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.

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.

This chapter deals with the treatment and management of sludge resulting from wastewater treatment using membrane bioreactor (MBR) technology. With the increase in world population and industrial activities, the demand for effective wastewater treatment has increased, generating significant amounts of sludge. Although MBR technology is more efficient in terms of effluent quality, it produces sludge with different rheological and morphological characteristics than conventional activated sludge. This chapter discusses various methods for treating MBR sludge, including stabilization, dewatering, and thermal treatment, which are essential for improving sludge quality and reducing disposal costs. It also examines the potential for the reuse of MBR sludge in agriculture, highlighting methods such as composting and pelletization as sustainable approaches. These methods not only mitigate environmental impacts but also contribute to a circular economy by converting waste into valuable resources. The chapter concludes by highlighting the importance of proper sludge treatment and management to ensure compliance with environmental regulations and to fully utilize the potential of MBR sludge as a resource.