to 1760 mg/L and 136.4 to 98.1 mg/L, respectively. Meanwhile, the fully aromatic
nanofiltration membrane demonstrated higher removals of total dissolved solids and
total organic carbon with the concentrations from 2090 to 1340 mg/L and 136.4 to
89.7 mg/L, respectively. Ebrahimi et al. (2010) treated the oily wastewater using two
different ceramic nanofiltration membranes composed of titania (with 1000 Da), and
titania and alumina (with 750 Da). Both the membranes were able to completely
remove the oil, and the total organic carbon concentration was reduced by 49.8% at a
low pressure of 1 bar.
11.3.4 Reverse Osmosis
The pressure-driven reverse osmosis technology has been widely used for various
water separation applications. Osmosis is a natural phenomenon in which the solvent
molecules travel from a region of lower solute concentration to a region with higher
solute concentration through a semipermeable barrier until the osmotic equilibrium
is reached. On the other hand, in reverse osmosis, the solvent molecules are forced to
flow in the direction towards a region of lower solute concentration with the aid of
applied pressure higher than the osmotic pressure. Reverse osmosis could reject all
sort of solutes including the monovalent ions, hence it usually achieves higher solute
rejections compared to nanofiltration (da Silva Biron et al. 2018; Li 2007). However,
due to small pore sizes, reverse osmosis and nanofiltration are not preferable for oily
wastewater treatment applications due to relatively low flux and high energy consumption (Wan Ikhsan et al. 2017).
Reverse osmosis membranes are made from various materials such as polyamide,
zeolite, polyethersulfone, and polyvinylidene fluoride. Past studies have witnessed
significant efforts to mitigate the limitations of the reverse osmosis membranes in
handling the oily wastewater with complex compounds (Mondal and
Wickramasinghe 2008; Fakhru’l-Razi et al. 2010; Murray-Gulde et al. 2003;
Barrufet et al. 2005; Franks et al. 2009). Lee and Dong (2004) used a synthetic
zeolite reverse osmosis membrane to reduce the salinity of the oily wastewater in the
upstream process of the oil production. The oily wastewater was reported to have a
high total dissolved solids concentration of 181,600 mg/L. The reverse osmosis
process managed to reduce the concentration to 32,700 mg/L with a permeate flux of
0.018 kg/m
2 h at the pressure of 55 bar. Liu et al. (2008) fabricated the MFI-typed
silicate zeolite reverse osmosis membrane for the treatment of the synthetic oily
wastewater that contained some organic solvents such as hexane. The membrane
demonstrated a high rejection performance of 96.5% with a permeate flux of
0.33 kg/m
2 h at a pressure of 27.6 bar. In addition, the membrane also exhibited a
salt rejection of 99.4% when 0.1 M salt solution was used.
Fakhru’l-Razi et al. (2010) studied the reverse osmosis performance of
polyethersulfone and polyvinylidene fluoride membranes in the oily wastewater
treatment. The study was conducted at an operating pressure of 60 bar. The results
revealed that the membrane exhibited outstanding removal efficiency of 92–94%
11 Oily Wastewater Treatment
369
nanofiltration membrane demonstrated higher removals of total dissolved solids and
total organic carbon with the concentrations from 2090 to 1340 mg/L and 136.4 to
89.7 mg/L, respectively. Ebrahimi et al. (2010) treated the oily wastewater using two
different ceramic nanofiltration membranes composed of titania (with 1000 Da), and
titania and alumina (with 750 Da). Both the membranes were able to completely
remove the oil, and the total organic carbon concentration was reduced by 49.8% at a
low pressure of 1 bar.
11.3.4 Reverse Osmosis
The pressure-driven reverse osmosis technology has been widely used for various
water separation applications. Osmosis is a natural phenomenon in which the solvent
molecules travel from a region of lower solute concentration to a region with higher
solute concentration through a semipermeable barrier until the osmotic equilibrium
is reached. On the other hand, in reverse osmosis, the solvent molecules are forced to
flow in the direction towards a region of lower solute concentration with the aid of
applied pressure higher than the osmotic pressure. Reverse osmosis could reject all
sort of solutes including the monovalent ions, hence it usually achieves higher solute
rejections compared to nanofiltration (da Silva Biron et al. 2018; Li 2007). However,
due to small pore sizes, reverse osmosis and nanofiltration are not preferable for oily
wastewater treatment applications due to relatively low flux and high energy consumption (Wan Ikhsan et al. 2017).
Reverse osmosis membranes are made from various materials such as polyamide,
zeolite, polyethersulfone, and polyvinylidene fluoride. Past studies have witnessed
significant efforts to mitigate the limitations of the reverse osmosis membranes in
handling the oily wastewater with complex compounds (Mondal and
Wickramasinghe 2008; Fakhru’l-Razi et al. 2010; Murray-Gulde et al. 2003;
Barrufet et al. 2005; Franks et al. 2009). Lee and Dong (2004) used a synthetic
zeolite reverse osmosis membrane to reduce the salinity of the oily wastewater in the
upstream process of the oil production. The oily wastewater was reported to have a
high total dissolved solids concentration of 181,600 mg/L. The reverse osmosis
process managed to reduce the concentration to 32,700 mg/L with a permeate flux of
0.018 kg/m
2 h at the pressure of 55 bar. Liu et al. (2008) fabricated the MFI-typed
silicate zeolite reverse osmosis membrane for the treatment of the synthetic oily
wastewater that contained some organic solvents such as hexane. The membrane
demonstrated a high rejection performance of 96.5% with a permeate flux of
0.33 kg/m
2 h at a pressure of 27.6 bar. In addition, the membrane also exhibited a
salt rejection of 99.4% when 0.1 M salt solution was used.
Fakhru’l-Razi et al. (2010) studied the reverse osmosis performance of
polyethersulfone and polyvinylidene fluoride membranes in the oily wastewater
treatment. The study was conducted at an operating pressure of 60 bar. The results
revealed that the membrane exhibited outstanding removal efficiency of 92–94%
11 Oily Wastewater Treatment
369