Rejection performance

Figure 2. Rejection performance of five different RO membranes (6). A, methanol B, aniline C, formaldehyde D, methyl acetate E, acetic acid F, urea G, ethanol H, acetone 1, hydroquinone J, isopropyl alcohol Kt glycerol L, sodium chloride M, ethyl ether N, phenol. Conditions pressure, 40.8 atm temperature, 24 °C feed, 0.30 gal/min.

Temperature influences system flux and rejection performance. Figures 9.3 and 9.4 shows the effect on water flux and salt... 

Microriltraticiii and ultraTiltratiop of lees or crude wines. More specifically, crossflow micro- and ultra-filtration ceramic membranes have the potential for replacing all the above separation steps except cold treatment [Castelas and Serrano, 1989]. When using inorganic membranes for removing bacterias, yeasts or suspended particles, the choice of the pore size is very important in determining the filtrate flux and the rejection performance of these materials from wines. 

Chan R., Chen V., and Bucknall M.P., Ultrafiltration of protein mixtures Measurement of apparent critical flux, rejection performance, and identification of protein deposition. Desalination 146 2002 83-90. 

Cellulose acetate (CA) is still considered the preeminent membrane for wastewater treatment because it is capable of producing the highest flux per unit surface area at specified levels of solute rejection. The rejection performance of RO using a 90% sodium chloride rejection CA membrane was studied. Phosphorous removal was greater than 95% in all cases. Ammonia removals were generally in excess of 90%, and nitrite and nitrate removals generally ranged from 84% to 97% (32). 

The thin film composite membrane exhibited superior overall rejection performance in these tests, with ammonia and nitrate rejection showing an outstanding improvement. It has also been reported that silica rejection by the thin film composite membranes is superior to that of cellulose acetate. While the above data indicates a marginal improvement in the rejection of chemical oxygen demand (COD), which is an indication of organic content, other tests conducted by membrane manufacturers show that the polyurea and polyamide membrane barrier layers exhibit an organic rejection that is clearly superior to that of cellulose acetate. Reverse osmosis element manufacturers should be contacted for rejection data on specific organic compounds. ... 

Sulfuric acid and sodium hexametaphosphate (SHMP) are injected in the feedwater line upstream of the cartridge filters. The sulfuric acid is injected to adjust the feedwater pH to a level of between 4 and 6. The purpose of acid injection is twofold. The primary purpose is to mitigate the possibility of calcium carbonate deposition by conversion of bicarbonate to carbon dioxide. Coincidentally, the rejection performance of the thin film composite membrane is pH sensitive and the optimum performance is at the operating pH level. SHMP is added to the feedwater as a threshold inhibitor to inhibit the crystalline growth of sparingly soluble salts such as calcium sulfate. 

The molecular architecture of PEO-PPO-PEO is more favorable than PPO-PEO-PPO. The larger mass fraction of Pluronic enhanced membrane hydrophilicity. Furthermore, the longer PEO and PPO chain could significantly improve rejection performance and block stability. 

Two concentrations of docosane (0.33 M and 0.67 M) in toluene were tested at various pressures and flow rates. The results for the permeate flux and docosane rejection are presented in Fig. 4.5 (A, A, B, B ). As can be seen from the figures, both docosane rejection and permeate flux decrease with decreasing pressure at both concentrations. The fluxes and rejections are lower at the higher docosane concentrations. This type of result is not surprising and has been observed previously with other systems [43, 44]. Experimentally, the flow rate through the crossflow cell does not have a significant effect on the flux or the rejection performance. 

Reflux, on the other hand, can only be used to control a temperature in the upper section of the column. The hydraulic lags of liquid flowing down the column from tray-to-tray are typically 3-6 s per tray. Thus, attempting to control a temperature 40 trays down in the column will introduce a 2-A min lag in the loop, which will adversely affect load rejection performance. 

The plant-wide control system developed before is finally applied to the modelled process in HYSYS.PLANT and evaluated based on its close-loop dynamic behaviour and disturbance rejections performance. Once the control system of the non-heat integrated plant is validated, the favoured HEN design, based on its operational performance, is integrated within the entire plant and its control system is linked with the proposed plant-wide control structure mainly through cascade control configurations. 

To overcome the problems of cellulose acetate membranes, many synthetic polymeric materials for reverse osmosis were proposed, but except for one material, none of them proved successful. The only one material, which could remain on the market, was the linear aromatic polyamide with pendant sulfonic acid groups, as shown in Figure 1.2. This material was proposed by DuPont, which fabricated very fine hollow fiber membranes the modules of this membrane were designated B-9 and B-10. They have a high rejection performance, which can be used for single-stage seawater desalination. They were widely used for mainly seawater or brackish water desalination and recovery of valuable materials such as electric deposition paints, until DuPont withdrew them from the market in 2001. 

Boron Rejection Performance of Used Membrane Element... 

From 2003 to 2005, Toray developed and released TM820A, whose performance was appreciably improved, and offered the membrane that showed around 95% boron rejection prior to other companies. However, the supportive systems are still required to meet the WHO proposal even by using TM820A as above. Thus, the next target is 97 or 99% boron rejection performance of renovative membrane. The further development of a new... 

Figure 1.7 History and prospect of boron rejection performance of SWRO membrane element in Toray and comparable companies.

Silica rejection performance of the cross-flow spiral-wound EDI test modules was also evaluated at various water temperatures and applied direct currents at a constant dilute flow rate in Figure 13.12. The dilute flow rate was kept constant at 8.5 gpm per EDI test module. 

Figure 13.12 clearly shows that increase in water temperatures and/or increase in applied current improves the sUica rejection performance of the EDI modules. 

The curves between sihca rejection efficiency and SWE in the beginning show a high sUica rejection plateau as the SWE decreased, which evenmaUy gives way to deterioration in product sUica at lower SWE values (Fig. 13.13). The rudimentary requirement is to operate the EDI modules at high SWE (low current efficiency) to attain the desired product water quahty in terms of resistivity and sUica rejection performance for a given feed water conductivity and temperature. 

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