Integration of Nanofiltration Hollow Fiber Membranes with Coagulation-Flocculation to Treat Colored Wastewater from a Dyestuff Manufacturer: A Pilot-Scale Study

A positively charged nanofiltration (NF) hollow fiber membrane with an antifouling feature has been fabricated and scaled up to pilot scale to treat colored wastewater from a dyestuff manufacturer with the aid of the coagulation-flocculation (CF) process. An effective CF formulation, i.e., iron chloride/anionic polyacrylamide (IC/APAM) = 800/100 ppm, has been identified to treat the NF concentrate stream. The challenges of membrane fouling and processing concentrate streams can be effectively managed by the integrated NF-CF process. The NF process is able to achieve 82% and 67% removal of color and chemical oxygen demand (COD) from the colored wastewater, respectively; while the CF process can remove 91% of color and 81% of COD from the NF concentrate stream. NF and CF were found to complement each other. The NF process alone always generates a concentrate stream, but it can effectively reduce the wastewater volume. The CF processes are particularly favorable for treating small volume concentrate streams. These advantages make the NF-CF process propitious for users located in land- or space-limited places and countries.