Search

Anaerobic membrane bioreactors (AnMBRs) are emerging as a promising technology to offer the prospect to achieve energy neutral sewage treatment. The key challenges limiting full-scale application of AnMBR for municipal wastewater treatment are high operational cost of energy demand for fouling control and high capital cost of membrane investments. This thesis explores a novel pseudo dead-end gas sparging regime for membrane fouling control, enabling a high sustainable flux (15 L m ¯² h¯¹) with low energy demand (0.14 kWh m⁻³ ) in upflow anaerobic sludge blanket (UASB) configured AnMBR, sufficient to achieve energy neutral sewage treatment. However, this strategy is only possible within low solids environment, emphasising the importance of solids management in the UASB reactor. Solids accumulated in the sludge blanket enhances UASB treatment efficiency during the steady-state operation, indicating to control the sludge blanket at a threshold between the sludge blanket development and steady-state period. The granular inoculum has good stability which exerts a positive influence on reactor stability and sustained permeability, whilst the flocculent inoculum enables to deliver similar sustained membrane operation provided the sludge blanket is controlled. Low temperatures (average temperature of 10 °C) cause the instability of UASB reactor especially for the one with flocculent inoculum biomass. It is therefore proposed to keep relatively high upflow velocity (Vup) of 0.8-0.9 m h⁻¹ in the UASB reactor for granular AnMBR to promote the stratification of particular and granular material, whilst reducing Vup to 0.4 m h⁻¹ for flocculent AnMBR to minimise solids washout and sustain membrane operation at low temperatures. The potential for permeability recovery following peak flow (diurnal peaks and storm water flows) has been investigated and evidenced, suggesting that membrane surface area for AnMBR can be specified based on average flow, providing a considerable (67 %) capital cost reduction compared with the design based on peak flows (three times of average flow). Importantly, this thesis promotes UASB configured AnMBR as a highly reliable and more economically viable technology, facilitating to achieve the energy neutral sewage treatment at ambient temperature.

Managed aquifer recharge (MAR) consists of artificially replenishing groundwater to facilitate reuse and/or the associated environmental benefits. Meanwhile, soil aquifer treatment (SAT) is a process of geo-purification designed and operated to improve the quality of the infiltrating water and is thus a type of MAR. SAT consists of a basin operating under rotation of drying and wetting periods. Often, SAT involves water of impaired quality applied onto soil and consequently it implies various risks of health, geochemical and physical nature with difficult or irreversible remediation. To study the effect of pre-treatment on SAT a pilot plant including conventional activated sludge (CAS), a membrane bioreactor (MBR), tertiary and secondary vertical flow reed beds (VFRB) and SAT soil columns. The sludge retention time (SRT) in the CAS and MBR processes was changed every 6 months to look at the impact of SRT on SAT. Each unit and treatment train effluent was characterised to determine the impact of effluent quality on SAT performance. This study showed that tertiary VFRB, especially when fed with MBR effluent, was the best option for SAT and irrigation reuse as it provided the best compliance with reuse standards and the best fertilisation potential. However, long-term clogging occurred in SAT after tertiary VFRB, suggesting the need for a longer resting period or shorter wetting period. This study also highlighted the importance of total suspended solids (TSS) content for SAT removal mechanisms and infiltration rate. In particular, SAT fed with high TSS content effluent was susceptible to temperature variation. Hence the duration of wetting and flooding periods should be adapted according to the season. Further, variation in SRT only indirectly affected pollutants removal by the system including CAS treatment set up at 6 d SRT where the N compounds balance was favourable to an autotrophic N removal.

Abstract: Municipal sewage contains significant embedded resources in the form of chemical and thermal energy. Recent developments in sustainable technology has pushed for the integration of resource recovery from household wastewater to achieve net zero energy consumption and carbon neutral communities. Sewage heat recovery and fit-for-purpose water reuse are options to optimize the resource recovery potential of municipal wastewater. This study presents a comparative life cycle assessment (LCA) focused on global warming potential (GWP), eutrophication potential (EUP), and human health – carcinogenic potential (HHCP) of an integrated sewage heat recovery and water reuse system for a hypothetical community of 30,000 people. Conventional space and water heating components generally demonstrated the highest GWP contribution between the different system components evaluated. Sewage heat recovery-based district heating offered better environmental performance overall. Lower impact contributions were demonstrated by scenarios with membrane bioreactor (MBR)/chlorination prior to water reuse applications compared to scenarios that use more traditional water and wastewater treatment technologies and discharge. The LCA findings show that integrating MBR wastewater treatment and water reuse to a district heating schema could provide additional environmental savings at a community scale.

The scarcity of potable water is becoming a global concern as the quality of drinking water sources faces enormous pressure from anthropogenic pollution. In urban areas, wastewater released form homes, businesses, and industries is collected and treated in municipal wastewater treatment facilities before discharge into streams and lakes, which are drinking water sources. Most wastewater treatment plants use conventional activated sludge (CSA) process during treatment. However, these plants are major point sources of pollution of the environment because of their inability to sufficiently remove nutrients, pathogens, and micro pollutants (pharmaceuticals and personal care products) from wastewater. The purpose of this study was to use MBR technology in combination with MgCO3 pellets column to address some of the challenges faced by CAS treatment plants and to produce an environmentally friendly and recyclable effluent free of particles, pathogen and low in nutrient concentration. The study also aimed at employing the technology to enhance the recovery and removal of P through EBPR and MgCO3 pellets from Municipal wastewater and to reuse it (P recovered) as an alternative for natural P reserve, which is currently under depletion. This technology achieved the following pollutant removal efficiencies: TSS > 99.9%, Fecal coliform > 99.999%, COD = 97.8%, TN = 76.3% and TP = 84.6% .The influence of EBPR was equally remarkable in P release during the experiment, where P concentration in the MgCO3 column's influent was increased, leading to a maximum adsorption capacity of 12.8 mg P/g MgCO3. Although the MBR + Ethanol + MgCO3 couple was effective in municipal wastewater treatment, membrane biofouling remains a barrier that significantly reduced MBR efficiency and smooth operation.

Abstract: The enormous volumes of oil sands process-affected water (OSPW) produced during oil sands bitumen extraction have been a public concern due to the toxicity and persistence of the organic contaminants contained in the water. Among all the contaminants in OSPW, naphthenic acids (NAs) are regarded as the most problematic due to their bio-persistency and acute toxicity to aquatic life. It has been suggested that biodegradation is the most cost-effective approach for OSPW treatment. However, the in situ biodegradation half-lives of NAs in tailings ponds could be as long as 13.6 years, making it necessary to accelerate the biodegradation process through the application of engineered bioreactors. To address this need, two identical anoxic-aerobic membrane bioreactors (MBRs) with a submerged ceramic membrane were continuously operated for 742 days to treat raw and mildly ozonated (utilized ozone dose 30 O3 mg/L) process-affected water. Efforts were made to firstly evaluate their feasibility for OSPW NA degradation and then optimize their treatment performance. A > 300-day system startup/sludge acclimatization phase was performed to gradually acclimatize microorganisms in the MBRs to 100% OSPW environment, revealing the feasibility of the MBR configuration for OSPW treatment. To better understand the contribution of anoxic and nitrifying aerobic compartments to the degradation of OSPW classical NAs and oxidized NAs (oxy-NAs), a batch study was performed on biodegradation of raw and ozonated OSPWs under decoupled anoxic and nitrifying aerobic conditions. The batch study suggested that both anoxic and aerobic conditions could contribute to biodegradation of OSPW NAs though the latter demonstrated much better NA degradation. Once the MBRs were stabilized on around Day 300, a 442-day continuous operating condition optimization phase was conducted. The MBR’s performance on OSPW NA degradation was successfully improved through changing the supplemented inorganic nitrogen composition and hydraulic retention time (HRT). To assess the systems’ classical and oxidized NA degradation performance, ultra performance liquid chromatography coupled with high resolution mass spectrometry (UPLC/HRMS) analysis was performed. Among all the six examined operating conditions, the condition with an NH4-N concentration of 25 mg/L and HRT of 12 h demonstrated the best removal rates of total classical NAs (37.6%) and total oxy-NAs (23.9%) from raw OSPW. Under this particular operating condition, the MBR removed 49.7% of total classical NAs and 35.4% of total oxy-NAs from the ozonated OSPW. The hybridization of low-dose ozone pretreatment and MBR process (HRT = 12 h) degraded 94.0% of classical NAs and 43.9% of total oxy-NAs from the raw OSPW. Impacts of molecular structures of NAs on their biodegradation efficiency were discussed; and possible correlations between certain microorganisms and biodegradation of NAs with particular molecular features were found. Meanwhile, the fouling behaviors of the two MBRs for raw and ozonated OSPW treatment were closely monitored and studied over the whole operation period. By performing mathematical model fitting, it is suggested that cake layer filtration was the dominating mechanism during the long-term slow TMP growth phase. In addition, HRT might be the factor that determined the dominating fouling mechanism during the sharp TMP jump phase. Moreover, the membrane fouling cake layers were examined using techniques including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) and confocal laser scanning microscopy (CLSM). Effects of ozone pretreatment on NA biodegradation, microbial community structure, and membrane fouling development were evaluated. NAs with more alkyl branches, longer carbon chains and higher cyclicity are undoubtedly the most bio-refractory fractions in OSPW. Through preferably degrading those recalcitrant NAs, the mild ozonation pretreatment remarkably enhanced subsequent biological treatment in terms of higher NA degradation rates and lower post-biodegradation residual NAs concentrations. In addition, the ozone pretreatment substantially affected the microbial community structure in the subsequent biological systems by altering the relative abundances of the dominant microbial species and encouraging existence of numerically minor species. Moreover, a prolonged long-term slow TMP growth phase and reduced frequency of TMP jump were observed in the MBR treating ozonated OSPW. To our best knowledge, this is the very first study that combines low-dose ozone pretreatment and MBR process for OSPW treatment. In addition, this project is one of the few studies that extensively investigate the biodegradation of oxy-NAs under various operating conditions throughout the whole system operation. Out of the limited research on MBR fouling mitigation using ozone pretreatment of feed water, this study provides insightful information on how mild ozonation pretreatment impacts the MBR’s feed water quality, microbial community structure, and fouling behavior. The results obtained in this study would be illuminating for future studies on improving biological systems treating OSPW and other industrial wastewaters containing bio-persistent organic contaminants. Industries in Canada, including oil sands exploitation, refinery plants, petrochemical industry, foundry industry, pulp and paper mills, produce large quantities of wastewater containing high recalcitrant organic contents. The knowledge gained in this study could be applied to these industrial scenarios to help improve their effluent water quality, and thus minimizing the impacts on receiving water bodies including rivers, lakes and groundwaters. It is, therefore, anticipated that this study may contribute in the future to the better protection of both environment and public health in Canada.

Membrane bioreactors (MBRs) are increasingly applied to achieve pathogen removal in water recycling schemes. To date, MBRs have been validated in an arbitrary manner, which has led to accreditation varying on a scheme-by-scheme basis and consequently an inequitable treatment of potential health risk. The aim of this thesis is to provide the information required in order to successfully validate a MBR, including: 1) current understanding of the pathogen removal mechanisms, 2) quantitative information on pathogen removal performance and variability, 3) knowledge of how operation and hazardous events influence removal performance and 4) a strategy to assure removal performance continually, through the use of an online monitoring. Surrogate measures for pathogen removal including indicator microorganisms, physiochemical and operational parameters were collected over the course of 18 months during a rigorous sampling campaign of 11 full scale MBRs resulting in a data set with over 250 removal data points for each pathogen group, paired with operating data. Statistical analysis of this data set determined that higher removal was favoured under operation at low range transmembrane pressure, flux and suspended solids concentration and high range pH, temperature, solids retention time and hydraulic retention time. In addition, it was determined that MBRs could consistently achieve 5th percentile log removal values exceeding 1.5, 4.0 and 2.0 for virus, bacteria and protozoa, respectively. High permeate turbidity was shown to correlate with lower removal performance at full scale and a site specific method was proposed and demonstrated at lab scale to calibrate permeate turbidity with removal to allow for continuous monitoring. Hazardous event scenarios, perceived to reduce removal performance, were also investigated. Chemical cleaning was found to have a slightly negative, but recoverable, impact on removal, depending on membrane pore size. Membrane breakage resulted in severely compromised removal, but was recoverable due to activated sludge plugging of defects in the hollow fibre membranes evaluated. Overall, this thesis provided detailed quantitative evidence to support creation of more appropriate and streamlined national validation guidelines for MBRs in Australia and, in doing so, has furthered the knowledge to support health risk management of MBRs internationally.

With the efficacy of antibiotics diminishing, owing to global increase in bacterial resistance, health authorities are becoming increasingly concerned. Strategies for identifying and remediating potential hot spot sites for bacterial antibiotic resistance gene (ARG) transfer have thus come to the fore. One such site is the wastewater treatment plant (WWTP) found in municipalities worldwide. There are typically two types of biological systems; the conventional activated sludge (CAS) reactor and the membrane bioreactor (MBR). In WWTP s, particularly those used in industry, the MBR is slowly replacing the conventional system due to its smaller footprint and cleaner effluent. Both systems have high microbial density, high nutrient content often with low levels of excreted or disposed of antibiotics, ideal conditions for promoting ARG transfer within the reactors bacterial community. The MBR process has a longer bacterial retention time which may be exacerbating the multi-resistance crisis. The published reports of effective removal of bacterial antibiotic resistance by the various treatment plants are conflicting. Some describe effective removal of bacterial antibiotic resistance by WWTP s prior to environmental release, others show otherwise. Currently, the release of effluent and solid waste from the WWTP is not monitored for multi-resistant bacteria. The concern is that ARGs are entering the environment either via treated effluent into the waterways or waste sludge spread onto fields. The aim of this study was to ascertain whether the MBR facilitates higher levels of antibiotic resistance within the bacterial community compared to the CAS reactor, and secondly to determine if lateral gene transfer could proceed in the presence of low (1ngL-1) and background (200ngL-1) antibiotic levels. Samples from two pilot-scale MBR and CAS bioreactors fed synthetic wastewater were subjected to various molecular studies (DGGE, LH-PCR, qPCR) designed to determine the impact of sulfamethoxazole (smx) on bacterial community dynamics. The potential for lateral gene transfer of the sulfonamide resistance genes (sul1, sul2) was determined using PCR, hybridisations and conjugation mating experiments. The study revealed that low smx levels did not lead to smx resistance gene increases in either reactor; however, high levels of ARGs were maintained in the MBR at typical WWTP background smx concentrations as demonstrated by quantitative PCR (qPCR). Potential for lateral gene transfer was verified with the sul resistant genes localised within integrons and plasmids. One particular plasmid, harbouring a sul1 gene within a Class 1 integron, was observed to be highly promiscuous transferring across species. According to denaturing gradient gel electrophoresis (DGGE) analysis, 690 cultured isolates comprised 16 different species types, all of which are reportedly associated with lateral transference of genes. All 16 representative bacterium harbored more than one antibiotic resistance trait, some to at least seven. High levels of cultiviable smx resistant isolates were found in both the CAS and MBR rectors (60 and 70%, respectively). The high levels were most likely due to clonality rather than acquired resistance based on the low diversity shown by SDI diversity plots. This implies that the total number of ARGs within the bioreactor community must be enormous. Based on the results of this study, recommendations have been made for WWTP bioreactor waste sludge to be subjected to a treatment that effectively destroys its microbial DNA content prior to environmental discharge, thus eliminating the release of highly antibiotic resistant gene pools into the environment.

Analysis of Residence Time Distribution (RTD) profiles of a 2000 m3/day hollow fibre (HF) membrane bioreactor located at North Head in Sydney and a 5000 m3/day flat sheet (FS) membrane bioreactor located at Victor Harbour in South Australia indicated that both membrane bioreactors (MBRs), including the respective membrane filtration tanks, are very close to completely stirred tank reactors (CSTR). Using conventional reaction engineering the systems were modelled using Tanks-in-Series approach with the data fitting a 1.12 for the flat sheet and 1.24 for hollow fibre system with corresponding Peclet numbers of 0.36 and 0.68 respectively. A three-dimensional multiphase (water-air) hydrodynamic model was built using Computational Fluid Dynamics (CFD) to assess the effects of the reactor characteristics of each plant on mixing performance. The model was calibrated using the site data collected from the two MBRs. The bio-reactions component of the model was benchmarked against the COST Activated Sludge Model No. 1 Benchmark. Evaluation of the energy consumption indicated that the HF membranes consumed 20% less of the total power demand and required 50% less of the energy required for membrane aeration than the FS membranes to produce the same amount of permeate. The sludge viscosity was found to be negligible in comparison to changes in turbulent viscosity and therefore does not affect the prediction of overall mixing. Macro-scale simulations of the entire MBR include a porous media model to account for the flow behaviour in the membrane filtration vessels. An experimental approach was explored to calibrate the inertial loss factor through the fibres. The pressure drop across the HF membrane bundle against various liquid velocities was measured at the flow direction either perpendicular or parallel to the membrane bundle and at different fluid viscosities. The comparison between the experimentally determined flow resistance values and those obtained from the empirical equations for tube banks indicated that the latter underestimated the flow resistance caused by the fibres (up to 350 times lower). The calibrated correlations were applied to the porous media model. Significant difference on the hydrodynamic descriptions of the membrane filtration zone was observed by coupling the porous media model with the MBR CFD model. The literature on MBR’s is silent on the effects of membrane geometry on mixing and contains no validation of the general assumption used in the design software that the systems are completely mixed. This research demonstrated that CFD could offer a more rigorous approach to modelling that account for system and membrane geometry to predict the hydrodynamics using the fundamental equations of fluid dynamics. It does not require assumptions with regards to the flow behaviour (ideal or non-ideal flow) in reactors to be made and therefore fill the gap in the current state of understanding of this field of knowledge.

Usually, image compression techniques that use only one transform exhibit some poor properties. For instance, the Discrete Cosine Transform (DCT) cannot efficiently represent high frequency components, resulting in blurred images. The Multiple Bases Representation (MBR) compression technique, which uses two or more transforms, is found to be superior to the single transform techniques in terms of representation efficiency. However, some bits in the MBR representation are needed to track the basis information. The MBR image quality is deteriorated by discontinuities at block boundaries, as is the standard DCT transform. In this thesis, test images are distorted by MBR compression using a Recursive Residual Projection algorithm. This algorithm is a sub-optimal method to find the best basis vector subset for representing images based on multiple orthogonal bases. The MBR distorted images are reconstructed by the iterative method of Projection onto Convex Sets (POCS). Many constraints that form convex sets are reviewed and examined. Due to the high distortion at the block boundaries, some constraints are introduced particularly to reduce artifacts at the boundaries. Some constraints add energy to the reconstructed images while others remove energy. Thus, the initial vectors play a key role in the performance of the POCS method for better MBR reconstruction. This thesis also determines the most appropriate initial vector for each constraint. Finally, the composite projections associated with the sign, minimum decreasing and norm-of-slope constraints are used to improve the reconstruction of the MBR distorted images and the effect of ordering of the projections is investigated.