In this review, the strategies being employed to exploit the inherent durability of biofilms and the diverse nutrient cycling of the microbiome for bioremediation are explored. Focus will be given to halogenated compounds, hydrocarbons, pharmaceuticals, and personal care products as well as some heavy metals and toxic minerals, as these groups represent the majority of priority pollutants. For decades, industrial processes have been creating waste all around the world, resulting in contaminated sediments and subsequent, far-reaching dispersal into aquatic environments. As persistent pollutants have accumulated and are still being created and disposed, the incentive to find suitable and more efficient solutions to effectively detoxify the environment is even greater. Indigenous bacterial communities are capable of metabolizing persistent organic pollutants and oxidizing heavy metal contaminants. However, their low abundance and activity in the environment, difficulties accessing the contaminant or nutrient limitations in the environment all prevent the processes from occurring as quickly as desired and thus reaching the proposed clean-up goals. Biofilm communities provide among other things a beneficial structure, possibility for nutrient, and genetic exchange to participating microorganisms as well as protection from the surrounding environment concerning for instance predation and chemical and shear stresses. Biofilms can also be utilized in other ways as biomarkers for monitoring of stream water quality from for instance mine drainage. The durability and structure of biofilms together with the diverse array of structural and metabolic characteristics make these communities attractive actors in biofilm-mediated remediation solutions and ecosystem monitoring.

Anaerobic microbial dechlorination is an important step in the detoxification and elimination of polychlorinated biphenyls (PCBs), but a microorganism capable of coupling its growth to PCB dechlorination has not been isolated. Here we describe the isolation from sediment of an ultramicrobacterium, strain DF-1, which is capable of dechlorinating PCBs containing double-flanked chlorines added as single congeners or as Aroclor 1260 in contaminated soil. The isolate requires Desulfovibrio spp. in coculture or cell extract for growth on hydrogen and PCB in mineral medium. This is the first microorganism in pure culture demonstrated to grow by dehalorespiration with PCBs and the first isolate shown to dechlorinate weathered commercial mixtures of PCBs in historically contaminated sediments. The ability of this isolate to grow on PCBs in contaminated sediments represents a significant breakthrough for the development of in situ treatment strategies for this class of persistent organic pollutants.Polychlorinated biphenyls (PCBs) were manufactured between 1930 and 1978, and their widespread use in high-temperature electrical coolants, hydraulic fluids, paints, carbonless paper, and as dedusting agents has resulted in their global distribution in even the most remote regions of the planet and throughout the food chain. The 2005 Priority List of Hazardous Substances (http: //www.atsdr.cdc.gov/cercla/) published by the U.S. Agency for Toxic Substances and Disease Registry ranks PCBs fifth out of 275 substances. Ranking on this list is a combined metric based on the compound's prevalence at facilities within the United States, known or suspected toxicity, and potential for human exposure. With the discovery of Desulfomonile tiedjei strain DCB1 (24) in 1984, the door was opened for the study of bacteria that can reductively dechlorinate halogenated organic compounds that were manufactured for a wide range of applications throughout the 20th century. Subsequently, it was discovered that such bacteria can couple their growth to reductive dehalogenation in a process referred to as dehalorespiration (15) or halorespiration (15,22). There has been an explosion of discoveries in this field, resulting in the identification of dozens of different species and strains that are capable of dechlorinating compounds ranging from chlorinated ethenes (19) to dioxins (5). Most of the bacteria that reductively dechlorinate toxic halogenated industrial pollutants have turned out to be members of the genus Dehalococcoides. Although several of these microorganisms have been successfully developed for commercially viable bioremediation of soils contaminated with chlorinated solvents, a proven effective treatment for in situ treatment of PCBs does not currently exist. As a result, the only accepted treatments for PCBs are remedial technologies such as dredging and capping, which are expensive, disruptive to the environment, and impractical to implement over large areas and in remote locations.Dehalococcoides ethenogenes strain 195, the first of the...

Strain DF-1 was inoculated into sediments contaminated with weathered Aroclor 1260 to determine whether the augmentation would stimulate the dechlorination of congeners as they occur in the environment, adsorbed to sediment particles and in the presence of an indigenous bacterial population. The 8.9 mol% net decrease in double-flanked chlorines observed after bioaugmentation with DF-1 cannot be calculated directly from the abridged data set in Table 1 on page 2092 that highlighted only some of the changes in absolute amounts. A revised Table 1 (see following page) shows the congener profile that was used to calculate the moles percent decrease catalyzed by DF-1. There are disparities between the tables that resulted from normalization of the data in the published Table 1 to dry mass of soil. The revised moles percent analysis shows that non-double-flanked PCBs 63 and 153 did not decrease with the addition of DF-1, but a slight reduction of non-doubleflanked PCBs 136 and 66/95 was significant, possibly a result of DF-1 dechlorination products serving as "primers" that stimulated the activities by the indigenous population. The relative reduction of double-flanked PCBs 180 and 202 (and coelutants) also appears to be greater. Although we cannot confirm which double-flanked dechlorination reactions were catalyzed exclusively by DF-1, the revised table clearly supports our conclusion that bioaugmentation with DF-1 stimulated reductive dechlorination of weathered Aroclor-contaminated soil.

Competitive PCR and denaturing HPLC analyses together with an assay detecting potential polychlorinated biphenyl (PCB) dechlorinating activities were combined with physical-chemical site characterizations to identify factors affecting the reductive dechlorination of PCBs in the three historically impacted sediments: Grasse and Buffalo Rivers, NY and Anacostia River, DC. In Grasse River sediment an in situ enriched population of Dehalococcoides phylotypes was abundant in high numbers together with a relatively high dechlorination activity and a high concentration of congeners containing unflanked chlorine substitutions. In contrast microbial communities in Anacostia and Buffalo Rivers sediments consisted of similar total numbers of putative dechlorinating bacteria, but the populations consisted of more diverse putative dechlorinating phylotypes and were associated with lower dechlorination activities and higher concentrations of flanked congeners. Differences observed in the PCB dechlorination activity were not influenced by the chemical PCB availability in spiked sediment or physical sediment characteristics, but were consistent with the concentration of PCBs and total organic carbon in the native sediment. Application of molecular methods for selective detection of indigenous microbial dechlorinating communities combined with assessment of the dechlorinating activity and analysis of the in situ congener profiles provided a comprehensive approach for characterization and identification of sites that are amenable to bioremediation, which is essential for the development of in situ treatment strategies.

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Polychlorinated biphenyls (PCBs) are one of the persistent organic pollutants (POPs) used worldwide between the 1930 and 1980s. Many PCBs can still be found in the environment such as in soils and sediments, even though their use has been heavily restricted. This review summarizes the most frequent remediation solutions including, phytoremediation, microbial degradation, dehalogenation by chemical reagent, and PCBs removal by activated carbon. New insights that emerged from recent studies of PCBs remediation including supercritical water oxidation, ultrasonic radiation, bimetallic systems, nanoscale zero-valent iron based reductive dehalogenation and biofilm covered activated carbon, electrokinetic remediation, and nZVI particles in combination with a second metal are overviewed. Some of these methods are still in the initial development stage thereby requiring further research attention. In addition, the advantages and disadvantages of each general treatment strategy and promising technology for PCBs remediation are discussed and compared. There is no well-developed single technology, although various possible technologies have been suggested. Therefore, the possibility of using combined technologies for PCB remediation is also here investigated. It is hoped that this present paper can provide a basic framework and a more profound prospect to select successful PCB remediation strategies or combined technologies.

In this study, 14 virus concentration protocols based on centrifugation, filtration, polyethylene glycol (PEG) precipitation and ultrafiltration were tested for their efficacy for the quantification of SARS-CoV-2 in wastewater samples. These protocols were paired with four RNA extraction procedures resulting in a combination of 50 unique approaches. Bovine respiratory syncytial virus (BRSV) was used as a process control and seeded in each wastewater sample subjected to all 50 protocols. The recovery of BRSV obtained through the application of 50 unique approaches ranged from <0.03 to 64.7% (±1.6%). Combination of centrifugation as the solid removal step, ultrafiltration (Amicon-UF-15; 100 kDa cut-off; protocol 9) as the primary virus concentration method, and Zymo Quick-RNA extraction kit provided the highest BRSV recovery (64.7 ± 1.6%). To determine the impact of prolonged storage of large wastewater sample volume (900 mL) at −20 °C on enveloped virus decay, the BRSV seeded wastewaters samples were stored at −20 °C up to 110 days and analyzed using the most efficient concentration (protocol 9) and extraction (Zymo Quick-RNA kit) methods. BRSV RNA followed a first-order decay rate ( k = 0.04/h with r 2 = 0.99) in wastewater. Finally, 21 wastewater influent samples from five wastewater treatment plants (WWTPs) in southern Maryland, USA were analyzed between May to August 2020 to determine SARS-CoV-2 RNA concentrations. SARS-CoV-2 RNA was quantifiable in 17/21 (81%) of the influent wastewater samples with concentration ranging from 1.10 (±0.10) × 10 4 to 2.38 (±0.16) × 10 6 gene copies/L. Among the RT-qPCR assays tested, US CDC N1 assay was the most sensitive followed by US CDC N2, E_Sarbeco, and RdRp assays. Data presented in this study may enhance our understanding on the effective concentration and extraction of SARS-CoV-2 from wastewater.

Among the filamentous bacteria occasionally causing bulking problems in activated sludge treatment plants, three morphotypes with attached microbial growth are common, Eikelboom Type 0041, Type 1851 and Type 1701. A better knowledge of the phylogeny and physiology of these filamentous bacteria is necessary in order to develop control strategies for bulking. In this study we have used a combination of fluorescence in situ hybridization (FISH) and microautoradiography (MAR) to investigate the identity and in situ physiology of the Type 0041-morphotype and its attached bacteria in two wastewater treatment plants. Identification and enumeration of Type 0041 using group-specific 16S rRNA-targeted FISH probes revealed that approximately 15% of the filaments hybridized with a gene probe specific for the TM7 group, a recently recognized major lineage in the bacterial domain. All other filaments morphologically identified as Type 0041 only hybridized to the general bacterial EUB338-probe, indicating that they probably do not belong to commonly isolated bacterial phyla such as the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, for which group-specific probes were used. The phylogenetic heterogeneity of Type 0041 again highlights the inadequacy of a morphology-based classification system. Like the filaments, most of the attached microbial cells were not identified beyond their affiliation to the Bacteria using the group-specific FISH probes. However, several different bacterial phyla were represented in the identified fraction suggesting that the attached microorganisms are phylogenetically diverse. The study of the in situ physiology of Type 0041 using MAR-FISH revealed that both the filaments and the attached bacteria on Type 0041 were versatile in the use of organic substrates and electron acceptors. It was observed that all Type 0041 could consume glucose, but none of the filaments were able to consume acetate under any conditions tested, in contrast to some of the attached bacteria. No significant physiological differences were found between TM7-positive and TM7-negative Type 0041 filaments, and only minor differences were observed between the two treatment plants tested. These are the first data on the physiology of the almost entirely uncharacterized TM7 phylum and show that TM7 filamentous bacteria can uptake carbon substrates under aerobic and anaerobic conditions.