Fate and impact of organics in an immersed membrane bioreactor applied to brine denitrification and ion exchange regeneration

The application of membrane bioreactors (MBRs) to brine denitrification for ion exchange regeneration has been studied. The developed culture was capable of complete brine denitrification at 50 gNaCl.l−1. Denitrification reduced to c.60% and c.70% when salinity was respectively increased to 75 and 100 g.l−1, presumed to be due to reduced growth rate and the low imposed solids retention time (10 days). Polysaccharide secretion was not induced by stressed cells following salt shocking, implying that cell lysis did not occur. Fouling propensity, monitored by critical flux, was steady at 12–15 l.m−2.h−1 during salinity shocking and after brine recirculation, indicating that the system was stable following perturbation. Low molecular weight polysaccharide physically adsorbed onto the nitrate selective anion exchange resin during regeneration reducing exchange capacity by c.6.5% when operating up to complete exhaustion. However, based on a breakthrough threshold of 10 mgNO3−-N.l−1 the exchange capacity was comparative to that determined when using freshly produced brine for regeneration. It was concluded that a denitrification MBR was an appropriate technology for IEX spent brine reco

Demonstration of a multi-technique approach to assess glacial microbial populations in the field

The ability to perform microbial detection and characterization in-field at extreme environments, rather than on returned samples, has the potential to improve the efficiency, relevance and quantity of data from field campaigns. To date, few examples of this approach have been reported. Therefore, we demonstrate that the approach is feasible in subglacial environments by deploying four techniques for microbial detection: real-time polymerase chain reaction; microscopic fluorescence cell counts, adenosine triphosphate bioluminescence assay and recombinant Factor C assay (to detect lipopolysaccharide). Each technique was applied to 12 subglacial ice samples, 12 meltwater samples and two snow samples from Engabreen, Northern Norway. Using this multi-technique approach, the detected biomarker levels were as expected, being highest in debris-rich subglacial ice, moderate in glacial meltwater and low in clean ice (debris-poor) and snow. Principal component analysis was applied to the resulting dataset and could be performed in-field to rapidly aid the allocation of resources for further sample analysis. We anticipate that in-field data collection will allow for multiple rounds of sampling, analysis, interpretation and refinement within a single field campaign, resulting in the collection of larger and more appropriate datasets, ultimately with more efficient science return

The potential for constructed wetlands to treat alkaline bauxite-residue leachate: phragmites australis growth

High alkalinity (pH > 12) of bauxite-residue leachates presents challenges for the long-term storage and managements of the residue. Recent evidence has highlighted the potential for constructed wetlands to effectively buffer the alkalinity, but there is limited evidence on the potential for wetland plants to establish and grow in soils inundated with residue leachate. A pot-based trial was conducted to investigate the potential for Phragmites australis to establish and grow in substrate treated with residue leachate over a pH range of 8.6–11.1. The trial ran for 3 months, after which plant growth and biomass were determined. Concentrations of soluble and exchangeable trace elements in the soil substrate and also in the aboveground and belowground biomass were determined. Residue leachate pH did not affect plant biomass or microbial biomass. With the exception of Na, there was no effect on exchangeable trace elements in the substrate; however, increases in soluble metals (As, Cd and Na) were observed with increasing leachate concentration. Furthermore, increases in Al, As and V were observed in belowground biomass and for Cd and Cr in aboveground biomass. Concentrations within the vegetation biomass were less than critical phytotoxic levels. Results demonstrate the ability for P. australis to grow in bauxite-residue leachate-inundated growth media without adverse effects

Investigating the influence of sulphur amendment and temperature on microbial activity in bioremediation of diesel-contaminated soil

This study investigated the effectiveness of incorporating sulphur (S) with nitrogen (N) and phosphorus (P) for enhancing microbial activity in diesel-contaminated soil during ex-situ bioremediation. While N and P amendments are commonly used to stimulate indigenous microorganisms, the potential benefits of adding S have received less attention. The study found that historically contaminated soil with a moderate concentration of total petroleum hydrocarbons (TPH; 1270 mg/kg) did not have nutrient limitation, and incubation temperature was found to be more critical for enhancing microbial activity. However, soil spiked with an additional 5000 mg/kg of diesel showed increased activity following NP and NPS amendment. Interestingly, NPS amendment at 10 °C resulted in higher microbial activity than at 20 °C, indicating the potential for a tailored nutrient amendment approach to optimize bioremediation in cold conditions. Overall, this study suggests that incorporating S with N and P can enhance microbial activity in diesel-contaminated soil during ex-situ bioremediation. Furthermore, the study highlights the importance of considering incubation temperature in designing a nutrient amendment approach for bioremediation, especially in cold conditions. These findings can guide the design and implementation of future effective bioremediation strategies for petroleum hydrocarbon-contaminated soil.The authors thank ERS and the BBSRC NIBB's Environmental Biotechnology Network, (EBNET, grant reference BB/S009795/1) for funding this research project

Human cadaver burial depth affects soil microbial and nutrient status

this can enhance the natural recycling of nutrients to the soil through improved interactions between the corpse and the soil ecosystem. However, there is a paucity of knowledge describing the interactions between the human cadaver and soil microbiology at any depth. The effects of shallow were compared to standard burial depth on soil chemical (available nitrogen and phosphorus, and organic matter) and microbial (total biomass and activity, fungal biomass, and microbial community composition) characteristics in two soil types (sandy loam and clay). Measurements were taken six and eight weeks after the burial of fresh pork ribs (used as a substitute for the human cadaver). Quantities of plant available nitrogen, as both ammonium-N (clay soil) and nitrate-N (both soil types), were greater where the pork was shallow buried. In addition, there was a shift in the composition of the bacterial component of the soil microbial community where the pork was shallow buried compared to deep burial (sandy loam soil only). There were no differences between the two burial depths (both soil types) in soil organic matter, available phosphorus, total microbial biomass or activity, or the proportion of fungi within the microbial community. The differences in available nitrogen and the lack of differences in the bacterial community composition between the two depths for the clay soils is likely to be due to reduced pore space and hence reduced oxygen at depth, which would dominate any response of the microbial community to the decomposing meat

Efficacy of bioadmendments in reducing the influence of salinity on the bioremediation of oil-contaminated soil

This study aimed to investigate the potential of three bioamendments (rice husk biochar, wheat straw biochar, and spent mushroom compost) to enhance microbial degradation of crude oil in saline soil. A soil microcosm experiment was conducted, comparing the response of soil microorganisms to crude oil under saline (1 % NaCl) and non-saline conditions. The soils were amended with different bioamendments at varying concentrations (2.5 % or 5 %), and degradation rates were monitored over a 120-day period at 20 °C. The results showed that the bioamendments significantly influenced the degradation of total petroleum hydrocarbons (TPH) in both non-saline and saline soils by 67 % and 18 % respectively. Non-saline soils exhibited approximately four times higher TPH biodegradation compared to saline soils. Among the bioamendments, rice husk biochar and spent mushroom compost had the greatest impact on biodegradation in saline soil, while wheat straw and rice husk biochar combined with spent mushroom compost showed the most significant effects in non-saline soil. The study also revealed that the bioamendments facilitated changes in the microbial community structure, particularly in the treatments with rice husk biochar and wheat straw biochar. Actinomycetes and fungi were found to be more tolerant to soil salinity, especially in the treatments with rice husk biochar and wheat straw biochar. Additionally, the production of CO2, indicating microbial activity, was highest (56 % and 60 %) in the treatments combining rice husk biochar or wheat straw biochar with spent mushroom compost in non-saline soil, while in saline soil rice husk biochar treatment (50 %) was the highest. Overall, this research demonstrates that the application of bioamendments, particularly rice husk biochar and wheat straw biochar combined with spent mushroom compost, can effectively enhance the biodegradation of crude oil in saline soil. These findings highlight the potential of such bioamendments as green and sustainable solutions for soil pollution, especially in the context of climate change-induced impacts on high-salinity soils, including coastal soils

The impact of anaerobic digestate on soil life: a review

Using organic amendments to fertilise crops is a crucial part in the sustainability of agricultural systems. The residual slurry remaining after biogas production (anaerobic digestate) contains a rich source of plant nutrients that provides an alternative to mineral fertilisers. The delivery of many nutrients to plants is facilitated by a healthy soil biota: free-living and symbiotic microflora (e.g. archaea, bacteria and fungi) mineralize, solubilize and facilitate plant uptake of nutrients and the soil fauna (e.g. protozoa, microarthopods and earthworms) influence nutrient cycling processes as higher-level consumers and litter transformers. The delivery of nutrients to plants via the activity of this soil food web is influenced by fertiliser inputs. Here we review the impact of anaerobic digestate on soil biota. The quantity and composition of the carbon in digestate has a large influence on soil heterotrophic microbial dynamics and their subsequent influence on nutrient bioavailability. The main points are (1) digestate low in carbon has little effect on soil microorganisms, whereas digestate higher in carbon increases soil microbial abundance and diversity; (2) labile carbon stimulates fast-growing bacteria, whereas recalcitrant carbon shifts the microbial community in favour of slower-growing fungi and Gram-positive bacteria; and (3) earthworms, springtails and nematodes dwelling in the soil surface layer can be negatively affected by digestate application due to toxicity when compounds such as ammonia are present in high concentrations. Generalized understanding of the effect by digestates on soil biota is made difficult by differences in digestate properties caused by varying feedstock and production methods and the inherent heterogeneity of soil. There is a lack of research investigating the impact of repeated digestate application on soil biota and subsequently soil health. This information would give end users more confidence to substitute mineral fertilisers with digestate

Immobilisation of anaerobic digestate supplied nitrogen into soil microbial biomass is dependent on lability of high organic carbon materials additives

Anaerobic digestate is a nutrient rich slurry by-product derived from biogas production, often used as a fertiliser due to its high nitrogen content. However, nitrogen losses from its application can lead to environmental pollution. In a laboratory experiment, the addition of high organic carbon materials to digestate-amended soil as a potential means to stimulate microbial immobilisation of digestate supplied nitrogen was investigated. Soil was incubated in pots for 5 months with digestate (equivalent to 250 kgN ha−1). The impact of adding carbon into the digestate (equivalent to 540 kgC ha−1) as either glycerol, straw, woodchip, or biochar on soil microbial and chemical parameters was quantified. Glycerol amended soils had significantly higher microbial biomass compared to digestate alone during the first month and at 30 days after application had a 4x higher on average microbial N. The digestate + straw treatment resulted in a 2.5x significantly greater nitrogen immobilisation compared to digestate alone after 3 months of incubation. The digestate + woodchip had a 2× higher mean microbial N after 5 months, whilst the biochar amendment did not stimulate significant nitrogen immobilisation at any time. These results suggest that mixing a labile to moderately labile organic carbon amendment, such as straw, with digestate has the greatest potential to reduce nitrogen losses following digestate application through microbial immobilisation.This research was funded by UKRI BBSRC FoodBioSystems Doctoral Training Partnership (DTP), grant number BB/T008776/1 and Future Biogas Ltd

Bioengineering remediation of former industrial sites contaminated with chemical mixtures

Former gasworks sites are known to be contaminated with complex chemical mixtures that require remediation before redevelopment. Bioamendments such as biochar and spent mushroom compost (SMC) offer a green and sustainable remediation approach to help tackle this issue. However, the effectiveness of different biochar types and their interactions with the soil microbial community is still not well understood. To address this, a full factorial microcosm experiment was carried out using biochar derived from rice husk (RHB) and wheat straw (WSB) mixed with soil from a former gasworks site at varying concentrations (0%, 2.5%, and 5%), with and without SMC. The experiment aimed to evaluate the fate of contaminants including alkanes, PAHs, and metals, and their effect on the soil microbial community, as well as the implications for remediation endpoints. The results showed that the bioamendments had an average TPH reduction of 92%, with SMC and WSB-SMC having the highest degradation rates at 93%. While the bioamendments did not significantly affect the extent of TPH removal compared to the control, they did improve the degradation of high molecular weight (HMW) PAHs, particularly in RHB-SMC for EC17-20 (60%) and EC21-35 (62%) of total PAH concentration, and in WSB-SMC for HMW bioavailable PAH concentration (89%). The bioamendments also affected the partitioning and distribution of metals after 120 days of treatment, leading to decreased available phase fractions. The treatments increased microbial abundance in the soil, with Gram positives, Gram negatives, and fungi increasing by 4%, 8%, and 38%, respectively, after 120 days, particularly in SMC and mixed treatments. This was mirrored in increased microbial soil respiration. After 120 days, low metal (178 ± 5 mg/kg) and TPH (21 ± 7 mg/kg) bioavailability translated into higher EC50 (10624 ± 710 mg/L), indicating lower toxicity. There was a strong correlation between bioavailability and toxicity of TPH and metals with microbial relative abundance and activity. In summary, while green and sustainable remediation may accelerate the remediation process, monitored natural attenuation may be sufficient for site reclamation. However, this strategy, as demonstrated here, can reduce metal bioavailability, and promote the biodegradation of HMW PAHs