Effect of Benzophenone-3 on performance, structure and microbial metabolism in an EGSB system.

Benzophenone-3 is an organic compound widely used as a UV filter, which has been reported as water pollutant and is connected with endocrine disruption in humans and animals. Expanded granular sludge beds (EGSB) are a form of an anaerobic digestion system, which has been successfully evaluated for wastewater treatment, and the removal of different compounds, however little is known about the effect of compounds as Benzophenone-3 in the performance of EGSB systems. In this study, we evaluate the effect of BP-3 on the performance, microbial structure and metabolism of EGSB reactors. For this purpose, biogas production, removal efficiencies of BP-3 and DQO were monitored. Changes in bacteria and archaea microbial structure were investigated using PCR-DGGE, and the effect on anaerobic metabolism was evaluated by measuring the expression of mcrA and ACAs genes through qRT-PCR. The systems remained stable and efficient throughout the operation stages, with CH4 percentages greater than 55% and COD and BP-3 removal percentages greater than 90%. The presence of different concentrations of Benzophenone-3 influenced the organization of microbial communities, especially archaea. However, this did not affect the stability and performance of the EGSB systems.

Acidogenesis is a key step in the anaerobic biotransformation of organic micropollutants.

Understanding the role of the different anaerobic digestion stages on the removal of organic micropollutants (OMPs) is essential to mitigate their release from wastewater treatment plants. This study assessed the fate of 21 OMPs during hydrolysis and acidogenesis to elucidate the contribution of these stages to the overall anaerobic removal. Moreover, the removal mechanisms and factors influencing them were investigated. To this purpose, a fermentation reactor was operated and fed with two different substrates: starch (to jointly evaluate hydrolysis and acidogenesis) and glucose (to isolate acidogenesis). Results indicate that sulfamethoxazole was highly biotransformed (>80 %), while galaxolide, celestolide, tonalide, erythromycin, roxithromycin, trimethoprim, octylphenol and nonylphenol achieved a 50-80 % biotransformation. Since no significant differences in the biotransformation efficiencies were found between starch and glucose fermentation, it is stated that the enzymatic activities involved in starch hydrolysis do not significantly contribute to the cometabolic biotransformation of OMPs, while acidogenesis appears as the major player. Moreover, a higher biotransformation (≥15 percentage points and p ≤ 0.05) was found for galaxolide, celestolide, tonalide, erythromycin and roxithromycin during acidogenesis in comparison with the efficiencies reported for the acetogenic/methanogenic step. The biotransformation of some OMPs was explained considering their chemical structure and the enzymatic activities.

Comparison of microbial and physicochemical behavior of expanded granular sludge bed system during methylparaben and triclosan removal.

Methylparaben and triclosan are antimicrobial agents widely used as preservatives in a variety of personal care and pharmaceutical products. Wastewater is considered the main source of these compounds in the environment. Expanded granular sludge bed (EGSB) reactors are a high rate technology for wastewater treatment based on biological processes and have been shown to be efficient in removing different types of compounds; however, little is known about the effect of contaminants such as methylparaben and triclosan on their behavior and effectiveness. In this study, we evaluate and compare the microbial and physicochemical behavior of EGSB systems during methylparaben and triclosan removal. The presence of different concentrations of pollutants had an influence on the cluster organization of microbial communities, especially bacteria. However, this did not affect the stability and performance of the EGSB systems. The banding patterns of the denaturing gradient gel electrophoresis of archaea demonstrated the constant presence and abundance of Methanosaeta concilii throughout all stages of operation, showing that this microorganism played a fundamental role in the stability of the reactors for the production of methane. The type of compound and its concentration influenced the expression of the mcrA and ACAs genes; however, these changes did not alter the stability and performance of the EGSB systems.

Anaerobic biological treatment of methylparaben in an expanded granular sludge bed (EGSB).

This study evaluated the behavior of an anaerobic expanded granular sludge bed system using different methylparaben (MPB) concentrations. The assay was conducted for 268 days and was divided into seven stages of operation, which included the starting stage and subsequent stages where the MPB concentration was increased. The inoculum that was used was a mixture of anaerobic granular sludge with flocculent active sludge that contained 21.7 g/L of total suspended solids and 17.4 g/L of volatile suspended solids, resulting in an organic content of approximately 80%. The MPB removals after applying concentrations of 300 mg/L, 500 mg/L and 1,000 mg/L during the different stages and adding glucose to the influent were 94±2.4%, 84±5.8% and 88±7.4%, respectively. For phases without glucose, the results were 97.4±0.4%, 96±1.6% and 98.2±0.3%, respectively. The results showed a high pollutant removal and good progress in terms of the physical and biological characteristics of the granular biomass, which showed no change in the presence of the compound or a concentration increase.

The operation of two EGSB reactors under the application of different loads of oxytetracycline and florfenicol.

This study evaluated the effect of the antibiotics oxytetracycline (OTC) and florfenicol (FLO) on the operation of two EGSB (expanded granular sludge bed) reactors. The experiment was conducted for 210 d in reactor R1 and 245 d in reactor R2. The reactors were inoculated with granular sludge from a upflow anaerobic sludge blanket (UASB) reactor on a local dairy farm. The sludge had an average pellet size of 2.35 mm, good sedimentability and a high percentage of organic material. The antibiotic tolerance and the inhibitory action on the bacterial population were different for each antibiotic studied. The results showed a more severe inhibitory effect on microorganisms that were in contact with increases in loads of FLO than those that were in contact with increasing loads of OTC, a condition reflected in the chemical oxygen demand (COD) removal efficiency.