The performance of a combined biological aerated filter (BAF) and an ultrafiltration (UF) system for the treatment of real and synthetic greywater, settled sewage, rainwater and borehole water has been assessed at both full-scale (at the Millennium Dome Water Recycling plant) and bench-scale. Irreversible membrane fouling was explained at bench-scale in terms of a simple but novel model whereby a proportion of the membrane area is progressively blocked, in proportion to the square root of the transmembrane pressure. This model provides a link between irreversible fouling and reversible cake filtration theory, as the predicted reduction in effective filtration area leads to increased solids loading on the unblocked area. In addition, the bulk properties (specific cake resistance and compressibility) of the filter cakes formed from biologically-treated real grey water and sewage were found to be indistinguishable. A statistical analysis of the results of longer term irreversible fouling trials at bench- scale led to numerical relationships between fouling rate and process conditions. These relationships facilitated the development of a process optimisation model, with the dual-aim of maximising output and minimising chemical consumption. At full-scale, a statistical technique was developed for calculating the relative fouling propensity of three water sources (real grey water, rainwater and borehole water) that were combined in the feed to a UP membrane. The technique was based on the relative volumes of the three sources and the mean operating trans membrane pressure. In addition, the impact of mechanical reliability on the financial viability of the full- scale plant was investigated. A Net Present Value analysis revealed that the break- even price (BEP) of the recycled water was reduced from £ 1.611m3 to £ 1.40/m 3 through increasing availability from 73.8% to 91.2%, and this can be achieved by investing in a targeted critical spares facility.

No description available.

Autoclaved aerated concrete (AAC) is a lightweight cellular building material. In Spring 2008, an experimental study was conducted at The University of Texas at Austin to evaluate the load-deflection behavior and capacity of six different factory-reinforced AAC lintel groups. The results the test program are used to evaluate the shear design provisions of ACI 523.4R “Guide for Design and Construction with AAC Panels”. / text

No description available.

The purpose of this thesis is to investigate the use of a single reactor to biologically treat wastewater by simultaneously oxidizing ammonia, and reducing nitrate and nitrite. The Environmental Protection Agency (EPA) places strict discharge restrictions on these compounds due to their inherent toxicity to humans, wildlife, and ecosystems. The use of a simultaneous system can assist the conventional wastewater treatment technology that requires separate systems, by creating a system that needs less time and smaller size to reach effluent requirements. To conduct this research, a bench-scale membrane aerated biofilm reactor was built using silicone tubing for aeration. Batch and continuous-flow experiments were conducted to investigate the reactor’s capability to oxidize ammonia using a defined growth media and monitor nitrate production and reduction. Also, wastewater from a local reclamation facility was used to determine the reactor’s ability to nitrify ammonia and denitrify nitrate concentrations within wastewater. The wastewater was taken from different locations within the reclamation facility, and combinations of primary and nitrified effluent were used to monitor ammonia and nitrate concentration changes. The batch experiments showed the greatest changes, and one batch experiment showed a 79% decrease in ammonium concentrations, and followed a first-order kinetics rate constant of -0.0284 hrs-1. The continuous-flow experiments showed much greater fluctuations in results, but one of the experiments showed an ammonia oxidation efficiency of 86%. The wastewater experiments had even greater fluctuations, and the effluent concentrations of ammonia, nitrate and nitrite showed no changes when compared to the influent.

A pilot-scale, two-stage (carbon oxidation stage one, ammonia oxidation stage two) fixed film biological aerated filter (BAF) process was operated on-site at a domestic wastewater treatment plant. Over the study period, hydraulic loadings to the system were varied, generating a range of organic and ammonia loading conditions. Nitrification was monitored along the length of the filters by measuring chemical nitrogen species and activity levels of ammonia oxidizing bacteria (AOB). During the first phase of the study, nitrification performance was characterized during the wintertime and compared with oligonucleotide probing results using an ammonia-oxidizer specific probe. Overall nitrification efficiency for wintertime conditions (average temperature 12.4 ± 0.1°C) was greater than 90 percent when ammonia-N loadings to the second stage were 0.6 kg/m3-day or less. Nitrification efficiency started to deteriorate at loadings beyond this point. Biofilm and liquid samples were collected along the distance of the two columns at high and low ammonia loadings. The degree of activity observed by ammonia oxidizing bacteria in the biofilm corresponded with the disappearance of ammonia and the generation of nitrate as water passed through the columns. During the second phase of the study, the probing methods were investigated and results of two approaches of analysis were compared to chemical nitrogen profiles. It was found that probe signals normalized to mass of total bacterial nucleic acid corresponded better with chemical profiles than using a novel method of standardizing against known nucleic acid mass standards. During both phases of the study, zones of ammonia oxidizing activity progressed along the length of the columns as organic and ammonia loadings to the system increased. The oligonucleotide probe data suggest that this shift in the location of the nitrifier population is due to higher BOD loads to the second stage, which supported higher levels of heterotrophic growth in the second stage of the system. It was concluded that the strongest influence on nitrification performance in this type of BAF system is likely to be competition between heterotrophs and autotrophs. / Master of Science

The use of chemically compatible nano and fine particle colloidal consolidants is a new development within the field of cultural heritage conservation and applied most widely so far to the historic built environment. The ability to introduce a significantly higher quantity of chemically compatible consolidant to a substrate in fewer treatments with the possibility for greater penetration and fewer possible side-effects compared to more established consolidants is a significant advantage. This fundamental scientific study examines the effects of a colloidal calcium hydroxide (nanolime) consolidant on medieval and quarried limestone and autoclaved aerated concrete and the efficacy of a colloidal hydroxyapatite treatment on archaeological human bone. Both calcium hydroxide and hydroxyapatite were synthesised. Characterisation of both compounds was performed by X-ray diffraction spectroscopy and particle morphology was confirmed by electron microscopy. Particle size was determined by laser diffraction and particle tracking analysis techniques, used together to study these particle systems for the first time, and electron microscopy. The location of particles within treated substrates was established by electron and optical microscopy whilst effects on water transport were determined by imbibition experiments and numerical modelling. For the first time a modified sharp front model was applied to [particle-material]-material composites to aid the understanding of water transport in such materials. Mechanical testing was used to identify differences in material strength depending on treatment layer thickness and mercury intrusion porosimetry suggested extent of pore blocking. It was found that non-classical effects occur in the calcium hydroxide system synthesised in this study and that particle stability can be influenced by reagent concentration. For the first time material sorptivity properties, modality and pore size distribution of Lincoln stone and archaeological bone are reported. The application of a nanolime consolidant to autoclaved aerated concrete allowed the nature of the particle transport through a highly complex material to be determined, showing that the particle concentration decreases with increasing penetration depth. Shallow nanolime particle penetration into limestone appeared ineffective on compressive strength. In a novel study the prospects of a hydroxyapatite consolidant treatment for bone were also evaluated, finding the results to be inconclusive in this small study. For all consolidants a small reduction in material water sorptivity after treatment demonstrated the permeable nature of the treatment layer and suggests the avoidance of damage mechanisms due to highly restricted water transport. Knowledge of the efficacy and location of treatment particles and their affect on water movement, particularly in weathered material, within limestones and archaeological bone is important and was determined for all materials used in this study. This work adds to the understanding of such treatments and their capabilities and the nature of the porous materials used herein.

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.

O presente trabalho buscou avaliar uma unidade de BAS (Biofiltro Aerado Submerso), em escala piloto, com volume útil de 66 litros, tratando esgoto doméstico, visando seu controle operacional, a remoção de matéria orgânica e nitrificação. O esgoto afluente passa por pré-tratamento e decantação antes de seguir para o BAS em estudo. A unidade piloto é constituída, basicamente, por um BAS de fluxo ascendente. O meio suporte utilizado é composto por biomídias de sistemas MBBR, as quais apresentam elevadas porosidade (>85%) e área superficial específica (650 m2/m3), além de baixa densidade (0,95 kg/L). Para avaliação do biofiltro em estudo, o trabalho foi divido em quatro fases (I a IV) para avaliação do comportamento do reator em diferentes condições operacionais. Para isso foram efetuadas variações no tempo de detenção hidráulica (I=8h, II=14h, III=10h e IV=6h) e na velocidade de escoamento (I=0,13m/h, II=0,07m/h, III=1,0m/h e IV=1,1m/h) através da recirculação do efluente tratado (I e II sem recirculação, III e IV com recirculação). Com relação à remoção de matéria orgânica, o BAS demonstrou bom desempenho em todas as fases de estudo, resultando em um efluente tratado com concentrações médias de DBO abaixo de 30 mg/L, com uma eficiência de remoção de DBO próxima de 90% ao longo de toda a pesquisa. Em termos de DQO, as concentrações médias ficaram abaixo de 82 mg/L, com uma eficiência de remoção de DQO próxima de 85% ao longo de todas as fases da pesquisa. Já com relação ao processo de nitrificação, na fase II o biofiltro estudado apresentou um efluente com 16 mgN/L de N-NTK e 35 mgN/L de NO3-, demonstrando potencial do processo para as situações em que se exige remoção de matéria orgânica e nitrificação. Nas fases I, III e IV a nitrificação não ocorreu de forma satisfatória. Com relação ao controle operacional do processo de lavagem, o intervalo necessário para a realização do processo de lavagem, de acordo com os processos definidos, foi consideravelmente prolongado, acima de 10 dias, ao longo de todas as fases do estudo, demostrando uma grande capacidade de retenção de sólidos no biofiltro estudado. Com relação à utilização de recirculação nas fases III e IV, esta operação não demonstrou vantagens com relação às fases sem recirculação. Dessa forma, neste trabalho foi possível observar que a qualidade do efluente final e a estabilidade operacional do biofiltro aerado submerso preenchido com biomídias reforçam a condição desta unidade como alternativa viável a ser considerada na concepção de sistemas de tratamento de esgotos sanitários. / The present work sought to evaluate a unit of a BAF (Biological Aerated Filter), in pilot scale, with working volume of 66 liters, treating domestic sewage, aiming its operational control, organic matter removal and nitrification. The affluent sewage is pre-treated and decanted before proceeding to the BAF under study. The pilot unit consists, basically, of an upflow BAF. The media used is composed of biocarriers of MBBR systems, which have high porosity (>85%) and specific surface area (650 m2/m3), besides low density (0,95 kg/L). For evaluation of the biofilter under study, the work was divided in four phases (I to IV) to evaluate the behavior of the reactor in different operating conditions. For this, variations were made in the hydraulic retention time (I=8h, II=14h, III=10h and IV=6h) and at the flow rate (I=0,13m/h, II=0,07m/h, III=1,0m/h and IV=1,1m/h) by recirculating the treated effluent (I and II without recirculation, III and IV with recirculation). Regarding the removal of organic matter, the BAF demonstrated good performance in all study phases, resulting in an effluent treated with avarage concentrations of BOD under 30 mg/L, with an efficiency of removal of BOD near 90% throughout the research. In terms of COD, the average concentrations were below 82 mg/L, with an efficiency of removal of COD near 85% throughout all phases of the research. Regarding the nitrification process, in the phase II the studied biofilter presented an effluent with 16 mgN/L of N-NTK and 35 mgN/L of NO3 -, demonstrating process potential for situations where organic matter removal and nitrification are required. In phases I, III and IV nitrification did not occur satisfactorily. Regarding the operational control of the washing process, the interval required to carry out the washing process, according to the defined processes, was considerably extended, over 10 days, throughout all phases of the study, demonstrating a great solids retention capacity in the biofilter studied. Regarding the use of recirculation in phases III and IV, this operation did not demonstrate advantages in comparison with the phases without recirculation. Thus, in this work, it was possible to observe that the final effluent quality and the operational stability of the biological aerated filter filled with biocarriers reinforce the condition of this unit as a viable alternative to be considered in the design of domestic sewage treatment systems.

This study was undertaken to examine the feasibilty of a low-cost aerobic system to treat greywater for reuse.Its purpose was to provide a system that would be easy to maintain, flexible and be affordable for households and small communities in developing countries. This thesis outlines and evaluates the key biological and chemical hazards associated with greywater reuse. It discusses the performance of a variety of wastewater treatment options in use. It presents details of the components of the greywater system,namely, an aerobic grease trap and slow sand filter. Reference is made to the evaporation and treatment bed and ultraviolet disinfection components, but these are not examined. The incorporation of vermitechnology in the preliminary stages of the system for reduction of organics in greywater is reviewed. This study takes the traditional approach to water quality assessment with the measurement of physical, chemical and biological indicators. Assessment of the system involved examining the input characteristics of the greywater, monitoring the vermiculture system and sampling the liquid discharge from the aerobic grease trap and slow sand filter for analysis of the quality indicators. The results obtained under the framework of this study have provided recommendations for further use of the aerobic grease trap and slow sand filter, while propsing an approach for an appropriate long-term monitoring program. / Master of Engineering (Hons)