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WI\ I I:. ll.'-U Water, the liquid of life
COMMERCIAL FIBREGLASS WOUND VESSELS
Capable of processing up to 396 m3/hr. Suitable for commercial, industrial, municipal and water treatment applications.
unable to restore membrane condition. Increasing the CEB soak duration was not able to counteract the fouling. It is likely that because the feed water quality was good (low DOC and turbidity) there was nothing for the Fe3 + to bind to, causing reaction with the membrane surface. Chemical cleaning using citric acid was performed twice during the trial period. CIPs are denoted by red arrows labelled "2 " in Figure 10. Citric acid CIPs were performed with a 2% w/v solution with pH adjusted to two with sulphuric acid. The solution was recircu lated for 30 minutes, left to soak overnight then recirculated for an additional 30 min prior to fl ushing. The first citric acid CIP was successful in reducing the TMP significantly. However, the second citric clean was only able to reduce the TMP t o 40 kPa (compared with 20 kPa for clean UF). This was attributed to excessive fouling from the ferric coagulant trial.
MULTICYCLONE CENTRIFUGAL FILTER No filter media to clean or replace. 3m 3/hr to 30m3/ hr Suitable for commercial and water treatment applications.
CARTRIDGE AND BAG FILTERS Capable of withstanding up to 600kPa. Suitable for commercial and water treatment applications.
ELECTRONIC COAGULATION Precipitates and coagulates a wide range of contaminants. Suitable for grey water recycling applications.
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In April 2009 a CIP was performed using 1 % w/v oxalic and 0.25% w/v ascorbic acid. This is illustrated in Figure 10 at the end of the trial period. The CIP was successful in reducing TMP to baseline levels. Starting TMP was observed at below 20 kPa after the clean. Oxalic acid is a powerful reducing agent and more effective than citric acid in removing iron foul ing. Ascorbic acid stabilises the oxalic acid structure but does not play an active role in removal.
Conclusion: Conventional Vs Membrane (UF) Pre-treatment Th e CPT produced acceptable filtered seawater quality (SDl 15 less than 4) after 2.5 hours ripening time. However, given a more challenging water quality target, the system was unable to perform adequately. The effective recovery was significantly reduced due to excessive filter ripen ing duration.
conditions, although the UF required more specialised cleaning chemicals to achieve ful l performance recovery. Improved performance and extended life of RO membranes is likely with better quality feed water and less biofouling potential. For these reasons it is evident that UF is a superior pre-treatment method for seawater RO.
Acknowledgments The work reported here could not have been completed without the contribution of Jek Rozitis (Process Engineer, SA Water) to the Pilot Plant day to day operation, monitoring and analysis. In addition, the assist ance and support from John Winter and the rest of the team at the Australian Water Quality Centre was gratefully appreciated .
The Authors
M att Blaikie (B.E. Civil/Environmental, BSc.) is a Water Treatment Engineer and Con Pelekani (B.E. Chemical, M.Sc., Ph.D.) is Principal Water Treatment Engineer with the South Australian Water Corporation. Both are members of the Process Team for the Adelaide Desalination Project. Email: matt. blai kie@sawater.com .au.
Glossary ADP - Adelaide Desalination Project ADPP - Adelaide Desalination Pilot Plant CEB - Chemically enhanced backwash CIP - Clean in place CPT - Conventional pre-treatment DP - Differential pressure
In contrast, UF was able to produce superior filtered water quality independent of filtration time. SDl 15 was observed to be less than 3.5 for 98.5% and less than three for 90% of data considered. In addition, UF achieved far greater removal of microbial cells from the raw seawater feed.
SDI - Silt density index
Both systems were able to recover well from challenging operating
TMP - Trans-membrane pressure UF - Ultra-filtration
ES - Effective size LRV - Log removal value MMF - Multi-media filter RO - Reverse osmosis SCADA - Supervisory control and data acquisition
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