Field assessment of coconut-based activated carbon systems for the treatment of herbicide contamination.

Once released into the environment, herbicides can move through soil or surface water to streams and groundwater. Filters containing adsorbent media placed in fields may be an effective solution to herbicide loss in the environment. However, to date, no study has investigated the use of adsorbent materials in intervention systems at field-scale, nor has any study investigated their optimal configuration. Therefore, the aim of this paper was to examine the efficacy of low-cost, coconut-based activated carbon (CAC) intervention systems, placed in streams and tributaries, for herbicide removal. Two configurations of interventions were investigated in two agricultural catchments and one urban area in Ireland: (1) filter bags and (2) filter bags fitted into polyethylene pipes. Herbicide sampling was conducted using Chemcatcher® passive sampling devices in order to identify trends in herbicide exceedances at the sites, and to quantifiably assess, compare, and contrast the efficiency of the two intervention configurations. While the Chemcatcher® passive sampling devices are capable of analysing eighteen different acid herbicides, only six different acid herbicides (2,4-D, clopyralid, fluroxypyr, MCPA, mecoprop and triclopyr) were ever detected within the three catchment areas, which were also the only acid herbicides used therein. The CAC was capable of complete herbicide removal, when the water flow was slow (0.5-1 m3 s-1), and the interventions spanned the width and depth of the waterway. Overall, the reduction in herbicide concentrations was better for the filter pipes than for the filter bags, with a 48% reduction in detections and a 37% reduction in exceedances across all the sampling sites for the filter pipe interventions compared to a 13% reduction in the number of detections and a 24% reduction in exceedances across all sampling sites for the filter bag interventions (p < 0.05). This study demonstrates, for the first time, that CAC may be an effective in situ remediation strategy to manage herbicide exceedances close to the source, thereby reducing the impact on environmental and public health.

Co-Selection of Bacterial Metal and Antibiotic Resistance in Soil Laboratory Microcosms.

Accumulation of heavy metals (HMs) in agricultural soil following the application of superphosphate fertilisers seems to induce resistance of soil bacteria to HMs and appears to co-select for resistance to antibiotics (Ab). This study aimed to investigate the selection of co-resistance of soil bacteria to HMs and Ab in uncontaminated soil incubated for 6 weeks at 25 °C in laboratory microcosms spiked with ranges of concentrations of cadmium (Cd), zinc (Zn) and mercury (Hg). Co-selection of HM and Ab resistance was assessed using plate culture on media with a range of HM and Ab concentrations, and pollution-induced community tolerance (PICT) assays. Bacterial diversity was profiled via terminal restriction fragment length polymorphism (TRFLP) assay and 16S rDNA sequencing of genomic DNA isolated from selected microcosms. Based on sequence data, the microbial communities exposed to HMs were found to differ significantly compared to control microcosms with no added HM across a range of taxonomic levels.

An assessment of potential pesticide transmission, considering the combined impact of soil texture and pesticide properties: A meta-analysis.

Pesticides are widely employed as a cost-effective means of reducing the impacts of undesirable plants and animals. The aim of this paper is to develop a risk ranking of transmission of key pesticides through soil to waterways, taking into account physico-chemical properties of the pesticides (soil half-life and water solubility), soil permeability, and the relationship between adsorption of pesticides and soil texture. This may be used as a screening tool for land managers, as it allows assessment of the potential transmission risks associated with the use of specified pesticides across a spectrum of soil textures. The twenty-eight pesticides examined were differentiated into three groups: herbicides, fungicides and insecticides. The highest risk of pesticide transmission through soils to waterways is associated with soils containing <20% clay or >45% sand. In a small number of cases, the resulting transmission risk is not influenced by soil texture alone. For example, for Phenmedipham, the transmission risk is higher for clay soils than for silt loam. The data generated in this paper may also be used in the identification of critical area sources, which have a high likelihood of pesticide transmission to waterways. Furthermore, they have the potential to be applied to GIS mapping, where the potential transmission risk values of the pesticides can be layered directly onto various soil textures.

Simultaneous adsorption and biodegradation of trichloroethylene occurs in a biochar packed column treating contaminated landfill leachate.

Trichloroethylene (TCE) is a human carcinogen that is commonly found in landfill leachate. Contaminated leachate plumes may be intercepted prior to reaching groundwater and treated in situ using permeable reactive barriers (PRB). This study used a packed column system containing herbal pomace and spruce biochar, previously shown to have TCE adsorptive capabilities. Influent containing raw or autoclaved landfill leachate was used to investigate the potential for environmental micro-organisms to establish a TCE-dechlorinating biofilm on the biochar, in order to prolong the operational life span of the system. TCE removal ≥ 99.7 % was observed by both biochars. No dichloroethylene (DCE) isomers were present in the column effluents, but cis-1,2 DCE was adsorbed to the biochar treating raw landfill leachate, indicating that dechlorination was occurring biologically in these columns. Known microbial species that are individually capable of complete dechlorination of TCE to ethene were not detected by 16S rRNA gene sequencing, but several species capable of partial TCE dechlorination (Desulfitobacterium spp., Sulfurospirillium spp. and Desulfuromonas spp) were present in the biofilms of the columns treating raw landfill leachate. These data demonstrate that biochar from waste material may be capable of supporting a dechlorinating biofilm to promote bioremediation of TCE.

Pyrolysed waste materials show potential for remediation of trichloroethylene-contaminated water.

Trichloroethylene (TCE) is an Environmental Protection Agency priority pollutant associated with cancer in humans. With numerous industrial applications and regular landfill disposal, TCE is a common landfill leachate pollutant. In situ treatment barriers use costly fill materials such as granular activated carbon (GAC). Here, we show that while a range of untreated waste materials had little ability to adsorb TCE, waste-derived biochar showed excellent capacity for TCE adsorption. TCE removal efficiencies by spruce and oak-derived biochars were > 99.5 %, outperforming GAC (95 %) and herbal pomace biochar (93 %). A contact time of at least 32 h was required to reach equilibrium for all of these media. Assessment of pollution swapping potential revealed release of phosphate by all biochars. Analysis of media surface characteristics by Fourier Transform Infrared Spectroscopy (FTIR) predicted that GAC should have the highest ability to adsorb TCE, followed by Oak Biochar, Herbal Pomace Biochar 1, and Spruce Biochar 2, which was not in agreement with the experimental adsorption data. These data demonstrate the potential for pyrolysed waste material to be used as an alternative fill material for in situ remediation applications, thereby also addressing the European Circular Economy Strategy.

Investigation of triclosan contamination on microbial biomass and other soil health indicators.

Triclosan (TCS) is an antimicrobial compound found in personal care products, and consequently in greywater. After its release to the environment, it continues its antimicrobial action on indigenous microbial communities. Little is known about the environmental impacts of high levels of TCS, which may occur due to accumulation following long-term greywater application to soil. Soil microcosms were established using a silty clay loam and augmented with a range of TCS concentrations ranging from 500 to 7500 mg kg-1. Samples were analysed for substrate-induced respiration, microbial biomass and sulphatase activity. The soil augmented with the lowest concentration of TCS (500 mg kg-1) significantly decreased microbial biomass, with a calculated EC20 of 195 mg kg-1. Substrate-induced respiration indicated that the soil microbial community was impacted for all TCS concentrations; however, the community showed potential to recover over time. Sulphatase activity was less sensitive to TCS and was significantly impacted at high concentrations of TCS (>2500 mg kg-1). It is likely that TCS has selective toxicity for more susceptible microbes when introduced into the soil environment. At high levels, TCS could overwhelm TCS-degrading soil microbes.

Effects of long-term greywater disposal on soil: A case study.

This study investigated the environmental health risks to soil and potential risks to groundwater associated with long term (8-18years) greywater disposal practices. Land application of greywater is likely to have environmental impacts, which may be positive or negative. Greywater can contain plant macronutrients that may benefit plant growth. Conversely, high levels of surfactants, oils, grease, sodium and potentially pathogenic organisms may negatively impact environmental and human health. In this study, land disposal of untreated greywater was practiced at five coastal domestic properties. At each property, soil samples were collected at two depths from areas used for greywater disposal and from control areas that were not exposed to greywater. Soils were analysed for chemical and biological responses to greywater exposure. Generally, greywater irrigated soils had higher pH, Olsen P, base saturation, and increased soil microbial activity (as measured by biomass carbon, basal respiration and dehydrogenase activity). A pH of >9 was recorded for some greywater treated soil samples. Escherichia coli (E. coli) were detected at up to 10(3)MPN/g in the greywater exposed surface soils at some sites. Terminal Restriction Fragment Length Polymorphism (TRFLP) analysis revealed that greywater affected the soil microbial community structure, which may have implications for soil health and fertility. Overall, this study shows that the long-term application of greywater at the investigated sites had a moderate impact on the soil environment. This may have been due to the sandy soils and high rainfall that would flush the soil. Increases in microbial biomass and dehydrogenase indicate that greywater application may be beneficial for plant growth. However, high levels of E. coli in some soils may be a risk to human health and sub-surface irrigation should be the recommended application method.

Low-temperature anaerobic digestion is associated with differential methanogenic protein expression.

Anaerobic digestion (AD) is an attractive wastewater treatment technology, leading to the generation of recoverable biofuel (methane). Most industrial AD applications, carry excessive heating costs, however, as AD reactors are commonly operated at mesophilic temperatures while handling waste streams discharged at ambient or cold temperatures. Consequently, low-temperature AD represents a cost-effective strategy for wastewater treatment. The comparative investigation of key microbial groups underpinning laboratory-scale AD bioreactors operated at 37, 15 and 7°C was carried out. Community structure was monitored using 16S rRNA clone libraries, while abundance of the most prominent methanogens was investigated using qPCR. In addition, metaproteomics was employed to access the microbial functions carried out in situ. While δ-Proteobacteria were prevalent at 37°C, their abundance decreased dramatically at lower temperatures with inverse trends observed for Bacteroidetes and Firmicutes. Methanobacteriales and Methanosaeta were predominant at all temperatures investigated while Methanomicrobiales abundance increased at 15°C compared to 37 and 7°C. Changes in operating temperature resulted in the differential expression of proteins involved in methanogenesis, which was found to occur in all bioreactors, as corroborated by bioreactors' performance. This study demonstrated the value of employing a polyphasic approach to address microbial community dynamics and highlighted the functional redundancy of AD microbiomes.

Impact of trichloroethylene exposure on the microbial diversity and protein expression in anaerobic granular biomass at 37°C and 15°C.

Granular biomass from a laboratory-scale anaerobic bioreactor trial was analysed to identify changes in microbial community structure and function in response to temperature and trichloroethylene (TCE). Two bioreactors were operated at 37°C, while two were operated at 15°C. At the time of sampling, one of each temperature pair of bioreactors was exposed to process failure-inducing concentrations of TCE (60 mg L(-1)) while the other served as a TCE-free control. Bacterial community structure was investigated using denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene clone library analysis. Temperature was identified as an important factor for bacterial community composition, while minor differences were associated with trichloroethylene supplementation. Proteobacteria was the dominant phylum in all bioreactors, while clone library analysis revealed a higher proportion of Bacteroidetes-, Chloroflexi-, and Firmicutes-like clones at 15°C than at 37°C. Comparative metaproteomics in the presence and absence of TCE was carried out by two-dimensional gel electrophoresis (2-DGE), and 28 protein spots were identified, with putative functions related to cellular processes, including methanogenesis, glycolysis, the glyoxylate cycle, and the methyl malonyl pathway. A good agreement between metaproteomic species assignment and phylogenetic information was observed, with 10 of the identified proteins associated with members of the phylum Proteobacteria.

Exploring mixed microbial community functioning: recent advances in metaproteomics.

System approaches to elucidate ecosystem functioning constitute an emerging area of research within microbial ecology. Such approaches aim at investigating all levels of biological information (DNA, RNA, proteins and metabolites) to capture the functional interactions occurring in a given ecosystem and track down characteristics that could not be accessed by the study of isolated components. In this context, the study of the proteins collectively expressed by all the microorganisms present within an ecosystem (metaproteomics) is not only crucial but can also provide insights into microbial functionality. Overall, the success of metaproteomics is closely linked to metagenomics, and with the exponential increase in the availability of metagenome sequences, this field of research is starting to experience generation of an overwhelming amount of data, which requires systematic analysis. Metaproteomics has been employed in very diverse environments, and this review discusses the recent advances achieved in the context of human biology, soil, marine and freshwater environments as well as natural and bioengineered systems.

Temperature dependent (37-15°C) anaerobic digestion of a trichloroethylene-contaminated wastewater.

The impact of a trichloroethylene (TCE) contaminated wastewater on the microbial community structure of an anaerobic granular biomass at 15°C compared to 37°C was investigated. Four expanded granular sludge bed (EGSB) bioreactors (R1-R4) were employed in pairs at 37 and 15°C. The influents of one of each pair were supplemented with increasing concentrations of TCE (max. 60 mgl(-1)). At 37°C, stable operation was maintained with 88% COD removal and >99% TCE removal at maximum influent TCE concentrations. R3 performance decreased at influent TCE concentration of 60 mgl(-1), although TCE removal rates of >97% were recorded. Archaeal community analysis via clone library and quantitative polymerase chain reaction (qPCR) analysis, and bacterial community analysis via denaturing gradient gel electrophoresis (DGGE), indicated that temperature resulted in a greater change in community structure than the presence of TCE, and clones related to cold adaptation of biomass were identified at 15°C.

Low-temperature (7 °C) anaerobic treatment of a trichloroethylene-contaminated wastewater: microbial community development.

The feasibility of low-temperature (7 °C) anaerobic digestion for the treatment of a trichloroethylene (TCE) contaminated wastewater was investigated. Two expanded granular sludge bed (EGSB) bioreactors (R1 and R2) were employed for the mineralisation of a synthetic volatile fatty acid based wastewater at an initial organic loading rate (OLR) of 3 kg COD m(-3) d(-1), and an operating temperature of 15 °C. Successive reductions in OLR to 0.75 kg COD m(-3) d(-1), and operational temperature to 7 °C, resulted in stable bioreactor operation by day 417, with COD removal efficiency and biogas CH(4) content ≥ 74%, for both bioreactors. Subsequently, the influent to R1 was supplemented with increasing concentrations (10, 20, 30 mg l(-1)) of TCE, while R2 acted as a control. At an influent TCE concentration of 30 mg l(-1), although phase average TCE removal rates of 79% were recorded, a sustained decrease in R1 performance was observed, with COD removal of 6%, and % biogas CH(4) of 3% recorded on days 595 and 607, respectively. Specific methanogenic activity (SMA) assays identified a general shift from acetate- to hydrogen-mediated methanogenesis in both R1 and R2 biomass, while toxicity assays confirmed an increased sensitivity of the acetoclastic community in R1 to TCE and dichloroethylene (DCE), which contributed to acetate accumulation. Quantitative Polymerase Chain Reaction (qPCR) analysis of the methanogenic community confirmed the dominance of hydrogenotrophic methanogens in both R1 and R2, representing 71-89% of the total methanogenic population, however acetoclastic Methanosaeta were the dominant organisms, based on 16S rRNA gene clone library analysis of reactor biomass. The greatest change in the bacterial community, as demonstrated by UPGMA analysis of DGGE banding profiles, was observed in R1 biomass between days 417 and 609, although 88% similarity was retained between these sampling points.

Methanogenic community development in anaerobic granular bioreactors treating trichloroethylene (TCE)-contaminated wastewater at 37 °C and 15 °C.

Four expanded granular sludge bed (EGSB) bioreactors were seeded with a mesophilically-grown granular sludge and operated in duplicate for mesophilic (37 °C; R1 & R2) and low- (15°; R3 & R4) temperature treatment of a synthetic volatile fatty acid (VFA) based wastewater (3 kg COD m(-3) d(-1)) with one of each pair (R1 & R3) supplemented with increasing concentrations of trichloroethylene (TCE; 10, 20, 40, 60 mg l(-1)) and one acting as a control. Bioreactor performance was evaluated by % COD removal efficiency and % biogas methane (CH(4)) content. Quantitative Polymerase Chain Reaction (qPCR) was used to investigate the methanogenic community composition and dynamics in the bioreactors during the trial, while specific methanogenic activity (SMA) and toxicity assays were utilized to investigate the activity and TCE/dichloroethylene (DCE) toxicity thresholds of key trophic groups, respectively. At both 37 °C and 15 °C, TCE levels of 60 mg l(-1) resulted in the decline of % COD removal efficiencies to 29% (Day 235) and 37% (Day 238), respectively, and in % biogas CH(4) to 54% (Day 235) and 5% (Day 238), respectively. Despite the inhibitory effect of TCE on the anaerobic digestion process, the main drivers influencing methanogenic community development, as determined by qPCR and Non-metric multidimensional scaling analysis, were (i) wastewater composition and (ii) operating temperature. At the apical TCE concentration both SMA and qPCR of methanogenic archaea suggested that acetoclastic methanogens were somewhat inhibited by the presence of TCE and/or its degradation derivatives, while competition by dechlorinating organisms may have limited the availability of H(2) for hydrogenotrophic methanogenesis. In addition, there appeared to be an inverse correlation between SMA levels and TCE tolerance, a finding that was supported by the analysis of the inhibitory effect of TCE on two additional biomass sources. The results indicate that low-temperature anaerobic digestion is a feasible approach for the treatment of TCE-containing wastewater.