Browsing by Author "Judd, Simon J."
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Item 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, PeterThis 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.Item Open Access Advanced oxidation processes for wastewater reuse - removal of micropollutants(Cranfield University, 2013-04) James, Christopher P.; Judd, Simon J.The removal of micropollutants (MPs) from secondary municipal wastewater by an advanced oxidation process (AOP) based on UV irradiation combined with hydrogen peroxide (UV/H2O2) has been assessed through pilot-scale experiments incorporating microfiltration (MF) and reverse osmosis (RO). Tests employed low concentrations of a range of emerging contaminants of concern, and the water quality varied by blending of waters from different sources. Under optimum H2O2 and lamp power conditions, the process achieved >99% removal of N-nitrosodimethylamine (NDMA) and endocrine disrupting compounds (EDCs) from all waters. Pesticide removal, in particular metaldehyde, atrazine and 2, 4 5-T, was dependent on water transmittance (UVT), and levels of Total Organic Carbon (TOC) and other hydroxyl radical (HO.) scavengers. Chloroform, a trihalomethane (THM), was not readily degraded (<10% removal in either stream), as was TOC removal. Further analysis of metaldehyde removal identified UVT, reaction time, and H2O2 dose to be influential parameters in determining degradation as a function of UV dose. In comparison, the impact of H2O2 dose and UVT was negligible on NDMA degradation; removal increased from 89 to >98% on increasing the UV dose from 200 to 680 mJ cm-2 from the MF permeate. Nitrite by-products were observed at elevated levels, promoted by low pH and high UV doses. An operational cost assessment revealed energy consumption to account for 65% with lamp replacement contributing 25%. A comparison of three unit process sequences, based on MF, RO, AOP and activated carbon (AC), revealed MF-RO-AOP to be the most cost effective provided management of the RO concentrate stream incurs no significant cost. Results demonstrated AOPs to satisfactorily reduce levels of the more challenging recalcitrant MPs to meet stringent water quality standards for wastewater reuse, but that practical limitations exist and the cost penalty is significant.Item Open Access Algal remediation of CO2 and nutrient discharges: a review(Elsevier, 2015-08-28) Judd, Simon J.; van den Broeke, Leo J.P.; Shurair, Mohamed; Kuti, Yussuf; Znad, HusseinThe recent literature pertaining to the application of algal photobioreactors (PBRs) to both carbon dioxide mitigation and nutrient abatement is reviewed and the reported data analysed. The review appraises the influence of key system parameters on performance with reference to (a) the absorption and biological fixation of CO2 from gaseous effluent streams, and (b) the removal of nutrients from wastewaters. Key parameters appraised individually with reference to CO2 removal comprise algal speciation, light intensity, mass transfer, gas and hydraulic residence time, pollutant (CO2 and nutrient) loading, biochemical and chemical stoichiometry (including pH), and temperature. Nutrient removal has been assessed with reference to hydraulic residence time and reactor configuration, along with C:nutrient ratios and other factors affecting carbon fixation, and outcomes compared with those reported for classical biological nutrient removal (BNR). Outcomes of the review indicate there has been a disproportionate increase in algal PBR research outputs over the past 5–8 years, with a significant number of studies based on small, bench-scale systems. The quantitative impacts of light intensity and loading on CO2 uptake are highly dependent on the algal species, and also affected by solution chemical conditions such as temperature and pH. Calculations based on available data for biomass growth rates indicate that a reactor CO2 residence time of around 4 h is required for significant CO2 removal. Nutrient removal data indicate residence times of 2–5 days are required for significant nutrient removal, compared with <12 h for a BNR plant. Moreover, the shallow depth of the simplest PBR configuration (the high rate algal pond, HRAP) means that its footprint is at least two orders of magnitude greater than a classical BNR plant. It is concluded that the combined carbon capture/nutrient removal process relies on optimisation of a number of process parameters acting synergistically, principally microalgal strain, C:N:P load and balance, CO2 and liquid residence time, light intensity and quality, temperature, and reactor configuration. This imposes a significant challenge to the overall process control which has yet to be fully addressed.Item Open Access Biological treatment and thickening with a hollow fibre membrane bioreactor(Elsevier Science B.V., Amsterdam., 2014-07-01T00:00:00Z) Zsirai, T.; Wang, Z-Z.; Gabarrón, S.; Connery, K.; Fabiyi, M.; Larrea, A.; Judd, Simon J.Aerobic operation of an immersed hollow fibre membrane bioreactor, treating municipal wastewater supplemented with molasses solution, has been studied across mixed liquor suspended solids (MLSS) concentrations between 8 and 32 g L-1, the higher concentrations being normally associated with thickening operations. Only a marginal loss in membrane permeability was noted between 8 and 18 g L-1 when operation was conducted without clogging. The sustainable operational flux attainable above 18 g L-1 was highly dependent upon both the MLSS concentration and the state of the membrane. A temperature-corrected flux of 28 L m-2 h-1 (LMH) was sustained for 18 h at an MLSS of 8 g L-1 using membranes close to initial their virgin-state permeability. This value decreased to around 14 LMH at 20 g L-1 and 5 LMH at 32 g L-1 MLSS for an aged membrane whose permeability had been recovered following clogging. Below the threshold flux operation without significant clogging was possible, such that the membrane permeability could be recovered with a chemically enhanced backflush (CEB). Above this flux clogging took place at a rate of around 7-14 g solids per m2 membrane per m3 permeate volume passed irrespective of the MLSS concentration. The permeability of the unclogged membrane was depressed and could not be recovered using a standard CEB, indicative of irrecoverable pore clogging. The outcomes corroborated previously reported observations concerning the deleterious long-term impacts of clogging, and confirmed the critical importance of operation at a sustainable flux valueItem Open Access Biomass effects on oxygen transfer in membrane bioreactors.(Elsevier, 2007-03) Germain, Eve; Nelles, F.; Drews, A.; Pearce, P.; Kraume, M.; Reid, E.; Judd, Simon J.; Stephenson, TomTen biomass samples from both municipal and industrial pilot and full scale submerged membrane bioreactors (MBRs) with mixed liquor suspended solids concentrations (MLSS) ranging from 7.2 to 30.2 g L−1 were studied at six air-flow rates (0.7, 1.3, 2.3, 3, 4.4 and 6 m3 m−3 h−1). Statistical analyses were applied to identify the relative impacts of the various bulk biomass characteristics on oxygen transfer. Of the biomass characteristics studied, only solids concentration (correlated with viscosity), the carbohydrate fraction of the EPS (EPSc) and the chemical oxygen demand (COD) concentration of the SMP (SMPCOD) were found to affect the oxygen transfer parameters kLa20 (the oxygen transfer coefficient) and α-factor. The relative influence on kLa20 was MLSS>aeration>EPSc>SMPCOD and on α-factor was MLSS>SMPCOD>EPSc>aeration. Both kLa20 and α-factor increased with increasing aeration and EPSc and decreased with increasing MLSS and SMPCOD. MLSS was found to be the main parameter controlling the oxygen transfer.Item Open Access BSM-MBR: A Benchmark Simulation Model to Compare Control and Operational Strategies for Membrane Bioreactors(Elsevier Science B.V., Amsterdam., 2011-03-01T00:00:00Z) Maere, Thomas; Verrecht, Bart; Moerenhout, Stefanie; Judd, Simon J.; Nopens, IngmarA benchmark simulation model for membrane bioreactors (BSM-MBR) was developed to evaluate operational and control strategies in terms of effluent quality and operational costs. The configuration of the existing BSM1 for conventional wastewater treatment plants was adapted using reactor volumes, pumped sludge flows and membrane filtration for the water-sludge separation. The BSM1 performance criteria were extended for an MBR taking into account additional pumping requirements for permeate production and aeration requirements for membrane fouling prevention. To incorporate the effects of elevated sludge concentrations on aeration efficiency and costs a dedicated aeration model was adopted. Steady-state and dynamic simulations revealed BSM-MBR, as expected, to out-perform BSM1 for effluent quality, mainly due to complete retention of solids and improved ammonium removal from extensive aeration combined with higher biomass levels. However, this was at the expense of significantly higher operational costs. A comparison with three large-scale MBRs showed BSM-MBR energy costs to be realistic. The membrane aeration costs for the open loop simulations were rather high, attributed to non-optimization of BSM-MBR. As proof of concept two closed loop simulations were run to demonstrate the usefulness of BSM-MBR for identifying control strategies to lower operational costs without compromising effluent quality.Item Open Access Carbonaceous and nitrogenous disinfection by-product formation from algal organic matter(Elsevier, 2016-12-10) Goslan, Emma Harriet; Seigle, Céline; Purcell, Diane; Henderson, Rita Kay; Parsons, Simon A.; Jefferson, Bruce; Judd, Simon J.Seasonal algal blooms in drinking water sources release intracellular and extracellular algal organic matter (AOM) in significant concentrations into the water. This organic matter provides precursors for disinfection by-products (DBPs) formed when the water is subsequently chlorinated at the final disinfection stage of the potable water treatment process. This paper presents results of AOM characterisation from five algal species (three cyanobacteria, one diatom and one green) alongside the measurement of the DBP formation potential from the AOM of six algal species (an additional diatom). The character was explored in terms of hydrophilicity, charge and protein and carbohydrate content. 18 DBPs were measured following chlorination of the AOM samples: the four trihalomethanes (THMs), nine haloacetic acids (HAAs), four haloacetonitriles (HANs) and one halonitromethane (HNM). The AOM was found to be mainly hydrophilic (52 and 81%) in nature. Yields of up to 92.4 μg mg−1 C carbonaceous DBPs were measured, with few consistent trends between DBP formation propensity and either the specific ultraviolet absorbance (SUVA) or the chemical characteristics. The AOM from diatomaceous algae formed significant amounts of nitrogenous DBPs (up to 1.7 μg mg−1 C). The weak trends in DBPFP may be attributable to the hydrophilic nature of AOM, which also makes it more challenging to remove by conventional water treatment processes.Item Open Access Ceramic membrane filtration of produced water: impact of membrane module(Elsevier, 2016-04-01) Zsirai, T.; Al-Jaml, A. K.; Qiblawey, Hazim; Al-Marri, M.; Ahmed, A.; Bach, S.; Watson, S.; Judd, Simon J.Produced water (PW) generated from oil exploration requires rigorous removal of suspended matter (free oil and particulate solids) as tertiary treatment (downstream of hydrocyclone and gas flotation) if it is to be re-injected into low-permeability reservoirs. The viability of membrane filtration for this duty is largely dependent on sustaining a high membrane flux to minimise the process footprint. A pilot-scale study of PW filtration using crossflow multi-channel ceramic membrane technology has been conducted to identify the appropriate membrane characteristics for sustaining the flux whilst maintaining the required treated water quality. Membranes based on two materials (silicon carbide, SiC, and titanium dioxide, TiO2) and two different pore sizes were challenged with real PW samples taken from oil platforms operating on the Arabian Gulf. The membranes were characterised according to the overall permeability decline rate and the end permeability. Results suggest that SiC membranes outperform TiO2 ones with respect to sustainable permeability under the same operating and maintenance conditions. The SiC microfiltration membrane provided anomalously high permeabilities but also the highest fouling propensity. Results suggest that whilst the high fluxes (1300–1800 L m−2 h−1) are attainable for the technology, this is contingent upon the application of an effective chemical clean.Item 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.Item Open Access Chemical cleaning of potable microfiltration and ultrafiltration membranes(Cranfield University, 2009-06) Porcelli, Nicandro; Judd, Simon J.Concerns over possible waterborne disease forced drinking water supply companies in England and Wales to adopt microfiltration and ultrafiltration technologies rapidly. MF and UF membrane plants are designed to produce water of a consistent quality regardless of throughput and fluctuations in the feedwater quality. To operate well they need to maintain flux and balance the rate of fouling, and chemical cleaning performance is critical to this. Giant steps have been taken into characterizing the foulants scientifically in the last few years while cleaning is reactive and ad hoc. This thesis explores the basis for a corresponding cleaning science for the technology to develop quantitively. Cleaning performance was defined in terms of a response to combinations of explanatory variables in a materials limited cleaning envelope. The study focused on applying variations of cleanant concentration, applied temperature and soak times to a variety of membranes fouled with different waters and regimes. An experimental design was developed and applied consistently to a number of different sampled sites; allowing an optimised recovery from the polynomial expressions for each treatment, through factorial analysis of the data. The size and variety of the data set analysed allowed comparison and quantification of the different deviations from optimal cleaning response. This effect was seen to vary temporally and with operating regime and the methods usefulness as a practical tool in the membrane plant lifecycle was considered. Cost evaluation of the variation in cleaning response showed that sub-optimal cleaning costs and energy use may be significant and the thesis also illustrated how module geometry affects initial cake deposition and thus cleanability. By demonstrating the potential for cleaning factor analysis, the potential for a combined heuristic and predictive cleaning control science is possible, but will need new strategies to manage technology change.Item Open Access Chemical cleaning of potable water membranes: A review(Elsevier Science B.V., Amsterdam., 2010-02-01T00:00:00Z) Porcelli, Nicandro; Judd, Simon J.The literature on chemical cleaning of polymeric hollow fibre ultrafiltration and microfiltration membranes used in the filtration of water for municipal water supply is reviewed. The review considers the chemical cleaning mechanism, and the perceived link between this and membrane fouling by natural organic matter (NOM)—the principal foulant in municipal potable water applications. Existing chemical cleaning agents used for this duty are considered individually and their cleaning action described, along with the most commonly applied cleaning protocols (i.e. the cleaning conditions, cleaning sequence and method of cleaning agent application). It is concluded that chemical cleaning is poorly understood and not extensively investigated, in marked contrast to the much more widely studied area of membrane fouling generally, for which there are thousands of published studies. Studies of chemical cleaning specifically have instead been generally limited either to qualitative measurements, such as the use of surface or other analytical tools to characterise membrane foulants and record their removal, or incidental permeability recovery recorded from cleaning events during pilot or full-scale trials. It is proposed that a chemical cleaning index is needed, analogous to the recently proposed general membrane fouling index, based on empirical data to inform cleaning protocols for specific duties and feedwater qualitItem Open Access Chemical cleaning of potable water membranes: The cost benefit of optimisation(Elsevier, 2010-03) Porcelli, Nicandro; Judd, Simon J.A study of the variability in chemical cleaning factors on permeability recovery for potable water microfiltration (MF) and ultrafiltration (UF) systems has been carried out employing a cost model simulating plant fouling and cleaning regimes. The impact of a range of operating and cleaning factors on operating cost variation was computed using algorithms describing operational and cleaning factor relationships with permeability recovery data measured from bench scale tests on fibres sampled from full-scale operational plants. The model proceeded through sequencing of the cleaning and backwashing operations to generate transmembrane pressure (TMP), and so head loss, transients. A number of cleaning scenarios were considered for each plant, based on employing either a threshold TMP or fixed chemical cleaning intervals. The resulting TMP profiles were then converted to operational costs. The effect of the variability in permeability recovery on annual operating costs was calculated for each of the simulations. It was evident that significant operating cost reductions were possible from optimisation of the cleaning protocol. Cost benefit varied according to facets of plant design and operation; the innate variability in permeability recovery precluded the correlation of cleaning efficacy with fouling characteristics.Item Open Access Cleaning of ceramic membranes for produced water filtration(Elsevier, 2018-03-09) Zsirai, T.; Qiblawey, Hazim; Buzatu, Pompilia; Al-Marri, M.; Judd, Simon J.The application of ceramic microfiltration membranes to the tertiary treatment of produced water from an Arabian Gulf oilfield has been studied using a dedicated pilot plant. Studies were based on a previously published protocol in which the retentate stream was recycled so as to successively increase the feed concentration throughout the experimental run. Chemical cleaning in place (CIP) was applied between each run and the flux and permeability recovery recorded for various cleaning protocols studied, the CIP being based on the combination of caustic soda (NaOH) and citric acid. Surface analysis of the membrane, and specifically its hydrophilicity, was also conducted. Results indicated the main influencing factor on permeability recovery from the CIP to be the employment of backflushing during the CIP itself. A final flux of 700 L m−2 h−1 was sustained through the application of 6 wt% NaOH with 6 wt% citric acid combined with backflushing at approximately twice the rate of the filtration cycle flux. A consideration of the impact of this flux value on the viability of two commercially-available ceramic membrane technologies indicated the footprint incurred to be slightly lower than that of the upstream induced gas flotation technology and corroborated a previously published estimate. The flux was sustained despite surface analysis indicating a loss of the innate hydrophilicity of the ceramic membrane.Item Open Access Clogging vs. fouling in immersed membrane bioreactors(Elsevier, 2018-07-09) Buzatu, Pompilia; Qiblawey, Hazim; Odai, A.; Jamaleddin, J.; Nasser, Mustafa; Judd, Simon J.Whilst the fouling of MBR membrane surfaces has been very extensively explored by the academic community, there is an increasingly widespread recognition by practitioners of the issue of clogging of membrane channels with sludge solids, sometimes termed “sludging”. The study undertaken has quantified this phenomenon using a bespoke test cell allowing a flat sheet membrane channel to be viewed directly during operation and the accumulated solids determined by digital image processing. Sludging behaviour has then been correlated both with the sludge properties, from sludge samples taken from both an industrial and municipal MBR, and the permeability decline rate data. The work has revealed the expected trends in fouling propensity, as quantified by the exponent n of the Δp/Δt = m.exp(nJ) correlation from classical flux-step tests. With zero membrane aeration the industrial samples exhibited sludging, the filling of the complete thickness of the membrane channel with sludge solids, whereas for municipal sludge the solids formed a cake layer which did not fill the channel. In the absence of sludging the permeability decline followed the expected pattern of increasing at the elevated soluble COD and capillary suction time values of the industrial sludge, compared with municipal sludge at the same solids concentration range (8–12 g.L−1). However, there was no evident correlation between fouling (permeability decline without sludging) and sludging: incipient sludging did not appear to influence permeability, though can be assumed to negatively impact on long-term operation, or relate to the sCOD concentration. Sludging instead appeared to depend on the sludge physical properties, and primarily the viscosity: sludge samples at high viscosities were found to exhibit a different air-scour pattern to that at normal MLSS concentrations. Outcomes suggest that sludging is caused by rheological conditions promoting bubble coalescence and bubble stream constriction, reducing the exposure of the membrane surface to scouring air.Item 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.Item 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.Item 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.Item Open Access Combined coagulation and membrane microfiltration for removal of natural organic material (nom)(1999-03) Hillis, Peter; Judd, Simon J.The removal of natural organic matter (NOM) is a key requirement of many processes in potable water treatment. Conventionally, removal of NOM and colloidal material has been achieved by coagulation with inorganic coagulants followed by either direct rapid gravity filtration alone or clarification (sedimentation or flotation) followed by at least one stage of rapid gravity filtration. An alternative to conventional processes is to combine membrane microfiltration (MF) with coagulation for NOM removal. The advantages of MF technology over traditional sand filters is the maintenance of an absolute barrier throughout the filtration process, thereby enhancing the physical separation process by presenting an absolute barrier to suspended materials. This thesis presents the results from such a system. A 9.6m2 hollow fibre hydrophilic polysulphone MF membrane system was used in combination with ferric sulphate under controlled pH conditions. The system was operated under constant flow condition and the coagulant concentration varied to assess performance. Coagulation conditions which promoted rapid aggregation of particles was found to give best performance with respect to pressure development, this coincided with a zeta potential at or near zero. Also, a pre-flocculation time of 20 seconds was found to be sufficient to allow complete removal of material associated with the coagulation process. Comparison with other workers showed similar results for the specific cake resistance despite considerable differences in both the scale and type of system used.Item Open Access Comparative power demand of mechanical and aeration imposed shear in an immersed membrane bioreactor(Elsevier, 2017-09-12) Buzatu, Pompilia; Nasser, M. S.; Qiblawey, Hazim; Judd, Simon J.The power demanded for the application of mechanically-imposed shear on an immersed flat sheet (iFS) membrane bioreactor (MBR) has been compared to that of conventional membrane air scouring. Literature correlations based on the Ostwald model were used to define the rheological characteristics of an MBR sludge. The correlation of specific power demand (, in Watts per m2 membrane area) with shear rate γ in s-1 was developed from first principles through a consideration of the force balance on the system in the case of mechanically-imposed shear. The corresponding aeration imposed shear correlation was interpreted from literature information. The analysis revealed the energy required to impose a shear mechanically through oscillation (or reciprocation) of the membrane to be between 20 and 70% less than that demanded for providing the same shear by conventional aeration of the immersed membrane. The energy saving increases with decreasing shear in accordance with a power demand ratio (aeration:mechanical) of 1400γ-1.4 for a specific sludge rheology. Whilst the absolute value is dependent on the sludge rheology, the aeration:mechanical power demand ratio is determined by the difference in the two exponents in the respective correlations between and γ. Consequently, aeration-imparted shear becomes energetically favoured beyond some threshold shear rate value (∼180 s-1, based on the boundary conditions applied in the current study). The outcomes qualitatively corroborate findings from the limited practical measurement of energy demand in MBRs fitted with reciprocating immersed membranes.Item Open Access The cost benefit of algal technology for combined CO2 mitigation and nutrient abatement(Elsevier, 2016-12-30) Judd, Simon J.; Al Momani, F. A. O.; Znad, Hussein; Al Ketife, Ahmed M. D.The use of microalgae culture technology (MCT) for mitigating CO2 emissions from flue gases and nutrient discharges from wastewater whilst generating a biofuel product is considered with reference to the cost benefit offered. The review examines the most recent MCT literature (post 2010) focused on the algal biomass or biofuel production cost. The analysis reveals that, according to published studies, biofuel cost follows an approximate inverse relationship with algal or lipid productivity with a minimum production cost of $1 L−1 attained under representative conditions. A 35–86% cost reduction is reported across all studies from the combined harnessing of CO2 and nutrients from waste sources. This compares with 12–27% for obviating fertiliser procurement through using a wastewater nutrient source (or else recycling the liquor from the extracted algal biomass waste), and 19–39% for CO2 fixation from a flue gas feed. Notwithstanding the above, economic competitiveness with mineral fuels appears to be attainable only under circumstances which also feature: a) The inclusion of cost and environmental benefits from wastewater treatment (such as the energy and/or greenhouse gas emissions benefit from nutrient and CO2 discharge abatement), and/or a) Multiple installations over an extended geographic region where flue gas and wastewater sources are co-located.