Challenge

As mining industry sites continuously expand into wilderness locations, developers are faced with the challenge of minimizing the impact on the local environment.  Typically, large volumes of water are produced from drainage and run off at the facility containing various contaminants from heavy metals, selenium to chlorides.

Typically reverse osmosis (RO) technology is used to treat these types of waste streams where stringent regulations are in place to limit discharge levels of dissolved solids.  There are two key areas of concern when using RO technology in this environment: reliant pretreatment to extend membrane life and minimize downtime for cleanings and minimizing the volume of concentrated solution to be disposed of.

Siemens Water Technologies is involved in numerous projects where our integrated solutions provide answers to the pretreatment and concentration volume issues.

Solution

Siemens Water Technologies provides a variety of state-of-the-art pretreatment technologies that are selected based on the incoming feed water chemistry and the target water quality required to feed a reverse osmosis system.

• The Trident® HS system offers four barriers of treatment protection.  These innovations allow the system to handle very high raw water turbidity and solids loading including iron and organics and maintain high-quality and low SDI feed to the RO.
• Memcor® ultrafiltration systems provide a verifiable barrier to assure removal of turbidity and suspended solids from the feed stream, providing RO systems with ultra-low SDI.

The high-quality feed stream to the RO system enables it to operate at levels from 75 to 90% recovery with limited downtime for membrane cleanings.  Ten to 25 percent of the initial volume remains as a concentrated solution and requires further volume reduction.

• The patented Memtek® microfiltration membrane softening process treats the concentrated waste stream, enabling it to be returned to a RO system for final volume reduction.

Results

• By working with one water treatment company for the entire system, mining customers save  time and money and are able to obtain environmental permitting with the system up and running faster with a single, integrated process warranty.
• Capacities for these systems range from a few hundred gallons per minute to many thousands.  The overall volume reduction of the waste streams ranges from 98 to 99 percent plus, depending on the salinity of the incoming water.