AWWA ACE59909

AWWA ACE59909 Regulatory Techniques for Addressing Major Seawater Ion Toxicity in Membrane Concentrate Disposal
Conference Proceeding by American Water Works Association, 06/17/2004

Weinberg, Edward R.

More info

Full Description

In the past ten to fifteen plus years, the concept of major seawater ion toxicity (MSIT) has gonefrom its infancy to near maturity as a general concern with membrane concentrates. Concerns with MSIT are relevant only in thosesituations where membrane concentrate disposal is through discharge to waters thatrequire compliance with state and/or Federal toxicity standards. In those cases wheremembrane concentrate disposal is through deep well injection or some other means thatdoes not require toxicity testing, MSIT is generally not an issue or concern.Although the concept had been identified and studied in relation to other industries andtoxicity analysis, the earliest applications of MSIT evaluation in relation to membraneconcentrates were formally conducted by the Florida Department of EnvironmentalProtection (FDEP) in the early 1990s. This effort culminated in the FDEP publication ofa 1995 guidance document entitled "Protocols for Determining Major-Seawater-IonToxicity in Membrane-Technology Water-Treatment Concentrate". The guidance wasbased on evaluations of concentrate from a variety of facilities around the state rangingfrom low TDS concentrates from membrane softening facilities up through highersalinity (20 to 25 ppt) concentrates from brackish water RO facilities.Since the publication of the 1995 guidance, evaluation of MSIT in membraneconcentrates has become more and more popular in Florida. The concept has gainedacceptance in both the regulatory arena as well as the regulated facilities. In fact, in thelast several years legislation has been introduced in Florida to codify exemptions andspecific regulatory mechanisms to streamline the application of MSIT evaluation inreview of membrane concentrate surface discharge.Due to increasing popularity, testing techniquesand permit evaluations for MSIT have been under way in several states in the southeastand elsewhere. The US Environmental Protection Agency has been reviewing the issue on a case by case basis in thegeneral context of Toxicity Identification Evaluation techniques and determinations. Ingeneral, the observed toxicity that results from MSIT is short-lived in the environment,with one to one dilution often more than enough to erase any toxicity that may beattributable to MSIT. Includes tables.