Organic compounds and microbial assessment of a seawater reverse osmosis facility at Tampa Bay Water, USA

The Tampa Bay Water seawater reverse osmosis (SWRO) facility is the first large-capacity seawater desalination plant in the United States. The feedwater source for the facility is an estuarine system that is biologically very productive and contains naturally-occurring high concentrations of algae, marine bacteria, total organic carbon (mostly dissolved), transparent exopolymer particles (TEP), the biopolymer fraction of natural organic matter, and phosphate. The high-organic composition of the feedwater places stress on the conventional sand pretreatment system utilized at the facility resulting in high organic passage into the membrane process and flow through into the permeate. In particular, the direct passage of particulate TEP (p-TEP) into the membranes has a major impact on the biofouling rate. Based on the data collected, the pretreatment is ineffective at removing key organic components that impact the rate of membrane biofouling, particularly bacteria and p-TEP. Perhaps the pretreatment could be re-designed to use a dissolved air floatation system (DAF) followed by ultrafiltration as a remedy that would likely move the biofouling problem to the ultrafiltration process, which has an easier cleaning process. Consideration could be given to using a groundwater source of feedwater as a permanent remedy to the operational issues.