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Facultative aerated lagoons are aerated lagoons operated at low power levels and are wastewater stabilization ponds with artificial aeration. These lagoons are used more commonly than aerobic aerated lagoons because a satisfactory effluent can be produced with a lower power input. The power level applied to facultative aerated lagoons is sufficient only to satisfy the oxygen demand but not adequate to keep all the solids in suspension and settled solids will decompose aerobically and anaerobically. In the study reported, laboratory-model facultative aerated lagoons of 81 litres volume, aerated with diffused air, were used to study the performance of such lagoons in the treatment of municipal wastewater. Different combinations of four power levels, 0.25,0.5,1 and 2.0 W/m3, three different organic loadings, 20,33 and 62 g BOD5/m3d. , and two temperature levels, 20°C and 30°C, were applied in twenty four experimental runs. Influent and effluent were sampled on a regular basis and their characteristics were determined. The effluent from the model facultative aerated lagoons was always of reasonable quality, with respect to BOD5, COD and suspended solids. This was achieved with no provision for effluent settling or additional treatment. Removals of 91 percent BOD5 and 67 percent COD could be achieved for unfiltered samples. Effluent BOD5 of 13 mg/l in the filtered samples and 31 mg/l in the unfiltered samples was attainable in these lagoons. Effluent suspended solids levels as low as 41 mg/i were also obtained. Thus facultative aerated lagoons will provide both biological and physical treatment operations in a single earthen tank. Because suspended solids in the effluent from facultative aerated lagoons are low, no sludge disposal or processing is needed on a continuous basis. Other performance criteria; nitrogen, phosphorus, iii chlorophyll "a", Escherichia. coli and faecal streptococci, are reported on in the thesis. It was observed that the level of power introduced into the facultative aerated lagoon had positive and significant effects on some performance parameters, including BOD5 and COD filtered removal rate coefficients, removal efficiencies for BOD5 and COD (except for COD removal in facultative aerated lagoons operated at high temperature, 30°C) and effluent suspended solids and negative and significant effects for others, such as suspended solids removal efficiency. The effect of power was insignificant for other parameters, especially BOD5 and COD unfiltered removal rate coefficients. The effect of power level on filtered removal efficiencies was higher than on unfiltered ones. BOD5 and COD removal efficiencies were negatively affected by organic loading (or positively by retention time) and the effect was found to be significant. The organic loading effect was significant and positive on filtered BOD5 and both filtered and unfiltered COD removal rate coefficients whereas it was negative on unfiltered BOD5 removal rate coefficients. Temperature had significant and positive effects on some parameters, including removal rate coefficients both filtered BOD5 and COD as well as unfiltered BOD5 and BOD5 and COD removal efficiencies, and insignificant effects on others, such as unfiltered COD removal rate coefficient. The effect of temperature on the removal rate coefficients, except the unfiltered COD removal rate coefficient, was higher at higher organic loadings (shorter retention times) whereas its effect on BOD5 and COD removals efficiencies was higher at lower power levels. The temperature correction coefficient for BOD5 at low power levels was higher than at higher levels of power. iv The effect of power level on the temperature correction coefficient was significant whereas the organic loading (or retention time) effect was insignificant. Relationships between the individual operating parameters and performance parameters are presented in the form of empirical equations and the combined effects of these operating parameters and performance parameters were also modelled. High organic loading (short retention time) in facultative aerated lagoons operated at low power levels proved to remove more organic material per day per unit of power introduced into the lagoon. Therefore, the optimum conditions of organic loading and power level at which a single facultative aerated lagoon used as a sole treatment process for treating settled sewage should be operated are 0.25 W/m3 for power level and 62 g BOD5 /m3. d for organic loading (3 to 4 days retentiom time). The effect of mixing, represented by the parameters in a simulation model, on performance was also modelled in the form of empirical equations. Nitrogen, phosphorus, Escherichia coli and faecal streptococci removals were considerable. Variations of their removal performance as well as algal concentration variations with the operating parameters were also studied and discussed. A mathematical equation was developed for the determination of the mean solids retention time (SRT) in facultative aerated lagoons. The relationship between SRT and power level and organic loading was determined and represented by an empirical equation. A power level of around 0.5 W/m3 was the threshold for settleable solids suspension below which no significant decrease in effluent or mixed liquor suspended solids concentration would take place.

A microwave enhanced advanced oxidation process using hydrogen peroxide (MW/H₂O₂-AOP) was used for the release of nutrients and the destruction of solids from secondary municipal sewage sludge. The significant factors affecting the MW/H₂O₂-AOP that would yield maximum soluble substrates were studied. Using a computer statistical software package for experimental design and data analysis, four factors including microwave heating temperature, heating time, hydrogen peroxide dosage, and sludge solids content, were selected and examined. The initial sludge TS content and hydrogen peroxide dosage were the most significant factors for the solubilization of COD and nutrients release under the experimental conditions selected in this study. Overall, the maximum solubilization of nutrients was obtained at 2.5 % of total solids content, 2% of hydrogen peroxide by weight, 5 min. of microwave heating and 120 ºC. The effects of combination of microwave treatment and oxidative reagents on solids destruction and nutrients release were also investigated. Microwave enhanced advanced oxidation processes (MW-AOP), such as MW/O₃, MW/H₂O₂ and MW/H₂O₂/O₃, were conducted at 100 °C. In terms of nutrients release and solids reduction, the MW/H₂O₂/O₃-AOP yielded the best result. Subsequently, three factors including microwave heating temperature, hydrogen peroxide dosage, and ozone dosage, were investigated. The best result, in terms of the release of phosphate and ammonia, and solids reduction, was obtained with additions of 2 % hydrogen peroxide by weight and ozone dosage of 5.09 mg/ml, and operating at 120ºC. About 95%, 32% and 78% of TP, TKN and COD were released into the solution, respectively. The microwave enhanced advanced oxidation processes, with and without an addition of ferrous sulfate (MW/H₂O₂-AOP and MW/H₂O₂/Fe+²-AOP), were also studied for reducing solids, and solubilizing nutrients from the secondary sewage sludge. For the MW/H₂O₂/Fe+²-AOP, the best results of solubilization, in terms of orthophosphate, ammonia and soluble chemical oxygen demand, were obtained at treatment temperatures of 40 ºC, the yields decreased as the temperature was increased. The highest yields of solubilization were obtained at 60 ºC for orthophosphate, and at 80 ºC for both ammonia and soluble chemical oxygen demand.

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>Magister Scientiae - MSc / Over the last decade polysulfone membranes have been demonstrated to be one of the best membrane types in wastewater treatment, especially in ultrafiltration, owing to its mechanical robustness, structural and chemical stability. Regrettably these membranes are mostly hydrophobic by nature and therefore highly vulnerable to fouling due to chemosorptive mechanisms. Fouling may be caused by cake formation on the surface of the membrane or by surface assimilation of the foulants. Many studies have been directed at improving hydrophilic properties of polysulfone membranes by introducing different types of nanoparticle composite such as TiO2, ZnO2, Au and Ag nanoparticles to the polymer matrix, in order to reduce fouling potential and increase membrane performance. In the present investigation a hydrogel material was developed by crosslinking polyvinyl alcohol (PVA) with polysulfone (PSF), using glutaraldehyde as crosslinker. PVA has excellent film formation, emulsifying and adhesive properties, it is highly flexible and has high tensile strength. Introducing PVA into the PSF polymer matrix was expected to impart its advantageous properties onto the resulting membrane and enhance hydrophilic characteristics of the membrane. The cross linking of PVA and PSF was controlled at three different ratios to evaluate the effect of the PSF contribution i.e. 25:75, 50:50 and 75:25. The crosslinked polymer composites produced three unique hydrogel materials, which were evaluated for the separation of selected small organic molecules, under hydrodynamic conditions, using rotating disk electrochemistry. The hydrogel thin film behaved as a chemical sensor for the oxidation of tannic acid in aqueous solution, with negligible shift in peak potential as a function of concentration. The nanomaterials prepared were characterised using spectroscopic, morphological and electrochemical techniques. Hydrogel performance in the presence of analyte molecule was evaluated by hydrodynamic voltammetry and electrochemical impedance spectroscopy. From calibration curves based on cyclic voltammetry, hydrodynamic, macroscopic and spectroscopic techniques, the 75% polysulfone and 25 % polyvinyl alcohol hydrogel (75:25 PSF-PVA) presented the best performance for quantitative detection and best sensitivity toward alginic acid and tannic acid than the corresponding composites (50:50 and 25:75 PSF-PVA). Optical results (contact angle) show an agreement with spectroscopic (EC) and microscopic (AFM) result. A decrease in contact angle gives an increase in roughness and diffusion coefficient. High surface roughness was linked to improved hydrophilicity of the polysulfone.

In many biological reactors' bicarbonate ions are the major species determining pH buffering capacity, or alkalinity. In anaerobic digesters the bicarbonate levels should be within 10 to 50mM to ensure stable operation. Bicarbonate concentration in wastewater treatment processes is routinely measured off-line by titration with standard acid to a set pH value. However along with the bicarbonate/carbonate system, the phosphate, ammonia, sulphides and volatile fatty acids systems are present in anaerobic process. These systems can exert a significant influence on the accuracy of bicarbonate titration's to a set pH. An overload of 4.7 to 13.6 kgCODm-3d-1 1 administered to a 5m3 pilot scale anaerobic filter reactor showed that bicarbonate alkalinity, measured off-line by titration responded rapidly to the organic overload, decreasing by 10% after only 1 hour of the overload initiation. The propionic acid concentration (often regarded as the best indicator of instability in anaerobic digestion) increased from 170ppm to 190 ppm in the same period, which corresponds to an increase of 12%. At present the use of anaerobic digestion as a waste treatment method is partly limited because of the lack of reliable control procedures. This thesis introduces a simple on-line instrument for direct determination of bicarbonate concentration especially for automatic control of anaerobic digesters. The proposed method is based on a continuous flow rate measurement of carbon dioxide evolved from a continuous stream of sampled (<15cm3min-1 ) solution after saturation with gaseous C02 and subsequent acidification with excess acid. Measurement of bicarbonate in this way eliminates the interferences of the phosphate, ammonia, sulphides and volatile fatty acids systems and removes the need for a pH probe which are subject to fouling.

Wastewater reuse, reclamation and recycling may provide beneficial strategies to manage limited water resources. However, insufficient treatment of municipal wastewater poses potential risk to environmental and public health regarding incidences of viral pathogens. The reduction of pathogenic microorganisms is essential to minimize human health risk associated with the reuse of wastewater. The United States Environmental Protection Agency is reviewing the use of coliphages as a potential indicator organism of fecal contamination in recreational waters. Coliphages are viruses than infect enteric coliform bacteria, and are consistently present in domestic wastewaters. They are similar in size and shape to human enteric viruses, and are more resistant to removal by disinfection than enteric bacteria. As such, they have long been proposed as indicators of fecal pollution. However, traditional bacterial indicators (i.e. Escherichia coli) are not reliable indicators for viral pathogens. Monitoring viral pathogens and utilizing the most sufficient wastewater treatment technologies are necessary to minimize public health risk associated with exposure. It is therefore of interest to better understand the removal of coliphages by sewage treatment processes.

This research has primarily been concerned with the study of the kinetics, design and operation of completely mixed aerated lagoons. Throughout the experimental research laboratory-size completely mixed aerated lagoons, composite synthetic substrate and mixed biological culture were used.

A microwave enhanced advanced oxidation process using hydrogen peroxide (MW/H₂O₂-AOP) was used for the release of nutrients and the destruction of solids from secondary municipal sewage sludge. The significant factors affecting the MW/H₂O₂-AOP that would yield maximum soluble substrates were studied. Using a computer statistical software package for experimental design and data analysis, four factors including microwave heating temperature, heating time, hydrogen peroxide dosage, and sludge solids content, were selected and examined. The initial sludge TS content and hydrogen peroxide dosage were the most significant factors for the solubilization of COD and nutrients release under the experimental conditions selected in this study. Overall, the maximum solubilization of nutrients was obtained at 2.5 % of total solids content, 2% of hydrogen peroxide by weight, 5 min. of microwave heating and 120 ºC. The effects of combination of microwave treatment and oxidative reagents on solids destruction and nutrients release were also investigated. Microwave enhanced advanced oxidation processes (MW-AOP), such as MW/O₃, MW/H₂O₂ and MW/H₂O₂/O₃, were conducted at 100 °C. In terms of nutrients release and solids reduction, the MW/H₂O₂/O₃-AOP yielded the best result. Subsequently, three factors including microwave heating temperature, hydrogen peroxide dosage, and ozone dosage, were investigated. The best result, in terms of the release of phosphate and ammonia, and solids reduction, was obtained with additions of 2 % hydrogen peroxide by weight and ozone dosage of 5.09 mg/ml, and operating at 120ºC. About 95%, 32% and 78% of TP, TKN and COD were released into the solution, respectively. The microwave enhanced advanced oxidation processes, with and without an addition of ferrous sulfate (MW/H₂O₂-AOP and MW/H₂O₂/Fe+²-AOP), were also studied for reducing solids, and solubilizing nutrients from the secondary sewage sludge. For the MW/H₂O₂/Fe+²-AOP, the best results of solubilization, in terms of orthophosphate, ammonia and soluble chemical oxygen demand, were obtained at treatment temperatures of 40 ºC, the yields decreased as the temperature was increased. The highest yields of solubilization were obtained at 60 ºC for orthophosphate, and at 80 ºC for both ammonia and soluble chemical oxygen demand. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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