Bioaugmentation for treatment of full-scale diethylene glycol monobutyl ether (DGBE) wastewater by Serratia sp. BDG-2

Application oriented bioaugmentation processes: Mechanism, performance improvement and scale-up

Bioaugmentation is an optimization method with great potential to improve the treatment effect by introducing specific strains into the biological treatment system. In this study, a comprehensive review of the mechanism of bioaugmentation from the aspect of microbial community structure, the optimization methods facilitating application as well as feasible approaches of scale-up application has been provided. The different contribution of indigenous and exogenous strains was critically analyzed, the relationship between microbial community variation and system performance was clarified. Operation regulation and immobilization technologies are effective methods to deal with the possible failure of bioaugmentation. The gradual expansion from lab-scale, pilot scale to full-scale, the transformation and upgrading of wastewater treatment plants through the combination of direct dosing and biofilm, and the application of side-stream reactors are feasible ways to realize the full-scale application. The future challenges and prospects in this field were also proposed.

Controlling pathogenic risks of water treatment biotechnologies at the source by genetic editing means

Antimicrobial-resistant pathogens in the environment and wastewater treatment systems, many of which are also important pollutant degraders and are difficult to control by traditional disinfection approaches, have become an unprecedented treat to ecological security and human health. Here, we propose the adoption of genetic editing techniques as a highly targeted, efficient and simple tool to control the risks of environmental pathogens at the source. An 'all-in-one' plasmid system was constructed in Aeromonas hydrophila to accurately identify and selectively inactivate multiple key virulence factor genes and antibiotic resistance genes via base editing, enabling significantly suppressed bacterial virulence and resistance without impairing their normal phenotype and pollutant-degradation functions. Its safe application for bioaugmented treatment of synthetic textile wastewater was also demonstrated. This genetic-editing technique may offer a promising solution to control the health risks of environmental microorganisms via targeted gene inactivation, thereby facilitating safer application of water treatment biotechnologies.

Immobilized-microbial bioaugmentation protects aerobic denitrification from heavy metal shock in an activated-sludge reactor

The inhibition of denitrification by heavy metals is a problem in nitrogen wastewater treatment, but the solutions are rarely studied. In this study, Pseudomonas brassicacearum LZ-4, immobilized in sodium alginate-kaolin, was applied in an activated-sludge reactor to protect denitrifiers from hexavalent chromium (Cr(VI)). Q-PCR result showed that the strain LZ-4 was incorporated into activated sludge under the help of immobilization. In the non-bioaugmentation system, the removal efficiency of nitrate was decreased by 86.07% by 30 mg/L Cr(VI). Whereas, denitrification was protected and 95% of nitrate was removed continuously in immobilized-cell bioaugmentation system. Miseq sequencing data showed that bioaugmentation decreased the impact of Cr(VI) on microbial communities and increased the abundance of denitrifiers. Based on the results of biomass and extracellular polymers, activated sludge was protected from Cr(VI) toxicity. This discovery will provide a feasible technique for nitrogen wastewater treatment in the presence of distressing heavy metals.

Sugar-alcohol industry: quality of its biotreated washing water for reuse in fertigation

All processes in agro-industries consume water and generate large volumes of nutrient-rich effluents. To recycle effluents from a sugar-alcohol industry in the Northeastern Brazil (Coruripe, Alagoas), the effect of a daily application of a microbial formulation (containing five indigenous bacteria and two fungi), at the entrance of the two first facultative ponds (D, E) of its treatment plant formed by seven ponds (A-G), was evaluated in the sugarcane harvests of 2014/2015 and 2015/2016. Fortnightly, the values of 11 physicochemical parameters were checked and statistically compared (one and two-way ANOVA) in untreated (sedimentation pond A) and post-treated effluent (last facultative pond G), during both harvests. The treated effluent presented statistically significant improvements (p > 0.05), even between harvests, with averages of removal of organic matter of ca. 79.21% and 90.62%, and increases of the dissolved oxygen (DO) of ca. 72% and 74%, as well as the average increase of pH was ca. 42% and 50%. This better quality residue generally satisfied the class III level of the Brazilian Resolution 357/2005 (National Council for the Environment (CONAMA)), for water reuse in sugarcane irrigation on the yellow clay latosol soil, since it still is a light source of organic matter, nitrites and phosphorus, reducing the need of fertilizers for maintaining the productivity with low risk of salinization. According to Pearson's bivariate correlation coefficient, while the DO and pH have positive correlation, they both have general inverse relation with the other physicochemical parameters evaluated and vice versa.

Biostimulants application for bacterial metabolic activity promotion and sodium dodecyl sulfate degradation under copper stress

In this study, the metabolic activity (adenosine triphosphate, ATP; electron transfer system, ETS; and dehydrogenase activity, DHA) response of a sodium dodecyl sulfate (SDS) degrading bacterium Pseudomonas sp. SDS-N2 to copper stress conditions were investigated. Results showed that the ATP content, ETS activity, and DHA activity of strain SDS-N2 were significantly correlated with substrate removal efficiency and bacterial growth under copper stress conditions. Based on the metabolic response patterns of strain SDS-N2, biostimulants citric acid, proline as well as FeSO₄ were used to promote the metabolic activity of strain SDS-N2 at 0.8 mg L^-1 copper stress condition. Plackett-Burman design and analysis proved that citric acid and FeSO₄ were significant factors for enhanced SDS removal; and the optimum biostimulation conditions (FeSO₄ 72 mg L^-1 and citric acid 100 mg L^-1) for SDS removal were obtained by using steepest ascent experiment and central composite design. Under the optimum biostimulation conditions, ATP, ETS, DHA activity as well as bacterial growth were 14.1, 45.5, 0.5 and 2.3-fold higher than that of the control (without FeSO₄ and citric acid addition) after 12.5 h biodegradation, and the substrate removal efficiency was increase by 37.6%.

Enhanced organics and Cu2+ removal in electroplating wastewater by bioaugmentation

With the improvement of electroplating process and products requirement, refractory organics, heavy metals or even heavy metal nanoparticles (NP) exist simultaneously in electroplating wastewater inevitably, makes electroplating wastewater treatment effluent difficult to meet the discharge standard. In order to improve the organics removal under the exposure of CuO NP, strains (designated as L1-L5) that have both organics degradation and Cu²⁺ tolerance capacities were isolated and employed in the electroplating wastewater bioaugmentation treatment using a hydrolytic/anoxic/oxic-membrane bioreactor. The Cu²⁺ adsorption process followed pseudo-second order kinetics and the isotherms fit well to Langmuir isotherm model. L2, L3 and L4 showed higher Cu²⁺ adsorption capacity than that of L1 and L5. Under the optimal condition, the maximum Cu²⁺ adsorption capacity of L2, L3 and L4 was 34.15, 45.68 and 26.72 mg g^-1, respectively. Their average COD removal efficiency achieved 65.7 ± 10.9%, 61.5 ± 6.7% and 71.6 ± 6.0%, respectively. The three isolates were used to construct consortia with the inoculum concentration of 400 mg L^-1. One-time and repeated inoculations were evaluated to find the applicable strategy. Repeated inoculation resulted in a better COD and Cu removal performance (76.2 ± 2.6% and 98.5 ± 0.3%, respectively) than those of one-time inoculation (69.0 ± 2.0% and 98.0 ± 0.3%, respectively). The most functionally stable, balanced and resistant bacterial community was formed in the one-time inoculation system while for fungal community it was formed in the repeated inoculation system.

Continuous treatment of Acid Red B with activated sludge bioaugmented by a yeast Candida tropicalis TL-F1 and microbial community dynamics

Continuous treatment of Acid Red B (ARB) with activated sludge (AS) bioaugmented by an azo-degrading yeast Candida tropicalis TL-F1 under aerobic conditions was investigated in the form of sequencing batch tests. Dynamics of both bacterial and fungal communities were analyzed using polymerase chain reaction followed by denaturing gradient gel electrophoresis (PCR-DGGE) method. The results showed that bioaugmentation with the yeast TL-F1 improved the performance of AS for continuously decolorizing, degrading and detoxifying ARB. Meanwhile, the AS systems bioaugmented by the yeast TL-F1 showed higher sludge concentration and better AS settleability. The result of PCR-DGGE suggested that microbial communities of both bacteria and fungi shifted due to treatment of ARB and bioaugmentation. Some dominant bacteria and fungi were identified as probably efficient degraders of ARB or its decolorization byproducts. Furthermore, the yeast TL-F1 was found as one of the dominant fungi in all the three bioaugmented systems, suggesting that bioaugmentation was successful due to the colonization of the yeast TL-F1 in AS systems.

A review: Driving factors and regulation strategies of microbial community structure and dynamics in wastewater treatment systems

The performance and stabilization of biological wastewater treatment systems ¹are closely related to the microbial community structure and dynamics. In this paper, the effects and mechanisms of influent composition, process configuration, operating parameters (dissolved oxygen [DO], pH, hydraulic retention time [HRT] and sludge retention time [SRT]) and environmental condition (temperature) to the change of microbial community structure and process performance (nitrification, denitrification, biological phosphorus removal, organics mineralization and utilization, etc.) are critically reviewed. Furthermore, some strategies for microbial community structure regulation, mainly bioaugmentation, process adjustment and operating parameters optimization, applied in the current wastewater treatment systems are also discussed. Although the recent studies have strengthened our understanding on the relationship between microbial community structure and wastewater treatment process performance, how to fully tap the microbial information, optimize the microbial community structure and maintain the process performance in wastewater treatment systems are still full of challenges.

Bioaugmentation: An Emerging Strategy of Industrial Wastewater Treatment for Reuse and Discharge

A promising long-term and sustainable solution to the growing scarcity of water worldwide is to recycle and reuse wastewater. In wastewater treatment plants, the biodegradation of contaminants or pollutants by harnessing microorganisms present in activated sludge is one of the most important strategies to remove organic contaminants from wastewater. However, this approach has limitations because many pollutants are not efficiently eliminated. To counterbalance the limitations, bioaugmentation has been developed and consists of adding specific and efficient pollutant-biodegrading microorganisms into a microbial community in an effort to enhance the ability of this microbial community to biodegrade contaminants. This approach has been tested for wastewater cleaning with encouraging results, but failure has also been reported, especially during scale-up. In this review, work on the bioaugmentation in the context of removal of important pollutants from industrial wastewater is summarized, with an emphasis on recalcitrant compounds, and strategies that can be used to improve the efficiency of bioaugmentation are also discussed. This review also initiates a discussion regarding new research areas, such as nanotechnology and quorum sensing, that should be investigated to improve the efficiency of wastewater bioaugmentation.