A comprehensive Investigation of the Co-precipitation of CaCO3 and SrCO3 Towards the Development of a More Reliable Fouling Propensity Prediction Model in Full-scale RO Process

Abstract

Over the past couple of decades, a clear shift has been observed from thermal desalination processes to membrane technologies. Although membrane technologies offer a variety of advantages, fouling is still a persistent issue which hinders the application of membrane processes for unconventional feed waters such as oil and gas produced water and nuclear waste water. The adverse effects of fouling include membrane damage, and permeate flux reduction which increases the costs of operation, maintenance, and energy requirements. The subject of fouling cannot be considered recent, since it has been studied and examined thoroughly for different units such as separators, cooling towers, and heat exchangers for many decades. Fouling in membranes, however, has relatively recently gained widespread interest due to the need to treat more complex feed waters. The first step in fouling mitigation consists of determining the fouling propensity of the feed through examining the scaling potential of precipitating salts i.e. CaCO3 and SrCO3 on the membrane surface. In this aspect, there are some gaps and limitations in current approaches. A major assumption with most existing approaches is the mere consideration of single salt precipitation, neglecting the interactive effects of other ions which are present in the feed and thus ignoring the effect of co-precipitation. For reverse osmosis membrane-based separation, this is an immense simplification which could result in inaccurate fouling prediction. Realistically, the feed water such as seawater and brackish water naturally contains ions which will co-precipitate and the possibility of co-precipitation will increase with applying membrane process to more complex feed water. The present work aims to develop a systematic assessment of fouling prediction by the development of a statistical screening model, taking into consideration co-precipitation, and interactive ion effects. This research will focus on CaCO3 and SrCO3 co-precipitation as a part of wider efforts in establishing a reliable database for all possible co-precipitation scenarios. In this work, experimental design as statistical approach has been applied for the first time to investigate the effect of co-precipitation in thermodynamics and kinetics of precipitate salts.

Date of Award	May 2020
Original language	American English