Reverse osmosis desalination system and algal blooms Part I: harmful algal blooms (HABs) species and toxicity

Abstract

Harmful algal blooms (HABs) are a serious concern in the countries surrounding the Arabian Gulf (AG). A recent HAB event (2008–2009) forced partial (or full) shutdown of desalination plants, and reduced their productivity. Strong fouling in filter media occurred, and frequent backwash was not sufficient to maintain their removal. Some plants were shut down for as much as 32–55 d—in places where water storage may only be a few days—when pretreatment processes struggled to remove the increased biomass caused by the HAB species, and were shut down before more irreversible fouling of the reverse osmosis (RO) membranes could occur. HAB challenges are not limited to the algal biomass that may foul membranes, but extend to the toxins that can pass through the membranes and find their way into finished water. Within the AG region, great care is given to the engineering part (operation and maintenance) under normal conditions of the seawater; however, challenges in all levels and scales emerge due to HAB incidents. This review article is the first part of three articles, focusing on the HAB identification and pretreatment technologies to deal with them. This part comprehensively focuses on the types of HAB species reported in AG seawater, physical conditions associated with HAB occurrence, morphology, taxonomy, and their potential impacts on desalination plants. The identification of the HAB species and their toxins is necessary to adopt the best pretreatment strategies to achieve the required feed water quantity and quality. As the AG countries are moving fast toward membrane desalination technologies to secure their municipal water requirements, they will need to adapt and deploy the technologies of HAB removal at very early stages of pretreatment.

Keywords:

• Harmful algal blooms (HABs)
• Reverse osmosis plants
• Water security
• Arabian seas

Acknowledgments

This article was made possible through the Water Grand Challenge project entitled “Constrains on Desalination Plants and the Challenge to Water Security-QEERI‐WGC‐4003”. The authors thank Dr Anne Dare and Dr Larry Pederson for their efforts to improve the quality of the paper.