La prolifération grandissante des épisodes de fleurs d’eau de cyanobactéries toxiques dans les plans d'eau potable et dans les usines de traitement d'eau potable est une préoccupation mondiale. L’utilisation de sondes in vivo, permettant la détection de la phycocyanine des cyanobactéries par fluorescence, est une technologie innovante, de plus en plus couramment utilisée. Néanmoins, pour favoriser son implémentation à grande échelle, elle doit être validée scientifiquement. De nombreuses sources d’interférences dans ces sondes sont à l’origine de biais de lecture. Les objectifs de cette recherche sont :1. La caractérisation des espèces dominantes et la succession des espèces de cyanobactéries dans deux grands lacs utilisés pour la production de l’eau potable2. L’analyse de la variabilité des espèces de cyanobactéries et d’autres groupes de phytoplancton en fonction de la température et des nutriments3. La validation du suivi des cyanobactéries par sonde fluorométriques aux sources d’eau potable en corrigeant le signal pour les interférences d’autres groupes de phytoplanctonLes résultats de ce travail de recherche ont montré qu’il existe de nombreses sources d’interférences aux sondes à fluoresence YSI, mais qu’il était possible de développer un facteur de correction afin d’éviter de surestimer les cyanobactéries. Suite à la validation de la sonde, celle-ci a été utilisée pour comprendre la dynamique des cyanobactéries à la baie Missisquoi afin de caractériser les espèces dominantes et de mieux comprendre la succession phytoplanctonique de la baie afin d’aider les opérateurs de l’usine de traitement d’eau potable à planifier les traitements en fonction de la qualité biologique de la baie. Parmi les résultats les plus intéressants, notons l’apparition précoce, de plus en plus marquée à travers les années, des blooms de Microcystis sp. et le développement de bloom co-dominés par des Chroococcales et des Nostocales. Le développement de fleurs d’eau dominées par Aphanizomenon sp. ou Dolichospermum sp. est généralement précédé d’une période où le milieu est limité en N ce qui favorise le développement de ces espèces fixatrices d’azote atmosphérique / The increase of toxic cyanobacterial blooms in source waters that can lead to breakthrough into drinking water treatments plants is a worldwide concern. The use of in situ probes allows for the detection of cyanobacterial phycocyanin through fluorescence. It is an innovative technology becoming more widely used. However, to facilitate the implementation of this technology, it must be validated. Several sources of interferences can lead to biases in their application. The objectives of this research are to :1. characterize the dominant species and cyanobacterial succession in two large lakes used for drinking water production2. analyse the variability of cyanobacterial species as well as other groups of phytoplankton as a function of temperature and nutrients3. validate cyanobacterial monitoring by fluorometric probe in drinking water sources by correcting the signal for other groups of phytoplanktonThe results of this research have shown that there are many sources of interference in fluorescence probes, but that a correction factor can be used to prevent the overestimation of cyanobacteria. Following the validation of the probe, it was used to improve our understanding of the dynamics of phytoplankton succession in Missisquoi Bay in order to characterize the dominant species and succession to improve the operation of drinking water treatment at Missisquoi Bay. Among the interesting findings was the earlier apparition of cyanobacteria throughout the years, Micocystis sp. blooms and blooms co-dominated by Chroococcales and Nostocales. The development of cyanobacterial blooms dominated by Aphanizomenon sp. or Dolichospermum sp. was generally preceded by a period where the water body was limited in nitrogen, which favours the development of these species capable of fixing nitrogen

>Magister Scientiae - MSc / South Africa is facing a problem of many municipal waste water treatment works (WWTW) not working efficiently. The environmental impacts of poorly treated effluents on receiving water bodies have required special attention from researchers. In this study, the relationships between water quality variables in the Baths River in the Western Cape province of South Africa were evaluated upstream, at the source and downstream of the Caledon wastewater treatment works between March 2013 to March 2016. The assumption has been tested that water quality is deteriorating downstream of the Caledon Waste Water Treatment Works (WWTW) discharge point in the Baths River and are affected by this change in water quality. / 2023

No description available.

Access to clean water is one of the world's greatest concerns. Because 97% of global water resources are seawater, desalination via reverse osmosis (RO) membrane process has become a vital technology to obtain drinkable water. At the same time, the discharge of industrial waste effluents containing heavy metal ions to the available water resources (seawater and brackish water) without adequate pre-treatment is a major cause of water pollution. Heavy metal rejection using nanofiltration (NF) membrane process is a recognized water treatment methodology. Thin-film nanocomposite (TFN) membranes have shown vast performance enhancement using both RO and NF processes. However, TFN membrane fabrication has been limited due to poor dispersion of the nanoparticles in the polyamide (PA) layer of the membrane, and the leaching of the often-hazardous nanoparticles from the TFN membranes. For various reasons such as their dispersibility in aqueous media, safety, high aspect ratio, and functionality, cellulose nanocrystals (CNCs) are an ideal nanoparticle for inclusion in TFN membranes. Because of their hydrophilicity, CNCs have more commonly been dispersed in the aqueous monomer solution during PA interfacial polymerization. In this thesis, we investigated two different CNC modification routes to improve CNC dispersion within the trimesoyl chloride (TMC)/n-hexane (non-aqueous) monomer solution. In one case, we acetylated the CNCs (ACNCs) using a straightforward, efficient, solvent-free method to achieve a more uniform CNC dispersion in the PA layer. The resulting ACNCs were less hydrophilic, which allowed increased nanoparticle loading and improved dispersion in the PA layer. In an RO desalination process, compared to unmodified CNC-TFN membranes, the NaCl rejection of the ACNC-TFN membranes remained stable (at 98-99%) up to a 0.4 wt% loading, while water permeability increased by up to 40%. For the second case, we synthesized L-cysteine functionalized CNCs (CysCNCs) and incorporated them into the PA layer for testing in an NF wastewater treatment process. The amine functional groups of L-cysteine covalently bonded with the acyl chloride groups of the TMC monomer. This resulted in improved nanoparticle dispersion but could also have prevented nanoparticle leaching. Moreover, because L-cysteine contains strong chelating groups, their inclusion in the PA layer led to improved heavy metal rejection. A loading of 0.1 wt% CysCNCs in the TFN membranes provided high rejection of both copper and lead ions, 98.1 and 95.2%, respectively. The CysCNCs were also evaluated in an NF desalination process resulting in a 40% increase in water permeability with almost no decline in Na₂SO₄ (97-98%), MgCl₂ and NaCl rejection. The modified CNCs enabled us to overcome the water permeability/selectivity trade-off in CNC-TFN membranes for both RO and NF membrane desalination. Finally, we developed an experimental protocol to investigate the effect of the adsorption of heavy metal ions (if any) on the performance of thin film composite (TFC) and TFN membranes in NF. We confirmed that adsorption occurred, and the equilibrium capacity of the membranes was reached after 8 - 12 h of the experiment. Despite reaching the equilibrium capacity, the water permeability and heavy metal rejection remained at their highest values. This led to the conclusion that the adsorbed heavy metals altered the membrane surface, thereby improving the performance of both TFC and TFN membranes. The ability to modify CNCs enables one to achieve a controlled range of hydrophilicity/ hydrophobicity. This allows one to fine-tune CNC compatibility with the TMC/n-hexane non-aqueous monomer solution and enable improved dispersion in the PA layer, eventually leading to improved TFN membrane performance for both RO and NF processes.

The discharge of poorly treated wastewater containing persistent organic contaminants, such as phenol, into water bodies is a major contributor to water pollution. This is of great concern as it poses health threats to human beings, aquatic species and the ecosystem as a whole. Amongst the water treatment technologies available, adsorption is highly recommended because of its ease of operation, simple design and economic viability. Commercial activated carbon (CAC) has previously been utilised as an adsorbent for remediation of recalcitrant pollutants from wastewater. However, high costs and the complexity of regenerating spent carbon has resulted in the need for economically viable adsorbents. The current research focused on the use of layered double hydroxide (LDH) clays for removal of phenol from contaminated water. The work is divided into two sections whereby the initial phase focuses on the use of commercial LDH clays, while the second phase is based on the in-house synthesised LDH clays guided by the performance of the commercial clays. Six commercial clays were sourced from different suppliers for the first phase, namely: DHT ̵ 4A and Alcamizer 1 from Kisuma Chemicals (Netherlands), Sorbacid 944, Sorbacid 911 and Hycite 713 from Clariant (Germany) and GF ̵ 450 from Greenfield additives (South Africa). Sorbacid 944 was the only clay which had three metallic constituents, magnesium Mg), zinc (Zn) and aluminium (Al) and was quantified to be 100% hydrotalcite; other clays had a substantial amount of impurities, such as calcite, boehmite and silica. Screening tests on the commercial clays were done by contacting 10 g L-1 of each clay with 40 mg L-1 synthetic phenol solution over 108 h. All the clays produced an adsorption efficiency of less than 10%. However, three clays which showed better adsorption efficiencies, namely: GF ̵ 450 (9%), Sorbacid (6%) and DHT ̵ 4A (3%) were utilised for further assessment. The three clays were thermally treated at 500°C for 4 h to produce mixed metal oxides (MMO), which are known to be good adsorbents. Calcination of the clays resulted in an increase in phenol adsorption efficiency over 24 h on Sorbacid 944 (87%) and DHT ̵ 4A (52%) while GF ̵ 450 remained below 10%. Having produced a higher adsorption efficiency, Sorbacid 944 was further assessed for optimisation of phenol removal process. The initial pH of the solution was established to have an inverse proportionality relationship with phenol adsorption. Elevated pH resulted in an increase in the concentration of hydroxyl ions (OH-) which increased the reformation rate of calcined LDH (CLDH) and reduced the adsorption efficiency, while acidic pH was not evaluated as it is known to cause dissolution of LDH. Neutral pH was established to be the optimum pH for phenol adsorption. An increase in operational temperature resulted in a faster phenol adsorption rate from 2 x 10-4 g mg-1min-1 at 25 °C to 3.8 x 10-3 g mg-1min-1at 65 °C. The optimum clay loading was 10 g L-1 and the clay proved to be effective over three cycles. The Freundlich equilibrium isotherm best fitted the phenol adsorption equilibrium data, with a maximum adsorption capacity of 16.6 mg g-1. The change in enthalpy of the adsorption process was determined to be ca.20 kJ mol-1 indicating an endothermic process dominated by physical adsorption. The changes in Gibbs free energy over the evaluated temperatures ranged between -12 kJ mol-1 and -16 kJ mol-1. This showed that the adsorption process was spontaneous irrespective of the operating temperature. The second phase of the study involved the synthesis of eight LDH clays containing varying compositions of Mg, Zn and Al with a carbonate interlayer anion. The clay which contained molar ratios of Mg (60%), Zn (20%) and Al (20%) (Mg0.6Zn0.2Al0.2) was found to possess higher adsorption efficiencies upon calcination at 450 °C for 4 h. Clays which had a Zn/Mg molar ratio greater than 1, Mg0.4Zn0.4Al0.2, Mg0.25Zn0.5Al0.25 and Zn0.75Al0.25 showed lower phenol adsorption efficiencies of 63%, 65% and 50% respectively. Clays with a Zn/Mg ratio less than 1, Mg0.6Zn0.2Al0.2 and Mg0.5Zn0.25Al0.25 showed optimal ratio of acidic and basic sites hence higher phenol adsorption efficiencies of 89% and 80% respectively. A higher aluminium content in the clay increased the spinel content (MgAl2O4) upon calcination resulting in a decrease in phenol adsorption. Phenol adsorption equilibrium data and kinetics for clay Mg0.6Zn0.2Al0.2 were comparable with those of Sorbacid 944. Column reactor configurations should be investigated for industrial applications. Furthermore, real wastewater matrices containing multi-contaminants should be used instead of synthetic wastewater with a few pollutants. This will provide insight in the applicability of LDH for impurity removal from wastewater on an industrial scale. / Dissertation (MEng (Water Utilisation))--University of Pretoria, 2021. / Technology and Human Resources for Industrial Support (THRIP) / Chemical Engineering / MEng (Water Utilisation) / Unrestricted

Effective adsorbents for polyfluorinated compounds (PFCs) were obtained and successfully tested in adsorption of perfluorooctanoic and perfluorooctanesulfonic acids. Bridged silsesquioxanes containing secondary and tertiary amino groups were synthesized by sol-gel condensation of bis[3-(trimethoxysilyl)propyl]amine and N-methyl-3,3′-bis(trimethoxysilyl)dipropylamine in acidic media in the presence of surfactants. Obtained materials were mesoporous with high BET surface area. They combine high structural stability with high concentration of surface amino groups serving as adsorption sites. Batch adsorption tests demonstrated their high adsorption capacity on PFCs: in some experiments it reached up to 88% of the adsorbent weight. Adsorption of PFCs changed the surfaces of the adsorbent nanoparticles from hydrophilic to hydrophobic thus providing their agglomeration and floatability. Column tests showed fast adsorption of PFCs even at high concentrations and high flow rates. Obtained results can be used in the development of an effective filtration device for clean-up of water contaminated by PFCs.

Yes / The Sustainable Development Goal (SDG) 6.1, established by the United Nations General Assembly in 2015, targets universal and equitable access to safe and affordable drinking water for all by 2030. An essential factor in achieving this goal is the harnessing of “green” coagulants – naturally occurring, environmentally friendly materials which are effective coagulants for use in water treatment, with good availability in developing countries, inherent renewable properties and ease of biodegradation. In order to gain from these benefits, it is essential to fully understand how such coagulants may best be utilised, particularly concerning their practical application in developing countries. In this study, three different plant-based coagulation products (PCPs), namely Hexane (HxKP), saline (StKP) and crude (CrKP) extracts of Kenaf plant seed (Hibiscus cannabinus, a species of the Hibiscus plant), were applied to high (HTW), medium (MTW) and low (LTW) turbidity water in order to determine their performance and coagulation ability. The ability of the three Kenaf coagulant products (KCPs) to remove hydrophobic fractions of natural organic matter (NOM) was measured. The impact of KCPs on the treated water organic matter content (a known disinfection by-product (DBP) precursor) was examined using known surrogates of natural organic matter (NOM) i.e. the dissolved organic carbon (DOC), ultraviolet absorbance at 254 (UV254) and specific ultraviolet absorbance (SUVA254). Results obtained quantify the implications of using these coagulants during the water disinfection process. A parametric study, measuring the effect of different operating parameters, such as untreated water turbidity, pH, dosages, retention time, and KCP storage time, was completed. Turbidity removal performance for HxKP and StKP was very good with > 90% removal recorded for HTW and MTW, respectively, at pH seven within 2 hours retention time. Images obtained from scanning electron microscopy (SEM) analysis revealed a high likelihood of the coagulation mechanism of KCPs to be adsorption-interparticle bridging brought about by their flake-like structures and surfaces charges. Varying pH had no measurable influence on the coagulation performance of the KCPs. Comparing their efficiency with Moringa Oleifera (MO, a previously researched PCP) and alum showed that HxKP had a negligibly different particle removal as MO. StKP turbidity removal performance was below HxKP by 1% for HTW and LTW and 2% for MTW but performed higher than the CrKP by 5% and 7% in HTW and MTW, respectively. The optimum dosage of HxKP and StKP reduced DBP surrogate values, indicating that its precursor is also minimized, although a slight shift from this optimum dosage showed a significant rise in their concentration thus signifying a potential increase in DBPs during disinfection.

No

Yes / This study used fluorescence excitation-emission matrices (EEMs) analysis to investigate the characteristics of natural organic matter (NOM) in treated water using okra crude extract (OCE), sabdariffa crude extract (SCE) and kenaf crude extract (KCE) as coagulants. In addition, an assessment of the impact of purified okra protein (POP), purified sabdariffa protein (PSP) and purified kenaf protein (PKP) was undertaken. The performance evaluation of these coagulants in terms of increase or decrease in dissolved organic carbon (DOC) was compared with Peak T fluorescence intensity observed at excitation wavelength 220–230 nm, and emission wavelength 340–360 nm. Fluorescence analysis of water treated with the crude extracts identified the removal of DOC in peaks A and C region whereas the increase in DOC from the protein was predominantly found in peaks T and B region. Furthermore, it was observed that the purified proteins were noted to be capable of reducing the DOC concentration in raw water where all fluorophores were not detected. The application of OCE, SCE and KCE yielded an increase in DOC of 65, 61 and 55% respectively, corresponding to increases of 65, 29 and 54% in peak T fluorescence intensities, at 100 mg/l dose. Furthermore, DOC concentration was reduced by 25, 24 and 18% using POP, PSP and PKP respectively as coagulants with corresponding decreases in fluorescence intensity of 46%, 44 and 36% in POP, PSP and PKP, at a lower dose of 0.1 mg/l. Therefore, it is clear that Peak T fluorescence intensity could be used to characterise organic matter in treated water using natural extracts to assess final water quality. / Financial support given to this research work by the Nigerian Government through the Tertiary Education Trust Fund (TETfund/AST &D/2013/2014/CE/02)

No description available.