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Research Publications (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215

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Author: search.filters.author.Pillay, Visvanathan Lingamurti

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    Fouling mitigation on a woven fibre microfiltration membrane for the treatment of raw water
    (Institution of Chemical Engineers, 2017-06) Chollom, Martha Noro; Pikwa, Kumnandi; Rathilal, Sudesh; Pillay, Visvanathan Lingamurti
    The main source of drinking water in rural areas of South Africa is surface water. Improving drinking water and sanitation facilities alone does not completely solve the problem of waterborne diseases. A novel simple gravity driven filtration unit incorporated with the woven fibre microfiltration (WFMF) membranes was developed for the treatment of raw water for drinking purposes. However, these membranes are susceptible to fouling which reduces flux permeation. This paper focused on evaluating the fouling mitigation strategies to improve on performance of the woven fibre membrane filtration unit with respect to fouling and flux recovery. The study found that the WFMF membrane fouled both internally by pore plugging and externally by adsorption and deposition on the membrane. As a result, a single flux enhancement strategy proved insufficient to maintain high flux successfully. A combination of strategies gave the best optimum conditions for flux production. Backwashing with a combination of brushing yielded the highest recovery of 187%. Soaking the membranes in 0.2% hypochlorite for an hour and thereafter by brushing them yielded 93% flux recovery. Mechanical cleaning however yielded the best result with 97% flux recovery. It was concluded that the selected strategies were the most successful strategies to prevent a sharp decline in flux due to fouling and giving high average flux for the filtration period.
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    Development and evaluation of a small scale water disinfection system
    (IWA Publishing, 2016-07-08) Alfa, Dorcas; Rathilal, Sudesh; Pikwa, Kumnandi; Chollom, Martha Noro; Pillay, Visvanathan Lingamurti
    Provision of microbiologically safe drinking water for people living in the rural areas of developing countries remains a major challenge to date. A simple gravity-driven membrane point of use system was developed based on woven fabric microfiltration (WFMF) membranes. The WFMF is a loose type of membrane (0.45 μm). However, complete disinfection is not achieved with the WFMF, hence it was incorporated with two disinfectants. This study aimed to combine the WFMF with two disinfectants (Water guard and bromochlor tablets) to bring the water to the accepted quality for drinking. Four different types of water were sourced, considering two factors; E. coli and turbidity content. The WFMF demonstrated excellent filtration performance by producing permeates with turbidity less than 1 NTU for feed turbidity ranging between 10 and 200 NTU. There was 95–99.8% E. coli removal for raw feeds with influent E. coli ranging between 500 and 44,500 CFU/100 mL. Total disinfection was achieved with both disinfectants, however, the effectiveness of the chemical disinfectants in E. coli removal was affected by the quality of water to be disinfected. The study showed that turbidity plays a major role in disinfection performances by increasing chlorine demand on water sources with high turbidity levels.
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    The applicability of nanofiltration for the treatment and reuse of textile reactive dye effluent
    (AJOL, 2015) Chollom, Martha Noro; Rathilal, Sudesh; Pillay, Visvanathan Lingamurti; Alfa, Dorcas
    The main aim of the study was to test the feasibility of using nanofiltration (NF) processes for the treatment of reactive dye-bath effluents from the textile industry, in order to recover the water and chemicals (salts) for reuse purposes. The study of the reusability of nanofiltered water for dyeing has been given little or no attention. About 30% of reactive dyes remain unfixed on fibres; the unfixed dyes are responsible for the colouration in effluents. Membrane processes were employed to treat reactive dye-bath effluents to recover the salts and water. Investigations were conducted firstly with ultrafiltration (UF) used as a pre-treatment for NF. Secondly, evaluations were performed for 2 types of NF membranes (SR90 and NF90), in terms of quality of permeate produced and fluxes achieved for 2 different samples of effluent. The effect of cleaning on membrane performance was assessed. A reusability test was carried out on both permeate samples for dyeing light and dark shade recipes. The use of UF as pre-treatment to NF resulted in rejection of colloidal substances > 90% and a 15% flux improvement. Permeate from NF90 had a conductivity of 76 µS/cm and total organic carbon (TOC) of 20 mg/ℓ, as compared to SR90 which had a conductivity of 8.3 mS/cm and a TOC of 58 mg/ℓ. Light shade from NF90 gave satisfactory results on dyeing, with no colour difference. However a variation in colour was noticed when the medium sample was used to dye the light shade. Both NF permeates gave satisfactory results when used to dye the dark shades. Permeate from NF90 was within the accepted range for reuse, while permeate from SR90 had a higher salt recovery. Chemical cleaning resulted in 80% flux recovery. From the reusability test it was concluded that permeate from NF90 met the reuse criteria for feed water to the dye bath.
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    Development and evaluation of woven fabric microfiltration membranes impregnated with silver nanoparticles for potable water treatment
    (Elsevier, 2014-02-06) Mecha, C.A.; Pillay, Visvanathan Lingamurti
    Access to clean and safe drinking water is a fundamental human need, which is commonly lacking in remote rural areas. A simple gravity-fed water treatment unit was developed based on woven fabric microfiltration (WFMF) membranes. However, since these membranes are loose micro-filters, the unit has to be used in conjunction with a disinfectant. This paper explores combining the WFMF membranes with silver nanoparticles (AgNPs) using a modified chemical reduction method. The originally white membranes turned brown–yellow due to the surface plasmon resonance of silver; however, there was no significant difference in the morphology of the membranes after the impregnation with 0.0117 wt%AgNPs. The coated membranes were more hydrophilic and had higher water permeability (po0.05). Filtration of turbid water (40–700 NTU) showed that both membranes produced clear permeate (o1 NTU). Treatment of water spiked with bacteria (2500–77,000 CFU/100 mL Escherichia coli) showed that the removal efficiency of uncoated membranes was 84–91% and that of coated membranes was 100%. Accordingly, the coated membranes depicted great potential for water treatment. To the best of our knowledge, this is the first study that investigated the incorporation of AgNPs in WFMF membranes and characterized their properties.
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    Membrane fouling characterization in membrane-based septic tank
    (Taylor and Francis, 2013-04-15) Ali, Saadat; Pillay, Visvanathan Lingamurti; Khan, Sher Jamal; Visvanathan, C.
    Septic tank is a conventional on-site wastewater disposal system providing only primary treatment (settlement of solids), while offering little biological degradation. To further improve the quality of treated water, the conventional septic tank can be modified by the introduction of membrane module capable of effective rejection of suspended solids as well as associated particulate organic matter. However, membrane fouling by partially-treated water can be considered as one of the major limitations of the membrane-based septic tank (MBST) system. The present study was carried out in a pilot-scale MBST by using flat-sheet woven fiber microfiltration (WFMF) membrane modules. WFMF membrane module having 1 m2 effective filtration area was submerged in septic tank of 4 m3 working volume and operated at different fluxes to investigate the fouling frequency and effects of cleaning protocols. It was found that the physical cleaning protocol was effective in removing cake as well as partial pore blocking resistance without requiring chemical cleaning. On the other hand, after each operation cycle, the irreversible fouling of membrane increased.