Investigating study on flux enhancement techniques in a Nanofiltration pilot plant – An Experimental overview

Abstract

Water consumption and utilization in chemical allied industries is increasing progressively and global availability of fresh water is reducing. Reclamation of water from various industrial waste streams is play very vital role to overcome the current situation of water scarcity. Various conventional treatment methods are available for water reclamation. The performance of the membrane separation process, in terms of flux and rejection of membrane is directly influenced by the resistances involved during the filtration. This paper examines the flow reversal and pressure pulsation techniques for the flux enhancement in nanofiltration of reactive yellow 160 dye synthetic wastewater in flat sheet membrane module with HPA 150 membrane. Reversing the flow of the feed stream after some definite time intervals by changing the position of the feed stream and the introduction of the compressed air pressure pulse at different frequency parallel to the feed stream helps to alleviate the permeate flux. Nanofiltration with the pulsation of 100 ppm reactive yellow 160 dye solution at 3, 5 and 7 kg/cm2 pressure with the frequency of 1, 2 and 3 min intervals increases the permeate flux as 2.58, 5.12 and 8.80 % respectively. A similar observation was found in reversing the feed (1 min reverse after every 5 min forward feed) at a different pressure. Flux alleviation was nearly 3.02, 6.9 and 10.2 % at 3, 5 and 7 kg/cm2 pressure with flow reversal. 0.70 % permeates flux loss found at 3 kg/cm2 pressure in case of flow reversal while it is 2.22 % in the feed forward system. Similarly, 0.59 and 0.33 % reduction in the permeate flux found at 5 and 7 kg/cm2 while to the same pressure conditions at unidirectional feed system, it is 1.31 % and 0.87 % respectively. Experiments also reveal that while pulsing at 3 kg/cm2 with a frequency of 1,2 and 3 min shows permeate loss of 2.58, 5.01 and 5.21 % respectively compared to the normal feedforward system. Similarly, at 5 and 7 kg/cm2, the % loss of permeate flux value at 1,2 and 3 min are 1.31, 2.03 and 2.69 % and 1.52, 2.06 and 2.60 % respectively.
Key words: Concentration polarization; flux decline; Transmembrane pressure; Nanofiltration.