Forward Osmosis: An Approach to Reclaim Dairy Waste Stream Whey

Recognizing the issues with conventional water resources and stricter wastewater effluent disposal standards, the treatment and recovery from wastewater are gaining impetus. The dairy industry consumes a substantial amount of water and generates a massive quantity of wastewater annually. Whey, which is about 94% water, is a waste stream produced in the dairy industry during the manufacture of cheese, paneer, yogurt, etc. Although various wastewater treatment technologies are available in the market, membrane technologies are considered the most advanced and reliable ones, but they are expensive. In recent years, Forward Osmosis (FO) is looked upon as a potential alternative to these costly and energy intensive pressure driven membrane processes. FO works on the principle of natural osmotic pressure where energy is just required to lift the solutions. The present lab-scale study investigates the partial reclamation of water from whey using FO technology. The Continuous Single Pass (CSP) and Recirculation mode (RC) study is conducted using high osmotic pressure (π = 375 bar at 298K) saturated aqueous(aq.) NaCl as the draw solution. The aq. NaCl solution is a potential brine stream in the dairy industry and finds applications in the manufacture of paneer, butter, cheese and ice cream eliminating the need for draw regeneration. The back diffusion study of the Hollow Fibre Forward Osmosis (HFFO) membrane revealed about 0.82% back diffusion of solute. The maximum water recovery of ~ 56% is achieved in CSP mode while 57.6% is achieved for RC mode with Feed/Draw ratio of 4.5:1. For F/D of 10:1, the maximum permeate flux of ~ 8.7 kg m− 2 h− 1 is observed for the CSP mode of operation for 10 minutes of study. Thus, FO is an efficient membrane technique that eliminates the need for draw regeneration and can be applied in the dairy industry.