Dataset - Continuous regeneration of the draw solution in textile wastewater treatment using a combination of simultaneous forward osmosis and reverse osmosis

Description

Methods

Materials and Methods

Membrane plant

A pilot plant, which combines an FO line and an RO line, was employed to perform the treatment of the textile wastewater. The employed pilot plant was designed for the simultaneous application of FO and RO. The pilot setup is equipped with two 200 L tanks corresponding to the feed solution for the RO process and the feed solution for the FO process. The plant contains three pumps (P1 and P2 were self-priming centrifugal pumps, whereas P3 was a high-pressure piston pump). Also, it was equipped with a SW30-2540 spiral-wound membrane (DuPont, USA) as the RO membrane, with an active area of 2.8 m2, and a HFFO14® membrane (Aquaporin, Denmark) as the FO membrane, with an active area of 13.8 m2.

Quality control

To assess the quality control of the FO line, the water permeability of the HFFO14® membrane was studied, employing NaCl 0.5 M (with an osmotic pressure of 24.9 bar at 25°C) as the draw solution. The flow rate was set at 400 L/h and 200 L/h for the feed and draw solution inlet, respectively. Similarly, the transmembrane pressure (feed to draw) was set at 0.2 bar. This test lasted 50 minutes. To assess the quality control of the RO line, a 0.5 M NaCl solution was employed as the feed stream. Three different transmembrane pressures were tested (30, 40 and 50 bar), at a feed flow rate of 650 L/h, during 30 minutes. The raw data derived from this operation can be found in the file "water tests"

Short-term operation
Flow rate was set at 400 L/h for the feed stream and at 80 L/h for the draw solution. The transmembrane pressure (feed to draw) was 0.2 bar. Regarding the RO line, the feed flow was adjusted to 650 L/h and the transmembrane pressure was 50 bar. The operation time was 2 hours. The raw data derived from this operation can be found in the file "Dataset A"

Longer-term operation
The concentrated textile wastewater that was obtained from the first set of in-line experiments was employed as the feed solution of a subsequent FO-RO process. Thus, the membrane was submitted to a more challenging feed solution, during a longer period of operation (6 hours). The RO step was conducted at a flow rate of 650 L/h and 50 bar. The raw data derived from this operation can be found in the file "Dataset B"

Cleaning in place
The plant, including the FO and RO lines, was cleaned with deionized water during 15 minutes after each experiment. This flushing was sufficient to clean the RO line. Furthermore, an osmotic backwash was applied during 1 hour to clean the FO membrane. 0.7 M NaCl, whose osmotic pressure is 34.7 bar at 25°C, was used as the feed solution. Deionized water was used on the other side of the membrane. Afterwards, the water permeability of the membrane was assessed, employing 0.5 M NaCl, whose osmotic pressure is 24.8 bar at 25°C, as draw solution.