AWWA MTC57671

AWWA MTC57671 Shallow Ocean Discharge Permitting of Brackish Water Reverse Osmosis Concentrate
Conference Proceeding by American Water Works Association, 03/05/2003

Weinberg, Ed; Potts, John

More info

Full Description

In the late 1990s, South Martin Regional Utility (SMRU) embarked on a program ofreplacing surficial aquifer raw water sources and conventional lime softening treatmentwith reverse osmosis technology. The SMRU came about from the merger of two privateutilities, both of which had experienced various difficulties with surficial sources,including salt water intrusion and pumping restrictions. The solution was to develop areverse osmosis treatment system utilizing a deep aquifer source of brackish water that isnot subject to seasonal variation and would not result in salt water intrusion.As with many such facilities, the logistical and financial feasibility of the project hingedon disposal of the reverse osmosis concentrate. Discharge to local brackish surfacewaters presented a cost effective and logistically simple solution. The prospect of deepwell injection for disposal was cost prohibitive in that the disposal costs approached thecosts of the RO facility itself. The SMRU embarked on a program of permit feasibilityanalysis and application for the most cost effective option. The result was significantpublic opposition that was aired in community meetings and public hearings related tothe permit review.The SMRU developed a third option that had incrementally higher costs and logisticaldifficulty, however, it addressed the expressed public concerns. An evaluation andpermit process was undertaken to discharge the concentrate to shallow (15 to 20 feetdeep) coastal ocean waters. Although the distance to the outfall was further andinstallation included directional drilling under the ocean floor, this solution met theproject requirements for cost effectiveness and addressed public concerns regardingconcentrate disposal.This paper describes the iterative permitting process, public input factors, development ofthe ocean discharge alternative, and implementation of the concentrate discharge forSouth Martin Regional Utility.