Challenge
A public water agency in California contacted Evoqua to treat remove arsenic from a groundwater supply. They needed to achieve a 1 ppb effluent level from the treatment system, 90% lower than the current drinking water standard in California. In addition they needed to have the treatment operating within weeks.
The treated groundwater is re-injected on the property to reduce the size and mass of the contaminated plume leaching from the property.
Solution
The Evoqua system employs a once through adsorptive media treatment to reduce arsenic levels from as high as 65 ppb to the 1 ppb goal. To achieve the lower standard at the 80 gpm continuous flow rate required a system with three media tanks operating in series.
The project was initiated as an emergency treatment requirement and later was modified as a permanent solution to increase the system flowrate. Additional expansion followed the permanent installation. Evoqua provided a complete, turn-key service solution which included pretreatment equipment, storage tanks, exchange vessels and media.
When the media capacity is exhausted, Evoqua's local service technicians remove spent media / vessels from the site and replace them with fresh tanks containing new media. The vessels are transported to our company-owned RCRA permitted and licensed TDSF treatment facility for compliant treatment and recovery of metals. The system's modular design allows for easy exchange and service with minimal disruption to daily operation.
The Evoqua system was installed quickly for 80 gpm operation and later expanded to a higher flow while treating to a 1 ppb arsenic limit. Evoqua provided installation of equipment and service availability and waste media is processed by Evoqua's RCRA-Permitted facility.
The treatment design also incorporates system backwash to eliminate back pressure by retreatment of the backwash water thereby eliminating any surface discharge on site.
Results
The exchange service at Evoqua eliminated the need for on-site storage of treatment chemicals for improved site and personnel safety. Removal of the contaminant off-site also eliminated the potential for recontamination.