Reverse osmosis (RO) is a proven method of treating water to a high quality and is the most
common technology utilized for waters with high dissolved solids. However, one of the biggest
concerns about using this technology is dealing with the brine residual that is generated. While
coastal RO installations usually have the luxury of continually discharging the brine into the
ocean, inland installations often faced with aquatic toxicity and agricultural use restrictions for
freshwater points of discharge.
Two ethanol facilities are being constructed in the Upper Midwest. Both facilities are nearly
identical in terms of water quality and quantity demands. Each facility requires 1.1 MGD of
water at a quality level higher than drinking water standards in order to support boiler and
cooling tower operations. As a result, this process generates a substantial amount of saline brine
waste. 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 the
process, it will generate brine that will be discharged to a stream several miles away. In
comparison, the second facility does not have available sewer service or nearby streams large
enough for stream discharge. As a result, the facility was permitted as a zero-liquid discharge
facility. 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 RO
reject is further processed through a series of chemical softening and membrane filtration steps
followed by a three-stage secondary RO system to recover more water and further concentrate
the reject. A brine crystallizer evaporates the remaining water from the brine, leaving a salt
slurry 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 brine
in different difficult conditions. The information being provided is predominantly related to the
design and operational parameters for the brine management and disposal at these two inland RO
facilities. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.1 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 14 |
| Published : | 11/01/2007 |
