To enhance the efficiency of water treatment and reduce the extent of membrane fouling, the membrane separation process is frequently preceded by other physico-chemical processes. One of them might be ion exchange. The aim of this work was to compare the efficiency of natural organic matter removal achieved with various anion-exchange resins, and to verify their potential use in water treatment prior to the ultrafiltration process involving a ceramic membrane. The use of ion exchange prior to ceramic membrane ultrafiltration enhanced final water quality. The most effective was MIEX, which removed significant amounts of the VHA, SHA and CHA fractions. Separation of uncharged fractions was poor with all the resins examined. Water pretreatment involving an ion-exchange resin failed to reduce membrane fouling, which was higher than that observed in unpretreated water. This finding is to be
attributed to the uncharged NOM fractions and small resin particles that persisted in the water.
natural organic matter; ion-exchange resin; pretreatment; ceramic membrane
Department of Environment Engineering, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27,
50-370 Wroclaw, Poland
This study employed the modified fouling index (MFI) to determine the performance of a two-step recycling system – a membrane filtration integrated laminar flow water storage (LFWS) tank followed by an ion exchange process to reclaim ultrapure water (UPW) from the wastewater generated from semiconductor wafer backgrinding and sawing processes. The first step consisted of the utilization of either ultrafiltration (UF) or nanofiltration (NF) membranes to remove solids in the wastewater where the second step consisted of an ion exchanger to further purify the filtrate. The system was able to produce high purity water in a continuous operating mode. However, higher recycling cost could be incurred due to membrane fouling. The feed wastewater used for this study contained high concentration of fine particles with low organic and ionic contents, hence membrane fouling was mainly attributed to particulate deposition and cake formation. Based on the MFI results, a LFWS tank that was equipped with a turbulence reducer with a pair of auto-valves was developed and found effective in minimizing fouling by discharging concentrated wastewater prior to any membrane filtration. By comparing flux behaviors of the improved system with the conventional system, the former maintained a high flux than the latter at the end of the experiment.
modified fouling index; UF/NF membrane; ultrapure water; water reuse
Darren Delai Sun : School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798
Raffles Institution, 1 Raffles Institution Lane Singapore 575954
Sun and You Wu : Raffles Institution, 1 Raffles Institution Lane Singapore 575954
Tri-n-butyl phosphate (TBP) was used as carrier for the transport of Golden yellow and Cibacron LSG dyes through a hexane bulk liquid membrane. The transport efficiency of dyes by TBP was investigated under various experimental conditions such as pH of the feed phase (dyes solution),
concentration of the receiving phase (NaOH solution), concentration of TBP in membrane, rate of stirring, effect of transport time, type of solvent, dye concentration in feed phase, effect of temperature.. The maximum transport dyes occurs at ratio of 1:1 TBP-hexane At pH 3.0 0.1 (feed phase) the transport dyes decreased. At high stirring speed (300 rpm) the dyes transport from the feed phase to the strip phase was completed within 60 minutes at 27oC. Under optimum conditions: Feed phase 100 mg/L dyes solution at
pH 1.0 0.1, receiving phase 0.1 mol/L NaOH solution, membrane phase 1:1 TBP-hexane , Stirring speed 300 rpm and temperature 27oC, the proposed liquid membrane was applied to recover the textile effluent.
G Muthuraman : University of Madras, Department of Chemistry, Presidency College, Chennai 600 005, India
P. Jahfar Ali : University of Madras, Department of Chemistry, The New College, Chennai 600 014, India
In this work, the effect of hybrid salts precipitation-nanofiltration (SP-NF) process on the scale deposits in thermal and membrane desalination processes has been studied. The analysis was carried out to study the scale formation from the Arabian Gulf seawater in MSF and RO reference processes by changing the percentage of pretreatment from 0 to 100%. Four different SP-NF configurations were suggested. A targeted Top Brine Temperature (TBT) of 130oC may be achieved if 30% portion is
pretreated by SP and/or NF processes. As a rule of thumb, each 1% pretreatment portion increases the reference TBT of 115oC by 0.6oC. For both MSF and RO, parallel pretreatment of certain percentage of the feed by SP and the rest by NF, showed the lowest scale values. The case showed the best values for sulfate scale prevention and the highest values of increasing the monovalent ions relative to the divalent
scale forming ions. Sulfate scale is significant in MSF process while carbonate scale is significant in RO. Salt precipitation was suggested because it is less costly than nanofiltration, but nanofiltration was used here because it is efficient in sulfate ions removal.
pretreatment; desalination; salt precipitation; nanofiltration; scale deposition
Aiman Eid Al-Rawajfeh : Tafila Technical University (TTU), Department of Chemical Engineering, P.O. Box 179, 66110 Tafila, Jordan
Jordan Atomic Energy Commission (JAEC), Shafa Badran, Amman, Jordan