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Research Publications (Engineering and Built Environment)

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Author: search.filters.author.Rathilal, SudeshSubject: search.filters.subject.Textile effluent

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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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    Reclamation of end-of-pipe textile effluent using low energy membrane systems
    (South African Institution of Chemical Engineers, 2015) Xaba, P; Rathilal, Sudesh; Pillay, L.
    In this study, the reclamation of end-of-pipe textile effluent originating from a reactive dyeing textile mill was investigated using low energy membrane based processes. Effluent quality, salt recovery and membrane recovery were the main parameters used to evaluate the membrane process. Flat sheets of the SR90 and NF90 Dow FilmTech nanofiltration (NF) membranes were used on a pilot scale membrane system. The UF multipore membrane was used in the pretreatment runs. The quality of reclaimed water was measured against the specified water quality in terms of the internal criteria for effluent recycle (ICFER) provided by the mill. It was required to optimize the SR90 and NF90 membrane performances so as to set operating parameters for pilot study. The average critical flux for the SR90 membrane was found to be ±31 LMH at 5 bar TMP when directly feeding the effluent without any pretreatment. The average critical flux for the NF90 membrane was found to be approximately ±15 LMH at 10 bar TMP when no pretreatment was used. All rejections were found to be >90% for all specified parameters as per Table 1. The quality results from the SR90 and NF90 membranes with pretreatment showed that the permeate could be recycled and reused in the dying processes within the mill. It was however concluded that the NF90 membrane produces high quality effluent as compared to the SR90. It was of importance to determine if the SR90 and NF90 membranes could be recovered and reused after directly feeding un-pretreated feed effluent. The flux recoveries on the SR90 and NF90 membranes were 84.72% and 82.17%, respectively after chemical cleaning. It was further concluded that the salt initially fed in the dying process could be recovered from the waste stream especially when using the SR90 membrane for reuse. However, the colour parameter was found to be slightly out of specification when using the SR90 membrane. To improve the colour of effluent produced when using the SR90, it was recommended that a granular activated carbon filter needs to be employed downstream of the process to polish the effluent.