Sea water desalination: a generalized model for feedwater intakes

Seawater desalination, especially with reverse osmosis, is developing as an alternative source of drinking water resource in coastal states. Desalting seawater requires a consistent and reliable source of feedwater to operate and produce potable water effectively and efficiently. Problems with the launch of Tampa Bay Desalination Plant related to characterization of the feedwater and pretreatment issues. Review of existing intake scenarios and their limitations provides a planning tool for seawater reverse osmosis facilities. Direct intake of surface seawater is hampered by impingement and entrainment of planktonic organisms that require additional filtration and pretreatment. Vertical beach wells provide high quality feedwater, but are limited by their infiltration rate. The radial collector wells with generally higher infiltration rates are also limited. Infiltration galleries provide large infiltration rates, but are restricted to select geological provinces. For reverse osmosis systems, the system preference is for water and salt with the widely fluctuating organic material removed. We suggest a generalized model to provide consistent source of screened water with biological materials eliminated. Several guidelines for placement of intakes are also provided from learnt rules of coastal engineering.