Application of a smart dosing pump algorithm in identifying real-time optimum dose of antiscalant in reverse osmosis systems

Abstract

The potential of membrane scaling control by a real-time optimization algorithm was investigated. The effect of antiscalant dosing was evaluated from the induction time measured in glass batch-reactors, and from the operational performance of a lab-scale reverse osmosis (RO) unit and two pilot-scale RO units. Step changes in the antiscalant dosing demonstrated that the accumulation of scaling is ‘paused’ during periods when the optimum dose is applied. This is paramount for the application of a dynamic dosing strategy that may briefly underdose, while searching for the optimum dose. It was found that antiscalant underdose and overdose were both detrimental to RO operation since underdose resulted in membrane scaling, while overdose led to membrane fouling due to calcium-antiscalant deposits. The dosing algorithm was used to minimize antiscalant consumption in two pilot RO units. The algorithm was able to lower the antiscalant doses to 0.2 mg/L and 0.6 mg/L, while the supplier's recommended antiscalant doses were 2.0 mg/L and 4.5 mg/L, respectively. As a result, the algorithm could reduce antiscalant consumption by up to 85–90% for the plants mentioned.