Effect of Elevated Salt Concentrations on the Aerobic Granular Sludge Process: Linking Microbial Activity with Microbial Community Structure

Abstract

The long-and short-term effects of salt on biological nitrogen and phosphorus removal processes were studied in an aerobic granular sludge reactor. The microbial community structure was investigated by PCR-denaturing gradient gel electrophoresis (DGGE) on 16S rRNA and amoA genes. PCR products obtained from genomic DNA and from rRNA after reverse transcription were compared to determine the presence of bacteria as well as the metabolically active fraction of bacteria. Fluorescence in situ hybridization (FISH) was used to validate the PCR-based results and to quantify the dominant bacterial populations. The results demonstrated that ammonium removal efficiency was not affected by salt concentrations up to 33 g/liter NaCl. Conversely, a high accumulation of nitrite was observed above 22 g/liter NaCl, which coincided with the disappearance of Nitrospira sp. Phosphorus removal was severely affected by gradual salt increase. No P release or uptake was observed at steady-state operation at 33 g/liter NaCl, exactly when the polyphosphate-accumulating organisms (PAOs), "Candidatus Accumulibacter phosphatis" bacteria, were no longer detected by PCR-DGGE or FISH. Batch experiments confirmed that P removal still could occur at 30 g/liter NaCl, but the long exposure of the biomass to this salinity level was detrimental for PAOs, which were outcompeted by glycogen-accumulating organisms (GAOs) in the bioreactor. GAOs became the dominant microorganisms at increasing salt concentrations, especially at 33 g/liter NaCl. In the comparative analysis of the diversity (DNA-derived pattern) and the activity (cDNA-derived pattern) of the microbial population, the highly metabolically active microorganisms were observed to be those related to ammonia (Nitrosomonas sp.) and phosphate removal ("Candidatus Accumulibacter").Numerous wastewaters, like those generated in seafood canning, pickling, and cheese-processing industries, can contain significant amounts of inorganic dissolved salts (14). The use of seawater for toilet flushing in ships, offshore installations, and regions with problems related to water supply also introduces salts into freshwater. Wastewaters with a high salt content require the activity of salt-tolerant microorganisms which may not be present in high numbers in microbial inocula from sewage treatment plants. Salt ions exert high osmotic pressure on the microorganisms, and most of the freshwater-based microbial populations are unable to survive at these high osmotic pressures and either die or become dormant under these conditions (40). Besides that, inorganic salts can affect the structure and settling properties of microbial flocs as well as the maximum solubility of oxygen and its transfer to the liquid phase, which can lead to oxygen limitation. Consequently, high salt concentrations have a negative influence on existing biological wastewater treatment plants, affecting organic matter, nitrogen, and phosphorus removal (17). So far, most studies on chemical oxygen demand (COD), N, and P removal from saline wastewa...

Simultaneous nitritation–denitritation for the treatment of high-strength nitrogen in hypersaline wastewater by aerobic granular sludge

“…Both ammoniumenitrogen and nitrate concentrations in the effluent wastewater were very low. The former confirms that ammonia oxidizing bacteria (AOB) are not affected by salt concentrations up to 30 gNaCl L À1 as also reported by Bassin et al (2011), whereas the latter demonstrates that nitrite oxidizing bacteria (NOB) are completely inhibited at this salinity level (Pronk et al, 2014). The total nitrogen removed by simultaneous nitritationedenitritation was almost 37%.…”

“…However, all of these studies noted remarkable issues regarding nitrogen removal. Bassin et al (2011) stated that ammonia-oxidizing bacteria (AOB) could tolerate salt concentrations of up to 33 gNaCl L…”

Bacterial Consortium and Axenic Cultures Isolated from Activated Sewage Sludge for Biodegradation of Imidazolium-based Ionic Liquid

“…The main features of WAS and AGS can be found in Additional file 4. The AGS was cultured in a laboratory up-flow anaerobic sludge bed (UASB) by synthetic wastewater (Additional file 5) prior to its use as the inoculum for methane production, where the use of synthetic wastewater for AGS culturing is a common practice in anaerobic digestion studies investigating the microbiology and biodegradability [4,73,74]. The hydrolytic retention time of UASB was 6 h, and the AGS concentration in UASB was approximately 29165 mg/L.…”

Sequencing Batch Reactor and Bacterial Community in Aerobic Granular Sludge for Wastewater Treatment of Noodle-Manufacturing Sector

“…These systems generally require large surface areas for treatment and biomass separation units which enable the sludge to settle down, separating from the treated water. Therefore, the settling velocity of activated sludge plays an important role in reducing the remaining time in the settlement/decanting tank, and as a result, boosts the treatment process [2]. Conventional activated sludge systems are limited, due to the generally poor settling properties of the sludge [3].…”