed that ammonium was predominantly removed by ammonium oxidizing archaea (AOA) and ammonium oxidizing bacteria (AOB), with a clear domination of archaea over bacteria in terms of total 16S rRNA gene copy number. 38 This result could happen also under the variable salinity conditions, and therefore more research should be conducted on competition of AOA and AOB for the treatment of variable salinity wastewater.…”

Bioremediation of Total Soluble Salt of Tannery Effluent Using Halophilic Microbial Consortium

“…Recent advancements have also proven successful via the addition of matched microbial strains to the medium to enhance the resident microbe's population ability to break down contaminants. Microorganisms used to perform the function of bioremediation are known as bioremediators [7]. Remediation is to find a remedy for neutralizing a toxin using living things due to their metabolic activity.…”