jog1641319262.docx Submitter: Date: Supervisor: Takahiro Fujioka June 2011 (1 May 2011 – 31 May 2011) Dr Long Nghiem Progress Report No.13 Assessment and optimisation of N-nitrosamine rejection by reverse osmosis for planned potable water recycling applications [Objectives] Evaluating the impact of flux on the rejection of N-nitrosamines with two RO membranes (TFC-HR and 70LW) [Conclusions] The rejection of N-nitrosamines increased with increasing flux The TFC-HR showed 36 % NDMA rejection with L/m2h flux, while the 70LW showed as low as 12 % NDMA rejection with L/m 2h flux [Materials and test protocols] Test conditions Flux: Retentate flow: N-nitrosamine concentration: Background electrolyte: Solution temperature: pH: 42, 30, 20, 10 and L/m2h 30.4 cm/s 250 ng/L 20 mM NaCl, mM NaHCO3, mM CaCl2 20 °C [Results] Rejections of N-nitrosamines The rejection of N-nitrosamines increased with increasing flux as shown in Figure This is attributed to the membrane rejection mechanism that increase in solute flux is slower than that in permeate flux Nevertheless, the rejections of NDMA and NMEA with flux 30 L/m 2h did not follow the trend Figure 1: Rejections against their molecular weight with five different flux (TFC-HR) 13-1 jog1641319262.docx Figure shows the rejection of N-nitrosamines tested for five different flux with the 70LW membrane Although the rejection of NDMA did not follow the increasing rejection trend with increasing flux, the rejection of other N-nitrosamines increased with increasing flux Figure 2: Rejections against their molecular weight with five different flux (70LW) The real rejections of NDMA, NMEA and NYPR with the TFC-HR membrane are plotted as a function of reciprocal flux in Figure Real rejection (Rreal) is calculated with observed rejection (Robs) and equation (3) Curves in the figure are calculated with equations (1) - (2) and the calculated reflection coefficient (σ) and solute permeability coefficient (p) are shown in Table The curves of NYPR and NMEA are agreed well with the experimental data NYPR 0.9 0.8 NMEA 0.7 NDMA* R () 0.6 0.5 NDMA 0.4 0.3 0.2 0.1 1/Jv (s/m) 10 x 10 Figure 3: Real rejection as a function of reciprocal flux for NDMA, NMEA and NYPR (TFC-HR) Table 1: Reflection coefficient (σ) and solute permeability coefficient (p) NDMA* NDMA NMEA (without 30 L/m2h result) 0.639 0.765 0.961 σ (-) 1.23E-06 1.71E-06 1.03E-06 p (m/s) 0.55 0.96 0.94 R2 (-) 13-2 NPYR 0.994 4.09E-07 0.90 jog1641319262.docx [Plans of next month] The tasks planned for the next month include: Continue to carry out rejection tests as shown in Table 2 Writing a review article Table 2: Test Plan for the coming month TFC-HR (Koch) Flux Analysis (Repeat) pH Analysis Ionic Strength Analysis N-nitrosamine JUN concentration Temperature Analysis *Analysis: Filtration test has been finished ESPA2 (Hydranautics) JUN JUN JUN JUN 70LW (Toray) JUN (Repeat) - BW30 (Dow) - JUN - - [Appendix: Model] Real rejection can be expressed by the following Spiegler-Kedem equations based on irreversible thermodynamic model (1) (2) where Cp = permeate concentration (ng/L), Cm = membrane concentration (ng/L), σ = reflection coefficient (-), p = solute permeability coefficient (m/s) and Jv = water flux (m/s) Since real rejection (Rreal) needs to be used to discuss about membrane rejection mechanism, real rejection (Rreal) is calculated with observed rejection (Robs) by following the concentration polarization equation: (3) where k = mass transfer coefficient (m/s) Mass transfer coefficient k can be calculated by Sherwood number In case the test is operated under laminar flow conditions (Re < 2000) and the length of the entry region (L*) is larger than the length of the membrane (L), Sherwood number can be expressed by Grover equation [1]: (4) where Sh = (dhk/D), Re = (dhu/ν), Sc = (ν/D), dh = hydraulic diameter, D = diffusion coefficient, u = feed velocity (m/s) and ν = kinetic viscosity (m2/s) Diffusion coefficient of each N-nitrosamine is based on the database from GSI Environmental Inc (http://www.gsi-net.com/en/publications/gsi-chemical-database.html) [Reference] van den Berg, G.B., I.G Rácz, and C.A Smolders, Mass transfer coefficients in cross-flow ultrafiltration J Membr Sci., 1989 47(1-2): p 25-51 13-3 ... 0.639 0.765 0.961 σ (-) 1.23E-06 1.71E-06 1.03E-06 p (m/s) 0.55 0.96 0.94 R2 (-) 1 3-2 NPYR 0.994 4.09E-07 0.90 jog1641319262.docx [Plans of next month] The tasks planned for the next month include:... Plan for the coming month TFC-HR (Koch) Flux Analysis (Repeat) pH Analysis Ionic Strength Analysis N-nitrosamine JUN concentration Temperature Analysis *Analysis: Filtration test has been finished... (m/s) and ν = kinetic viscosity (m2/s) Diffusion coefficient of each N-nitrosamine is based on the database from GSI Environmental Inc (http://www.gsi-net.com/en/publications/gsi-chemical-database.html)