Textile wastewater reusability in knitted fabric washing process using UF membrane technology

Abstract

The textile industry is a massive consumer and polluter of our fresh water. This paper focuses on wastewater produced by the textile industry with the aim of treating and reusing it for certain wet processes in the textile industry, i.e., washing dyed knitted cotton fabric. Accordingly, UF membranes (GH, GK, PT, PU, PW, MW) with different molecular weight cut-offs (MWCO) ranging from 2 to 50 kDa were used. Wastewater treatment studies were performed on a lab scale and all samples were subjected to the following tests: chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total bound nitrogen (TNb), turbidity, conductivity, color, and concentration of SO42−, Na+, Ca2+, K+. The permeate flux was also monitored and investigated in the process due to possible fouling and its effect on membrane performances. Based on the conducted tests, results for the membrane with the lowest MWCO (GH), were 79.8% COD, 56.0% BOD5, 82.4% TOC, 81.0% TNb, > 99.3% turbidity, 79.2% conductivity, 93.1% SO42−, 79.3% Na+, 98.6%, Ca2+, and 53.3% K+ removal which is the highest value of all investigated membranes. For this reason, the same permeate was tested for its suitable use in the process of washing dyed knitted cotton fabric. The results showed a high reuse potential of textile wastewater due to the same quality of dyed knitted cotton fabric washed with the UF permeate and with water used in the factory. The innovative aspect of this research is as follows: 1) direct use of UF membranes (without pre- and post-treatments) for the purpose of reusing treated wastewater in the textile industry in processes as yet not investigated and 2) identifying reuse criteria for washing dyed knitted cotton fabric.