CERES :: Browsing by Author "Jarvis, Peter"

Browsing by Author "Jarvis, Peter"

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Open Access
Acidified and ultrafiltered recovered coagulants from water treatment works sludge for removal of phosphorus from wastewater
(Elsevier, 2015-10-21) Keeley, James; Smith, Andrea D.; Judd, Simon J.; Jarvis, Peter
This study used a range of treated water treatment works sludge options for the removal of phosphorus (P) from primary wastewater. These options included the application of ultrafiltration for recovery of the coagulant from the sludge. The treatment performance and whole life cost (WLC) of the various recovered coagulant (RC) configurations have been considered in relation to fresh ferric sulphate (FFS). Pre-treatment of the sludge with acid followed by removal of organic and particulate contaminants using a 2kD ultrafiltration membrane resulted in a reusable coagulant that closely matched the performance FFS. Unacidified RC showed 53% of the phosphorus removal efficiency of FFS, at a dose of 20 mg/L as Fe and a contact time of 90 min. A longer contact time of 8 h improved performance to 85% of FFS. P removal at the shorter contact time improved to 88% relative to FFS by pre-acidifying the sludge to pH 2, using an acid molar ratio of 5.2:1 mol H+:Fe. Analysis of the removal of P showed that rapid phosphate precipitation accounted for >65% of removal with FFS. However, for the acidified RC a slower adsorption mechanism dominated; this was accelerated at a lower pH. A cost-benefit analysis showed that relative to dosing FFS and disposing waterworks sludge to land, the 20 year WLC was halved by transporting acidified or unacidified sludge up to 80 km for reuse in wastewater treatment. A maximum inter-site distance was determined to be 240 km above the current disposal route at current prices. Further savings could be made if longer contact times were available to allow greater P removal with unacidified RC.
Open Access
Application of activated carbon fabric for the removal of a recalcitrant pesticide from agricultural run-off
(Elsevier, 2022-01-08) Cosgrove, Stephanie; Jefferson, Bruce; Jarvis, Peter
Removal of pesticides from agricultural run-off close to the point of application has the potential to prevent or reduce the pollution of water sources used for drinking. This research considered the novel application of activated carbon (AC) fabric as a sorbent material for removal of pesticides from field run-off. AC fabric was tested for the removal of the molluscicide pesticide metaldehyde under a range of flow rates at both laboratory and pilot scale. Metaldehyde at an initial concentration of 10 μg/L was removed effectively from deionised (DI) water and real source water by the AC cloth under all conditions tested, reaching removal of 1375 and 876 μg/g (equivalent to 169 and 264 mg/m2), respectively. The adsorption followed pseudo-second order kinetics (k2 of 29.9 and 34.8 g/μg min for the AC fabric and GAC), providing rapid removal of metaldehyde within the first 5 min of contact. In single pass and flow through conditions, stabilised removal of 46% metaldehyde was achieved by the AC fabric bundle for treatment of 700 L of real water in a pilot scale flume. This equated to removal of 454 μg/m2, although significantly more removal would be expected over longer duration testing given the stabilised removal and the equilibrium capacity of the fabric seen during the batch isotherm testing. The work provides evidence to show that AC fabric could be used in the catchment to reduce peak loads of pesticides in sources used for drinking water.
Open Access
Application of microbubbles to ozonation for drinking water treatment.
(Cranfield University, 2022-11) John, Alexander; Jarvis, Peter; Carra ruiz, Irene; Jefferson, Bruce
Ozonation is a widely used water treatment process that is used to oxidise contaminants as well as disinfect water. Conventional ozone contactors have a large energy requirement and deep tanks to ensure adequate mass transfer. As a result, the delivery of ozone into water is an energy intensive and expensive process. The use of microbubbles in water treatment is a new technology that has been shown to significantly improve gas-liquid contacting processes. Microbubbles have diameters ranging from 1 – 100 µm, whereas conventional bubbles used in typical ozone contactors have diameters ranging from 2 – 6 mm. Due to their small size, microbubbles have a larger interfacial area and a lower rise velocity than conventional bubbles. Therefore, ozone in the gas phase may be transported more efficiently into the liquid phase. Despite the favourable properties of microbubbles, the mechanism by which microbubbles outperform conventional bubbles is not fully understood, with various conflicting interpretations having been presented in the literature. This work is comprised of several direct-comparison studies of microbubble and conventional bubble ozonation systems under identical conditions. Experiments were normalised for both input and effective ozone dose in order to determine a number of critical performance parameters including: hydroxyl radical production, volumetric mass transfer coefficient, ozone self-decomposition, rate and extent of compound removal and bromate formation. Overall, the observed performance enhancement was attributed to an increase in the volumetric mass transfer coefficient through the combination of an increase in bubble specific interfacial area and a decrease in the mass transfer coefficient. When normalised to effective ozone dose, no enhancement in hydroxyl radical production or increase in bromate formation was observed. In addition, the generation of microbubbles results in a distribution of bubbles containing both micro- and nanobubbles. It was concluded that in order to optimise the overall ozonation process, emphasis should be placed on understanding how to manage the size distribution of the microbubble fraction as the risk of residual ozone from nanobubble survival was deemed insignificant. These findings were then applied to the design of microbubble contactors to determine the economic viability of microbubble generation when applied to ozonation at full scale compared with a conventional bubble ozone contactor.
Open Access
Application of suspended ion exchange, in-line coagulation and ceramic membranes for surface water treatment
(Cranfield University, 2016-04) Metcalfe, David Christopher; Jarvis, Peter
A long term, large scale pilot study was performed to assess the use of a novel process based on suspended ion exchange (SIX®) and in-line coagulation (ILCA®) pretreatment for ceramic membrane filtration (CeraMac®), for treating three variable quality UK surface waters. SIX was shown to remove similar quantities of dissolved organic carbon (DOC) to coagulation for low to moderate DOC source waters. However, during periods of high DOC concentrations and high specific UV absorbance, the removal of organic compounds was reduced. The long term DOC removal data for the SIX process indicated good performance, which was in line with previously reported results from studies using other suspended ion exchange processes. Organic characterisation using liquid chromatography–organic carbon detection (LC-OCD) revealed the differing selectivities of the SIX and ILCA processes, for low and high molecular weight organic fractions respectively. When these processes were used in combination, a broad range of organic compounds were removed, leading to a 50% reduction in DOC concentration in comparison with an existing full scale conventional treatment process. Subsequently, disinfection by-product (DBP) formation was significantly reduced (62% vs. the conventional process) due to the lower DOC concentration, reduced specific reactivity of the residual organic compounds and reduced formation of brominated DBPs. Removal of high molecular weight organic compounds (biopolymers) was shown to be critical for stable operation of ceramic membranes at high flux. Optimised in-line coagulation (ILCA) pretreatment (which flocculated the biopolymers) led to negligible membrane adsorption of organic compounds, as low molecular weight (LMW) fractions (which are recalcitrant to coagulation) were shown not to be retained by the membrane. Due to this, when using optimised ILCA, additional removal of LMW organic fractions by using SIX in combination with ILCA provided no measureable benefit with regards to membrane fouling suppression. Automation of coagulant dosing was achieved for the high SUVA waters tested, using simple feed forward control based on the UV transmittance of the feed water. The application of this automated system led to very low membrane fouling rates (0.24kPa/day), despite highly challenging operating conditions of elevated fluxes (185 L m- 2 h- 1 ) and highly variable feed water dissolved organic carbon concentrations (1-10mg/l).
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, Francis
Ultraviolet 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.
Open Access
Are microbubbles magic or just small? a direct comparison of hydroxyl radical generation between microbubble and conventional bubble ozonation under typical operational conditions
(Elsevier, 2022-01-24) John, Alexander; Carra, Irene; Jefferson, Bruce; Jodkowska, Monika; Brookes, Adam; Jarvis, Peter
The application of microbubbles for water treatment is an emerging technology which has been shown to significantly enhance gas–liquid contacting processes. When applied to ozonation, microbubble technology has been shown to enhance mass transfer and the speed and extent of compound removal compared with conventional bubbling techniques. One explanation as to why microbubble systems outperform conventional systems is that microbubbles shrink, collapse and spontaneously generate hydroxyl radicals which is thought to enhance the speed of compound removal. This study compared microbubble (mean diameter 37 μm) and conventional bubble (mean diameter 5.4 mm) ozonation systems under identical conditions. The experiments were normalised for effective ozone dose to determine whether microbubble ozonation generated significantly more hydroxyl radicals than conventional bubble ozonation. 4-chlorobenzoic was used as the hydroxyl radical probe and the proportion of hydroxyl radicals generated for a given effective ozone dose was quantified. The •OH-exposure to O3-exposure (the ) was used to compare the systems. The ratio of the mean to mean was 0.73, 0.84 and 1.12 at pH 6, 7 and 8 respectively. Statistical assessment of the showed that there was no significant difference between the bubble systems. No evidence was found to support the hypothesis that microbubble systems generate more •OH. Instead, the level of •OH-exposure is linked to the effective dose and pH of the system and future designs should focus on those factors to deliver •OH based benefits.
Open Access
Bactericidal efficiency and photochemical mechanisms of micro/nano bubble–enhanced visible light photocatalytic water disinfection
(Elsevier, 2021-08-08) Fan, Wei; Cui, Jingyu; Li, Qi; Huo, Yang; Xiao, Dan; Yang, Xia; Yu, Hongbin; Wang, Chunliang; Jarvis, Peter; Lyu, Tao; Huo, Mingxin
Microbial contamination of water in the form of highly-resistant bacterial spores can cause a long-term risk of waterborne disease. Advanced photocatalysis has become an effective approach to inactivate bacterial spores due to its potential for efficient solar energy conversion alongside reduced formation of disinfection by-products. However, the overall efficiency of the process still requires significant improvements. Here, we proposed and evaluated a novel visible light photocatalytic water disinfection technology by its close coupling with micro/nano bubbles (MNBs). The inactivation rate constant of Bacillus subtilis spores reached 1.28 h−1, which was 5.6 times higher than that observed for treatment without MNBs. The superior performance for the progressive destruction of spores’ cells during the treatment was confirmed by transmission electron microscopy (TEM) and excitation-emission matrix (EEM) spectra determination. Experiments using scavengers of reactive oxygen species (ROSs) revealed that H2O2 and •OH were the primary active species responsible for the inactivation of spores. The effective supply of oxygen from air MNBs helped accelerate the hole oxidation of H2O2 on the photocatalyst (i.e. Ag/TiO2). In addition, the interfacial photoelectric effect from the MNBs was also confirmed to contribute to the spore inactivation. Specifically, MNBs induced strong light scattering, consequently increasing the optical path length in the photocatalysis medium by 54.8% at 700nm and enhancing light adsorption of the photocatalyst. The non-uniformities in dielectricity led to a high-degree of heterogeneity of the electric field, which triggered the formation of a region of enhanced light intensity which ultimately promoted the photocatalytic reaction. Overall, this study provided new insights on the mechanisms of photocatalysis coupled with MNB technology for advanced water treatment.
Open Access
Ballasted flotation with glass microspheres for removal of natural organic matter
(Taylor & Francis Inc., 2013-01-23) Jarvis, Peter; Martin, John; Winspear, Tracey; Jefferson, Bruce
Low density microspheres were used to float flocs formed from the coagulation of natural organic matter (NOM) using ferric sulphate coagulant. Microspheres were visually observed to be incorporated into the floc structure during the coagulation phase. In comparison with conventional flotation with air bubbles, the residual turbidity after flotation using the microspheres was very favourable and did not impact on overall NOM removal. Spheres of the lowest density and largest particle size gave the most rapid floc clearance, but the residual turbidity after 10 minutes flotation was similar for all of the spheres investigated. The results of this work have shown that floating microspheres offer an effective, energy efficient alternative to conventional dissolved air flotation for removal of flocs containing high concentrations of NOM.
Open Access
Bioaugmentation of pilot-scale slow sand filters can achieve compliant levels for the micropollutant metaldehyde in a real water matrix
(Elsevier, 2022-01-14) Castro-Gutierrez, V. M.; Pickering, Laura; Cambronero-Heinrichs, J. C.; Holden, B.; Haley, J.; Jarvis, Peter; Jefferson, Bruce; Helgason, T.; Moir, J. W.; Hassard, Francis
Metaldehyde is a polar, mobile, low molecular weight pesticide that is challenging to remove from drinking water with current adsorption-based micropollutant treatment technologies. Alternative strategies to remove this and compounds with similar properties are necessary to ensure an adequate supply of safe and regulation-compliant drinking water. Biological removal of metaldehyde below the 0.1 µg•L−1 regulatory concentration was attained in pilot-scale slow sand filters (SSFs) subject to bioaugmentation with metaldehyde-degrading bacteria. To achieve this, a library of degraders was first screened in bench-scale assays for removal at micropollutant concentrations in progressively more challenging conditions, including a mixed microbial community with multiple carbon sources. The best performing strains, A. calcoaceticus E1 and Sphingobium CMET-H, showed removal rates of 0.0012 µg•h−1•107 cells−1 and 0.019 µg•h−1•107 cells−1 at this scale. These candidates were then used as inocula for bioaugmentation of pilot-scale SSFs. Here, removal of metaldehyde by A. calcoaceticus E1, was insufficient to achieve compliant water regardless testing increasing cell concentrations. Quantification of metaldehyde-degrading genes indicated that aggregation and inadequate distribution of the inoculum in the filters were the likely causes of this outcome. Conversely, bioaugmentation with Sphingobium CMET-H enabled sufficient metaldehyde removal to achieve compliance, with undetectable levels in treated water for at least 14 d (volumetric removal: 0.57 µg•L−1•h−1). Bioaugmentation did not affect the background SSF microbial community, and filter function was maintained throughout the trial. Here it has been shown for the first time that bioaugmentation is an efficient strategy to remove the adsorption-resistant pesticide metaldehyde from a real water matrix in upscaled systems. Swift contaminant removal after inoculum addition and persistent activity are two remarkable attributes of this approach that would allow it to effectively manage peaks in metaldehyde concentrations (due to precipitation or increased application) in incoming raw water by matching them with high enough degrading populations. This study provides an example of how stepwise screening of a diverse collection of degraders can lead to successful bioaugmentation and can be used as a template for other problematic adsorption-resistant compounds in drinking water purification.
Open Access
Biodegradation of (Aminomethyl)phosphonic acid (AMPA) by isolated microbial consortia extracted from biological filters at drinking water treatment plants
(Elsevier, 2024) Pickering, Laura; Folkes, Miles; Holden, Barrie; Jarvis, Peter; Campo, Pablo; Hassard, Francis
The widespread use of glyphosate has significantly increased its presence in drinking water sources. Aminomethylphosphonic Acid (AMPA), a breakdown product of glyphosate, is challenging to remove from water using conventional treatment methods, posing risks to public health and environmental safety. This work investigates the biodegradation of AMPA by bacteria isolated from three environmental sources, with a focus on determining their potential application in water treatment systems. Two samples were collected from granular activated carbon (GAC) filters of different operational durations at a water treatment facility, and one sample was taken from soil that had historically been treated with glyphosate-based herbicides. Bacterial isolates capable of degrading AMPA were identified from these samples through selective enrichment, and kinetic degradation experiments were then conducted to assess their effectiveness. In environmental samples, after 48 hrs AMPA removal was > 70 % using GAC from an active treatment plant and soil samples removed 19 %. After bacterial isolation a consortium was isolated and from these four isolates were identified, comprising three species, including novel AMPA degraders M−S3 and M−SS (Myroides sp. mNGS23), and P-S92 (Pseudochrobactrum saccharolyticum). Within both minimal media supplemented with AMPA and raw untreated showing substrate concentrations above 10 mg/L whilst the specific degradation rates saw a decrease in substrate concentrations above 100 mg/L. AMPA removal occured in pilot scale sand filters augmented with P-S92 but removal was inconsistent. These findings show the potential of using biodegradation as an effective treatment strategy for AMPA removal from water. The identification of AMPA-degrading bacteria offers a promising solution for enhancing the removal of this persistent pollutant from contaminated waters. Further research is recommended to explore the full-scale application of these isolates in water treatment processes. This study contributes to the development of sustainable water treatment technologies by harnessing the natural degradative capacities of environmental bacteria.
Open Access
Ceramic vs polymeric membrane implementation for potable water treatment
(Elsevier, 2022-03-08) Jarvis, Peter; Carra, Irene; Jafari, M.; Judd, Simon J.
The continued technological developments and decreased purchase costs of ceramic membranes have seen increased recent interest in the technology as an alternative to the more widely used polymeric membranes. This paper assesses the relative technical, practical and economic merits of the two membrane materials in the context of potable water production from surface water sources. The work focuses on phenomena of direct technoeconomic significance, namely cleaning efficacy (manifested as permeability recovery), membrane integrity and incurred labour effort. Topics reviewed thus comprise: (a) practical comparison of the two technologies challenged with the same feedwater, (b) comparative technoeconomic analyses, (c) membrane integrity studies of polymeric membranes - incorporating aged samples extracted from operating installations, (d) sludging incidents, and (e) pilot and full-scale data. Available relevant data reveal: (a) bench-scale comparative tests do not indicate a consistent significant difference in the net permeability between the two membranes; (b) polymeric membranes are subject to a decline in both mechanical strength and permeability from the loss of the hydrophilic agent over a period of years from the action of hypochlorite used for cleaning; (c) the decreased mechanical strength with age of polymeric membranes increases the manual repair requirement and shortens membrane life, respectively impacting on labour and membrane replacement costs where the latter is also determined by the permeability; (d) the chemical and mechanical robustness of ceramic membranes permits more aggressive chemical cleaning, which then affects the chemicals consumption cost; and (e) anecdotal evidence suggests that polymeric membranes challenged with pre-coagulated surface waters may be subject to sludging, the agglomeration of solids in the membrane channels, which may also be age-related. Notwithstanding the above, data from published comparative technoeconomic studies indicate a linear relationship between the overall cost benefit and the membrane module cost ratio mitigated by the relative membrane life and operating flux.
Open Access
Chlorine disinfection of drinking water assessed by flow cytometry: new insights
(Elsevier, 2020-07-10) Cheswick, Ryan; Moore, Graeme; Nocker, Andreas; Hassard, Francis; Jefferson, Bruce; Jarvis, Peter
The efficacy of chlorine disinfection was assessed for the first time over a range of disinfection conditions using flow cytometry (FCM) to provide new insights into disinfection processes. Inactivation was assessed for pure culture bacteria (Escherichia coli) and micro-organisms in real treated water from operational water treatment works (WTWs). A dose dependent increase in inactivation rate (k) was observed for both test matrices, with values of 0.03 to 0.26 and 0.32 to 3.14 L/mg min for the WTW bacteria and E. coli, respectively. After 2 min, E. coli was reduced by 2 log for all chlorine doses (0.12 to 1.00 mg/L). In the case of the WTW filtrate bacteria, after 2 min log reductions were between 0.54 and 1.14 with increasing chlorine concentration, reaching between 1.32 and 2.33 after 30 min. A decrease in disinfection efficacy was observed as temperature decreased from 19 to 5 °C for both microbial populations. With respect to chlorination at different pH (pH 6, 7, 8), membrane damage was more pronounced at higher pH. This was not consistent with the higher disinfection efficacy seen at lower pH. when culture based methods are used to assess bacterial reductions. This provides evidence that more understanding into the fundamental mechanisms of chlorine disinfection are required and that methodological alterations may be required (e.g. pH standardisation) to fully utilise FCM over the entire range of chlorination conditions observed in operational environments
Open Access
Clarifying the absence of evidence regarding human health risks to microplastic particles in drinking-water: High quality robust data wanted
(Elsevier, 2020-10-07) Gouin, Todd; Cunliffe, David; De France, J.; Fawell, John; Jarvis, Peter; Koelmans, A. A. (Bart); Marsden, Peter; Testai, Emanuela E.; Asami, Mari; Bevan, Ruth; Carrier, R.; Cotruvo, Joseph; Eckhardt, Alexander; Ong, ‪Choon Nam
In a recently published article, Leslie and Depledge (2020) raise concerns regarding statements on the risk that microplastic particles represent to human health and which have been attributed to reports published by both the Science Academies’ Group, Science Advice for Policy (SAPEA) (part of the European Commission’s Science Advice Mechanism) and the World Health Organization (WHO) (SAPEA. Science Advice for Policy by European Academies, 2019, WHO, 2019). Leslie and Depledge (2020), for instance, suggest that WHO (2019) conclude that there is ‘no evidence to indicate a human health concern.’ This statement, taken out of context from the WHO report (WHO, 2019), is then used to imply that the WHO conclude there is ‘no risk’ related to the exposure of microplastic particles (Leslie and Depledge, 2020). While, Leslie and Depledge (2020) highlight the importance of debate and systematic assessment of claims related to the assessment of risk, observations that we agree are important to highlight, there are a number of points raised in the article that require clarification.
Open Access
Coagulant recovery and reuse for drinking water treatment
(Elsevier, 2015-10-21) Keeley, James; Jarvis, Peter; Smith, Andrea D.; Judd, Simon J.
Coagulant recovery and reuse from waterworks sludge has the potential to significantly reduce waste disposal and chemicals usage for water treatment. Drinking water regulations demand purification of recovered coagulant before they can be safely reused, due to the risk of disinfection by-product precursors being recovered from waterworks sludge alongside coagulant metals. While several full-scale separation technologies have proven effective for coagulant purification, none have matched virgin coagulant treatment performance. This study examines the individual and successive separation performance of several novel and existing ferric coagulant recovery purification technologies to attain virgin coagulant purity levels. The new suggested approach of alkali extraction of dissolved organic compounds (DOC) from waterworks sludge prior to acidic solubilisation of ferric coagulants provided the same 14:1 selectivity ratio (874 mg/L Fe vs. 61 mg/L DOC) to the more established size separation using ultrafiltration (1285 mg/L Fe vs. 91 mg/L DOC). Cation exchange Donnan membranes were also examined: while highly selective (2555 mg/L Fe vs. 29 mg/L DOC, 88:1 selectivity), the low pH of the recovered ferric solution impaired subsequent treatment performance. The application of powdered activated carbon (PAC) to ultrafiltration or alkali pre-treated sludge, dosed at 80 mg/mg DOC, reduced recovered ferric DOC contamination to <1 mg/L but in practice, this option would incur significant costs. The treatment performance of the purified recovered coagulants was compared to that of virgin reagent with reference to key water quality parameters. Several PAC-polished recovered coagulants provided the same or improved DOC and turbidity removal as virgin coagulant, as well as demonstrating the potential to reduce disinfection byproducts and regulated metals to levels comparable to that attained from virgin material.
Open Access
Coagulant recovery from water treatment residuals: a review of applicable technologies
(Taylor and Francis, 2014-02-25) Keeley, James; Jarvis, Peter; Judd, Simon J.
Conventional water treatment consumes large quantities of coagulant and produces even greater volumes of sludge. Coagulant recovery (CR) presents an opportunity to reduce both the sludge quantities and the costs they incur, by regenerating and purifying coagulant before reuse. Recovery and purification must satisfy stringent potable regulations for harmful contaminants, while remaining competitive with commercial coagulants. These challenges have restricted uptake and lead research towards lower-gain, lower-risk alternatives. This review documents the context in which CR must be considered, before comparing the relative efficacies and bottlenecks of potential technologies, expediting identification of the major knowledge gaps and future research requirements.
Open Access
Coagulant Recovery from Waterworks Sludge
(Cranfield University, 2014-10) Keeley, James; Jarvis, Peter; Judd, Simon J.
Coagulation is a ubiquitous process in the treatment of raw surface water for eventual potable use. Despite its capabilities, the sheer scale of its use is manifested in the volumes of chemicals it demands and waste sludge it produces. Recovering and reusing the chemical activity of the coagulant sludge in water treatment is a logical solution but this practice has been restricted by the presence of contaminants within the sludge. This thesis has investigated methods that can separate the coagulant metals from these primarily natural organic contaminants, with an aim of producing a sufficiently pure coagulant for effective treatment performance when reused. A process of ultrafiltration of the impure regenerated coagulant followed by a powdered activated carbon polishing stage compared favourably to a number of other separation processes and was found to remove the most dissolved organic compounds. When the purified coagulant was used to treat raw water, it provided better turbidity removal than commercial coagulant and matched its removal of trihalomethane precursors, making the process suitable for consideration at full-scale. Analysis of the whole life cost suggested that such performance could be reproduced at full-scale within a 25 year payback period. The reuse of even purified recovered coagulants in drinking water treatment still carries risks which may deter its implementation. Therefore the efficacy of recovered coagulants in the role of phosphorus removal from wastewater was also investigated. This showed that both acidified and unacidified waterworks sludges, with sufficient contact time, could remove similar levels of phosphorus as fresh coagulants, at approximately half the whole life cost.
Open Access
The combined influence of hydrophobicity, charge and molecular weight on natural organic matter removal by ion exchange and coagulation
(Elsevier, 2019-08-21) Finkbeiner, Pascal; Moore, Graeme; Pereira, Ryan; Jefferson, Bruce; Jarvis, Peter
Three different source waters were investigated using virgin and pre-used anion exchange resins, coagulation, and ion exchange combined with coagulation (IEX&Coagulation). The hydrophobicity, size distribution and charge of natural organic matter (NOM) were used to evaluate its removal. Dissolved organic carbon (DOC) removal by pre-used IEX resin was 67–79%. A consistent ratio of different hydrophobicity fractions was found in the removed DOC, while the proportion and quantity of the molecular weight fraction around 1 kDa was important in understanding the treatability of water. For pre-used resin, organic compounds were hypothesised to be restricted to easily accessible exchange sites. Comparatively, virgin resin achieved higher DOC removals (86–89%) as resin fouling was absent. Charge density and the proportion of the hydrophobic fraction were found to be important indicators for the specific disinfection byproduct formation potential (DBP-FP). Treatment of raw water with pre-used resin decreased the specific DBP-FP by between 2 and 43%, while the use of virgin resin resulted in a reduction of between 31 and 63%. The highest water quality was achieved when the combination of IEX and coagulation was used, reducing DOC and the specific DBP-FP well below that seen for either process alone.
Open Access
Comparative evaluation of competing technologies through rapid prototyping
(2018-07) Hart, Connor; Collins, Matt; Jarvis, Peter
A major difficulty often experienced by multidisciplinary teams, particularly between scientific and design led approaches, is how to resolve the conflict which arises between competing ideas, in order to facilitate the most efficient path towards a successful technological innovation. This project has attempted to demonstrate the vital role which agile innovation, made possible only through rapid prototyping, can optimise two competing technologies in-order that they can be tested and evaluated across a spectrum of qualitative and quantitative parameters. The results of which can enable the wider project team to select the correct path forward. A systematic review of literature revealed that design literature in this space is limited, with few real-world case studies conducted in this area. This research provides a valuable practical case study which shows agile innovation in action and the critical role which rapid prototype plays in that process. A multi-category matrix was newly created, providing metrics for both qualitative and quantitative data, and which uses a colour-coded scoring system to give a detailed and overall rating for each technology. The findings were controversial, but unequivocal, and could have a major impact on the development of the wider project going forward.
Open Access
Comparing flow cytometry with culture-based methods for microbial monitoring and as a diagnostic tool for assessing drinking water treatment processes
(Elsevier, 2019-06-18) Cheswick, Ryan Ashley; Cartmell, Elise; Lee, Susan; Upton, Andrew; Weir, Paul; Moore, Graeme; Nocker, Andreas; Jefferson, Bruce; Jarvis, Peter
Flow cytometry (FCM) and the ability to measure both total and intact cell populations through DNA staining methodologies has rapidly gained attention and consideration across the water sector in the past decade. In this study, water quality monitoring was undertaken over three years across 213 drinking water treatment works (WTW) in the Scottish Water region (Total n = 39,340). Samples subject to routine regulatory microbial analysis using culture-based methods were also analysed using FCM. In addition to final treated water, the bacterial content in raw water was measured over a one-year period. Three WTW were studied in further detail using on-site inter-stage sampling and analysis with FCM. It was demonstrated that there was no clear link between FCM data and the coliform samples taken for regulatory monitoring. The disinfectant Ct value (Ct = mg·min/L) was the driving factor in determining final water cell viability and the proportion of intact cells (intact/total cells) and the frequency of coliform detections in the water leaving the WTW. However, the free chlorine residual, without consideration of treatment time, was shown to have little impact on coliform detections or cell counts. Amongst the three treatment trains monitored in detail, the membrane filtration WTW showed the greatest log removal and robustness in terms of final water intact cell counts. Flow cytometry was shown to provide insights into the bacteriological quality of water that adds significant value over and above that provided by traditional bacterial monitoring.
Open Access
Comparison of coagulation performance and floc properties using a novel zirconium coagulant against traditional ferric and alum coagulants
(Elsevier Science B.V., Amsterdam., 2012-09-03T00:00:00Z) Jarvis, Peter; Sharp, Emma; Pidou, Marc; Molinder, Roger; Parsons, Simon A.; Jefferson, Bruce
Coagulation in drinking water treatment has relied upon iron (Fe) and aluminium (Al) salts throughout the last century to provide the bulk removal of contaminants from source waters containing natural organic matter (NOM). However, there is now a need for improved treatment of these waters as their quality deteriorates and water quality standards become more difficult to achieve. Alternative coagulant chemicals offer a simple and inexpensive way of doing this. In this work a novel zirconium (Zr) coagulant was compared against traditional Fe and Al coagulants. The Zr coagulant was able to provide between 46 and 150% lower dissolved organic carbon (DOC) residual in comparison to the best traditional coagulant (Fe). In addition floc properties were significantly improved with larger and stronger flocs forming when the Zr coagulant was used with the median floc sizes being 930 υm for Zr; 710 υm for Fe and 450 υm for Al. In pilot scale experiments, a similar improved NOM and particle removal was observed. The results show that when optimised for combined DOC removal and low residual turbidity, the Zr coagulant out-performed the other coagulants tested at both bench and pilot sca