Browsing by Author "Autin, Olivier"
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Item Open Access Application of ultraviolet light-emitting diodes (UV-LED) to full-scale drinking-water disinfection(MDPI, 2019-09-11) Jarvis, Peter; Autin, Olivier; Goslan, Emma Harriet; Hassard, FrancisUltraviolet light-emitting diodes (UV-LEDs) have recently emerged as a viable technology for water disinfection. However, the performance of the technology in full-scale drinking-water treatment systems remains poorly characterised. Furthermore, current UV disinfection standards and protocols have been developed specifically for conventional mercury UV systems and so do not necessarily provide an accurate indication of UV-LED disinfection performance. Hence, this study aimed to test the hypothesis that a full-scale UV-LED reactor can match the Cryptosporidium inactivation efficiency of conventional mercury UV reactors. Male-specific bacteriophage (MS2) was used as the Cryptosporidium spp. surrogate microorganism. The time-based inactivation efficiency of the full-scale reactor was firstly compared to that of a bench-scale (batch-type) UV-LED reactor. This was then related to mercury UV reactors by comparing the fluence-based efficiency of the bench-scale reactor to the USEPA 90% prediction interval range of expected MS2 inactivation using mercury UV lamps. The results showed that the full-scale UV-LED reactor was at least as effective as conventional mercury UV reactors at the water-quality and drive-current conditions considered. Nevertheless, comparisons between the bench- and full-scale UV-LED reactors indicated that improvements in the hydraulic flow profile and power output of the full-scale reactor could help to further improve the efficiency of UV-LED reactors for municipal drinking water disinfection. This represents the world’s first full-scale UV-LED reactor that can be applied at municipal water treatment works for disinfection of pathogenic microorganisms from drinking water.Item Open Access Controlling shell-side crystal nucleation in a gas-liquid membrane contactor for simultaneous ammonium bicarbonate recovery and biogas upgrading(Elsevier, 2014-09-17) McLeod, Andrew J.; Autin, Olivier; Jefferson, Bruce; McAdam, Ewan J.A gas–liquid hollow fibre membrane contactor (HFMC) process has been introduced for carbon dioxide (CO2) separation from biogas where aqueous ammonia (NH3) is used to chemically enhance CO2 absorption and initiate heterogeneous nucleation of the reaction product ammonium bicarbonate at the membrane–solvent interface. Aqueous ammonia absorbents (2–7 M) were initially used in single pass for CO2 separation from a synthetic biogas where nucleation of ammonium bicarbonate crystals was observed at the perimeter of the micropores. Recirculation of the aqueous ammonia absorbent encouraged the growth of ammonium bicarbonate crystals on the shell-side of the membrane that measured several microns in diameter. However, at high aqueous NH3 concentrations (3–7 M), lumen side crystallisation occurred and obstructed gas flow through the lumen of the HFMC. The suggested mechanism for lumen-side crystallisation was absorbent breakthrough into the lumen due to pore wetting which was promoted by low absorbent surface tension at high NH3 concentration. Preferential shell-side nucleation can therefore be promoted by (1) raising surface tension of the absorbent and (2) selection of a membrane with a more regulated pore shape than the PTFE membrane used (d/L 0.065) as both actions can diminish solvent ingress into the pore. This was evidenced using 2 M NH3 absorbent where shell-side crystallisation was evidenced without the onset of lumen side crystallisation. Raising surface tension through the inclusion of salt into the chemical absorbent also promoted greater CO2 flux stability. Importantly, this study demonstrates that chemically enhanced HFMC are an attractive prospect for gas–liquid separation applications where reaction product recovery offers further economic value.Item Open Access Disinfection by-product formation during UV/Chlorine treatment of pesticides in a novel UV-LED reactor at 285 nm and the mitigation impact of GAC treatment(Elsevier, 2020-01-07) Carra, Irene; Lozano, Javier Fernandez; Autin, Olivier; Bolton, James R.; Jarvis, PeterThe UV/Chlorine process has gained attention in recent years due to the high quantum yield and absorbance of the chlorine species. However, there are still many unknowns around its application as a treatment for drinking water. The potential for the formation of disinfection by-products (DBPs) is one of them. There are no studies reporting on the formation of trihalomethanes (THMs) or haloacetic acids (HAAs) in complex matrices, such as real source waters, at UV wavelengths tailored to the UV/Chlorine process, which has been possible thanks to the development of light emitting diodes (LEDs). In addition, consideration of mitigation measures that might be needed after UV/Chlorine treatment for full scale application have not been previously reported. Specifically, the novelty of this work resides in the use of an innovative reactor using UV-LEDs emitting at 285 nm for the removal of three pesticides (metaldehyde, carbetamide and mecoprop), the evaluation of THM, HAA and bromate formation in real water sources by UV/Chlorine treatment and the mitigation effect of subsequent GAC treatment. A new parameter, the applied optical dose (AOD), has been defined for UV reactors, such as the one in the present study, where the irradiated volume is non-uniform. The results showed the feasibility of using the UV/Chlorine process with LEDs, although a compromise is needed between pH and chlorine concentration to remove pesticides while minimising DBP formation. Overall, the UV/Chlorine process did not significantly increase THM or HAA formation at pH 7.9–8.2 at the studied wavelength. At acidic pH, however, THM formation potential increased up to 30% after UV/Chlorine treatment with concentrations up to 60 μg/L. HAA formation potential increased between 100 and 180%, although concentrations never exceeded 35 μg/L. In all cases, GAC treatment mitigated DBP formation, reducing THM formation potential to concentrations between 3 and 16 μg/L, and HAA formation potential between 4 and 30 μg/L.Item Open Access Effect of elevated UV dose and alkalinity on metaldehyde removal and THM formation with UV/TiO2 and UV/H2O2(Elsevier, 2015-11-26) Jefferson, Bruce; Jarvis, Peter; Bhagianathan, Govind Kannoly; Smith, Heather M.; Autin, Olivier; Goslan, Emma Harriet; MacAdam, Jitka; Carra, IreneDrinking water production needs to increasingly consider removal of background organic matter and trace micropollutants without increasing disinfection-by-product (DBP) formation potential. The presented data demonstrates the efficacy of both UV/H2O2 and UV/TiO2 in removing the pesticide metaldehyde to below drinking water compliance levels in both real and synthetic waters. This pesticide has proven to be unaffected by conventional water treatment processes such as granular activated carbon and is responsible for many of the water company compliance failures in the UK. The potential of UV/H2O2 is further demonstrated to offer an alternative approach for the removal of recalcitrant organic matter to ensure DBP compliance as long as extended UV doses of over 10,000 mJ cm−2 are applied at the optimum peroxide dose of 8 mM. Alkalinity and UV dose have an impact on DBP formation: at low UV fluences, increased alkalinity reduced the DBP formation. The UV/TiO2 process was observed to be inhibited in the presence of alkalinity. Aggregation studies and comparison of the catalyst fractal dimension showed that the process inhibition is mainly due to aggregation. This restricts the surface area available for reactions, rather than changes in the catalyst properties or carbonate radical scavenging, which is often the reasoning attributed to photocatalysis inhibition. Hence, the presented results indicate that decreasing the catalyst aggregation is the key to apply photocatalysis as drinking water treatment.Item Open Access Fluorescence enabled direct visual observation for diagnosis of ultrafiltration membrane fouling by bi-disperse submicron particle suspensions(Wiley, 2018-04-24) Autin, Olivier; Sakar, H; McAdam, Ewan J.Whilst direct observation (DO) methodologies can describe back‐transport of supra‐micron particles, present technologies are unable to discriminate submicron particles, which are primarily responsible for membrane fouling. In this study, we therefore introduce a fluorescence enabled direct visual observation (RLF‐DVO) methodology to permit visual characterisation of submicron particle transport during cross‐flow filtration. Particle discrimination was achievable for particle diameters exceeding 0.25 µm; however, this was dependent upon particle concentration and the cross‐flow velocity employed. Nevertheless, this is considerably below the detection limit of current techniques (around 3 µm). During filtration of a binary dispersion comprised of submicron particles, deposition was observed before a change in transmembrane pressure was detected, which underpins the important role of DO for fouling diagnosis. Based on observations made during this study, recommendations are proposed that will further improve resolution. Importantly, this study demonstrates RLF‐DVO can provide real‐time description of submicron particle transport during cross‐flow filtration.Item Open Access Impact of fouling, cleaning and faecal contamination on the separation of water from urine using thermally driven membrane separation(Taylor & Francis, 2018-02-12) Kamranvand, Farhad; Davey, Christopher; Sakah, H.; Autin, Olivier; Mercer, E.; Collins, Matt; Williams, Leon; Kolios, Athanasios; Parker, Alison; Tyrrel, Sean; Cartmell, Elise; McAdam, EwanIn this study, membrane distillation is evaluated as a technology for non-sewered sanitation, using waste heat to enable separation of clean water from urine. Whilst membrane fouling was observed for urine, wetting was not evident and product water quality met the proposed discharge standard, despite concentration of the feed. Fouling was reversible using physical cleaning, which is similar to previous membrane studies operating without pressure as the driving force. High chemical oxygen demand reduction was achieved following faecal contamination, but mass transfer was impeded and wetting occurred which compromised permeate quality, suggesting upstream intervention is demanded to limit the extent of faecal contamination.Item Open Access Incorporating biodegradation and advanced oxidation processes in the treatment of spent metalworking fluids(Taylor & Francis, 2012-04-27T00:00:00Z) MacAdam, Jitka; Ozgencil, Haci; Autin, Olivier; Pidou, Marc; Temple, Clive; Parsons, Simon A.; Jefferson, BruceThe treatment of spent metalworking fluids (MWFs) is difficult due to their complex and variable composition. Small businesses often struggle to meet increasingly stringent legislation and rising costs as they need to treat this wastewater on site annually over a short period. Larger businesses that treat their wastewater continuously can benefit from the use of biological processes, although new MWFs designed to resist biological activity represent a challenge. A three-stage treatment is generally applied, with the oil phase being removed first, followed by a reduction in COD loading and then polishing of the effluent's quality in the final stage. The performance of advanced oxidation processes (AOPs), which could be of benefit to both types of businesses was studied. After assessing the biodegradability of spent MFW, different AOPs were used (UV/H2O2, photo-Fenton and UV/TiO2) to establish the treatability of this wastewater by hydroxyl radicals (•OH). The interactions of both the chemical and biological treatments were also investigated. The wastewater was found to be readily biodegradable in the Zahn–Wellens test with 69% COD and 74% DOC removal. The UV/TiO2 reactor was found to be the cheapest option achieving a very good COD removal (82% at 20min retention time and 10Lmin−1 aeration rate). The photo-Fenton process was found to be efficient in terms of degradation rate, achieving 84% COD removal (1M Fe2+, 40M H2O2, 20.7Jcm−2, pH 3) and also improving the wastewater's biodegradability. The UV/H2O2 process was the most effective in removing recalcitrant COD in the post-biological treatment stage.Item Open Access Investigating the significance of coagulation kinetics on maintaining membrane permeability in an MBR following reactive coagulant dosing(Elsevier, 2016-06-11) Autin, Olivier; Hai, F.; Judd, Simon J.; McAdam, Ewan J.In this study, the impact of kinetically controlled floc growth on sustaining membrane permeability following reactive coagulant dosing was determined using a model particle system. Floc formation was indicated to comprise of two stages following coagulant addition: (i) an initial destabilisation phase which encouraged complexation of protein and polysaccharide; and (ii) entrapment of the coarse model particles (3 µm Firefli™ microspheres) in the polymeric complex during the floc growth phase. Floc growth was characterised by an expected time lag as with conventional flocculation systems and biopolymer aggregation was kinetically favoured. When coagulant was dosed during the filtration cycle, the intermediate biopolymer aggregates (comprised of protein and polysaccharide) were preferentially transported toward the membrane increasing fouling. However, when coagulant was dosed at the onset of filtration, membrane fouling was constrained. It is asserted that by dosing at the onset of filtration: (i) early development of biopolymer aggregation is initiated which inhibits transport of the individual biopolymers to the membrane; and (ii) by dosing coagulant in the absence of a developed polarised layer, formation of biopolymer complexes local to the membrane is obviated. However, when dosing coagulant at the onset of filtration, only limited floc growth occurred which can be explained by the low applied wall shear rate and the absence of a ‘polarised’ region which ostensibly promoted floc growth when coagulant was dosed mid-filtration. Based on results from the model particle system studied, it is proposed that reactive coagulant dosing is best undertaken when: (i) filtration is stopped; (ii) modest shear is applied within the bioreactor to promote coagulant dispersion; and (iii) sufficient contact time is allowed to promote floc growth before commencement of filtration.Item Open Access Micropollutant removal by advanced oxidation processes(Cranfield University, 2012-10) Autin, Olivier; Jefferson, BruceThe use of pesticides in agriculture has been associated to high concentrations found in surface waters and ultimately to the tightening of drinking water regulations. Whilst traditional granular activated carbon filtration or ozone are effective barriers for the large majority of pesticides, new polar pesticides such as clopyralid or metaldehyde are not readily removed by such technologies. The use of advanced oxidation processes (AOPs) is suggested as an effective alternative for metaldehyde removal. Although metaldehyde’s reactivity towards •OH appears in the last third of an extensive list of various pesticides’ reactivity, it was still well removed by the two AOPs tested: UV/H2O2 and UV/TiO2 in pure systems at similar rates of degradation under optimised doses of 100 mg.L-1 of TiO2 and 8 mM of H2O2. The presence of scavengers in natural waters such as natural organic matter (NOM) and carbonate ions reduced the effectiveness of metaldehyde removal. Experiments were undertaken using model compounds in order to evaluate the influence of these scavengers by directly monitoring the competition for •OH between background organic matter and metaldehyde. It was found that the concentration of background scavengers rather than the concentration of micropollutant had the greatest impact on both AOPs. In addition, whilst the alkalinity did not significantly influence the UV/H2O2 process, it totally inhibited the UV/TiO2 photocatalytic process due to the aggregation of TiO2 particles and further investigations are critical in order to break these aggregates for UV/TiO2 photocatalysis to become a competitive alternative to traditional treatments. Finally, a cost analysis showed that AOPs already appear as an economically viable technology for metaldehyde removal. Development of UV/LEDs will provide a lower energy option which will be economically competitive within the next 7-8 years.