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The aim of this study was to investigate the best pretreatment of textile wastewater (TWW) for membrane separation processes and the previously unexplored reuse of treated TWW for washing dyeing machines. Sand filtration (SF), coagulation, coagulation/flocculation, and ultrafiltration (UF) with hollow fiber membrane (ZW1) were used for pretreatment. Pretreatment selection was based on turbidity, total organic carbon (TOC), and color. SF and ZW1 were found to be the best pretreatments. In addition, the SF and ZW1 effluents were subjected to the 5 (PT) and 50 (MW) kDa UF flat sheet membranes to test removal efficiency. ZW1-PT was better in terms of removal results and fouling. To reduce the use of drinking water for washing dyeing machines, the characteristics of ZW1-PT effluent were compared with drinking water from a textile factory. TWW treated with this hybrid process fulfils the purpose of reuse for washing dyeing machines and can be used in Galeb d.d., Croatia, or in any other textile factory, saving up to 26,000 m3 of drinking water per year. This contributes to both sustainable production and the conservation of water resources.

Otpadne vode tekstilne industrije pripadaju kategoriji najjače onečišćenih industrijskih otpadnih voda te su posebna opasnost za vodeni okoliš. Cilj ovog istraživanja bio je ispitati membransku učinkovitost zadržavanja bojila iz tekstilne otpadne vode (TOV) s komercijalnim ultrafiltracijskim (UF) membranama (GH, GK, PT, PU, PW, MW) širokog područja graničnih molekulskih masa (MWCO), od 2 do 50 kDa. Testirane UF membrane rezultirale su smanjenjem obojenja i intenziteta obojenja od 56,35 % do 97,93 %. Membrane nižih MWCO vrijednosti (ispod 3 kDa) mogu se smatrati prikladnim za uklanjanje bojila iz realnog uzorka TOV-a.

Pharmaceuticals are present in various waters and can be almost completely rejected by membrane separation processes, i.e., nanofiltration (NF) and reverse osmosis (RO). Nevertheless, the adsorption of pharmaceuticals can decrease their rejection, so adsorption can be considered a very important removal mechanism. In order to increase the lifetime of the membranes, the adsorbed pharmaceuticals must be cleaned from the membrane. The used pharmaceutical (albendazole), the most common anthelmintic for threatening worms, has been shown to adsorb to the membrane (solute-membrane adsorption). In this paper, which is a novelty, commercially available cleaning reagents, NaOH/EDTA solution, and methanol (20%, 50%, and ≥99.6%) were used for pharmaceutical cleaning (desorption) of the NF/RO membranes used. The effectiveness of the cleaning was verified by Fourier-transform infrared spectra of the membranes. Of all the chemical cleaning reagents used, pure methanol was the only cleaning reagent that removed albendazole from the membranes.

The influence of textile wastewater (TWW) secondary effluent on ultrafiltration (UF) membrane characteristics was investigated. TWW treated with a membrane bioreactor was subjected to four commercial UF membranes (2, 3, 5, and 10 kDa). Both the pristine membranes and the membranes after TWW secondary effluent treatment were characterized. Surface roughness, microscopic analysis of the membrane surface and cross-section, zeta potential, contact angle, membrane composition, and membrane flux were compared. After treatment of secondary effluent, the zeta potential decreased for 5 and 10 kDa membranes, while the contact angle and surface roughness increased for all investigated membranes. In addition, a fouling layer formed on all membranes, and new interactions with pollutants and membranes were confirmed. Membranes with larger pores (5 and 10 kDa) showed a greater decrease in permeate flux during treatment. Detailed analysis showed variations in membrane characteristics after TWW secondary effluent treatment, indicating the stability of the membranes used.