See the Cascade System In Action Here
The Kansas Department of Health and Environment (KDHE) State Water Plan Program and the City of Frankfort, Kansas contracted with Aquaterra to design/build a remediation system to address the
source area of contamination affecting the City’s three public water supply (PWS) wells. The source area is a farm approximately ½‑mile north of the well field where historically grain storage bins had been located.
As requested by KDHE in the fall of 2008, Aquaterra researched alternative methods to conventional air stripping towers or tray aerators, and proposed a cascade aerator for the groundwater treatment technology. The cascade system is essentially a waterfall where the contaminated well water cascades down the waterfall, which aerates the water and transfers the contaminant (in this case, carbon tetrachloride – CCL4) from the water to the ambient air. The advantages of the cascade system over conventional systems was the reduction of the required maintenance due to hard water fouling of tray and tower aerators that would not be an issue with the cascade aerator, and the reduction in motors and system complexity that reduced long term energy costs and equipment replacement. The primary disadvantage of the system was that the cascade could not operate for approximately three months during the winter. Following a 
meeting with KDHE and City personnel to discuss the design scope and preliminary plan, Aquaterra was authorized to proceed with the final design of a 25 gallon per minute (gpm) system and to evaluate green alternatives to further reduce the energy demand of the system.
The cascade system design incorporated gravity flow through the three cascades, so that the only motor required for the system operation was the well pump. Aquaterra contacted solar and wind generator companies to investigate the feasibility of powering the well pump using either solar or wind. In the final analysis, the cost of the batteries alone, to store the energy for times when power could not be generated, exceeded the 10‑year energy cost of the system. KDHE agreed to use the local electric company to power the system. Treated water is discharged into an onsite
pond and used for irrigation.
Due to the unproven nature of the cascade technology, a recirculation pump was added to the end of the second cascade to re-circulate 25 gpm of water back to the top of the cascade for additional treatment. The recirculation system increased the effective treatment length of the system, in the event the removal efficiency of the system was less than indicated in the design research, or in the event the influent concentration of the system increased above the design value.
The control panel for the well pump and the recirculation pump was fitted with a radio to allow city personnel to monitor and operate the system from the city offices via the new telemetry system Aquaterra installed. The telemetry system included the ability to start and stop both pumps, monitor the water level in the recovery well, monitor the flow rate of the recovery well pump, and monitor the amperage draw of the recovery well pump. The system will shut down the well pump or recirculation pump if parameters fall outside of prescribed limits.
The system was put on-line on April 10, 2009. The cascade system is sampled monthly by city personnel and Aquaterra staff review the laboratory data to evaluate the performance of the system. The influent concentration of the well water and the effluent concentration from the cascades are used to evaluate the removal efficiency of the cascade system.
The collected data confirms that the system is meeting the design requirements. In 2009, removal efficiencies ranged from a low of 83.2 percent to a high of 93.1 percent. The removal efficiency based on the 2010 monthly sampling events was generally above 90 percent (peaking in October at 94.7 percent removal). Data collected in 2011 since the system was re-started on March 22, 2011 indicates the removal efficiencies range from 93.6 to 93.8 percent.
The cascade system continues to operate as designed and treated water is below the NPDES permit discharge limit of 5 micrograms per liter for carbon tetrachloride.
