51 research outputs found
Performance of septic tanks for pharmaceutical removal and their impact to river water quality.
No full textPharmaceuticals enter surface water after incomplete removal in wastewater treatment works (WWTWs) and are known for their potential ecotoxicological hazard to the environment. Septic tanks (STs) treat wastewater of individual houses and small communities in rural and semi-urban areas and are an understudied pathway of surface water contamination. Therefore, the aim of this research was to understand the performance of STs for pharmaceutical removal and their impact to river water quality. A methodology for the analysis of 68 pharmaceuticals, including prescription and over-the-counter drugs, related metabolites, hormones, and other human wastewater marker (emerging contaminants; ECs), by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) in ST influent and effluent, total suspended solids (TSS), sludge and river water was developed. Five community STs and the receiving rivers were studied over 12 months. Concentrations were similar in influent and effluent, exceeded those previously found in centralised WWTWs and surpassed freshwater predicted no-effect concentrations (PNECs) for some pharmaceuticals and samples. Hence, dilution of the ST discharges is required to mitigate environmental hazard. Influenced by the small contributing population, monthly variability was high, especially for pharmaceuticals with acute use, e.g., antifungals. Generally, the contribution of TSS to the total pharmaceutical concentration was small, but high contributions of TSS were for example observed for fluoroquinolone antibiotics and antidepressants. Approximately half of pharmaceuticals are chiral, existing as two or more enantiomers with differences in their environmental occurrence, fate, and toxicity. For 26 chiral pharmaceuticals, the enantiomer composition of ST was determined. Most pharmaceuticals were found racemic in wastewater, containing the same amount of both enantiomers. However, a strong enantioselectivity in influent and effluent was for example found for fluoxetine, naproxen, citalopram, omeprazole, and cotinine. The similar enantiomeric composition of ST influent and effluent suggests that unlike in aerobic WWTWs, no enantioselective degradation occurs in STs. Potentially, the unchanged enantiomeric composition in ST wastewater, can be used to distinguish between pharmaceutical discharges from STs and other WWTWs in the environment, e.g., naproxen. A wide range of ECs were also detected in rivers upstream and downstream of the ST discharge points, and concentrations increased by up to 95% downstream. In general, hazards in the rivers were low. However, PNECs were exceeded for ibuprofen, diclofenac and ciprofloxacin in few samples. Overall, the similarities in number of compounds detected, concentrations, and enantiomeric composition, indicate that STs are less effective in removing pharmaceuticals than centralised WWTWs. Alternative wastewater treatment might be needed at locations with low dilutions. Finally, pharmaceuticals were analysed in influent and effluent of twelve pilot-scale STs (control, insulated, 20°C and 30°C) to assess the temperature effect on removal, as biodegradation is influenced by microbial activities and can increase with increasing temperature. For most pharmaceuticals, no temperature effect was found. However, lower concentrations of metformin and sanitary determinands at 30°C, highlight the potential for a seasonal effect for some pharmaceuticals. Higher temperatures above 30°C may further enhance the removal. In summary, STs contribute to pharmaceutical concentrations in rivers, but due to the mostly high dilutions, hazards are low
Demulsification and recycling of spent oil based drilling fluid as nanofiller for polyamide 6 nanocomposites.
No full textSpent oil-based drilling fluid and cutting wastes are global liabilities due to their hazardous hydrocarbon content, which impacts negatively on flora, fauna, and global carbon footprint. The formulation of two demulsifiers to ensure chemically-enhanced phase-separation of this waste into oil, water and solid components was successfully carried out in addition to recycling the solid phase into PA6 nanocomposite materials. Initial characterisation of the untreated waste was carried out by Fourier Transform Infra Red (FTIR) for total petroleum hydrocarbon (TPH) analysis, inductively-coupled plasma optical emission spectrometry (ICPOES) for quantitative elemental analysis, and energy dispersive X-ray analysis (EDXA) for qualitative elemental composition - amongst other characterisation methods. The analysis showed that the sample had a high hydrocarbon load of 662,500mg/kg and a high heavy metal load for Pb of 122mg/kg. No As, Cd, Hg were detected. The demulsifier formulations were composed of isopropanol, sodium dodecyl sulphate, poloxamer, sodium chloride, chitosan in 0.2M acetic acid and deionised water for demulsifier S4 and addition of phosphoric acid for demulsifier S3. Hydrocarbon reduction on the extracted solid phase nanofiller S3 and nanofiller S4 was 98.6% and 98.5% respectively after demulsification. The demulsified spent oil-based drilling fluid solid extracts were below OSPAR regulation of less than 1% oil on cutting by weight. However, recycling of the recovered solid was carried out in order to achieve environmentally sustainable management of the waste in polyamide 6 (PA6) nanocomposite manufacture/fabrication. The formulation of different blends of PA6 nanocomposite materials from untreated, demulsifier treated and thermally treated drilling fluid and cuttings was successfully achieved. Nanocomposite leaching test showed Pb immobilisation. The flexural and compressive modulus and strength of the PA6 were markedly improved in the presence of the nanofillers and glass fibre. This was attributed to the reinforcement, exfoliating, stiffening, rigidity effect of the nanofillers. S6 (untreated drilling fluid) nanofillers significantly improved the mechanical properties of PA6. This was attributed to the increased interfacial bonding between the fillers and the polymer matrix as a result of the petroleum hydrocarbon present in the sample. The thermogravemetric analysis (TGA) results showed that nanocomposites PA6/S3 and PA6/S3/GF30 had improved the thermal stability of PA6 by 13.6% and 38.8% respectively compared to PA6/S2 and PA6/S2/GF30 (simulated commercial nanocomposite materials) that improved PA6 by 9.7% and 35.8% respectively
Sustainable treatment of oil contaminated waste: oil-based mud (OBM) drill cuttings and soil.
No full textEnvironmental pollution from oilfield drilling waste poses potential hazards which can lead to ecological imbalance. The predominant pollutant from oilfield waste is petroleum hydrocarbons. Some effects of petroleum hydrocarbon contamination in soil include loss of nutrients, reduced fertility, foul odour, flora/fauna imbalance and potential for transport and distribution to other media. Several studies have been carried out to develop technologies for the reduction of petroleum hydrocarbons in oil based mud (OBM) drill cuttings and soil. Soil washing using biosurfactant is one of such technological developments. Biosurfactants are surface active compounds produced from biological origin. They are amphiphilic molecules, consisting of hydrophilic and hydrophobic moieties. The major advantage biosurfactants have over their synthetic counterpart is that they have low toxicity and are biodegradable. They can be produced from natural and renewable feedstock (agricultural and industrial waste). This work focused on the production, purification and characterisation of rhamnolipid (RL) biosurfactant, produced from Pseudomonas aeruginosa ST5 and Pseudomonas aeruginosa PS1, and its consequent application for the removal of total petroleum hydrocarbon (TPH) in OBM drill cuttings and petroleum contaminated soil. First, the OBM drill cuttings and soil were characterised to investigate the following parameters; particle size analysis by laser diffraction and sieve, morphology and elemental content (qualitative) by Scanning Electron Microscope – Energy Dispersive X-ray Analysis (SEM-EDXA), elemental content by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis (quantitative), hydrocarbon profile by Gas Chromatography–Mass Spectrometry (GC-MS) and TPH by Fourier-Transform Infrared Spectroscopy (FT-IR). Second, the rhamnolipid was produced from both bacteria using mineral salts media with glycerol as carbon source in shake flask cultivation process. Approximately 3.5 g/L yield of crude ST5 rhamnolipid extract (ST5-RL) was determined from the culture broth from Ps. ST5 and PS1. Thin layer chromatography analysis carried out on the crude ST5 rhamnolipid extract detected two fractions with retardation factors 0.76 and 0.39, which were purified by column chromatography and confirmed to be monorhamnolipid (R1) and dirhamnolipid (R2) respectively, consequent upon structural characterization using FTIR, NMR and LC-MS/MS. The surfactant potential of R1, R2 and ST5-RL were determined by investigating their surface active properties such as critical micelle concentration (where R1 = 28 ppm, R2 = 24 ppm and ST5-RL = 48 ppm), surface tension and emulsification index after 24 hours (E24). The crude ST5 rhamnolipid, R1 and R2 were applied for the removal of total petroleum hydrocarbon (TPH) in diesel contaminated soil at 10, 100 and 1000 ppm concentration levels. R1 and R2 both showed TPH removals at approximately 77% at 10 ppm, approximately 87% at 100 ppm and approximately 91% at 1000 ppm. However, ST5-RL showed over 90% TPH reduction from the oil contaminated soil at 10, 100 and 1000 ppm, validating the potential of RL in the removal of TPH from soil without purification. Approximately 91% of TPH was removed at the optimum washing condition using ST5-RL. The rhamnolipids were able to remove TPH from the sample by the mechanism of solubilisation. Also, the biocidal effect of RL and RL-washings (from the soil treatment) at 10, 100 and 1000 ppm was studied by carrying out cytotoxicity test on breast cancer MDA-MB-231 cells using MTT assay. The unused RL showed significant anti-proliferative against the cancer cells at 100 and 1000 ppm, while RL-washings showed significant anti-proliferative against the cancer cells at only 1000ppm. The RL was seen to be safe at 10 and 100ppm where over 90% TPH was achieved. This result shows the crude ST5 rhamnolipid is safe to use at concentrations not exceeding 100ppm. The study shows that biosurfactants can be applied to remove TPH from the environment at room temperature
Bioavailability of organic contaminants in sediments.
No full textThe bioavailability of polycyclic aromatic hydrocarbons (PAHs) and chlorobiphenyls (CBs) in sediments is largely dependent on the freely dissolved concentration of these pollutants. However, measuring these is challenging, due to the low concentrations of lipophilic contaminants in the environment and their strong affinity for particles and for traditional sampling (filtration and centrifugation) equipment. An equilibrium passive sampling device made of silicone rubber was developed in this research to measure the freely dissolved concentrations of lipophilic contaminants and other parameters (water extractable proportions and sediment-water partition coefficients) that describe the availability of these contaminants in the environment. Equilibration between sampler and sediment for PAHs and CBs was found to be adequately achieved after 20 days shaking of a silicone rubber sampler in sediment slurry on an orbital shaker at 200 rpm. The reproducibility of uptake was better than 5 %. Silicone rubber-water partition coefficients for 34 PAHs and 32 CBs were measured in the laboratory using a co-solvent method using methanol as co solvent. Strong linear correlations of log K(sr,w), with octanol-water partition coefficients (log K(ow)). (log K(sr,w) = 0.97; log K(ow) -0.01; r2 = 0.94) and (log K(sr,w) = 1.17; log K(ow) -1.82; r2 = 0.90) were found for PAHs and CBs, with a systematic difference in correlations observed for the different classes of compounds which was attributed to structural differences of the compounds. The silicone rubber samplers were then used to measure concentrations of PAHs in the pore water of sediments from the Fladen Ground of the North Sea, Loch Shell, Firth of Forth, Firth of Clyde, Loch Etive and Aberdeen Harbour in Scotland and the Vefsn fjord, Norway. A proportion of the PAHs were found to be unavailable for exchange into the aqueous phase, and this was reflected in the high log K(oc) measured in all the sediments studied. The sediment-water partition coefficients also correlated positively with the octanol-water partition coefficients. Accumulation of PAHs in Nereis virens from sediments was better predicted from literature bio-concentration factors and pore-water concentrations obtained using the silicone rubber samplers, than from sediment concentrations traditionally used in risk assessments. Participation in an International Council for the Exploration of the Seas (ICES) passive sampling trial survey using silicone rubber in sediments and water is described, and demonstrated the potential of passive sampling in monitoring environmental pollution. The log BCF (bio concentration factor) for PAHs in mussels increased with increasing log K(ow) at both Loch Etive and Aberdeen Harbour locations, and could be used to estimate concentrations in mussels directly. The survey data also showed the use of silicone rubber in assessing the diffusive exchange of PAHs across sediment-water interfaces
Bioaccumulation of persistent organic pollutants and trace metals in Scottish marine food webs and their relationship with trophic level and fatty acid signatures.
No full textThere is a global programme of action in place for the protection of the marine environment to ensure our seas are clean and safe. One of the biggest threats to our oceans is man-made pollution and it is the responsibility of governments to conduct assessments to advise policy. Across the North-East Atlantic, Contracting Parties to the OSPAR Convention for the Protection of the Maine Environment of the North-East Atlantic, including the United Kingdom, are required to undertake monitoring and assessment of contaminants. The assessment utilises assessment criteria, including Background Assessment Concentrations (BAC) and Environmental Assessment Criteria (EAC). Guidelines for monitoring contaminants in biota include specific shellfish, flatfish and roundfish, as well as seabird eggs. Extending the assessment to other species has considerable merit, but such species may, for example, be more difficult to sample, with generic trophic level values obtained from literature and databases adding additional uncertainty to assessments. Currently, assessment criteria for organic and inorganic contaminants either do not account for secondary poisoning as a route of exposure, or a proxy is used due to the lack of ecotoxicological data available. Secondary poisoning is a result of biomagnification, which can be expressed as the trophic magnification factor (TMF; the average increase in concentration per trophic level). Fatty acid (FA) signatures and stable isotope (SI) ratios were used to develop an understanding of Scottish marine food web ecology and reliably ascribe trophic levels to a wide range of species. Analysis was conducted on 215 samples from different locations around Scotland which comprised of seven fish species, one shark species, fourteen marine invertebrate species, three marine mammal species and two zooplankton species. The concentrations of three priority heavy metals and six additional trace metals and metalloids, thirty-two PCB congeners and nine PBDE congeners were determined to investigate the relationship between concentration and potential influencing factors (trophic level, region, sample categorisation and physiological features). TMFs were calculated using two methods on selected PCB and PBDE congeners and metals and metalloids possessing a significant trophic relationship. It was concluded that ecosystem specific TMFs can be used as a reliable tool, permitting the assessment of a wider range of species, but a reasonable balance with respect to sample numbers of lower- versus higher-trophic level organisms is highly recommended when calculating TMFs
Chemical and physical effects of interaction between oilfield chemicals and formation rocks and integration with sand failure prediction models.
No full textSand failure may result in the production of formation sand at the same time the formation fluids are being produced. Sand failure occurs when the formation stress exceeds the strength of the formation, which is derived mainly from the natural material that cements the sand grain and cohesive forces. The sand failure and production is a serious challenge that, if not properly handled, can have a drastic effect on oil and gas production rate, cause downhole and subsea equipment damage, and also increase the risk of catastrophic failure. Several models exist for the prediction of sand failure in oil and gas wells, but none of these models account for the failure effects of oilfield chemicals on the reservoir rock, which is exposed to significant amounts of these chemicals. Oilfield chemicals have many applications in the oil and gas industry, and have been used extensively as inhibitor, surfactant, biocide, stabilizer, depressant, retarder, scavenger, defoamer, demulsifier, stimulant, and so on. However, the weakening effect that the chemical/formation interaction may have on the grain fabrics has not yet been given due attention as part of the industry's current approach to geomechanical evaluation of reservoir rock for sand failure and production forecast. This thesis investigates the failure effects of some oilfield chemicals (corrosion inhibitor, scale inhibitor and biocide) on the geomechanical strength of reservoir rocks, the mechanisms of interaction and the mechanism of failure. The research used a combination of rock mechanical testing, grain size distribution analysis, analytical techniques and numerical modelling to establish and define the geomechanical and mechanical failure effects of these chemicals and the mechanisms of failure. The failure effects of the oilfield chemicals on sandstone and carbonates may be integrated within any suitable and relevant existing sand failure prediction models. Results clearly show that a dissolution/precipitation reaction took place, weakening the reservoir grain fabrics and reducing the geomechanical strength, which in turn causes sand failure/production. This work has established that volume fraction and porosity change are functions of dissolution and precipitation reactions, and that the dissolution/precipitation reaction is a function of the type of minerals in the rock
Determining the spatial and temporal distribution of macro- and microplastics in soil and their impact on soil function.
No full textMicroplastics are long-term anthropogenic terrestrial ecosystem stressors that are ubiquitous in the natural environment, found in all ecological niches including aquatic and terrestrial environments. Consequently, microplastics have been found within organisms and plants, where they have the potential to induce adverse effects. Little is known of microplastic distribution in Scotland (or worldwide), their fate over time, and how they interact with organic pollutants or the impact of these interactions on soil function. It was the overarching aim of this project to determine the extent of macro- and microplastics in Scottish surface soils, both spatially and temporally, and evaluate the impact of microplastics on soil function and ecosystem services. The novel high-gradient magnetic separation (HGMS) methodology was developed to overcome the challenges faced using the commonly used density separation method, and to improve recovery rates of all microplastic types, compositions and sizes regardless of soil type. HGMS was able to recover microplastics consistently across different soil types and their recovery rates ranged between 91- 96%, which was statistically higher than that achieved by density separation (0-89%; p 0.05). Fibres degraded over time, showing the greatest reduction in size, highlighting the possibility that fibres release secondary micro(nano)plastics. Films were also highly susceptible to degradation, while other microplastic morphologies were more resistant. Coloured fibres showed dye loss over time, which possibly leached into soil. The sludges contained different microplastic compositions (e.g., polyester, polyurethane), reflecting the possible different sources of the sludges. This evidence is useful in informing regulation on sewage sludge use and management, and in assessing the fate and impact of microplastics in soil. The first national-scale study on microplastic prevalence in soils was conducted using the National Soils Inventory of Scotland. Results highlighted that microplastic "hotspots" could be identified through distribution mapping, which demonstrated that geography played a role in microplastic distribution e.g., spatial variation in land use or rural locations impacted by tourism. Fibres were the most abundant microplastic morphology (≥ 88.91%). Microplastic data was correlated to anthropogenic, topographical, soil physicochemical and environmental factors that influenced microplastic distribution in Scotland. Largely, land use was a significant factor in the distribution of microplastics, such that high-intensity land management resulted in higher microplastic pollution (average 3756 microplastics L-1 soil) compared to unmanaged soils (average 562 microplastics L-1 soil) (p < 0.05). Microplastics were also correlated with persistent organic pollutants (rS = 0.18-0.46), including compounds linked to plastic manufacturing and degradation, suggesting that microplastics may contribute to pollution of these contaminants through leaching or that they share a common anthropogenic source. Further, sorption and desorption kinetics of 16 priority polycyclic aromatic hydrocarbons (PAHs) were investigated using two different sizes of polyethylene microfilms derived from mulch film mixed into an agricultural soil. Sorption data fitted a first order equilibrium model while desorption data fitted an exponential decay model. Sorption and desorption kinetics were influenced by physico-chemical properties of PAHs, and no significant differences between the rate of sorption or desorption were observed. Decreases in soil organic matter indicated that smaller-sized microfilms sequestered a higher amount of PAHs (3.36% decrease compared to 2.93% for the larger microfilm) and sorption to microfilms prevented soil acidification likely caused through microbial degradation (2.67% decrease in soil pH opposed to 4.10%). The effect of microfilms, chrysene and chrysene-bound microfilms on ecosystem function (soil respiration) and microbial activity (substrate-induced respiration) was then investigated. The treatment groups showed differences in function and activity, with chrysene inducing reduced soil respiration and microbial activity (p < 0.05), microfilms inducing increased soil respiration and microbial activity, and chrysene-bound microfilms not significantly changing ecosystem function compared to a soil negative control. These were attributed to changes in the microbial biomass. Evaluation of the microbial community composition through sequencing of the 16S rRNA gene showed differences in the microbial communities was more pronounced at a lower taxonomic level (family) and that there were significant changes in beta diversity of the microbial communities between treatments (p < 0.05). Sorption of chrysene to microfilms appear to limit the availability of chrysene to soil micro-organisms and may alleviate the immediate effects of chrysene. However, this may pose a greater threat, as chrysene could be slowly released into the soil environment and persist over a prolonged period. Key findings are discussed throughout this thesis, which highlight the importance of understanding the extent and impact of microplastics in Scotland to enable future work to be conducted, and inform future mitigation and remediation strategies for the protection of one of Scotland's most valuable natural assets
Development of a novel photocatalytic reactor for the treatment of polycyclic aromatic hydrocarbons.
No full textWater pollution through the discharge of contaminated water into the environment has been a major problem, both to humans and aquatic life. These potential consequences mean that water pollution has therefore received major attention. In industry, a group of contaminants still facing challenges with regards to effective remediation are the polycyclic aromatic hydrocarbons (PAH) present in water. These PAHs impose significant risk due to their carcinogenic, mutagenic and teratogenic potential. 18 of these PAHs are classified as high priority by the Environmental Protection Agency (EPA) due to their toxic and harmful nature. This research investigated two remediation methods - coagulation-flocculation and photocatalysis - for the remediation of these 18 PAHs in water. In each remediation method investigated, preliminary works were first carried out on 3 PAHs (naphthalene, phenanthrene and fluorene) before then applying the method to the other 15 PAHs. The coagulation-flocculation remediation method was investigated because the literature review proved that it was an effective method in the adsorption of pollutants from water. Also in the investigation, powder and solubilized (in acetone) chitosan were used as an adsorbent to remove the PAHs in water. Results from this investigation showed little significance in the removal of PAHs with a removal efficiency of 15% attained for phenanthrene using powder chitosan (25 ppm) at 30 minutes contact time. An increase in contact time to 120 hours increased the removal efficiency to 88%. To attain sustainable removal from an industrial treatment point of view, a fast and effective remediation method is required. At 120 hours duration, this method is too slow, meaning that further investigation for a more rapid and effective method required. The photocatalysis remediation method was identified as an alternative. Investigation carried out using the photocatalytic remediation method involved the design and construction of a photocatalytic reactor. Preliminary work was first carried out in a constructed batch suspended photocatalytic reactor to investigate the photodegradation of naphthalene, phenantharene and fluorene, in order to confirm the photocatalytic ability of TiO2 to photodegrade PAH under the influence of UV light. A high removal efficiency of 99% was achieved, but with the limitation of needing to subsequently remove the TiO2. Due to the secondary treatment required to remove TiO2, an immobilized photocatalyst reactor was then investigated. Preliminary work was first carried out on a batch immobilized TiO2 coated photoreactor. This achieved significant results with 83% removal of naphthalene from water over 20 minutes. As a result of this investigation, this study then moved to focus on the design and construction of a flow-through photocatalytic reactor. The developed reactor included both an immobilized TiO2 photocatalyst and UV light radiation. In testing, the novel reactor achieved a high removal rate of 84% in the removal of naphthalene in water. Further investigation with the PAH present in synthesized sea water achieved a similarly high removal rate of 77%. This novel flow-through photocatalytic reactor therefore provides a solution to the challenge of effective removal of PAHs in water
The concentration and biomagnification of PCBs and PBDEs across four trophic levels in a marine food web. [Dataset]
No full textContracting Parties to the OSPAR Convention for the Protection of the Maine Environment of the North-East Atlantic are required to undertake monitoring and assessment of both inorganic and organic contaminants. There is a requirement to assess contaminants across different trophic levels on an ecosystem-specific basis. However, this is currently constrained by the availability of relevant samples to cover the full range of trophic levels. This study investigates the variability (inter- and intra-species variation) of the concentrations and distributions of thirty-two polychlorinated biphenyl (PCB) congeners and nine polybrominated diphenyl ether (PBDE) congeners in twenty-six species covering four trophic levels from different geographic locations around Scotland. Trophic magnification factors (TMFs) were calculated using a traditional method and a balanced method for both the ICES-7 PCBs and BDE47, to refine and improve the application of TMFs to assess and predict biomagnification risk to biota in the marine environment. There were clear differences in congener percentage distribution between sample categories and species, with differences influenced by physiological processes and eco-biological parameters. Trophic magnification was found to occur for the ICES-7 PCBs and BDE47 using the traditional method, with the highest degree of trophic magnification reported for CB52. An unbalanced dataset was found to influence the calculated TMF and in some cases, the overall conclusion of the trophic transfer of PCB and PBDE congeners. The balanced method is highly recommended for calculating TMFs to ensure that the TMF is a true indication of the biomagnification potential, particularly when conducting regional comparisons for which sampling requirements are difficult to achieve. The accompanying file contains supplementary material to the main text
Thermal stability, flame retardancy and mechanical properties of polyamide/montmorillonite nanocomposites prepared by melt processing.
No full textThe increase in thermal stability, flame retardancy, and mechanical properties of Polyamide 6 (PA6)/montmorillonite (MMT) nanocomposites open a new research window in respect to successful technical application of PA6/MMT nanocomposites on the industrial scale. This illustration provides important indication to understand a widely reported but poorly identified phenomena of catalysing effect of different ions, materials, or compounds present in MMT during the combustion of PA6/MMT nanocomposites
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