Community systems achieve arsenic removal well below new standard
Tijeras, N.M., Project
In 2005, AdEdge Technologies, Inc. was selected to implement an arsenic treatment project for the Green Ridge Community Water System, located in Tijeras, N.M. The Green Ridge system had been without potable water for three years. Local residents hauled 100 to 300 gal per week to meet their water needs. It was determined that the groundwater resource in Tijeras contained arsenic concentrations above the new maximum contaminant level. The arsenic concentration was 95 parts per billion (ppb), and the pH was 8.6.
Souder Miller & Associates (SMA) chose Pumps & Service and AdEdge to execute the turnkey project. Adedge worked closely with SMA to provide submittals and plans for permitting and operating the 20-gal-per-minute (gpm) arsenic treatment system. A summary of Green Ridge’s water quality, shown in Table 1, served as the basis for design. The system was fabricated and installed in June 2005.
The AdEdge arsenic treatment system consists of a skid-mounted Adsorption Package Unit (Model APU-20LL) rated for 20 gpm. Arsenic treatment occurs in a series (i.e., lead/lag reversible) configuration. Groundwater is pumped from the water supply well through a prefilter, through the APU and into a 53,000-gal storage tank. From the storage tank, groundwater flows through booster pumps, a hydropneumatic tank, and into the distribution system. The 24-in.-diameter APU vessels each contain approximately 8 cu ft of Bayoxide E33 adsorption media, which is a granular ferric oxide (GFO) media that has been commercially used since 1999. Since 2002, AdEdge has deployed GFO media in more than 100 public water and commercial systems in the U.S. and in more than 2,500 residential applications.
The skid-mounted pre-engineered APU system is equipped with automatic controls, backwashing features, switches, gauges and sample ports for a complete functioning packaged unit. Instrumentation is provided on a control panel to measure critical operating parameters. Total gallon throughput and flow rate for each unit is measured continuously with dedicated flow totalizing meters. The AdEdge adsorption system does not require any chemicals or regeneration, and the process does not generate liquid or hazardous waste.
The system was started up and placed into operation in June 2005 and has been successfully treating arsenic well below the standard of 10 ppb. System oversight is provided by the site’s certified water treatment operator. The project also received the American Public Works Association Project of the Year award in New Mexico. A special open-house event and ribbon cutting ceremony to celebrate this new treatment milestone with Sen. Pete Domenici was held in August 2005 with the community, local leaders and the press.
Moulton, Texas, Project
AdEdge Technologies was selected by the city of Moulton, Texas, and Hejl, Lee, and Associates (HLA) to design a full-scale arsenic treatment project using its AD26 and GFO adsorption technology. In addition to designing the system, AdEdge assisted HLA in obtaining a construction permit from the Texas Commission on Environmental Quality (TCEQ) for the system. Supporting documentation on the extensive piloting and field performance along with design and construction documents were submitted to the TCEQ to obtain technology approval and a construction permit. The TCEQ issued the approval and the construction permit on July 29, 2005. Fabrication of the system was conducted concurrently.
The arsenic treatment system consists of a completely integrated packaged treatment system with two main components: an AD26 system for iron and manganese removal and an Arsenic Package Unit (APU) for arsenic removal, both skid-mounted and automated to accommodate a maximum 100-gpm design flow. The first component in the treatment train is the iron/manganese removal system, which consists of twin 30-in. vessels and AD26 media. The AD26 system is augmented by a chlorine-feed module prior to the treatment system. This module injects and monitors free chlorine to enhance iron and manganese oxidation and subsequent filtration prior to arsenic polishing.
The second component is an arsenic adsorption skid-mounted unit rated for 100 gpm. Arsenic treatment and removal occurs in an APU configured in parallel. Treated water is pumped from the water-supply well through the AD26 pretreatment unit and the APU and into a 10,000-gal storage tank. From the storage tank, groundwater flows through booster pumps, a hydropneumatic tank, and into the distribution system. The 42-in.-diameter APU vessels each contain Bayoxide E33 adsorption media. The Bayoxide E33 is also being implemented in Alvin, Bruni and Wellman, Texas, as part of the U.S. EPA’s Arsenic Demonstration Program.
The skid-mounted systems are equipped with automatic controls, backwashing features, switches, gauges, flowmeters and sample ports for complete functioning packaged units. A PLC and color touchscreen interface allow for simple user access and operation. Since operations began in early November 2005 treating approximately 35,000 gal per day, effluent samples have indicated excellent iron and manganese removal with high-efficiency arsenic removal to non-detectable levels, well below the new arsenic treatment standard of 10 ppb.