Browsing by Author "Parsons, Simon"

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    Application of ion exchange for ammonium removal from municipal wastewaters
    (Cranfield University, 2007-01) Thornton, A.; Parsons, Simon
    Traditional methods of ammonium removal from municipal wastewaters rely on naturally occurring biological processes, where ammonium is converted into less harmful substances before being released into the environment. These processes are extremely effective at nitrogen removal but are less responsive to shock loads, in which case they can fall short of achieving the required effluent quality. In recent years research has been conducted into the possibility of using ion exchange technology as a complementary process for the. removal of ammonium from wastewater streams. Much of the research has been concerned with the .performance of naturally occuring materials, zeolites, with much of the work being undertaken at laboratory scale using synthetic solutions. This study investigates the performance of the modified media, MesoLite, using real and synthetic solutions, at both laboratory and pilot scale, in the presence of competing cautions. Initial studies were performed under batch conditions to assess the effect of a number of parameters such as contact time, solution ammonium concentration and pH on the uptake of ammonium on to MesoLite. This was followed by a investigation into a number of design parameters under dynamic conditions, leading to a pilot scale examination of the potential of the process to be used for the application of removing ammonium from low concentration wastewater treatment works effluents. Subsequent experiments were performed pilot scale to investigate the benefit of using the ion exchange process for ammonium removal from high strength liquors arising from the sludge dewatering process. Results indicate that a range of parameters affects the performance of the media and optimum performance is observed at high ammonium concentrations with increased contact time at pH 6-7. Results also show that MesoLite was successful in removing ammonium from high concentration sludge liquors, giving a total capacity of 47-51 g + -1 + -1 NH4 N kg and a operational capacity of 27 36 g NH4 N kg . The treatment of low concentration effluents return a total capacity of 19 g NI-14+-N kg`1 and a operational capacity of 9.5 g NI-14+-N kg`1. However, this reduced capacity is offset by the significant increase run time, from 1.5 to 22 days, and a increase in the amount of liquid treated from 140 bed volumes to in excess of 6000 bed volumes.
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    Assessing the potential of full-scale phosphorus recovery by struvite precipitation
    (2000-09) Jaffer, Yasmin; Parsons, Simon
    Formation of struvite (MgNH4P04.6H20) at sewage treatment works can cause major operational problems and decrease efficiency. Struvite has a commercial value and the controlled formation of it, in a specified location, would be beneficial. A mass balance was conducted at full-scale across a whole sewage treatment plant, to identify a stream to conduct bench-scale struvite crystallisation studies on. The most suitable stream was identified as the centrifuge liquors. The average flow of the liquor stream was 393 m3 d'1 and the composition was as follows: 167 mg L'1 phosphorus, 44 mg L'1 magnesium, 615 mg L 1 ammonium, 56 mg L 1 calcium and 2580mg L'1 of alkalinity. The pH averaged at 7.6 and the stream had a predicted struvite precipitation potential of 140 mg L'1. Struvite crystallisation occurred quickly during the trials, by raising the pH of the centrifuge liquors to 9.0 and dosing with magnesium. Up to 97% phosphorus removal, as struvite was achieved. Struvite formation occurred when the molar ratio of magnesium : phosphorus was at least 1.05 : 1. Below this ratio phosphorus removals of 72% were observed, but not exclusively as struvite. Annual yields of struvite were calculated to be 42-100 tonnes a year, depending on the dose regime. Revenue from the sale of produced struvite could be £8,400-20,000 a year.
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    carbonate scale formation and control
    (Cranfield University, 2005-03) MacAdam, Jitka; Parsons, Simon
    Scale formation in domestic appliances is a widespread problem in the UK. This project has focussed on calcium carbonate scale formation in electric showers. A literature survey identified that CaCO; deposition on heated surfaces could be controlled by chemical or non chemical methods, each with various degrees of effectiveness. One of the most effective control methods was the addition of chemicals, although this may not be the most suitable option for the domestic environment. So here the chemical inhibitors tested were used for a benchmark for all the other studies. Two laboratory tests were involved t allow u to study CaCO; precipitation and scale formation. The effect of chemical additives on CaCO; precipitation was investigated using a jar tester. The longest delay to precipitation was obtained by polyacrylic acid dosing, closely followed by zinc. To study CaCO; formation on a heated surface, a rapid scaling test was developed. This test was conducted at 42°C and 70°C to examine and compare a range of treatment options, including chemical dosing, electrolytic, magnetic and electronic water conditioning and low fouling surfaces. From the options examined, the most successful was electrolytic dosing of zinc/copper media with over 95% reduction in scaling at both temperatures. Further, the use of low fouling surfaces, such as Diamond - like carbon coating could also potentially be used in electric showers. Reduction in scaling achieved on this surface was on average 68%. Surface properties of the materials were analysed using an atomic force microscope and their relationship with the scaling behaviour of the surfaces examined. The scaling rates at both temperatures typically increased with increasing adhesion force but no clear relationship was found between the roughness of the surfaces and their scaling behaviour. The relationship between CaCO3 precipitation and scale formation in synthetic solution and natural hard water was also explored here. The induction period in natural hard water was 55 minutes longer and the scaling rate 40% lower than i synthetic hard solution of similar composition. In addition, two shower test rigs, one based at Cranfield University and the other in Attleborough were used in this study. These were used primarily to enable the compilation of background data on scale formation in electric showers, where it was found that the design of the unit has a significant influence on the scale formation. The test rig was also used t test the strategies identified during the laboratory phase of the work. It was found that electrolytic zinc dosing reduced scaling by up to 54%, depending on the shower unit design.
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    Evaluation of the potential for struvite and calcite formation at seven sewage treatment works within the Severn Trent region
    (2000-09) Wall, F.; Parsons, Simon
    Scale formation on the pipes, pumps and dewatering equipment succeeding anaerobic digesters leads to reduced hydraulic capacity and increased downtime and pumping costs. The increasing use of biological nutrient removal (BNR), in particular biological phosphorus removal (BPR) leads to the production of phosphorus rich sludges. Anaerobic digestion solubilises ammonia, magnesium and orthophosphates (stored with micro-organisms) which are then available for scale formation. Scale formation in pipes means either replacement or repeated scouring, the expense and inconvenience involved with such measures demand research into the extent of the problem within the Severn Trent region. During this extensive study of seven full-scale sewage treatment works (STWs) throughout the Severn Trent region, the levels of scale forming elements within digested sludge liquors and centrate were monitored. Sampling took place on a weekly basis over a period of six weeks. A computer model was used to evaluate the struvite or calcite formation potential of the liquors and centrate. The model is affected by concentrations of the key elements phosphorus, calcium, magnesium and ammonia, in addition to pH, total dissolved solids and alkalinity. A strong correlation has been found between the models predictions and reality. Four out of the seven works were predicted to have a scale problem by the model, and by the end of the project, this was indeed the case. The type of scale forming was also correctly predicted, though the degree of scale formation was not always as predicted. Bench-scale experiments with real sludge liquors are planned to validate the precipitation potentials indicated by the model. This will allow Severn Trent to take a more proactive approach to the growing scale problem.
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    Haloacetic acids and other disinfection by-products in UK treated waters : occurence, formation and precursor investigation
    (Cranfield University, 2009-06) Bougeard, Cynthia; Parsons, Simon; Jefferson, Bruce
    Disinfection by-products (DBPs) in drinking water are formed when natural organic matter (NOM) that remains after initial treatment reacts with disinfectants, such as chlorine or chloramines. DBPs, which are of health concern, can take the form of trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs), haloacetaldehydes (HAs), halonitromethanes (HNMs) and a host of other halogenated DBPs. So far, regulations in the United Kingdom (UK) only encompass the group of THMs allowing a maximum level of 100 µg/L. HAAs, the second most prevalent class of DBPs, are currently under consideration by the European Union to be regulated at 80 µg/L. Reliable and reproducible quantification methods are required for DBP detection. To address this need, the presented work includes a comparative study between analytical devices, which concludes that GC/ECD is the only approach with suitable detection limits. This work reports an investigation of the DBP formation potential (FP) of waters from 11 water treatment works (WTWs) at different locations in the UK. Several of these waters have shown to form significant levels of HAAs and THMs. Furthermore, other DBPs, such as iodo-THMs (i-THMs), HANs, HKs, HAs and HNMs were detected. It has also been confirmed that improving the control of these DBPs can be achieved by using monochloramine instead of free chlorine. A statistical analysis revealed that THMs correlated well with the HAAs, and as a result the regulatory limit of 100 µg/L for the THM4 would fail a regulation of 80 µg/L for the nine HAAs. A number of parameters have been identified, which have particular relevance when considering the formation of HAAs and THMs in treated waters. Threshold bromide level was determined beyond which speciation of DBPs shift toward brominated species. The pH, which significantly affected THMs, was less strongly linked to the HAAs. The temperature had a consistent impact with a decreasing DBP formation at lower temperatures. Increasing the contact time with the disinfectant resulted in parallel first order reaction kinetics of the HAAs and THMs. Finally, the precursors involved in the formation of DBPs were found to be specific to water sources.
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    Impact of magnetic resin on DOC removal and downstream water treatment processes
    (Cranfield University, 2008-01) Mergen, Maxime Rodolphe Denis; Parsons, Simon; Jarvis, Peter; Jefferson, Bruce
    Seasonal periods of high rainfall and changes in land management have led to difficulties for UK water companies to remove sufficient natural organic matter (NOM) to stay in compliance with the tightening trihalomethane (THMs) standards. Hence alternative treatment options have come into focus of research and development. The continuous anion exchange process based on a novel magnetic resin (MIEX® resin) has emerged as a promising method to increase NOM removal and has been compared in this thesis to the most widely spread drinking water treatment method of coagulation with hydrolysing metal salts. Therefore the removal efficiency of both processes was investigated by treating different natural waters sources as well as selected organic model compounds of different hydrophobicity and molecular weight (MW). Magnetic resin was thereby seen to be competitive with coagulation for DOC removal in low SUVA sources dominated by mid to low MW material and to outperform coagulation for the treatment of low MW, hydrophilic acids. However magnetic resin had to be used in combination with subsequent coagulation using largely reduced Fe doses to ensure high levels of DOC removal in sources dominated by high MW NOM. This was related to a physical blockage mechanism of the easily accessible external resin bead surface by this high MW material. An effect that could be reduced by applying increased resin doses, which provided a larger external surface area for DOC removal. A combination of magnetic resin treatment with coagulation was nonetheless seen to be able to increase DOC removal as well as to generate enhanced floc properties in terms of strength, settling velocity and size. Beside a reduced THM formation potential, making magnetic resin an effective tool to help meet legislative standards, an increased solid-liquid separation was seen in pilot-scale to result from these effects.
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    The Impact of Natural Organic Matter on Floc Structure
    (Cranfield University, 2004-10) Jarvis, Peter; Parsons, Simon; Jefferson, Bruce
    The removal of natural organic matter (NOM) at water treatment works (WTW) is essential in order to prevent toxic compounds forming during subsequent disinfection. Coagulation and flocculation processes remain the most common way of removing NOM. The properties of the resulting flocs that form are fundamental to the efficient removal of organic material. Periods of elevated NOM loads at WTW can lead to operational problems as a result of the deterioration in floc structural quality. Assessment of floc physical characteristics can therefore be a crucial tool in order to determine and predict solid-liquid removal performance at WTW. Here the growth, size, breakage, strength, re-growth, fractal dimension and settling velocity were measured for flocs formed from a NOM rich water source. NOM floc structural characteristics were measured and evaluated over a one year period in order to monitor the seasonal variation in floc structure. The results showed that a significant improvement in floc size and strength was seen during autumn and summer months. It was subsequently shown that as the organic fraction in the floc increases the floc size, settling velocity and fractal dimension all decrease. A model was proposed showing how these changes were dependent upon the adsorption of NOM onto primary particle surfaces. A range of different chemical coagulant treatment options were applied for NOM removal and the resulting floc structure compared. Considering both floc structure and optimum NOM removal the treatment systems were of the following order (best to worst): MIEX® + Fe > Fe > Fe + polymer > Al > polyDADMAC. NOM floc re-growth was shown to be limited for all the treatment systems investigated. The practical implications of the results were: (1) The requirement for careful coagulant dosing or order to achieve optimum floc characteristics. (2) The use of a pre-treatment anionic ion-exchange stage prior to coagulation. (3) A comparison of alum and ferric based coagulants suggested the ferric coagulants gave better floc structure and improved NOM removal rates.
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    Investigating the relationship between shear and floe fate using CFD
    (2006-11) Bridgeman, Jonathan Matthew; Parsons, Simon; Jefferson, Bruce
    The size, density and strength of floes play a major role in the removal of contaminants from water in physico-chemical treatment processes. The efficiency of the main removal processes is a function of floe size, strength and density. Changes in these parameters affect floe removal and hence the removal of adsorbed organic matter. Coagulation and flocculation efficiency and floe strength are often assessed using ajar tester. Here, computational fluid dynamics (CFD) was used to model the flow field within standard jar test apparatus and, using a Lagrangian particle trajectory model, to study the effects of turbulence on individual floes. The hydrodynamic environments were also investigated experimentally using laser Doppler anemometry (LDA) and particle image velocimetry (PIV) measurement techniques. Combining numerical and experimental data, velocity gradient values at which floe breakage occurs were postulated for three different floe suspensions. Although the threshold values are determined using jar test and CFD data in combination, they are based on the floes’ resistance to induced velocity gradients. This is a significant result, as previous breakage thresholds have been expressed only in terms of mixing speed and cannot be applied at full scale. With this in mind, work was subsequently undertaken to use CFD to model numerically the hydrodynamic conditions within two full scale flocculation vessels; one mechanically mixed, the other hydraulically mixed. This section of work had two principal aims; firstly, to investigate the perceived benefits of using CFD to model the hydraulic performance of the flocculation process at two large surface water treatment works, and secondly, to investigate the practicality and effectiveness of using CFD and jar test results in combination to consider floe fate in the flocculation vessels (in terms of growth, breakage and residence time). This work drew upon the results and conclusions of the previous laboratory scale work and facilitated a greater insight into flocculation processes. Improved understanding of flocculator hydrodynamics can only serve to improve design procedures and standards for future installations.
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    Maximising struvite recovery from real wastewater sources
    (2007-04) Thomas, David J. L.; Parsons, Simon
    Formation of struvite (MgNFLjPCU.ôFfeO) in reactors is proposed to limit struvite problems in sewage treatment works (STW) and offer a method of phosphorus recovery and recycling. Four sites of interest were identified by Severn Trent Water Ltd: Derby, Wanlip, Stoke Bardolph STW and Coleshill sludge destruction plant for their potential to produce struvite. Initial tests on sludge liquors collected from the four sites showed that >80% of initial orthophosphate could be removed when the Mg:PC>4 ratios was adjusted to >2:1 for Wanlip, Stoke Bardolph STW and Coleshill at pH 9. Two reactor types, a fluidised bed reactor (FBR) and a stirred tank reactor, were trialled in Phase 1 testing with Wanlip STW liquors. The FBR was able to achieve a >90% orthophosphate removal with Mg additions of 3.5 to 5 mmol but produced a suspended solid content of -300 mg L"1. To overcome the problem of ‘fines’ a metallic mesh accumulation device was fitted to the reactor. The mesh system was able to reduce the suspended solids within the liquors <50mg L' 1 when the reaction time was increased from two to three hours. The stirred tank reactor was able to remove on average 55% of the phosphate content of the liquors with a magnesium addition of 5mmol. In Phase 2 testing both types of reactor were run side-by-side in a continuous operation. In the three experiments carried out the initial orthophosphate concentration was adjusted to 95 mg L' 1 (Immol). The stirred tank reactor was able to consistently remove -65% of the influent orthophosphate concentration in the 3 experiments at a Mg:P0 4 ratio of 3.5:1. The FBR removal steadily improved from 25% to 65% over the 3 experiments. The metallic mesh system was further trialled here and successfully captured 4.1 g of struvite. A cationic polymer, polyDADMAC, was also tested for the capture of fines with less success than in previous reports. The precipitate from each reactor was analysed with SEM-EDS and XRD. The FBR produced relatively pure struvite and stirred tank a struvite and amorphous material mixture.
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    Natural organic matter character and reactivity: assessing seasonal variation in a moorland water
    (Cranfield University, 2003-10) Goslan, Emma Harriet; Parsons, Simon
    Natural organic matter (NOM) is described as an intricate mixture of organic compounds that occurs universally in ground and surface waters. After treatment for potable use, there is NOM remaining in the water that reacts with the chlorine used for disinfection to form disinfection by-products (DBPs). Some of the DBPs, trihalomethanes (THMs) are regulated. Several water treatment works (WTWs) in the Yorkshire Water and United Utilities (previously North West Water) region in England have recently experienced difficulty in meeting THM limits (100 µg L-1) in their finished drinking water at certain times of the year. An investigation into how NOM changes seasonally, pragmatic methods of NOM analysis and its reactivity with chlorine was undertaken. By separating the NOM using adsorbent resins into fractions, it was possible to gain an insight into the seasonality of NOM. It was observed that a particular, difficult to remove fraction was always more reactive with respect to THM formation in autumn. Some of the methods proposed in the literature were used here with varying successes. It was found that High Performance Size Exclusion Chromatographic methods were most useful to the WTW operators for optimising treatment processes. It is known that the formation of DBPs is very complex. An attempt was made to predict the reactivity of a raw water in terms of THM-FP by looking at the NOM makeup. However, it was found that the fluorescence spectra combined with the fluorescence index of raw water and chlorinated samples gave more insight into the reactivity of the raw water at a particular time than knowing the fraction distribution. The use of fluorescence as a tool for understanding chlorine-NOM reactions is promising.
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    Natural organic matter coagulation
    (Cranfield University, 2005-10) Sharp, Emma; Jefferson, Bruce; Parsons, Simon
    The removal of natural organic matter (NOM) is one of the main challenges facing water utilities in both the UK and the US. As a consequence of changes in land management and an increased carbon loss from solids, a greater amount of accumulated organics is now being flushed into the aquatic environment during increased surface run-off events such as snowmelt or heavy rainfall. Furthermore, whilst traditional treatment with trivalent coagulants has proven a successful strategy in the past, operational problems are now being reported during periods of elevated organic levels in the water. These include the formation of fragile flocs, a greater particulate carryover onto downstream processes and increased disinfection by product (DBP) formation. Resin adsorption techniques were employed to fractionate the water samples into their hydrophobic and hydrophilic components. This, coupled with raw water monitoring, revealed that NOM composition and characteristics can vary, even if the total organic concentrations appear stable. In particular, hydrophobic NOM fractions contribute the majority of the charge compared to the hydrophilic fractions, and therefore exert a greater impact on coagulation conditions. Comparison across different source waters, seasons, at varying experimental scales and under varying coagulation conditions, revealed that zeta potential monitoring during coagulation takes into account the changing electrical property of the water, and in general, maintaining a value between -10<ζ<+3 mV will result in low and stable residuals. A similar operational zeta potential range exists for clarification processes, although the zeta potential value at the positive threshold is influenced by the hydrophobic NOM content, such that the range is extended as the specific UV absorbance (SUVA) value of the raw water decreases. Whereas the hydrophilic concentration was found to control the achievable dissolved organic carbon (DOC) residual, attributed to a negligible charge density and poor coagulant-interactions. Consequently, the key finding of this study is that raw water characterisation coupled with zeta potential monitoring will provide a straightforward guide to the mechanistic understanding of treating NOM rich waters.
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    Novel treatment options for coagulant and potable sludge
    (Cranfield University, 2005-10) Murray, C. A.; Parsons, Simon
    increases in coagulant required to remove sufficient quantities of natural organic matter (NOM) to ensure compliance with trihalomethane (THM) regulations lead to an increase in the volume of potable sludge generated. Here options to treat the sludge or reduce the amount of sludge produced are assessed. The results from assessing advanced oxidation processes for the treatment of potable sludge showed that although feasible it would be more advantageous to remove the NOM from the water via a process that generates less sludge. For the removal of NOM the main focus was on the adsorption of NOM onto TiO2 powder and this was optimised in terms of the removal of bulk water parameters, namely dissolved organic carbon (DOC) and ultraviolet (UV) absorbance at 254 m (UV254). The results showed that both the DOC and UV254 absorbance could be reduced by over 90%. Secondly the immobilisation of TiO2 as a thin lm coated on a supporting substrate was evaluated. To obtain a uniform coating was complex and the NOM removal was much poorer than that achieved using the TiO2 powder due to the reduced surface area. To overcome the complex issue of separating the TiO2 powder from the treated water larger pellets sized TiO2 particles were used as a adsorbent coupled with side-stream UV regeneration. Results from both bench and pilot scales showed that the DOC concentration could be reduced by 86% and the UV254 absorbance by 75%. In addition low M compounds which are untouched by conventional coagulation were removed. Combining NOM adsorption onto TiO2 pellets with ferric coagulation increased the reduction in UV254 absorbance to 94% at a reduced coagulant dose. This reduction in coagulant dose of over 80% will have a major impact on the volume of potable sludge generated.
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    Optimisation and effects of coagulant type, pH and ozonation on clarification for automatic coagulation control
    (1998-09-11) Marshall, N. I.; Parsons, Simon
    Four phases of studies were carried out at Burham Water Supply Works in Kent. Firstly jar testing was used to compare and evaluate the performance of five coagulants. The coagulants tested were Polyaluminium Chlorides (PAC) from two suppliers, Aluminium Sulphate (Alum), Polyaluminium Silicate Sulphate (Pass 100) and Alba 18. Jar tests were carried out with coagulant alone and with non-ionic (LT20), weakly cationic (LT22s), and anionic (LT25) polymers. Secondly tests were also carried out at ambient and lower pH’s, at various pre-ozone concentrations. Jar tests indicated PAC with LT20 polymer at a pre-ozone dose of 1.5 mg/1 at pH 7.4 produced the highest water quality. Alum with LT20 was next, giving good and consistent settled water qualities. Pass 100 was circumspect and dependent upon the jar test procedure, but at optimum doses gave water qualities comparable to that of PAC. Alba 18 consistently produced poor settled water qualities. For the third phase, PAC supplied by Industrial Alum Limited (INDA) and Water Treatment Solutions (WTS), Pass 100 and Alum were selected and tested on the clarifier. Alum and PAC (WTS) were tested at pH 7.5, pH 7.3 and ambient pH at pre-ozone concentrations 0.5, 1.0, 1.5 and 2.0 mg/1 with various coagulant and polymer combinations. Pass 100 and PAC (INDA) were tested as describes but at a pre-ozone concentration of 1.5 mg/1. At optimum doses PAC (INDA) was found to perform best at a pre-ozone concentration of 1.5 mg/1 at pH 7.5. PAC (WTS) was next, with similar results. Alum produced good and consistent water qualities. Pass 100 was affected by polymer addition and was out-performed by PAC and Alum coagulants. The parameters taken into account were settled turbidity, residual aluminium, and removal of TOC, chlorophyll, phaeophytin, iron, manganese, and colour. If PAC with acid dosing can be shown to work full scale annually it would be economic to do so and to dose acid to achieve a pH of 7.5 when required. Phase four involved the evaluation of an automatic coagulant control system that would automatically optimise the coagulant, acid and polyelectrolyte doses added to the water. This was evaluated using jar tests with PAC and Alum coagulants. The AC250 system indicated the potential to improve the quality of treated water whilst minimising the coagulant dose. In this case PAC would provide further coagulant savings, with consequent sludge savings.
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    The potential of barley straw as an algal and cyanobacterial growth control
    (Cranfield University, 2009) Murray, Daniel; Parsons, Simon; Jefferson, Bruce
    Algal and cyanobacterial1 blooms are increasingly becoming a problem to water utilities in the UK and around the world. Conditions such as increasing eutrophication and poor management of water bodies are consequently leading to increases in the number and severity of algal bloom events. These blooms present serious issues to both utilities and the environment; problems include deoxygentation of water bodies leading to fish kill and rapid algal growth leads to overgrowing of other plant species in the water, while blooms of toxic cyanobacteria can lead to the closure of reservoirs and a number of algae can lead to pump and filter blockages in treatment works. The problems created by algal and cyanobacterial blooms are becoming increasingly expensive to offset and while some technologies such as dissolved air flotation exist to control them at treatment level, there are few effective options to tackle blooms where control would be most effective, at the source. What methods there are for source control are often unreliable or almost as bad for the environment as the blooms themselves such as, in the use of chemical pesticides. Barley straw has been shown to have to potential to be an effective control of algal and cyanobacterial blooms at the reservoir level, being able to inhibit a variety of species at practical straw concentrations, but little is known about how it functions or how its ‘effect’ is developed. This study identified spcific areas which when investigated provided insight into these gaps in current knowledge. An analysis of the chemicals proposed as released by decaying barley straw has shown that they can control algal blooms at concentrations similar to what has been detected in the field. Investigations into the decay of barley straw has shown that barley straw decays in water in a way consistent with species that breakdown the lignin section of the straw potentially releasing the proposed chemicals. This finding was supported by the effect being consistent when field rotted straw, fresh straw rotted in the lab, and straw cultured in the lab with species specifically adapted to breaking down the lignin section of the straw were compared. Attempts at pre-treating the straw have shown that microbiological activity is important in developing the algistatic effect, which could lead to the possibility of keeping straw ‘ready for use’ thus removing the current need of several months wait before barley becomes effective. These findings have also provided a definitive route by which barley straw develops its effect, namely, microbiological decay of the lignin fraction of the straw leading to the production of phenol chemical release.
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    Potential of ultrasound treatment for sludge reduction
    (Cranfield University, 2008-09) Minervini, Davide; Cartmell, Elise; Parsons, Simon
    The potential of ultrasound treatment for sludge reduction during the activated sludge process was assessed. Batch and dynamic disintegration studies were completed using an activated sludge pilot-scale plant fed with settled sewage that was comprised of two 1.2 m3 lanes, operated as a test and control. A 1 kW ultrasound system was integrated into the test lane of the pilot-scale plant to allow continuous in-line ultrasound treatment of the return activated sludge (RAS). Seven dynamic trials were completed over an 8-month period, treating from 1.7 to 12.5% of the RAS with energy densities between 42 and 168 kJ L-1. During the batch disintegration studies, it was observed that ultrasound treatment at 42 to 186 kJ L-1 caused floc breakage and sludge solubilisation. Floc size was reduced by 88% at 42 kJ L-1 while the degree of soluble COD release increased almost linearly from 11 to 36 % between 42 to 168 kJ L-1. A change in the biological activity was observed only at 168 kJ L-1 with an 8.5 % increase in the specific oxygen consumption of the treated RAS samples in comparison to the untreated ones. During the dynamic studies, a 20% degree of sludge reduction was observed treating 10% of the RAS at 42 kJ L-1. At these operational conditions, there was no significant difference in the total COD and nitrogen removal between the control and test lanes. However, a 5.5-fold increase in the capillary suction time and a 3.6-fold increase in the specific resistance to filtration in the RAS from the test lane indicated a detrimental impact on dewaterability. Increasing the energy input, by treating 12.5% of the RAS at 84 kJ L-1, did not result in a significant increase in sludge reduction, which indicates that there might be limits to the degree of reduction achievable with the ultrasound treatment. Results from the dynamic studies suggested that lysis-cryptic growth was the main mechanism behind the observed sludge reduction. Based on modelling, lysis-cryptic growth could justify 98 % of the sludge reduction observed. Cost analysis results indicated that sludge reduction by ultrasound disintegration was not currently economically viable unless the cost for sludge treatment and reuse increased to £ 961 from the reference price of £ 423 per tonne of dry solids.
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    Process modelling of the MBBR / AS hybrid process
    (2000-10) Berry, Nicholas D.; Parsons, Simon
    With the UK water companies under increasing financial and environmental pressures they are having to look for innovative options to provide lower capital and operational cost solutions to asset management in order to maintain profits. Process modelling provides a tool which can be used to help identify more cost effective options through a better understanding of processes and their limitations. Although modelling can be used in this way, sound judgement needs to be applied in using models as misinterpretation of simulated results could lead to the wrong option being selected. Processes which combine fixed and suspended biomass have been used to improve the performance of existing wastewater treatment works which previously had either a fixed or a suspended growth process only. In addition to improved efficiency, the processes have been found to be more robust. Full scale trials of a fixed film / activated sludge hybrid process, supported by model simulation, have shown that the hybrid process would enable a 120 000 PE sewage treatment works to meet a new, stricter effluent discharge consent without the construction of new tanks.
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    Process options for the treatment of humic rich waters
    (Cranfield University, 2004-04) Fearing, David Andrew; Parsons, Simon
    Seasonal periods of high rainfall have led to difficulties in removing sufficient natural organic matter (NOM) to meet trihalomethane (THM) standards, and hence better or alternative treatments are required. Typically bulk water parameters such as dissolved organic carbon (DOC) and UV absorbance at 254nm (UV254) are used to optimise treatment processes. Here the isolated fraction character and molecular weight (MW) distribution was used in conjunction with bulk water parameters to tailor process options for the treatment of humic rich waters. Three options for the removal of NOM were proposed. A staged coagulation based on the optimisation of isolated fractions. The results showed that although no significant reduction in DOC or UV254 was observed filter breakthrough was significantly reduced. Secondly a novel magnetic ion exchange process (MIEX®) for the removal of NOM was evaluated. The results showed that a combination of MIEX® and ferric reduced the THM formation potential (THMFP) by more than 50% and lower MW compounds that are known to be untreated by conventional coagulation were reduced. This option was also shown to be the most robust option for the treatment of waters with differing quality caused by seasonal changes and different catchments. Finally the addition of a range of adsorbents including carbons, hydroxides and clays to both the raw water and the isolated low MW fractions showed that an increase in DOC and UV254 removal was achievable. This was proposed as a post coagulation option during times of high organic loading. All processes provide viable options for the treatment of humic rich waters during times when current processes are being challenged and having difficulty meeting THM standards.
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    The relationship between UVT and turbidity, with respect to the disinfection of surface waters
    (Cranfield University, 2009-09) Roussillon, Guillaume; Parsons, Simon
    UV transmittance (UVT) is a parameter very closely related to the efficiency of any UV processes. Firstly a theoretical model of UVT proposed by Gregory (2006) was assessed and secondly an experimental approach was undertaken to find out any relationship between turbidity and UVT. UVT calculations were made for a range of particle diameter from 100nm to 5µm and to assess the impact of particle characteristics (particle size, particle number concentration and refractive index) on UVT. The theoretical model showed that the most important parameter affecting UVT was particle size and this was attenuated when the refractive index of the particle was small. The sensitivity of turbidity measurement required to show a 1% variation in UVT for UVT (for UVT above 90%) was calculated to be 0.01NTU which is below the level of sensitivity of most commercial system. Experiments with made solution containing one pollutant showed that turbidity is linearly related to the UVT (turbidity range between 0.14-5 NTU), but for real and non commercial water compositions UVT cannot be estimated using turbidity measurement. The nature of turbidity cannot be directly related to the particle characteristics which are particle size, chemical composition and hence absorbance and scattering coefficient. Finally from comparison between experimental results and theoretical calculation of UVT it appears that difference in UVT prediction (given values from 0% to 100% of UVT whereas measurement are between 90-99%) was mainly due to an error in theoretical determination of particle number concentration measurement. As an improvement of the theoretical model it was proposed to calculate the particle number concentration from 4 size particle fractionated solutions and then these solutions were diluted and UVT calculations and measurement were performed. Difference between predicted and measured UVT was still too important (but lower than 4%) to get a good correlation and use the theoretical model as a tool to predict UVT.
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    Removal and recovery of phosphorus from municipal wastewaters using a ferric nanoparticle adsorbent
    (Cranfield University, 2010-11) Martin, Benjamin David; Jefferson, Bruce; Parsons, Simon
    Phosphorus is removed from wastewater streams to prevent the ecologically harmful effects of eutrophication in receiving natural systems. Current chemical and biological techniques for removing phosphorus from wastewater are not able to practicably achieve the new discharge limit expected under the Water Framework Directive of 0.1 mg phosphorus L- 1 . In addition, they do not represent an economically viable route for the recovery and reuse of the phosphorus they remove. Cont/d.
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    The role of advanced oxidation processes in drinking water treatment
    (Cranfield University, 2010-05) Philippe, Karine K.; Parsons, Simon
    Removal of natural organic matter (NOM) is an ever growing challenge for water utilities as many surface waters used for drinking water in the UK exhibit increasing organics levels and it is well known that these organics can lead to problems such as water colouration, unpleasant odour and taste, bacterial growth and disinfection by-products (DBPs) formation. NOM is traditionally removed by coagulation, however in the case of hydrophilic organic matter rich waters the performances of these processes are not able to remove sufficient organic matter leading to potential failures of DBP regulations. Here two advanced oxidation processes (AOPs) UV/H2O2 and TiO2 photocatalytic oxidation were studied to investigate how they could be integrated in a drinking water flowsheet to meet this challenge. Substantial structural changes in the organic matter were observed: loss of aromaticity and double bonded character, shift towards lower molecular weight (MW) more hydrophilic compounds and formation of oxygenated by-products. Although hydrophobic rich waters seem more suitable to AOP treatment as preferential attack of high MW hydrophobic compounds was demonstrated, no correlation was found between physical properties of nine NOM surrogates and removal by UV/TiO2. Dark adsorption onto TiO2 was shown to remove preferentially high molecular weight hydrophobic anionic compound such as tannic acid. UV/H2O2 combined with coagulation did not show any significant benefits in NOM removal as UV/H2O2 appeared to target similar components as coagulation (high MW, hydrophobic and charged) and to form by-products recalcitrant to coagulation. The combination of both AOPs with fresh GAC showed moderate benefits in Abstract ii trihalomethane formation potential (THMFP) and non purgeable organic carbon (NPOC) removal highlighting the role of size and surface chemistry on adsorption onto GAC. Biodegradability of the water did not exhibit any significant change after both AOP treatments within the studied conditions possibly due to insufficient UV irradiation and presence of organics recalcitrant to biodegradation.