AWWA WQTC65799

Reverse osmosis (RO) is a proven method of treating water to a high quality and is the mostcommon technology utilized for waters with high dissolved solids. However, one of the biggestconcerns about using this technology is dealing with the brine residual that is generated. Whilecoastal RO installations usually have the luxury of continually discharging the brine into theocean, inland installations often faced with aquatic toxicity and agricultural use restrictions forfreshwater points of discharge.Two ethanol facilities are being constructed in the Upper Midwest. Both facilities are nearlyidentical in terms of water quality and quantity demands. Each facility requires 1.1 MGD ofwater at a quality level higher than drinking water standards in order to support boiler andcooling tower operations. As a result, this process generates a substantial amount of saline brinewaste. Both facilities are located in areas where sewer discharge of the brine was not an option,so alternative brine handling methods were selected.The first facility produces high purity water from a two-stage, single-pass RO system. In theprocess, it will generate brine that will be discharged to a stream several miles away. Incomparison, the second facility does not have available sewer service or nearby streams largeenough for stream discharge. As a result, the facility was permitted as a zero-liquid dischargefacility. The second facility uses two separate RO systems to treat the water. The first (primary)two-stage RO system produces the majority of the high-quality permeate required. Primary ROreject is further processed through a series of chemical softening and membrane filtration stepsfollowed by a three-stage secondary RO system to recover more water and further concentratethe reject. A brine crystallizer evaporates the remaining water from the brine, leaving a saltslurry that is mixed in with other plant residuals for eventual solids disposal.This paper uses these two sites as case studies in examining the logistics of discharging RO brinein different difficult conditions. The information being provided is predominantly related to thedesign and operational parameters for the brine management and disposal at these two inland ROfacilities. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

14

File Size:

1 file , 1.1 MB