Paint wastewater treatment using Fe3+ and Al3+ salts

A PhD thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering. JohannesburgThis study involves the investigation of the paint wastewater treatment using inorganic coagulants such as FeCl3, Fe2(SO4)3, AlCl3 and Al2(SO4)3 in a jar test during rapid and slow mixing for 250 and 100 rpm respectively, settled the samples, measure the pH and turbidity. The pH, turbidity and area covered by the flocs were used as measurements in this study to determine the quality of treated paint wastewater. In the first experiment, 200 mL sample of 169.2 g of paint wastewater dissolved in 1L of potable water was poured into six 500 mL glass beakers sample dosed with FeCl3 only, combined FeCl3 and Ca(OH)2 or Mg(OH)2 as well as FeCl3-Ca(OH)2 and FeCl3-Mg(OH)2 polymers respectively, run through a jar test with rapid and slow mixing. The supernatant was extracted after 1 hour settling to measure the pH and turbidity. The observations showed that combined FeCl3 and Mg(OH)2 as well as FeCl3-Mg(OH)2 polymers yielded identical and slightly higher turbidity removal than combined FeCl3 and Ca(OH)2 and FeCl3-Ca(OH)2 polymers. Another batch of experiments was carried out using the same metal salts with Ca(OH)2 and Mg(OH)2 respectively for pH adjustment. The samples were treated in a jar test using various dosing patterns such as dosages, dosing prior or during mixing, combined dosages interchangeably, retention time. A third batch of experiments was carried out by dosing synthetic polymers of FeCl2-Ca(OH)2 and FeCl2-Mg(OH)2 respectively using similar dosing patterns. The results obtained in first set of experiments, were Fe3+ and Al3+ salts were added in paint wastewater showed that the changing pH correlates with turbidity removal. It was also observed that dosing prior or during mixing do not play any significant role in wastewater treatment. Another observation showed that flocculation of the paint wastewater dosed with FeCl2-Ca(OH)2 or FeCl2-Mg(OH)2 polymers do not show correlation between the pH and turbidity, which indicates that the pH is not an indicator of turbidity removal in a more alkaline solutions such as paint wastewater. A second study was carried out using the same paint wastewater samples (200 mL) and samples dosed with Fe3+ and Al3+ salts treated in a jar test and immediately two drops of supernatant were placed on a microscope slide and view it under a microscope connected to a camera, images were captured after 1, 60 and 90 minutes respectively (Exp A). Samples were prepared from the original paint wastewater and the standard solution of Fe3+ and Al3+ in a small scale using identical metal salt/paint wastewater volume ratios as above. Two drops from the paint wastewater and metal salt solution were place on a microscope slide and images were captured as above using 1, 60 and 90 minutes respectively (Exp B). All the visuals were printed and the visuals obtained in Exp A were compared with their corresponding visuals in Exp B in accordance with time. The results obtained showed that the percentage area covered by flocs treated in a jar test (Exp A) correlates linearly with the percentage area covered by the flocs from a microscope slide (Exp B). The results obtained using this technique also confirm that the reaction between the drops of a sample and the drops of coagulant produces well-developed solid hydrolysis species. A third study was carried out by pouring 200 mL of the same paint wastewater samples into six 500 mL glass beakers and with Fe3+ and Al3+ salts as above, run through a jar test during 30, 45 and 60 seconds rapid mixing (250 rpm) only for 2 minutes respectively. The samples settled for 1 hour, and then pH and turbidity were measured. Another experiment was carried out using the similar method as above with samples run through a jar test at 250 rpm during 30, 45 and 60 seconds rapid mixing (250 rpm) for 2 minutes followed by slow mixing (100 rpm) for 10 minutes (combined rapid and slow mixing). The samples settled for 1 hour, and then pH and turbidity were measured. The results obtained from the jar tests (comparison between flocculation during rapid mixing only and combined rapid and slow mixing) showed that the pH in the samples with rapid mixing shows an insignificant change compared to their corresponding samples with combined rapid and slow mixing; turbidity in the samples with 30, 45 and 60 seconds rapid mixing showed that most of the flocs are formed within 30 seconds. There is a correlation between the pH and turbidity when paint wastewater is dosed with Fe3+ or Al3+ metal ions in their respective metal salts without pH adjustment. The Fe3+ and Al3+ of the same concentration yield a similar pH and turbidity trend

Removal of Heavy Metals Using Bentonite Clay and Inorganic Coagulants

Heavy metals have always been defined as elements with a density higher than 5 g/cm3. They are regarded as serious wastewater contaminants with detrimental effect to human and environment. Their removal from wastewater poses a serious challenge as they require cost-effective reagent and treatment technique. About 200 mL solution of acid mine drainage (AMD) collected from the Western decant in Krugersdorp, South Africa was poured into five 500 mL glass beakers. Three different sets of experiments (employing mixing, shaking and no mixing) were conducted using a jar test and a shaker with 1.5 g bentonite clay, 20–60 mL of 0.043 M FeCl3 and Al2(SO4)3 and a flocculent of bentonite clay and FeCl3 dosage, respectively. The experiments were conducted without pH adjustment. The samples settled for 1 hour after which the pH, conductivity and turbidity were measured. The results show that a combination of bentonite clay and FeCl3 exhibits a better turbidity removal efficiency compared to the samples with bentonite clay, FeCl3 and AlCl3 respectively. The variation of the turbidity removal in the samples with mixing shaking and without mixing is insignificant, showing that destabilization-hydrolysis depends upon the strength of the reagent and the physicochemical properties of the solution. The results also show that hydrolysis occurs at low pH, indicating that it plays an insignificant role in destabilization. The SEM micrographs show that turbidity removal is a physical phenomenon

Investigation of the Effect of a Flocculent of Bentonite Clay with MgCO3 in Synthetic Acid Mine Drainage (AMD) Treatment

Effect of a flocculent of bentonite clay with MgCO3 in Synthetic AMD was investigated in present study. The AMD samples were collected from the western decant in Krugersdorp, South Africa was modified by adding arsenic, zinc and cobalt. The pH, conductivity, dissolved oxygen (DO), oxygen reduction potential (ORP) and turbidity were measured. Those samples were treated with bentonite clay, MgCO3 and a flocculent of bentonite clay and MgCO3 respectively in a jar test, employing either rapid or slow mixing. Results showed that the conductivity of the samples with increasing bentonite clay while keeping MgCO3 constant decreased with increasing dosage, which was attributed to adsorption of the ions onto the negative sites of the porous bentonite when ionic strength increased. The oxygen content of the DO and ORP was not influenced by the rate of mechanical agitation, i.e. rapid and slow mixing respectively. Destabilization-hydrolysis was not influenced by the pH but the ionic strength of the colloidal AMD suspension, valence and electronegative of the metal ions. Turbidity removal of the synthetic flocculent used occured through physico-chemical phenomenon (SEM micrographs) and charged porous bentonite clay. In conclusion: Bentonite clay controls equilibrium state of the ionic strength of the system through adsorption of excess ions added to the system. Velocity gradient induced by mechanical agitation does not have an influence on the turbidity removal. Keywords: wastewater, coagulants, AMD, mixing, shaking, turbidit

Determination of the Efficiencies of Clay and PFCL or PACL with Na2CO3 Flocculent in the Removal of TSS from the AMD

Abstract: The experiment was conducted on the acid mine drainage (AMD) that was sampled from the Krugersdorp decant in South Africa. Five 500 ml glass beakers were filled with 200 ml of AMD sample and dosed with synthetic flocculent of FeCl3 and Na2CO3 (PFCl) and treated in jar test (exp. A). pH, conductivity, total suspended solids (TSS), dissolved oxygen (DO) and oxidation reduction potential (ORP) were measured after treatment and an hour settling. Another identical set of experiments was carried out with a combination of clay and PFCl dosage (exp. B). A third similar set of experiments was conducted with dosages of a combination of clay with PFCl or clay with AlCl3 and Na2CO3 (PACl) including another set of experiments using five 500 ml Erlenmeyer flasks in a shaker (exp. C). The pH results of the samples dosed with PFCl are relatively lower than that of the samples with a combination of clay and PACl dosage. The pH changing pattern with PFCl exhibited an increasing rate with increasing dosage whereas the pH of the sample dosed with a combination of clay and PFCl decreases with increasing dosage. The results show that bentonite clay does not have significant impact on pH of the samples. The ORP in treated AMD samples of experiments A and B is lower than in raw AMD sample. Residual TSS of the AMD samples which were treated with mixing are similarly identical to those of the samples treated on a shaker. TSS removal of the AMD samples with clay and PFCl is better than that with FeCl or PACl only

Optimal sulphuric acid production using Acidithiobacillus caldus (DSM 8584): Bioprocess design for application in ion-exchange

An optimised bioprocess was designed for the optimal production of sulphuric acid for application in an isotope recovery ion-exchange process. Firstly, the production of sulphuric acid (H2SO4) was optimised in aerated batch bioreactors using Acidithiobacillus caldus (DSM 8584) using elemental sulphur, achieving H2SO4 concentration of >0.4 to ~0.5 M (0.45 M average) with the following bioprocess parameters: product yield of 3.06 (Yp/s), oxygen uptake rate of 1.35 g/L.day (OUR), 52% sulphur conversion at a rate of 0.83 g/L.day (dS°/dt), achieving a sulphuric acid production rate of 2.76 g/L.day (dP/dt), while the oxidation of elemental sulphur per dissolved oxygen consumed was 0.67 g S°/g O2. Secondly, after 80% (v/v) moisture loss from the recovered biological H2SO4 titres, the acid solution was used for the recovery of nuclear grade lithium 7 (7Li+) from a degraded resin, achieving >80% recovery rate within two bed volumes (60 ml) at an averaged desorption rate K¯ of 0.1829 min -1 and eluent rate of 6.65 ml.min-1 in comparison to the ~60% 7Li+ recovery rate using a commercial grade mineral H2SO4 using similar operational ion-exchange reactor parameters. The designed bioprocess proved to be an effective and environmentally friendly bioprocess for the recovery of valuable metals adsorbed onto ion-exchange resin.Keywords: Acidithiobacillus caldus, sulphuric acid, ion-exchange, desorption, lithium 7 isotop

Water-immiscible dissolved oxygen carriers in combination with Pluronic F 68 in bioreactors

The supply and availability of dissolved oxygen (DO) in aerobic bioprocesses is often a limiting factor for the scaling up, improvement and general performance of these bioprocesses. The use of different DO carriers, particularly the use of perfluorocarbons as oxygen carriers, is discussed in this review. It also highlights interactions of microbial cultures with the surfactant, Pluronic F 68. Although oxygen carriers have been used extensively in the medical field, this review only focuses on their use in microbial bioprocess used for the production of high-value bioproducts. The use of water-immiscible compounds in combination with Pluronic F 68 in bioprocesses is discussed with the intention of analysing their combined effect where bioreactor and biomass performance is affected by DO limitations, nutrient starvation, high concentrations of trace element ions, oxidative stress and cell death from mechanical stress

The Membrane Gradostat Reactor: Secondary metabolite production, bioremediation and commercial potential

This manuscript focuses on the aspect of a membrane gradostat as an entirely different concept compared to submerged hollow fibre modules. The use of membrane bioreactor (MBR) technology is rapidly advancing in the wastewater treatment industries. However, this is not the case in the biopharmaceutical manufacturing industries. The MGR has shown great potential and versatility in terms of industrial applications. It can be used in both wastewater treatment and biopharmaceutical manufacturing using different modes of operation to meet any predetermined process  requirements. The MGR concept uses capillary membranes, which contain microvoids in the substructure to immobilise microbial cells or enzymes, depending on the bioreactor’s application. Operational requirements of the MGR and its commercial potential are discussed from a bioprocess engineering perspective

Bioremediating silty soil contaminated by phenanthrene, pyrene, benz(a)anthracene, benzo(a)pyrene using Bacillus sp. and Pseudomonas sp.: Biosurfactant/Beta vulgaris agrowaste effects

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant contaminants which are routinely found in numerous environmental matrices, contributing to ecological degradation. In this study, the removal of LMW and HMW PAHs with 4- and 5 benzene rings, by Bacillus licheniformis STK 01, Bacillus subtilis STK 02 and Pseudomonas aeruginosa STK 03, was evaluated in silty soil for a period of 60 days. Subsequently, a biosurfactant produced from Beta vulgaris agrowaste was used to augment the removal of the aforementioned PAHs in mono- and co cultures. The isolates proved to be proficient in removing the contaminants, with B. licheniformis STK01 cultures achieving the highest removal rates. Biosurfactant supplementation significantly enhanced the removal of benzo(a)pyrene- a 5-ring benzene HMW PAH. The highest removal rates achieved in biosurfactant supplemented cultures were: 100% for phenanthrene, 95.32% for pyrene, 82.71% for benz(a)anthracene and 86.17% for benzo(a)pyrene. The kinetic data used to simulate removal rates were suitably described by first-order kinetics, with the rate constants showing that phenanthrene removal was rapid in cultures without biosurfactant (k = 0.0620 day-1) as well as with biosurfactant (k = 0.0664 day-1), while the removal rates for others followed in the order of their increasing molecular weight. The synergy of the bacterial isolates and the biosurfactant produced from B. vulgaris agrowaste could be used in environmental bioremediation of PAHs even in silty soil.Keywords: Benz(a)anthracene, benzo(a)pyrene, bioremediation, biosurfactant, Beta vulgaris, polycyclic aromatic hydrocarbon

Buccal corridor changes in orthodontically treated extraction and non-extraction Class 1 patients

Patients seek orthodontic treatment mainly to improve their facial aesthetics and obtain an acceptable smile. It is purported that orthodontic extraction treatment may result in narrow buccal corridors which in turn may lead to unaesthetic smile. To determine if the dimensions of the buccal corridors are influenced by extraction or non-extraction treatment in Class 1 patients. Retrospective record-based study conducted between 2012 and 2017 at University of Pretoria Orthodontic department. Smile pictures of pre- and post-treatment Class 1 patients treated with or without premolar extractions were matched. Buccal corridors between the two groups were measured by measurement of visible maxillary dentition and oral aperture dimensions. Data analysis included frequencies and correlations using chi-square test, with a significance level set at p<0.05. Seventy-one patient records met the selection criteria with the majority being females (70%). The age range was between 10 and 37 with a mean of 17.5 years. Thirty-five patients were treated with extractions and thirty-six patients with non-extraction treatment. There was a significant difference in the visible maxillary dentition pre and post treatment with extraction patients showing a 6 to 6 and non-extraction showing 5 to 5 dentition post treatment (p<0.05). There were no differences in the ratios of the visible maxillary dentition and oral aperture in both groups pre and post treatment (p> 0.05). Orthodontic treatment of Class 1 cases with premolar extraction did not lead to deleterious changes in the buccal corridors

The roots of civic apathy in local government

The dissertation deals with the roots of civic apathy in local government, and the main emphasis is to establish the root cause/s of civic apathy. The hypothesis: 'civic apathy is a phenomenon intensified by ignorance and a feeling of powerlessness and frustration on the electorate' is tested in this study. To examine further specific aspects of civic apathy, including establishing the cause/s and effects of apathy, the author conducted a quantitative research in the Northern Metropolitan Area m Johannesburg, using questionnaires and literature study as the research method. The hypothesis advanced in the dissertation has been validated insofar as it has been argued and demonstrated that indeed people can feel powerless and frustrated if they are deliberately being excluded from, or denied the opportunity to participate actively in their local government activities. The main finding is that civic apathy is intensified by ignorance. However, the most important finding is that there ts a causal relationship between powerlessness, frustration and apathy.Public Administration and ManagementM. Admin. (Public Administration