Reuse of reactive dyehouse wastewater by nanofiltration: Process water quality and economical implications

This paper presents the permeate water quality and economy of reuse by nanofiltration membranes in reactive dyeing. Actual remazol dye bath wastewater, which contains high concentrations of NaCl at the level of 80 g/l, was studied during experiments. Experimental results showed that permeate samples were colorless and remained enough NaCl to be reused in reactive dye bath preparation again. Neutralization by HCl decreased the permeate flux and also increased the NaCl recovery. Permeate flux value was about 10 l/m² h and Cl^- rejection was achieved at the level of 10%. In addition, economical analyses were done based on experimental results and the payback period of the reuse system was calculated as less than 2 years.