Faculty of Engineering and Built Environment
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Item Treatment of industrial effluent using specialized, magnetized coagulants(2023-05) Sibiya, Nomthandazo Precious; Rathilal, SudeshThe rapid degradation of water quality caused by industrial effluent presents a significant threat to public health and the ecosystem. This necessitates ecologically sustainable solutions through the coagulation treatment method. Coagulation with chemical coagulants (e.g. alum) is costeffective, but comes with non-recoverability, health and environmental risks. As a result, this study proposes a magnetic-coagulation separation technique as an alternative. Against this brief, the goal of this research was to produce specialized magnetic coagulants for the treatment of industrial wastewater. Three magnetized coagulants (MCs) viz. chitosan magnetite (CF), eggshell magnetite (EF), and rice starch magnetite (RF) were synthesized via the co-precipitation technique by using chitosan, eggshell, or rice starch with Fe3O4 nanoparticles (F) in three distinct ratios (1:2, 1:1, and 2:1). The analytical results via the Fourier-transform infrared (FTIR) spectroscopy, Brunauer– Emmett–Teller (BET) analyzer, X-ray diffraction (XRD) analyzer, and scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) spectroscopy respectively affirmed the success of MCs functional and molecular properties, surface area, crystal structure, surface morphology, and elemental compositions. Following that, a series of investigations were carried out utilizing coagulation and dissolved air flotation (DAF) methods to investigate the application and treatability performance of the MCs. Amongst the MCs, the RF(1:1) was found to be the most successful, removing over 75% of the turbidity, total suspended solids (TSS), and over 50% of the chemical oxygen demand (COD) from a local industrial effluent. Furthermore, response surface methodology (RSM) based on a Box–Behnken design (BBD) was used to optimize and compare the coagulation and DAF methods. With coagulant dose (2 – 4 g), settling/flotation time (10 – 60 min) and mixing rate (50 – 150 rpm), the optimum coagulation conditions of 4 g dose, 30 minutes of settling time, and a mixing rate of 50 rpm, achieved a desirability of 87.20%. A 15-min flotation time, with a mixing rate of 50 rpm, and a coagulant dose of 4 g resulted in 77.4% desirability in the DAF method. The DAF method was considered to be more favorable with a shorter settling/flotation time and a desirability of 75% with 95% confidence. Notably, the RSM-BBD models demonstrated a strong correlation (0.9 < R 2 < 1) with predicted results that were consistent with the experimental data. The recent findings indicate that the prospects of MCs are possible for wastewater treatment, and hence magnetic separation technology should be given consideration in water and wastewater treatment settings.Item Production of biogas from sugarcane residues(2018) Malunga, Sthembiso Patrick; Isa, Yusuf MakarfiDue to high production costs facing South African sugar manufacturing industries, production of sugar alone may not be profitable. For sugar manufacturing industries to be economically viable, a novel approach research on other value-added potential products is of paramount importance. The aim of this work was to conduct a feasibility study on biogas production from anaerobic digestion (AD) of sugarcane bagasse, molasses and leaves using cow dung as co- substrate. Three sets of 12 independent batch laboratory experiments for each residue were carried out at temperature of 35oC and hydraulic retention time (HRT) of 14 days using 500 ml bottles as digesters. Design-Expert software was used for design of experiment, process optimisation and process modelling. One variable at a time (OVAT) and 2-Dimensional (2-D) graphical analysis methods were used to analyse the effects of cow dung to sugarcane residues (C:SR) feed ratio, media solution pH and digester’s moisture content on biogas volume, methane yield and kinetic constants. The results indicated that the effect of C:SR feed ratio, media solution pH and digester’s moisture content on biogas volume, methane yield, biogas production potential, maximum biogas production rate and lag phase is mutually reliant between all variables, i.e., depended on conditions of other process variables. The optimum biogas volume generated by bagasse, sugarcane leaves, and molasses experiments were found to be 305.87 ml, 522.69 ml and 719.24 ml and respectively. The results showed that the optimum methane yield achieved by bagasse, sugarcane leaves, and molasses experiments were 28.75 ml/gVS, 87.18 ml/gVS, and 85.32 ml/gVS respectively. The overall results showed that sugarcane bagasse, molasses and leaves can be potentially converted into biogas through AD process.Item The effect of biomass acclimation on the co-digestion of toxic organic effluents in anaerobic digesters(2008) Chamane, Ziphathele; Pillay, Lingam; Buckley, Chris; Remigi, EnricoCurrently KwaZulu-Natal (KZN) province is populated with textile industry, which produces wastewater, some of which is not biodegradable. Due to the stringent environmental regulations the wastewater cannot be discharged into the rivers or public owned treatment systems. The alternative solution is to co-dispose this wastewater with easily biodegradable waste (labile effluent). The aim of this investigation was to develop a process protocol for the codigestion of high strength and toxic organic effluents under mesophilic conditions (35°C ± 2°C), with emphasis on the effect of biomass acclimation. A total of four effluents were chosen for this study, two labile (distillery and size) and two recalcitrant (scour dye and reactive dye). Two anaerobic batch experiments and two pilot scale trials were performed. The first batch anaerobic experiment investigated the influence of biomass source in anaerobic treatability. The second batch test investigated, whether biomass acclimation enhanced the biodegradability of pollutants. The pilot scale trials were the scale up version of the biomass acclimation test. The results showed sludge from Umbilo Wastewater Treatment Works was a superior biomass source, producing more gas and methane compared to Mpumalanga waste. For the high strength organic waste, the acclimated size and distillery samples produced 50% more biogas and methane compared to non-acclimated samples. This confirms that the biomass acclimation enhances the biodegradability. The biomass acclimation did not enhance the biodegradability of the recalcitrant effluent (scour dye). The pilot scale trials did not yield meaningful data; therefore it could not be proven if acclimation works on a larger scale.