Concentrate disposal guidance from WRF/WERF research

A cooperative research effort, led by the WateReuse Foundation and co-funded by the Water Environment Research Federation, is providing utility managers and others with needed guidance and resources for addressing concentrate disposal issues.

The concentrate produced from membrane treatment processes presents a significant disposal issue that must be managed, particularly in inland areas that do not have the benefit of inexpensive dilution and mixing from the ocean. Traditional disposal methods currently used in the USA include surface water discharge, discharge to sanitary sewer systems, deep well injection, evaporation ponds and land application. Each approach has its own environmental, regulatory, and technical challenges.

This cooperative research has developed a series of guidance reports and resources (see list below) to assist with concentrate disposal, regardless of method. The reports include information on performance and costs of new high-recovery and zero-liquid discharge technologies, and address beneficial and non-traditional uses of concentrate that could help agencies develop creative local options for concentrate disposal.

These options include oil wellfield injection to aid secondary recovery of oil and gas, feedstock for solar ponds from which heat energy could be derived, aquaculture, wetland creation and restoration (eg inland salt marsh) and salt separation and recovery.

The research also investigated the effects of membrane concentrate residuals, in particular total dissolved solids, on wastewater treatment including biological processes, settling, effluent quality and water-reuse options. A decision methodology designed for managers, regulators and stakeholders will help each assess the viability of concentrate disposal options on a regional and local basis.

In addition to WERF and WRF, the project was cosponsored by the US Bureau of Reclamation, California State Water Resources Control Board and the City of Phoenix.

Title/Project Number/Principal Investigator/Description

Survey of High-Recovery and Zero Liquid Discharge Technologies for Water Utilities (03-CTS-17aCO) Michael Mickley, Mickley & Associates
This is an essential reference for utilities considering high recovery processing for desalination projects. The research provides a systematic characterization of high recovery performance and costs over a range of size, salinity and composition.

Beneficial and Nontraditional Uses of Concentrate
(03-CTS-17bCO) Jim Jordahl, CH2M HILL Inc
Provides a comprehensive review and evaluation of the full range of potential beneficial and nontraditional uses of concentrate and to assess the feasibility of implementation, economic considerations and environmental safety.

Impacts of Membrane Process Residuals on Wastewater Treatment (03- CTS-17cCO) Alan Rimer, Black & Veatch
Provides a guidance manual to help utilities identify potential impacts of membrane discharges on wastewater collection and treatment. An accompanying CD-ROM provides utilities with two types of mass balance models. A sewer line discharge model helps in forecasting potential damage to the collection system from membrane concentrate loadings and a system-wide model helps predict the increase in solids throughout the system.

Regional Solutions for Concentrate Management (03-CTS-17dCO) Erin Mackey and Tom Seacord, Carollo Engineers
Surveys concentrate disposal and management practices and develops a decision methodology that can be used across the country to assess the viability of concentrate disposal options on a regional and local basis.