A B S T R A C TLarnaca Desalination Plant (LDP) has lead the way in operating for a number of years at elevated pH both at the first and second Reverse Osmosis (RO) stages at higher feed sea water temperature up to 30 C. The main reason for the higher pH was to enhance the boron rejection capability of existing membranes and thus reduce the need for a second stage at lower sea water temperatures and subsequently produce more water at less energy. However, higher pH in conjunction with high sea water temperatures create conditions for membrane scaling. Therefore an appropriate cost effective antiscalant has to be used with minimum dosing rate. This article describes field trials of choosing and applying an appropriate antiscalant and dosing optimisation as a function of feed sea water temperature and pH.
A B S T R A C TLarnaca Desalination Plant (LDP) has lead the way in operating for a number of years at elevated pH both at the first and second Reverse Osmosis (RO) stages at higher feed sea water temperature up to 30 C. The main reason for the higher pH was to enhance the boron rejection capability of existing membranes and thus reduce the need for a second stage at lower sea water temperatures and subsequently produce more water at less energy. However, higher pH in conjunction with high sea water temperatures create conditions for membrane scaling. Therefore an appropriate cost effective antiscalant has to be used with minimum dosing rate. This article describes field trials of choosing and applying an appropriate antiscalant and dosing optimisation as a function of feed sea water temperature and pH.
2013) The impact of sulphuric acid replacement by a phosphonate-based antiscalant on operational costs of seawater desalination, Desalination and Water Treatment,[192][193][194][195][196][197][198][199]
A B S T R A C TThe operation and maintenance of a seawater desalination plant have many challenges. One of the major challenges is to ensure the economic viability while complying with all the terms of the operation and maintenance contract, hence the constant quest for cost savings. One area for potential improvement is to rethink or optimize the use of chemicals and in particular the use of sulphuric acid. Sulphuric acid is used to lower the pH of feed water in order to reduce the risk of mineral precipitation on the reverse osmosis membranes. Simply eliminating sulphuric acid will result in a substantially higher operating pH and an associated increased risk of mineral precipitation. Managing this risk involves the injection of a properly selected high performance phosphonate-based threshold scale inhibitor. This article describes the details of a field trial in a two-pass seawater desalination plant during which sulphuric acid was phased out and replaced by a phosphonate-based antiscalant. The results show that the critical operating parameters remain stable, indicating the successful prevention of scale formation, throughout the trial period during which sulphuric acid was replaced by a phosphonate-based threshold scale inhibitor. A holistic approach was used to understand the full impact of the replacement of sulphuric acid by a phosphonate-based threshold scale inhibitor on the operating costs of this seawater desalination facility.
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