A novel configuration of vertical downflow constructed wetland was used to treat up to 75 m3 per day of sugar beet processing wastewaters. The 403 m2, two-stage pilot system included planted and unplanted cells of a variety of sand depths (0.15 - 0.4 m) and sand particle size distributions (d10 = 0.07 - 1.2 mm). The hydraulic regime of each bed was also manipulated. Typical beet processing wastewaters contained 235 mg BOD l-1, 45 mg NH4-N l-1, 0.03 mg PO4-P l-1, 16 mg TSS l-1, at pH 8.2 and 29 °C. Overall performance of the pilot system, with respect to BOD, NH4-N, and TSS removal, was similar to, or better than, comparable two-stage vertical flow wetland systems. In vertical flow systems, influent BOD concentrations >600 mg l-1 were coincident with reduced rates of nitrification. Mean BOD removal rate in the pilot system was 38.8 g BOD m-2 d-1, with a mean loading rate of 40.4 g BOD m-2 d-1. The first-order reaction rate for BOD removal was calculated to be 0.369 m d-1 over the whole system. High rates of oxygen transfer and efficient removal of organic solids were seen as the most important factors enhancing BOD removal. Mean NH4-N removal rate in the pilot system was 5.6 g NH4-N m-2 d-1, with a mean loading rate of 7.3 g NH4-N m-2 d-1. The temperature corrected first-order reaction rate for NH4-N removal was calculated to be 0.23 m d-1 over the whole system. Nitrification accounted for between 85% and 99% of TKN removal. Evidence is presented which supports the hypothesis that cycles of assimilation/adsorption and release of NH4-N may play an important role in nitrification mechanisms in vertical flow constructed wetlands. In bed 1, removal of BOD and NH4-N were at their most efficient in the vegetated cell with the deepest (0.21 m), coarsest (d10 = 1.2 mm) sand layer. TSS removal was highest in an unvegetated cell with shallower (0.15 m), finer (d10 = 0.56 mm) sand. In bed 2, removal of BOD, NH4-N, and TSS were all at there most efficient in the vegetated cell with the deepest (0.4 m), coarsest (d10 = 0.1 mm) sand layer. Low influent phosphate concentrations may have limited nitrification rates in the pilot system. The surface area available for biofilm attachment, and media depth, both provided good models of NH4-N removal, whilst cell surface area was more important in solids removal. Media hydraulic conductivity at the beginning of the dosing cycle was five times higher in vegetated cells than in unvegetated cells. After 12 hours of dosing, media particle size distribution became the dominant factor determining media hydraulic conductivity. High influent BOD concentration was more closely associated with cell logging than hydraulic loading, TSS concentration, or BOD or TSS loading. Growth of one provenance of Phragmites australis was limited by phosphate availability. However, populations of nitrifying bacteria were highest in samples of media and roots taken from plots containing this provenance. No correlation was demonstrated between nitrifying bacteria population and root biomass. Water stress caused by high media hydraulic conductivity and inadequate influent distribution resulted in sub-optimal conditions for reed growth in bed 1. The study concludes with details of the proposed design of a full scale system designed to treat up to 1000 m3 d-1 of beet processing effluents.

La connaissance du comportement hydrodynamique et du transfert de matière de la bulle est importante car elle fournira des indications pour la sélection des conditions de fonctionnement et la conception du réacteur dans de tels processus. Cette thèse a réalisé une étude expérimentale pour les bulles d’air isolées en ascension dans diverses solutions de polymères (Breox, Polyacrylamide (PAAm) and Xanthan gum) qui peuvent simuler les propriétés des eaux usées. Les travaux sont divisés en trois parties: Tout d’abord, en dressant l’état de l'art sur les techniques de visualisation pour le transfert de matière, trois techniques ont été testées pour les bulles d’air (diamètre équivalent ≈ 1 mm) en ascension dans l'eau, notamment la fluorescence induite par plan laser (PLIF, fluorophore: résorufine fluorescente), la PLIF avec inhibition (fluorophore: complexe de ruthénium) et techniques colorimétriques (colorant: résorufine rose), respectivement. Par la suite, sur la base des images capturées par une caméra haute vitesse, le comportement hydrodynamique des bulles d'air (diamètres équivalents: 0,7 à 7 mm) s'élevant dans les solutions de polymères (PAAm et Xanthan) a été étudiée, notamment la vitesse, la trajectoire et la forme de la bulle. Enfin, appliquant la technique PLIF-I, les phénomènes de transfert de matière et de diffusion dans le sillage de bulles d'air (diamètre équivalent 1 ≈ mm) dans différentes solutions aqueuses de polymères (PAAm et Breox) ont été étudiés. / The knowledge on the hydrodynamic property and mass transfer of bubbles is important since it will give guidelines for selecting the operation condition and for reactor design in such processes. For this purpose, this PhD manuscript has implemented an experimental investigation of single air bubbles rising in various polymer solutions (Breox, Polyacrylamide (PAAm) and Xanthan gum) which can simulate the property of the sewage. The works can divided into three parts: Firstly, with a review of the current visualization techniques for mass transfer, three techniques have been tested for air bubble (equivalent diameter ≈ 1 mm) rising in water including traditional Planar Laser Induced Fluorescent (PLIF, dye: fluorescent resorufin), Fluorescent quenching technique (PLIF with Inhibition, dye: ruthenium complex) and colorimetric techniques (dye: pink resorufin), respectively. Secondly, based on images captured by a high speed camera, the hydrodynamics of the bubble single air bubbles (equivalent diameters: 0.7-7 mm) rising in the polymer solutions (PAAm and Xanthan) have been investigated including the bubble velocity, trajectory and bubble shape. Finally, based on PLIF-I technique, the mass transfer and diffusion phenomena in the wake of single air bubbles (equivalent diameter ≈ 1 mm) rising in various aqueous polymer solutions (PAAm and Breox) are investigated.

The overall aim of this research was to contribute to the optimisation of aerobic wastewater treatment processes in sequencing batch reactors, by investigating the performance of the process with real and model wastewaters in order to achieve the highest possible reduction of influent COD with the minimum reactor volume and oxygen consumption. Six industrial wastewaters from the food and drink companies were treated in lab-scale aerobic sequencing batch reactors (SBRs) inoculated with soil and monitored for COD and total suspended solids (TSS) removal. The results showed high COD removal efficiencies for all the wastewaters, in the range of 64-95 %. Extended aeration tests were carried out on the reactor effluents and the results indicated that the residual soluble COD was not further biodegradable. This indicates that the soluble BOD removal in the reactors was virtually 100 %. The biodegradation efficiency was investigated over two values of the solids retention time (SRT) and the performance of the reactors was essentially unaffected by the SRT (in the range of 7-18 days considered in this study). This means that very good COD removal can be achieved at relatively lower SRT, with potential savings in capital and operating costs. The removal of TSS for the wastewaters was not satisfactory, largely due to the low food to microorganism (F/M) ratios (0.13-0.29 kg COD/kg biomass.day) in the reactors. Three batch tests at different initial substrate to biomass (So/Xo) ratios were carried out on each of the two industrial wastewaters for kinetic characterisation of the wastewaters. Oxygen uptake rate (OUR) was measured during the tests and the OUR profiles were used for the estimation of the kinetic parameters using a mathematical model consisting of substrate hydrolysis, biomass growth and endogenous metabolism. The results showed large variations with regards to the values of the parameters for each wastewater due to day-to-day variability in the biomass's response to substrate utilisation. For the two industrial wastewaters, the hydrolysis rate constant (kh) and half saturation constant for slowly biodegradable substrate (KX) were found to be in the range of 2.21-14.8 kg COD/kg biomass.day and 0.006-0.45 kg COD/kg biomass respectively. The maximum growth rate (μmax) and the half saturation rate constant for readily biodegradable substrates (KS) ranged between 1.21-7.3 day-1 and 0.004-0.89 kg COD/m3 respectively. The biomass growth yield (YX/S) and the endogenous metabolism coefficient (b) were found to be 0.3-0.57 kg biomass/kg COD and 0.001-0.41 day -1 respectively. The hydraulic retention time (HRT) and SRT were optimised in order to minimise the SBR volume and maximise the organic loading rate (OLR) of the SBR process. Two model wastewaters, glucose and ethanol, were used in the study. An experiment of eleven different SBR runs (HRT in the range of 0.25-4 days and SRT of 1-65.3 days) was carried on the glucose wastewater. Nine different SBR runs were carried out on ethanol wastewater (HRT in the range of 0.5-4 days and SRT of 1-73.6 days). The minimum HRT and SRT values for the successful operation for glucose wastewater treatment were 0.25 days and 3.1 days respectively while the minimum HRT and SRT for ethanol were 0.5 days and 4.9 days respectively. The highest corresponding OLR values from the minimum HRT and SRT which gave satisfactory process performance were 4.28 g COD/l.day and 4.14 g COD/l.day for glucose and ethanol wastewaters respectively, which are among the highest OLRs reported in the literature for aerobic conventional dispersed-growth processes. The calculated oxygen consumption and biomass production were found to depend on the SRT as well as the OLR, where in general, oxygen consumption increased while biomass production decreased at higher OLR. Batch tests were also carried out on the two model wastewaters for kinetic characterisation. The kinetic parameters for glucose wastewater were: 1.07-4.79 day -1 for μmax, 0.24-0.45 kg COD/m3 for KS, 0.04-0.1 day-1 and 0.47-0.6 kg biomass/kg COD for b and YX/S respectively. For ethanol wastewater, the kinetic parameters were: 0.99-2.3 day -1 for μmax, 0.001-0.04 kg COD/m3 for KS, 0.05-0.2 day-1 and 0.38-0.51 kg biomass/kg COD for b and YX/S respectively. A new mathematical model and procedure to calculate the periodic steady state of the SBR using a kinetic model of the biological process and values of the kinetic parameters was developed. This new procedure allows the direct calculation of the steady state profiles of biomass and substrate in the SBR without calculating the dynamics of the system from start up to steady state. The numerical accuracy of the procedure was discussed and the model was applied to show the effect of the operating parameters (SRT, HRT, length of the phases and number of cycles) on the steady state performance in terms of biomass and substrate concentrations. It was also shown how the model can be used for various applications like: optimisation of operating parameters for a minimum reactor volume; simulation of the competition between filamentous and floc-forming bacteria for bulking control; and calculation of the minimum volumetric mass-transfer coefficient required to maintain a desired oxygen concentration. In the end, the periodic steady state of the SBR was simulated for the industrial and model wastewaters at various values of the operating conditions (e.g. HRT, SRT, number of cycles) using the developed SBR model with values of kinetic parameters obtained from the various batch tests. The predicted model performance in terms of effluent quality and biomass concentration was compared with experimental results achieved during the treatment of the wastewaters. The simulation gave very good prediction of the extent of substrate removal for all the wastewaters. However, the prediction was not very accurate for biomass concentration. The study indicated that a good model prediction in terms of biomass production is strongly dependent on the values of the kinetic parameters especially b and YX/S.

Mesophilic anaerobic digestion is one of the most used and successful technologies to treat the sludges resulting from wastewater treatment. However, traditional approaches to digester design are firmly rooted in empiricism and rule of thumb rather than science. Mixing is an energy-intensive operation, and therefore the need to lower the wastewater process carbon footprint requires searching how to lower the input mixing energy without compromising–and indeed enhancing–biogas production. In particular, the literature on gas mixing is still particularly poor. For the first time, an Euler-Lagrangian CFD model was developed for gas mixing in anaerobic digestion. The model was validated against laboratory experiments with PIV and PEPT techniques. Full-scale simulations reproducing a real digester were performed with the validated model, and different scenarios were reproduced. Shear rate distribution was used as a parameter to assess the most appropriate value of input mixing power. The simulations also low-viscosity flow patterns for the first time. This phenomenon is intrinsically linked to the non-Newtonian nature of sludge, and leads to short-circuited mixing. Switching biogas injection between two different nozzle series was found to be an effective strategy to mitigate the issue of the low-viscosity flow patterns. Final recommendations on input mixing power and switching time were given to improve mixing efficiency in the full-scale design taken into consideration. A journal paper published in Water Research and a conference paper presented at the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing (Civil-Comp) were produced. Two other papers are currently in preparation.

Urban waste water production increases day by day and its safe treatment and disposal need efficient procedures. In many areas, such effluents are discharged to open water bodies such as lakes, rivers and sea coastal areas. Since there are no perennial streams in arid and semi-arid regions the disposal of treated outfalls is often to dry wadis. However developing an understanding of complex urban systems, where processes act at different space and time scales, is not easy. Dynamical systems approaches have been used for many years in complex feedback systems. So in this work the use of dynamical system modelling is investigated to see if this approach can help develop at least in semi-quantitative way an understanding good enough to aid managers of urban water systems where wadis are involved. The approach taken was to develop a flow and then a solute transport model for the urban system of Riyadh City - Wadi Hanifah. The softwares used was ‘Stella’, and a representation of two aquifers, two soil systems, the sewerage system, the water supply system, the non-urban catchments and the urban drainage system was set up and run using daily meteorological data for about 20 years. The model was compared with limited field data on water levels, flows, flooding, and water quality and modified until results were consistent with field data. Model was then investigated by looking at effects of changing a wide range of hydrogeological and other parameter values, including pipe leakage rates, rainfall, and water supply rate.

Floating macrophyte pond systems, with the ability to produce nutrient enriched plants simultaneously with wastewater treatment, are a sustainable solution to contribute to environmental protection and safe nutrient recovery from domestic wastewater. However, to meet the requirements for reuse with high strength wastewater containing high levels of metal pollution generated in developing countries, an adequate combination of water hyacinth and duckweed ponds is proposed in order to take advantage of the best characteristics of each of these macrophyte ponds. This research focused on the advancing of the understanding of the effectiveness of treatment and resource recovery under the effect of changing operational parameters such as pH, light intensity, influent metal content and fluctuating pollutants loading rate on pond performance and recycling ability in order to fill the noticed gap of knowledge. Experiments conducted in water hyacinth ponds (WHP), under batch and tropical natural weather conditions, revealed that pH between 6.4 and 7.1, full sunlight and seven days hydraulic retention time were optimum for plant biomass production and pollutant removal in WHP. WHP was able to regulate pH when the initial pH values moved outside this interval with a drop in biomass production as a side effect. These ponds showed a first order kinetic for the removal of iron, zinc and copper from aqueous solution and their accumulation in plants biomass with a preferential sequence Fe > Zn > Cu. However the presence of metals in water hyacinth biomass led to the reduction in ponds performances and a risk of re-pollution of the effluent through the release of metals into water. A comparative study carried out over sixty-two weeks in a pilot scale combined water hyacinth and duckweed ponds (DWP) channel and waste stabilization ponds channel working under fluctuating loading rates showed different environmental conditions occurred these ponds. The fluctuating loading rate was also found to have a reduced effect on the combined WHP/DWP channel performance and effluent quality stability with the effluents meeting the entire reuse requirement at high hydraulic flow rate (retention time greater than 20 days). Fish was able to grow in the WHP/DWP channel. Results suggested some guidelines on WHP/DWP system design, operation and maintenance. The overall outcome of this research is a significant contribution to the development of integrated combined WHP/DWP technology for treatment of wastewater and resource recovery on site.

Pharmaceutical compounds comprise a wide range of substances that are consumed in large quantities by modern societies and are generally released into local sewer networks through excretion. This research aimed to identify the factors affecting the removal efficiencies of these compounds in biological wastewater treatment plants (WWTPs) under different environmental conditions. Of the pharmaceutical compounds selected for this study, the highest influent concentrations measured in municipal wastewater treatment plants (MWWTPs) were for paracetamol, naproxen and bezafibrate (> 1 μg/L), followed by carbamazepine, atenolol, lidocaine, sulfamethoxazole and NACS (<1 μg/L). In hospital wastewater treatment plants (HWWTPs), the highest concentrations measured were for paracetamol and caffeine (> 10 μg/L), followed by ciprofloxacin and NACS (1–6 μg/L), and finally bezafibrate, carbamazepine, atenolol, lidocaine, clarithromycin and sulfamethoxazole (< 1μg/L). Antibiotic drugs were detected in HWWTPs, but rarely detected in MWWTPs. In general, the hospital wastewaters contained relatively higher levels of pharmaceuticals than municipal wastewaters. The removal efficiencies of the pharmaceutical compounds ranged widely. This was found to be related to characteristics and operational parameters of the individual WWTPs. The MWWTPs that utilized long aeration and biomass retention times (HRT,SRT), as evidenced by the occurrence of complete nitrification, were more efficient at removing paracetamol, naproxen, bezafibrate and atenolol, than the non-nitrifying plants with relatively shorter HRT and SRT. HWWTPs that operated under elevated ambient temperatures (> 26°C) achieved higher removal efficiencies (90%) for several compounds, including paracetamol, caffeine, sulfamethoxazole, ciprofloxacin, clarithromycin, NACS, atenolol, carbamazepine and lidocaine. In addition to the elevated ambient temperatures, elevated HRT and SRT and less dilution can lead to increased active biomass and can result in higher removal rates for the pharmaceutical compounds. Overall, the removal efficiencies of pharmaceuticals in WWTPs have been correlated to the type of treatment plant, the plants’ operational parameters (HRT, SRT), the climatic conditions (temperature and dilution effect of rainfall) and characteristics of the micropollutants (type and concentration). Aerobic and anaerobic batch biodegradation experiments were conducted to observe the removal of paracetamol, naproxen, ibuprofen and sulfamethoxazole at various SRTs. The biodegradation rates varied widely ranging from poor, to moderate, to high, depending on the SRT. Paracetamol was highly biodegradable under both aerobic and anaerobic conditions. Sulfamethoxazole was poorly biodegradable under aerobic conditions but highly biodegradable under anaerobic conditions. Relatively slow biodegradation rates were observed for ibuprofen and naproxen under both conditions; longer microbial adaptation periods for these two compounds were probably required. The most important factor affecting the removal of the compounds was the SRT. Therefore, the conclusion was drawn that combining anaerobic and aerobic systems with longer SRT and HRT could bring about significant reductions in the emissions of these contaminants into the environment via WWTPs; this is also a cost-effective option.

The design demands on water and sanitation engineers are rapidly changing. The global population is set to rise from 7 billion to 10 billion by 2083. Urbanisation in developing regions is increasing at such a rate that a predicted 56% of the global population will live in an urban setting by 2025. Compounding these problems, the global water and energy crises are impacting the Global North and South alike. High-rate anaerobic digestion offers a low-cost, low-energy treatment alternative to the energy intensive aerobic technologies used today. Widespread implementation however is hindered by the lack of capacity to engineer high-rate anaerobic digestion for the treatment of complex wastes such as sewage. This thesis utilises the Expanded Granular Sludge Bed bioreactor (EGSB) as a model system in which to study the ecology, physiology and performance of high-rate anaerobic digestion of complex wastes. The impacts of a range of engineered parameters including reactor geometry, wastewater type, operating temperature and organic loading rate are systematically investigated using lab-scale EGSB bioreactors. Next generation sequencing of 16S amplicons is utilised as a means of monitoring microbial ecology. Microbial community physiology is monitored by means of specific methanogenic activity testing and a range of physical and chemical methods are applied to assess reactor performance. Finally, the limit state approach is trialled as a method for testing the EGSB and is proposed as a standard method for biotechnology testing enabling improved process control at full-scale. The arising data is assessed both qualitatively and quantitatively. Lab-scale reactor design is demonstrated to significantly influence the spatial distribution of the underlying ecology and community physiology in lab-scale reactors, a vital finding for both researchers and full-scale plant operators responsible for monitoring EGSB reactors. Recurrent trends in the data indicate that hydrogenotrophic methanogenesis dominates in high-rate anaerobic digestion at both full- and lab-scale when subject to engineered or operational stresses including low-temperature and variable feeding regimes. This is of relevance for those seeking to define new directions in fundamental understanding of syntrophic and competitive relations in methanogenic communities and also to design engineers in determining operating parameters for full-scale digesters. The adoption of the limit state approach enabled identification of biological indicators providing early warning of failure under high-solids loading, a vital insight for those currently working empirically towards the development of new biotechnologies at lab-scale.

The increasing concern about water quality and energy demand promotes the development of innovative and low-cost processes to improve the nutrient uptake and energy efficiency of existing wastewater treatments (WWT). In this context, the inclusion of a microalgae system (MAS) in the flowsheet of a WWT plant represents a sustainable alternative to conventional technologies, as it combines a low-cost nutrient uptake system with the production of biomass suitable for biofuel production. However, at present, the energy required to cultivate and process the algae cells is often too high to justify their use. The adoption of a low energy harvesting system and an efficient energy conversion process are the sine qua non requirements to guarantee the sustainability of the process. In this thesis, current and innovative harvesting technologies for large scale applications have been reviewed to identify the optimal working conditions of each system and their link to the main characteristics of the algae suspension. In particular, the performance of the Ballasted Dissolved Air Flotation (BDAF) system was investigated using different algae and compared to the conventional Dissolved Air Flotation (DAF). BDAF was demonstrably a very viable harvesting method where the use of floating microspheres as ballasting agents allowed significant coagulant savings, reduced the level of energy dissipation within the flotation chamber, and lowered the overall carbon emissions and the process costs. Cont/d.

Prior to the implementation of the European Union Urban Waste Water Treatment Directive (91/271/EEC) in 31 Dec 1998, around a quarter of the sewage sludge produced in the UK was either discharged to surface waters via pipes or disposed from ships at sea. Discontinuing this route together with the quality requirements of the European Waste Water Directive, led to the generation of significant quantities of sewage sludge. It has therefore become required to treat this waste effectively before it can be sent back to the environment. Consequently, this added greater challenges for the environmental agencies, as well as local authorities. The treatment process comprises costly and energy consuming applications including physical, chemical, biological and thermal. In addition to the sewage sludge, the power generation industry produces massive quantities of fly ash from burning coal. In the UK, there is about 5,300,000 tonnes of fly ash that are generated annually, which require to be processed and classified in order to meet the standard requirements before it can be used in the construction applications. The classifying process also involves a series of costly and energy consuming mechanical and physical applications. This research programme has introduced an innovative alternative to the traditional re-use and disposal routes of Raw Sewage Sludge (RSS) and unprocessed fly ash. It has suggested the utilisation of RSS and unprocessed fly ash as raw ingredients for the production of sustainable construction materials. This research programme has therefore examined the performance of cement-based materials containing Raw Sewage Sludge (RSS) as a water replacement and unprocessed fly ash as cement replacement. Mortar and concrete mixes incorporating these materials were tested for their flowability/workability, density, Total Water Absorption (TWA), Ultrasonic Pulse Velocity (UPV), compressive strength, flexural strength, drying shrinkage, sulphate attack and leaching properties. Three series of cement-based materials were studied including mortar mixes with RSS and unprocessed fly ash (Series 1), mortar mixes with RSS and large proportions of unprocessed fly ash (Series 2), and concrete mixes with RSS and unprocessed fly ash (Series 3). The outcomes of the investigation were encouraging in that cement-based materials containing RSS and unprocessed fly ash that were produced demonstrated relatively good engineering, durability and environmental properties in comparison to the control mixes. The inclusion of unprocessed fly ash significantly reduced flowability/workability; however it improved long-term compressive strength for both mixes with RSS and water. The best compressive strength results were recorded when cement was replaced with 10-20% unprocessed fly ash by weight of total binder. The results also showed that sulphate attack resistance improved when fly ash was included. Moreover, safe concentration levels of heavy metals and free ions were detected when leaching test was performed. However, it must be kept in mind that more environmental tests must be performed before any large scale use is undertaken.