Nitrogen pollution is an increasingly important global concern because it has multiple impacts on terrestrial, aquatic and atmospheric environments. Nitrogen is usually present in wastewater as ammonium. Ammonium can be removed from wastewater by a variety of physicochemical and biological processes, but biological processes are preferred because they are usually more efficient and environmentally friendly. Conventional biological nitrogen removal is carried out by autotrophic nitrification and heterotrophic denitrification via nitrate, which use biodegradable organic matter as electron donor. However there are some kinds of wastewater with low concentrations of biodegradable organic matter such as landfill leachate and anaerobic digester supernatant. In these cases an external organic carbon source is necessary in order to obtain a complete denitrification, which implies higher economic cost. Partial nitrification- Anammox process as a promising and novel biological technology of removing nitrogen from high-strength ammonium wastewater with a low C/N ratio has attracted increasing attention due to its higher efficiency and cost-effectiveness compared with the conventional nitrification-denitrification nitrogen removal process. However, many challenges were faced during the development of stable and high-efficiency partial nitrification-Anammox performance, such as NOB activity, the effort to save energy, strict conditions and influent with favourable composition for Anammox. In order to improve the efficiency of Partial nitrification- Anammox process as much as possible whereas using the least energy, the microbubble generation system was firstly applied into the partial nitrification-Anammox process. The steady microbubble cloud produced by fluidic oscillator was verified size ranging from 60 μm to 600 μm which provides higher mass transfer rates and gas hold-up in gas-liquid phase bioreactor due to the fact that the microbubble was characterized by higher surface area to volume ratio and slower rising velocity. The simulation of the inner motion of the airlift loop reactor with COMSOL offered a visual difference between microbubble aeration and fine bubble aeration. In the partial nitrification process dissolved oxygen is a key factor for the growth of ammonia oxidizing bacteria (AOB). Two contrasting experiments in sequencing batch airlift loop reactors (SBAB) with and without fluidic oscillator were conducted over 200 days to investigate the effect of microbubble aeration system on the long term partial nitrification process. The results showed the microbubble aeration system can significantly enhance the activity of AOB to speed up the biological treatment with fewer oxygen requirements and effectively prevent the production of nitrate. The performance of the partial nitrification in an airlift loop bioreactor with fluidic oscillator was greatly improved in terms of treatment capacity and stability compared to the one without fluidic oscillator. Thereafter different operational parameters such as temperature and pH were examined to optimize the operational strategies for the partial nitrification process. The microbial communities that catalyse partial nitrification were analysed by molecular biotechnology. The morphology of bacteria at different growth stages was observed by SEM and TEM. Real-time PCR was used to quantify populations of ammonia-oxidizing bacteria and nitrite oxidizing bacteria. For the Anammox process, a strict anaerobic condition is required to operate successfully. As we all know, the stack gas is usually consists of depleted oxygen but mostly nitrogen (typically more than two-thirds) derived from the combustion, carbon dioxide (CO2), and water vapour, among which CO2 is considered as a greenhouse gas contributing to global warming. Bubbling the synthetic power station stack gas into the Anammox reactor by means of the microbubble generation system not only obtain this circumstance but also provide the heat required by good activity of anammox bacteria. In addition to maintaining desirable conditions, the dissolved CO2 can provide a carbon source for the growth of anammox bacteria and adjust the value of pH in the reactor which is able to save substantial operational cost caused by pH control. Two contrasting experiments in round sequencing batch gas lift loop bioreactors (SBGB) with and without fluidic oscillator were carried out nearly 100 days. The performance of Anammox process in the SBGB with fluidic oscillator was noticeably improved comparing to the one without fluidic oscillator. The size distribution of granular Anammox sludge was analysed by ImageJ to investigate the effect of microbubble on the granulation. The batch assays were conducted to measure the maximum specific Anammox activity in different gas lift loop bioreactors. The morphology of Anammox bacteria at different growth stages was observed by SEM and TEM. Real-time PCR was used to quantify populations of Anammox bacteria in different stage and different bioreactors. The kinetic model for laboratory-scale partial nitrification and Anammox (anaerobic ammonium oxidation) process with sequencing batch gas lift loop bioreactors (SBGB) with and without fluidic oscillator were investigated. According to Monod model and Stover-Kincannon model the kinetic parameters of the model including maximum specific rates and half-maximum rate concentrations for partial nitrification and Anammox were estimated respectively from the results obtained from a laboratory-scale SBGB fed with synthetic wastewater.

Phosphorus occurs in natural water and wastewater mainly as orthophosphates and polyphosphates. The major sources of phosphorus arising in municipal wastewater originate from both domestic and industrial waste flows. Approximately 50 to 70% of the phosphorus in domestic wastewater comes from human wastes and the remaining 30 to 50% comes from synthetic detergents containing phosphate components that are utilised for washing clothes. The fertiliser industry and commercial laundry systems comprise the bulk of industrial sources of phosphorus. The presence of excess phosphorus in the effluent discharged to natural waters has long been viewed as the cause of algae blooms and eutrophication. The average molar ratio of nitrogen, phosphorus and carbon in algae protoplasm is approximately 15:1:105, and therefore represents an optimum nutrient requirement ratio. The constituent that is present in the lowest concentration, taking into account this ratio requirement, will effectively limit algal growth. It can be deduced, therefore, that a minimal amount of phosphorus can still support substantial algae growth and its removal is more effective than nitrogen removal for preventing eutrophication in surface water. To this end, feasible methods for the removal and recovery of phosphorus from wastewater need to be studied. This study aimed to investigate the feasibility of using liquid-liquid extraction and enhanced coagulation methods to remove and recover phosphates from wastewater and water resources. The results revealed that to achieve the maximum phosphates removal by a liquid-liquid extraction method, the best extractant was a mixture of kerosene and benzyldimethylamine at a volume ratio of 2:1. The optimum volume ratio of the extractant and wastewater sample is 1:1, while the optimum extraction period was 6 hours with a shaking speed of 250 rpm. A phosphate extraction efficiency of greater than 80% was achieved across the three categories of water samples tested; a model water, lake water in the UNIS campus and real wastewater. A high stripping efficiency of greater than 90% was achieved from stripping the extractant used in treating each of the wastewater samples, using 6M sulphuric acid at a volume ratio of 1:1 with an agitation speed of 250 rpm. It was possible to re-use the resulting extractant from the stripping process nine times, when the overall phosphate removal efficiency was maintained by mixing the recycled to fresh extractant (kerosene and benzyldimethylamine at a volume ratio of 2:1) at volume ratios of 4:1 and 2:1 for the lake water and wastewater samples respectively. Aluminium sulphate, aluminium chloride and anhydrous iron chloride were used as chemical coagulants in the enhanced coagulation study. The doses applied for the two aluminium salts used were 4, 8, 12, 16 and 20 mg/L as while that of anhydrous iron chloride was 8, 16, 24, 32, and 40 mg/L as Fe3+. Turbidity removal efficiency of >80% was achieved when aluminium salts were used. The iron salt produced an efficiency of >80% for the sample pH 6 and 8. In addition, the removal efficiency increased with increase in the coagulant dose for all the coagulant salts used. The phosphates removal efficiency increased with increase in the coagulant dose and showed dependency on the pH of the wastewater samples. The major drawback of coagulation/precipitation is the excess sludge production in the process. This research revealed that a liquid-liquid extraction method is superior in respect of phosphate removal and recovery and has potential for use as an alternative method for industrial applications.

Dilute metallic ion treatment (< 10 mg/L) remains a challenge in water purification and resource recovery. A novel and inexpensive treatment process that employs polymer-surfactant aggregates (PSAs) has been developed and applied to remove and recover dilute metallic ions, such as Cr3+, Rh3+, Cd2+, Fe(CN)6 3- and CrO42-, from industrial process and effluent. At the heart of this process is a material that comprises a colloidal structure of polymers and surfactants, named a polymer-surfactant aggregate (PSA), that trap metallic ions. The ion loaded PSAs then coalesce and settle out. The flocs are then treated separately by acid-base wash to recover the ions in a concentrated salt and regenerate the polymer and surfactant. The regenerated polymer and surfactant can then be recycled without a deterioration of removal ability in the next cycle. This process is simple, uses low energy, and generates little material loss or discharge. The thesis is divided into three main parts: fundamentals, cation treatment and anion treatment. First, the mechanism of formation of PSAs and their interactions with metallic ions are investigated using surface tension and electrical conductivity measurements. Both measurements reveal that the PSA is formed by surfactant monomers binding to the oppositely charged polymer chains and forming micelle-like aggregates via hydrophobic and electrostatic forces. These aggregates, like micelles, can bind to the oppositely charged metallic ions, but the surfactant concentration required is a few orders of magnitude lower than that required for micelle formation. The resulting nano-size PSA has a large surface area to volume ratio, and can effectively treat dilute aqueous streams. Each PSA consists of positive and negative charges. Within a near charge neutralisation range, they can quickly self-flocculate to simultaneously remove metallic ions and settle the flocs out of aqueous solutions. Correlating the removal efficiency of ions with surface tension and electrical conductivity measurements, the results suggest that the PSA is indeed responsible for removing the ions from the streams. Based on the fundamentals, a PSA process consisting of three stages (removal, recovery and recycle) is developed to treat metal cations in dilute streams. At the removal stage, polymer and surfactant (i.e. removal agent) are used to form PSAs and trap 99% of 0.1 mM metal ions into flocs. At the recovery stage, a small amount of acid solution is added to leach out 95% of the trapped metal ions into a concentrated salt, and then using a base solution to completely dissolve and regenerate the removal agent. After that, the removal agent are recycled in the next cycle without the need for any make-up, and little deterioration of removal ability is found. The same three-stage process is also applied to recover dilute metallic anions. As the targeted ions are negatively charged, the charge of polymer and surfactant used and the order of acid-base wash are reversed as compared with the cation treatment process. The PSA process is robust under different conditions, e.g. pH, temperature, salinity and organic contaminants. Such a sustainable process thus has potential applications for the efficient removal and recovery of dilute metallic ions during process effluent water treatment.

No description available.

This thesis investigated the influence of septic tanks (ST) on stream water quality. Characterisation of septic tank effluent (STE) revealed that STE were enriched in phosphorus (P), nitrogen (N), organic matter (OM) and metals relative to stream waters and large proportions of these parameters were present in the soluble reactive forms. Human factors such as tank design, number of users, dishwasher use and infrequent desludging significantly (P < 0.05) influenced effluent quality. ST that received roof runoff had reduced effluent retention time, while infrequent desludging was linked to increased OM, bacteria and P concentration in the effluent. Tanks that served larger numbers of people had elevated microbial abundance, P and N concentrations. Effluent composition was not consistent throughout the year, but exhibited similarity in warmer drier months that was different from effluent in colder wetter months for biological oxygen demand and heavy metals. Effluent attenuation in a test soil revealed that 14%-35% of P was attenuated by sorption processes, while saccharin was strongly attenuated by soil microbial degradation. The complex composition of STE reduced the ability of the test soil to adsorb P, as other substances in the effluent were competing for soil binding sites. Calculated P annual loadings from STE were 0.797 and 0.956 kgP/person/year for water usage of 150 and 180 l/person/day, respectively, while, effluents P load from detergents was 0.154 kg P/person/year. Newly developed tracing studies showed that ratios of chloride to other effluent indicators (e.g. EC, NH4-N, TSS, turbidity, total coliforms, sucralose, saccharin and Zn) and the detection of effluent tryptophan-like peak by fluorescence spectroscopy may be useful in tracking effluent discharge to streams with low levels of dilution. However, effluent caffeine and saccharin were more effective tracers in streams with low and high levels of dilutions. A single individual tracer alone was not sufficient to evaluate STE contamination sources, but combined chemical and physical tracing approaches show promise as tools to identify STE inputs that continue to pose risks to watercourses and where mitigation measures could be effectively targeted.

No description available.

In this study the microbiological aspects of constructed wetlands were investigated during treatment of industrial effluents, using experimental reed beds in the UK, and also during the installation of reed beds for a commercial company in Ghana. The results showed that the microbiology of a reed bed is affected by the type and concentration of effluent that it is used to treat. Observational study, effluent treatment analysis and microbiological investigation of reed bed substrate, under various loading conditions, revealed that there may be an effect exerted by certain fractions of industrial waste streams that were detrimental to reed flora and the microbiological fauna of the reed beds. Inhibition of the microbial community of the reed bed substrate occurred in the reed beds treating factory effluent which were found to have had a significantly reduced microbial community in terms of colony forming units when compared to the reed beds treating domestic effluent. Treatment efficiency for biological oxygen demand ranged from 48-93%. In the UK, treatment of landfill leachate and tannery effluent showed that reed beds are effective in reducing effluent parameters such as chemical oxygen demand and total nitrogen. Treatment performance for landfill leachate showed total nitrogen reduction ranging from 37-97%. Chemical oxygen demand treatment efficiency ranged from 28-95%. Treatment performance in terms of total nitrogen reduction in tanner effluent ranged from 66-99%, and for chemical oxygen demand 53-87%.

This study evaluated the potential for efficient treatment of domestic wastewater, while satisfying energy efficiency requirements. Various treatment systems and the influences of their physical configurations and operational characteristics on wastewater treatment and energy efficiency were initially considered and evaluated. Review of literature identified high rate anaerobic systems as viable low energy systems for domestic wastewater treatment, with reported high removal of influent chemical oxygen demand (COD) and high net energy balance for the anaerobic baffled reactor (ABR). Low energy recovery is reported in literature as a limitation of anaerobic domestic wastewater treatment, and anaerobic domestic wastewater treatment systems have failed to meet effluent discharge standards, and post-treatment using aerobic processes have been recommended in order to ensure high effluent quality. Therefore, the ABR was selected as a feasible option that can be developed as the first stage of an anaerobic-aerobic low energy domestic wastewater treatment system. The literature review also identified the net energy consumption per cubic metre (m3) of treated wastewater during the treatment process as an energy efficiency evaluation criterion. Energy efficiency for domestic wastewater treatment facilities should be achieved if efficient treatment performance can be sustained at ambient temperature, instead of the fixed mesophilic temperature that is commonly adopted in anaerobic treatment processes. To identify an energy efficient design of the ABR in terms of hydraulic retention time and operational temperature, the performance efficiencies of ABR bench models were monitored at ambient temperature and 37oC at hydraulic retention times (HRT) of 48, 36, 24, 12 and 6 hours, which corresponded to organic loading rates (OLR) of 1.25, 1.67, 2.5, 5.0 and 10.0 kg COD/m3 day. 88.43, 90.00, 84.03, 77.01 and 59.35% of the influent COD (mean = 2479.50 mg/L) were removed at 48, 36, 24, 12 and 6 hour HRTs, respectively, in the 37oC bench reactor, while 70.16, 70.36 and 74.99% of the influent COD were removed at 48, 36 and 24 hour HRTs, respectively, in the ambient temperature bench reactor. Steady state performance, in the form of stable pH values, was not observed in the ambient temperature reactor at 12 hours HRT before the end of the bench experiments. Retention of influent total solids was observed to correlate to hydraulic retention time, with increase retention of total solids corresponding to increase in hydraulic retention time. Furthermore, observed total solids retention in the ambient temperature reactor were less than the total solids retention in the 37oC reactor. Anaerobic reduction of domestic wastewater sludge and the corresponding methane production were also evaluated using bio-chemical methane potential (BMP) batch assays at ambient temperature and compared to a fixed mesophilic temperature of 37oC. Low reduction of volatile solids was observed in the BMP assays, with 40% at ambient temperature compared to 56% at 37oC for primary sludge, and 22% at ambient temperature compared to 38% at 37oC for secondary sludge. Critical limitations of the anaerobic stage at ambient temperature were determined to be the biological reduction and conversion of the organic contaminants to soluble COD and volatile fatty acids (VFA). Also, achieving and maintaining steady state performance required a longer time period at ambient temperature than at 37oC, potentially due to the slow growth of the anaerobic microorganisms at ambient temperature. These limitations indicate the need for long (≥ 24 hours) retention periods for efficient operation at ambient temperature. The ABR bench models were evaluated for energy efficiency with the identified energy efficiency criteria, and the operational condition with the highest energy efficiency was determined to be 12 hours HRT at 37oC. Finally, design criteria for the anaerobic stage of the anaerobic-aerobic system were proproposed, along with a process model as a preliminary step for future process research.

The treatment of municipal and industrial wastewaters in conventional wastewater treatment plants (WWTPs) requires a significant amount of energy in order to meet ever more stringent discharge regulations. However, the wastewater treatment industry is undergoing a paradigm shift from a focus on waste-stream treatment and contaminant removal to a proactive interest in energy and resource recovery facilities, driven by both economic and environmental incentives. The main objective of this thesis is the development of a decision-making tool in order to identify improvement opportunities in existing WWTPs and to develop new concepts of sustainable wastewater treatment/recovery facilities. The first part of the thesis presents the application of a model-based methodology based on systematic optimisation for improved understanding of the tight interplay between effluent quality, energy use, and fugitive emissions in existing WWTPs. Plant-wide models are developed and calibrated in an objective to predict the performance of two conventional activated sludge plants owned and operated by Sydney Water, Australia. In the first plant, a simulation-based approach is applied to quantify the effect of key operating variables on the effluent quality, energy use, and fugitive emissions. The results show potential for reduced consumption of energy (up to 10-20%) through operational changes only, without compromising effluent quality. It is also found that nitrate (and hence total nitrogen) discharge could be signficantly reduced from its current level with a small increase in energy consumption. These results are also compared to an upgraded plant with reverse osmosis in terms of energy consumption and greenhouse gas emissions. In the second plant, a systematic model-based optimisation approach is applied to investigate the effect of key discharge constraints on the net power consumption. The results show a potential for reduction of energy (20-25%), without compromising the current effluent quality. The nitrate discharge could be reduced from its current level to less than 15 mg/L with no increase in net power consumption and could be further reduced to < 5 mg/L subject to a 18% increase in net power consumption upon the addition of an external carbon source. This improved understanding of the relationship between nutrient removal and energy use for these two plants will feed into discussions with environmental regulators regarding nutrient discharge licensing. The second part of the thesis deals with the application of a systematic, model-based methodology for the development of wastewater treatment/resource recovery systems that are both economically and environmentally sustainable. With the array of available treatment and recovery options growing steadily, a superstructure modeling approach based on rigorous mathematical optimisation provides a natural approach for tackling these problems. The development of reliable, yet simple, performance and cost models is a key issue with this approach in order to allow for a reliable solution based on global optimisation. it is argued that commercial wastewater simulators can be used to derive such models. The superstructure modeling framework is also able to account for wastewater and sludge treatment in an integrated system and to incorporate LCA with multi-objective optimisation to identify the inherent trade-off between multiple economic and environmental objectives. This approach is illustrated with two case studies of resource recovery from industrial and municipal wastewaters. The results establish that the proposed methodology is computationally tractable, thereby supporting its application as a decision support system for selection of promising wastewater treatment/resource recovery systems whose development is worth pursuing. Our analysis also suggests that accounting for LCA considerations early on in the design process may lead to dramatic changes in the configuration of future wastewater treatment/recovery facilities.

There has been increasing concern about the widespread occurrence of emerging organic contaminants (EOCs) in the aquatic environment which could pose potential risks to humans and ecosystems. Wastewater treatment plants (WWTPs) are significant sources and major routes of EOCs entering the environment. There is therefore a need to study the fate of EOCs in WWTPs to improve the risk assessment for these EOCs. In this thesis, the passive sampling technique of diffusive gradients in thin-films (DGT) for in situ measurement of selected EOCs in water was developed in the laboratory and validated under the real world condition-a WWTP. This sampler was then employed to study the occurrence and removal efficiencies of EOCs in Chinese WWTPs, as China represents a significant and growing market for many of these chemicals. A novel DGT technique was developed for in situ measurement of EOCs in water, with hydrophilic-lipophilic-balanced (HLB) resin as the binding agent and agarose gel as the diffusion layer. The performance of DGT sampler (indicated by ratio of DGT-measured concentrations (CDGT) to the directly-measured concentration (Cb), the ratio of CDGT/Cb ranged from 0.9 to 1.1 indicating the excellent performance of DGT) in different pH, ionic strength and dissolved organic matter contents was tested with 11 chemicals and found to be relatively independent of pH (3.5-9.5), ionic strength (0.001-0.1 M) and dissolved organic matter (0-20 mg L-1). Time and diffusion layer thickness dependence experiments confirmed the principle of DGT for accumulated chemicals consistent with theoretical predictions. The performance comparison of three types of resins (HLB, XAD18 and Strata-XL-A) was undertaken. Resin properties and the interactions of functional groups between the resin and chemicals controlling the uptake of EOCs for DGT sampler were evaluated by comparing the uptake capacities and the kinetics of the test chemicals among three resins. The study in the laboratory, which is similar to above section for three types of DGT devices with HLB, XAD18 and Strata-XL-A resins as the binding gels, confirmed the potential application of DGT principle for in situ measurement of EOCs in water. This DGT sampler was then compared with active sampling approaches, auto-sampling and grab-sampling in a WWTP. This study showed that the DGT sampler can continuously uptake the majority of detected EOCs in wastewater for 7-18 days. The time-weighted average concentrations measured by DGT were found to be comparable with the results delivered from the auto-samplers, showing similar concentrations and patterns. The effect of diffusive boundary layer was estimated, and was found to be relatively limited and much less compared with other passive samplers, demonstrating the advantage of DGT sampler. The field validation confirmed applicability of DGT sampler for studying the fate of EOCs in the wastewater. Before application of the DGT sampler into a large scale of fate study in Chinese WWTP, a sensitive analytical method was developed for simultaneous determination of target EOCs in surface water and wastewater. This method was optimised from solid-phase extraction (SPE) procedures to liquid chromatography-mass spectrometer (LC-MS) analysis, and was demonstrated to provide reliable data for the samples with complex matrix and low enough detection limits for EOCs in the water. This analytical method could perform similarly or even better to some related studies for detection of the EOCs in wastewater. DGT devices with HLB resin gels were then applied to 10 WWTPs in China for studying the occurrence and removal of EOCs. All target EOCs could be found in the raw influent and majority of them (18 of 20) could still be detected in the final effluent. Removal efficiency of the EOCs varied, showing the performance of different treatment technology/processes on the EOCs removal in wastewater. The primary and secondary treatment units contributed to the most removal of the EOCs. This demonstrated that DGT sampler can be an effective and simple tool to study in fate of EOCs in wastewater. This research programme has shown that DGT sampler is an effective tool for studying the fate of wide range of emerging organic chemicals in the aquatic environment and assessing their risk/ toxicity of EOCs to the human and ecosystem.