Reverse osmosis desalination system and algal blooms part III: SWRO pretreatment

This study is the third part of a comprehensive review on the effect of algal blooms (ABs) on seawater reverse osmosis (SWRO) desalination plants. The first part covered in depth the physical situation of the Arabian Gulf (AG), the occurrence of AB events, the major technical challenges of the existing and proposed reverse osmosis desalination plants (RODPs), and taxonomy and toxicity of ABs. The second part covered the seawater intake technologies affecting SWRO systems with respect to the ABs. This part covers the different SWRO pretreatment methods and issues arising from ABs. All countries of the Gulf Cooperation Council (GCC) are moving to implement energy efficient SWRO desalination technologies and are facing its main challenge: membranes fouling. The degree, level and complexity of fouling are proportional to the feed-seawater pretreatment methods. A robust pretreatment is the key factor for reliable continuous SWRO plant operation and performance. This paper reviews the available pretreatment methods for SWRO desalination including disinfection (mainly chlorination), coagulation and flocculation or dissolved air flotation (DAF), sedimentation, granular media filtration (GMF), low pressure membranes ultrafiltration (UF), and microfiltration (MF). Effective integration among these processes can be highly effective in enhancing the removal of ABs and their toxins and in protecting the SWRO membranes.