Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / Globally, water is considered an essential resource as it sustains human, animal and plant life. Water is not only essential for all forms of life but imperative for economic growth. The world’s population is increasing at a disquieting rate, which will result in an increased demand for fresh water and food security. The agricultural industry is the main consumer of global freshwater and utilises fertilisers in order to meet food demands. The demand for water in South Africa (SA) has increased considerably due to the rapid expansion of the agricultural industry, and of the municipal and industrial sectors. Agricultural developments in SA are affected greatly as the country is facing a current drought crisis as a result of low rainfall and large water demands. With an abundance of saline water globally, desalinisation will be a major contributor to solving the global freshwater crisis. With limited fresh water resources accompanied by the agricultural industry as a major consumer, alternative measures are required to desalinate water specifically for agricultural use. Forward osmosis (FO) is a membrane technology that gained interest over the past decade because it has several advantages over pressure-driven membrane processes such as reverse osmosis (RO). FO technology is based on the natural osmotic process which is driven by a concentration gradient between two solutions separated by a semi-permeable membrane. Naturally, water will permeate through the membrane from a solution of low solute concentration or low osmotic pressure (OP) known as a feed solution (FS) to a solution of a higher concentration or higher OP also known as a draw solution (DS). Whilst various research studies have contributed to several advances in FO, several process limitations such as reverse solute flux (RSF), concentration polarisation (CP) and membrane fouling remain problematic, hindering FO for large-scale applications. Further investigation is therefore warranted and crucial in order to understand how to mitigate these limitations to develop/improve future processes. The aim of this study was to evaluate a fertiliser-drawn forward osmosis (FDFO) system by investigating the effects of membrane orientation, system flow rate, DS concentration, and membrane fouling on an FDFO systems performance and energy consumption. The FS used was synthetic brackish water with a sodium chloride (NaCl) content of 5 g/L whereas a potassium chloride (KCl) synthetic fertiliser was used as a DS. The membrane utilised was a cellulose triacetate (CTA) membrane and was tested in forward osmosis mode (FO mode) and pressure retarded osmosis mode (PRO mode) whilst the system flow rate was adjusted between 100, 200 and 400 mL/min. Additionally, the DS concentration was altered from 0.5, 1 and 2 M KCl, respectively. Experiments were performed using a bench scale FO setup which comprised of an i) FO membrane cell, ii) a double head variable peristaltic pump for transporting FS and DS’s respectively, iii) a digital scale to measure the mass of the DS, iv) a magnetic stirrer to agitate the FS, v) two reservoirs for the FS and DS, respectively, vi) a digital multiparameter meter to determine FS electrical conductivity (EC) and vii) a digital electrical multimeter to measure system energy consumption. Each experiment comprised of seven steps i) pre-FDFO membrane control, ii) membrane cleaning, iii) FDFO experiment, iv) post-FDFO membrane control, v) membrane cleaning, vi) membrane damage dye identification and vii) membrane cleaning. Pre- and post-FDFO membrane control experiments operated for 5 h whilst each membrane cleaning procedure operated for 30 min. The FDFO experiment operated for 24 h whilst the membrane damage dye identification operated until a minimum of 10 mL water was recovered. The process parameter which largely contributed to a beneficial system performance and specific energy consumption (SEC) was the increase in DS concentration. Water fluxes increased approximately threefold from a DS concentration increase from 0.5 to 1 M, followed by an additional 30 to 50 % rise in water flux at a DS concentration increase 1 to 2 M. SEC decreased by 58 and 53 % for FO and PRO modes, respectively, with a DS concentration increase from 0.5 to 1 M. An additional 35 and 37 % SEC reduction for FO and PRO modes was obtained for a DS concentration increase from 1 to 2 M. Altering the membrane from FO to PRO did not contribute to a beneficial system performance nor did it improve SEC. However, at a DS concentration of 0,5 M, the PRO mode obtained a 5.3 % greater water recovery compared to the FO mode. Conversely, at a DS concentration of 1 and 2 M, the FO mode achieved 5.4 and 7.0 % greater water recoveries compared to the PRO mode. The increase in flow rate also did not increase system performance significantly, however, a fluctuation in system SEC was observed. Throughout the study, no membrane fouling was observed, however, possible minute traces of membrane fouling could be observed from the membrane surface electron microscope (SEM) images. Additionally, minor changes in post- FDFO membrane control water recovery results were noticed which support the possible occurrence of membrane fouling during the FDFO experiment.

Global warming is becoming more concerned by the public. The escalating atmospheric CO₂ level has introduced the intensification of greenhouse effect which brought enormous impact to the environment and climate. Among different methods for CO₂ mitigation, biological treatment on CO₂ emission using microalgae is regarded to be more economical and beneficial. On the other hand, countries around the world are projected to face water scarcity in the coming decades. Therefore alternatives to the finite fresh water resources for consumption have to be explored. Seawater has been introduced for toilet flushing in Hong Kong since 1950s. The flushing water is mixed with the consumed fresh water in the sewage treatment process to give a sewage effluent with high salinity, which still contains nutrients to support the growth of algal cells. Using sewage effluent as an algal culture medium not only can have a lower operation cost while saving fresh water for food crops, but also the effluent can be purified before discharging. Besides Hong Kong, there is an increase in numbers of cities incorporating seawater in toilet flushing systems as an economical and sustainable solution to fresh water scarcity. / Taking sustainable development into consideration, the use of algal cell for the fixation of CO₂ in saline sewage effluent is proposed, which should be an effective mitigation for CO₂ emissions, removal of nutrient in sewage effluent as well as production of useful products such as biofuel feedstock. In order to find out a suitable algal species for CO₂ the bioremediation, commercially available algal strains were compared against the locally isolated species on the growth and CO₂ removal efficiency in saline sewage effluent. Chlorogonium capillatum, the algal strain isolated from a local fish pond, was found to be the best candidate for CO₂ sequestration and nutrient removal in the non-sterile saline sewage effluent since it could grow much better in the presence of other microorganisms, comparing with the majority of other algal species could not grow under this situation. / The effect of CO₂ enhancement on algal photosynthetic rate and growth was studied in terms of the change in cell number, biomass and lipid production, and the fatty acid profile. The optimisation of CO₂ mitigation was achieved by deploying the response surface methodology (RSM) approach with a model describing the change in CO₂ consumption rate being developed. In the minimal run resolution V (MR5) screening test, it was found that salinity, pH, CO₂ and PO₄³⁻-P levels were influential to CO₂ removal by C. capillatum in non-sterile sewage effluent. Further optimisation of the CO₂ consumption rate was performed using the Box-Behnken design. The results of study showed that C. capillatum was able to deliver its maximum CO₂ consumption rate at 58.96 mg L⁻¹ d⁻¹ at the optimal condition, which was very close to the ordinary condition in the average sewage. In addition, the lipid content of C. capillatum could reach 24.26±2.67% with fatty acid profile conforming to typical biodiesel composition, delivering a high potential for biofuel feedstock production. Together with a high nutrient removal rate, C. capillatum could be used to produce a promising waste-recycling oriented simultaneous treatment system. / Since the CO₂ consumption rate was not dependent to light intensity, the spectral effects on the light-enhanced algal growth and carbon sequestration were investigated to find the best culture condition and how the carbon sequestration process was being influenced. Five LED light spectra were chosen for the analysis and it was found that growth parameters and cell compositions were influenced by the colour of the light very differently. The results indicated that under the irradiation of white LED light, C. capillatum had the highest CO₂ consumption rate and lipid content. Red LED light induced the highest amount of cellular protein as well as the chlorophyll a content. However, the performance of the light dependent reaction of the red LED light culture did not show apparent improvement. Regarding the CO₂ fixation enzyme, the spectral effect on RuBisCO content was marginal and there was no obvious relationship between the light induced CO₂ consumption and solely the light induced RuBisCO content change. Chemical analysis on the algal biomass indicated the C. capillatum culture would be a suitable microbial system to mitigate CO₂ emission, remove nutrients from saline sewage effluent and produce biomass suitable for biofuel production. / This study delivers a bioremediation system which is capable of simultaneous CO₂ mitigation, nutrient removal and biofuel feedstock production with a newly isolated algal species in a waste recycling manner. The findings of this study are not limited to the application locally in Hong Kong, but hopefully all these can also be useful in similar works in other places to help with the sustainable development. / 全球暖化正越來越受到公眾關注，大氣中不斷上升的二氧化碳水平已經加劇了溫室效應，並對環境和氣候帶來了巨大的影響。在不同的二氧化碳緩減方法中，利用生物方法以微藻處理二氧化碳排放被認為是更具效率和回報價值。另一方面，世界各地已經預計會在未來幾十年面臨水荒，因此是有必須要為有限的淡水資源尋找代替品。自五十年代起，香港便引入了海水作沖廁用途。沖廁用水會在污水處理過程中混合經使用過的淡水而產生高鹽度的污水，而污水當中仍含有營養物質，以支持藻類細胞生長。使用污水作為藻類培養介質不但可以降低營運成本，並有助於節省淡水用以耕種糧食作物，而且可以在污水排出前進行純化。除香港以外，一些引入海水用於沖廁系統的城市數目正在增加。 / 考慮到可持續發展，我們提出利用微藻細胞在帶鹽污水中進行二氧化碳固定。這應該是一個有效的緩解二氧化碳排放，清除污水中養份，以及產生有價值產品的綜合方案。為了找出一種合適的微藻進行生物整治，我們比較了市面上買到的品種和於本地環境分離出來的藻種於帶鹽污水中生長和去除二氧化碳的表現。經過實驗後我們確定一種從魚塘中分離出來的綠梭藻(Chlorogonium capillatum)是能夠在未經消毒的帶鹽污水中進行碳封存和去除養份的最佳選擇，因為綠梭藻能夠在其他微生物存在下仍可以良好地生長，反觀其他大多數的藻種就不能在這情況生長。 / 我們從細胞數、生物量、脂質和脂肪酸譜的變化方面研究了二氧化碳量增強對微藻光合速率和生長的影響。我們利用了反應曲面法(Response Surface Methodology)對微藻的二氧化碳緩減進行最佳化，並將二氧化碳緩減率的變化製成模型。在條件篩選實驗，我們找出鹽度、酸鹼、二氧化碳和磷質水平是會影響二氧化碳緩減率。在隨後的二氧化碳緩減率的最佳化後，綠梭藻的最大二氧化碳緩減率為58.69微克每公升每天。研究發現綠梭藻能夠於接近平常環境條件下達成最高效的二氧化碳緩減。除此之外，綠梭藻的脂質含量可達24.26±2.67百份比。加上脂肪酸分佈符合典型的生物柴油成份和具有高度養份去除率，綠梭藻可以用來創造以廢物回收作主導的多功能的生物修復系統。 / 由於二氧化碳緩減率並不依賴於光的強度，我們進行了光譜對微藻生長和碳封存的影響的研究，以找出最佳的培養條件和了解碳吸收的過程如何被影響。我們分析了五種發光二極管光譜，發現燈光顏色對微藻的生長參數和細胞組合物有明顯的影響。結果顯示，在白色燈的照射下，綠梭藻有最高的二氧化碳緩減率和脂質含量。紅色燈引發了最高的細胞蛋白質，以及葉綠素a含量。然而，紅光並沒有明顯提升光依賴反應。關於固定二氧化碳的酶，光譜對羧化/加氧酶的數量變化效果細微。另外，羧化/加氧酶跟二氧化碳緩減率之間沒有明顯關係。從微藻生物質中的化學分析，我們認為綠梭藻是一個合適的微生物系統以達成二氧化碳的排放緩減，去除帶鹽污水中的養份和生產適用於生物燃料製造的生物質。 / 這項研究提供了一個生物修復系統，它能夠以廢品回收方式同時減少二氧化碳排放、去除營養和生產製作生物燃料的原料。這項研究的結果並不只限於香港使用，我們希望這些東西也可以應在其地方類似的工程上，為可持續發展出力。 / Lee, Kwan Yin. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 115-134). / Abstracts also in Chinese. / Title from PDF title page (viewed on 05, January, 2017). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

No description available.

Chitosan is a biopolymer resulting from the deacetylation of chitin, the second most abundant biopolymer in nature. Chitosan has been successfully used in systems to remove metal ions and other pollutants from wastewater. Chitosan has shown promise as a sorbent for radionuclides in some aqueous waste streams. The sorption of these radionuclides by chitosan is studied to determine if chitosan could be used as a sorbent for aqueous waste streams containing these metals. The effect of various experimental conditions including sorbent particle size, agitation rate, hydration, temperature, pH, metal concentration and sorbent concentration are examined in this study. Results showed that sorption depends on the availability of access sites, controlled by the specific surface area of the sorbent. Sorption was observed to decrease with increasing temperature. The sorption isotherms and kinetics for Co(II), Eu(III) and U(VI) sorption onto chitosan were determined experimentally by batch sorption. Isotherms were fitted using the Langmuir and Freundlich models. Kinetics were modeled using the pseudo- first order, pseudo-second order, Elovich, and intraparticle diffusion models in order to determine possible rate-limiting steps. Most data were well described by the pseudo- second order and Elovich models. Multi-linearity was observed in the intraparticle diffusion model. The sorption capacity of the metals on chitosan was found to follow the order Co < Eu < U. / Graduation date: 2013

This study investigated the effect of plant surface area (plant density) on the efficiency of organic carbon removal in a bench-scale constructed wetland. Constructed wetlands are commonly assumed to be biofilm reactors in which organic carbon removal occurs primarily through sedimentation and aerobic degradation by attached microbial biofilms. In conventional biofilm reactors, aerobic degradation of organic carbon is proportional to the amount of surface area for microbial attachment, provided that sufficient oxygen is available. In contrast, current design equations for constructed wetlands assume that the amount of surface area is not an important parameter. A bench-scale simulation of a constructed wetland was conducted, using bulrushes planted at varying plant densities in soil with a free water surface depth of about 0.27 m. The carbon source was diluted ENSUR (TM). Total organic carbon (TOC) removal was measured. Concentration of TOC was correlated with biochemical oxygen demand (BOD). Tests were conducted in conditions of light and dark, and under two different carbon loadings. Performance of bulrushes was compared with that of inert acrylic rods. The rate of carbon removal by mature bulrushes was found to increase with increasing plant density until oxygen became depleted. Higher densities degraded carbon at rates much faster than those predicted by current design equations. Young bulrushes degraded carbon at faster rates than mature bulrushes. Once oxygen was depleted, rates of degradation were reduced to rates anticipated by current models. When plant density was 15% or greater, oxygen became depleted in less than 6 hours. Removal efficiency was greater at higher loadings (70 mg/l BOD) than at lower loadings (25 mg/l BOD). Bulrushes performed significantly better than inert rods, sometimes by a full order of magnitude. The microbial community on the bulrushes appeared to be more complex and robust than that on the rods. Also, the presence of light did not significantly increase degradation rates for the bulrushes but was significant for the rods. The microbial community on the rods contained a larger proportion of epiphytic algae. The presence of light did result is greater overall efficiency of removal for both bulrush and rods. Currently, a major drawback of constructed wetlands in wastewater treatment has been their demand for large areas of land. This study suggests that it would be possible to reduce the land area requirements for constructed wetlands for both carbon removal and nitrification/denitrification provided designs gave more consideration to oxygen supply. Using current designs, a retention time of 4-8 days typically results in 70% BOD removal. This experiment suggests that wetlands with a retention time of about 1 day could provide the same performance if additional oxygen were supplied. / Graduation date: 1995

Treatment efficiency in a constructed wetland is related in part to the amount of time that a wastewater remains in the system. Current design methods idealize the system as a plug flow reactor and use a "residence time" based solely on the volume of the cell and the flow rate. Under this assumption, every element of wastewater entering the wetland cell experiences the same residence time. It is understood that this idealization ignores the existence of longitudinal dispersion, short circuiting and stagnant regions within the wetland cell. The result of these phenomena is a distribution of residence times. In other words, portions of the effluent exit the cell earlier than predicted, resulting in undertreatment, and portions exit late, resulting in excess treatment. The average concentration of treated wastewater at the outlet is a function of this distribution and the reaction kinetics associated with the waste. The overall effect of a distribution of residence times is reflected in a reduction of treatment efficiency at the outlet. Hydraulic regimes of constructed wetland systems were investigated at a pilot project site providing tertiary treatment of a pulp mill wastewater. Two vegetation types, bulrush and cattail, were investigated and compared to nonvegetated and rock-filter cells with identical configurations. Tracer studies used a fluorescent dye and were performed over the course of a year. Dye was input as a pulse at the inlet end of the cell and sampled over time at the outlet end to obtain concentration breakthrough curves. From these curves, time to peak, actual mean detention times, degree of dispersion, and extent of dead space were calculated, as well as predicted treatment efficiency. Results indicated varying degrees of dispersion, short circuiting, and dead space in the individual cells. Analysis of the residence time distributions provided estimates of the "active" volume of the treatment cell and the degree of short circuiting in the system. Effective volume of the planted cells ranged from 15 to 25% of full volume. Early arrivals of the peaks of the distributions, indicative of short circuiting, ranged from 30% to 80% of the theoretical detention times. A first order treatment model and a kinetic coefficient, k, were assumed, and corresponding treatment efficiencies were compared to the theoretical treatment of an ideal plug flow reactor. Reduced treatment efficiencies for the planted systems ranged from 2 to 20 %, by this estimation. Many references attempt to analyze wastewater treatment systems by refering to two models: dispersed plug flow and an approximation of tank-in-series. These models were investigated as potential descriptions of the hydraulic regime present in constructed wetlands. Residence time distributions of the constructed wetlands in this study indicated flow was not exclusively dispersed plug flow. This simplified model does not account for the exchange of material with "dead" space in the wetland cell. The data suggest a combination model of dispersed plug flow with a transient storage zone component may be more appropriate. / Graduation date: 1994

No description available.

M. Tech. Chemical Engineering / The lack of clean and fresh water has become a worldwide problem because of water pollution caused by industrialization. Contamination of natural water sources by heavy metal is a worldwide public health problem, leading to waterborne outbreaks of infectious hepatitis, viral gastroenteritis, and cancer. Therefore it very important to remove these toxic metal ions from municipal and industrial effluents in order to protect plants, animals and human beings from their adverse effect before discharging into natural water bodies. Although, several separation methods such as filtration, reverse osmosis and membrane technology have been developed to remove these toxic heavy metal ions from wastewater, however these conventional treatments technologies were found to be expensive on a sustainable basis. Adsorption process was identified as the most effective, and extensively used essential process in wastewater treatment, and in order for adsorption process to feasibly remove pollutants from wastewater, there should be a need for a suitable adsorbent which will have a large porous surface area, and a controllable porous structure. Through the application of nanotechnology, nano adsorbents can be developed as effective adsorbents to treat wastewater. The main objective of this project was to apply magnetic metal doped iron oxides as an efficient adsorption media for the removing of Cr(VI), Cd(II) and V(V) ions from wastewater.

M. Tech. Engineering: Chemical. / Focuses on the emerging application of clinoptilolite in removing aspirin and cephalexin from municipal wastewater streams. The mechanisms of sorbent-organic compounds interaction was studied in detail. Specifically, this research aims to achieve the following objectives: I. to investigate the sorption capacity of surfactant modified clinoptilolite on the removal of aspirin and cephalexin ; II. To relate sorbents performance to process variables with sorbent properties and water quality ; III. to compare the sorption capacity of surfactant modified clinoptilolite to commercial emerging adsorbents on the removal of aspirin and cephalexin from aqueous solution ; IV. to apply existing mathematical models to describe isotherms and kinetic data in order to extract design parameters.

M. Tech. Chemical Engineering. / In this study, nano-structure hydrotalcite material was used as an adsorbent for the removal of heavy metals of lead (Pb), nickel (Ni), cadmium (Cd) and cobalt (Co) from wastewater. It was observed that, in comparison with single component system (Ni, Cd and Co only), the presence of co-ions reduced the Ni (II), Cd (II) and Co (II) adsorption suggesting suppression of the desired ion by the presence of co-existing ions. The kinetic data fitted well to pseudo-second order model while the equilibrium data were satisfactorily described by Langmuir isotherm. The adsorption capacities of Ni (II), Cd (II) and Co (II) at pH 6.0 were found to be 142.8, 200 and 142.8 mg/g at 25oC.