Experiences from the Adelaide Desalination project: ultrafiltration cleaning optimisation—from pilot to full-scale operation

Abstract

Membrane fouling remains a major concern for ultrafiltration (UF) pretreatment for seawater reverse osmosis (RO). The focus of this study was the optimisation of the chemical cleaning regime and any associated impact on the downstream cartridge filters (pre-RO). Different shock acidification/chlorination and maintenance wash (MW) regimes for the pilot UF were tested. The results of the study at the Adelaide Desalination Pilot Plant (ADPP) are summarised as follows:

•	Sulphuric acid shock dose alone at pH 4 was ineffective for prevention of UF biogrowth, when performed for one hour per week or less.
•	Shock chlorination provided an effective tool for limiting biogrowth in UF systems.
•	Relocating the sodium metabisulphite dechlorination dosing point downstream of the cartridge filters was essential for controlling biogrowth and to ensure stable operation of the filters.
•	Chlorine MWs provided better UF permeability and transmembrane pressure (TMP) recovery than sulphuric acid MWs.
•	A chlorine MW frequency once in every 4 days and sulphuric acid MW frequency more than once in every 2 weeks was chosen for the full-scale plant.
•	Addition of ferric sulphate into the UF feed significantly impaired operational performance with respect to TMP and permeability decay rate. This is most likely due to the low seawater turbidity and dissolved organic carbon levels.

Data from the ADPP were used to optimise operation conditions for the full-scale plant during commissioning. The Operator of the Adelaide Desalination Plant, AdelaideAqua Pty. Ltd. used the pilot plant findings to assist with optimisation of the dose/frequency regime for chlorine and sulphuric MWs. A comparison of pilot operation and full-scale plant commissioning performance is discussed.

Keywords:

• Ultrafiltration
• Fouling
• Biofouling

Acknowledgement

The authors wish to thank Ambrose McGrath and Imants Didrichsons from AdelaideAqua for their work at the Adelaide Desalination Pilot Plant.

Notes

Presented at the International Conference on Desalination for the Environment, Clean Water and Energy, European Desalination Society, 23–26 April 2012, Barcelona, Spain