So Maui, ''What Would You Do with the Concentrate?''

Maui is experiencing significant population growth in its most water-short areas in Central and South Maui. Recently, the feasibility of using desalination to provide alternative supplies to meet future needs has been studied. The Maui Department of Water Supply determined a 5-mgd brackish water Reverse Osmosis (RO) facility was feasible in Central Maui. A private developer is planning on a 1.5-mgd brackish water RO facility to meet potable water needs for a 670-acre, 1400-unit development in South Maui. For desalination projects, one of the toughest questions to answer is "What would you do with the concentrate?" For both projects, various concentrate management alternatives were evaluated including surface water discharge, disposal to sewer, evaporation ponds, subsurface injection, and land application. For the 5-mgd Central Maui facility, subsurface injection was determined to be the best option because of its simplicity, low cost, and ease of implementation. For the 1.5-mgd South Maui facility, land application through irrigation was determined to be the best option because of the relatively high quality concentrate and the opportunity to blend with other source waters (recycled water and brackish water) to meet a large irrigation demand (golf course).