Clark Installs First AirPrex Phosphorus Precipitation System in the U.S. at Howard County’s Little Patuxent Water Reclamation Plant

Howard County, MD – Clark Civil, a division of Clark Construction Group, and the Howard County Department of Public Works celebrated a major milestone at the Little Patuxent Water Reclamation Plant (Little Patuxent) with the installation of the first AirPrex Phosphorus Precipitation System in the United States. This innovative system will increase plant capacity and improve efficiency by turning excess phosphorus, a biproduct of the new anaerobic digesters, into struvite, a potential resource.

The Little Patuxent Water Reclamation Plant project, which processes 20 million gallons of water per day, serves 66% of Howard County’s residents.

The successful process commissioning was the 11th of 12 new Plant Process Systems to go online at Little Patuxent as part of the largest upgrade in the plant’s history.

The AirPrex system targets the phosphorus sludge accumulation common in Biological Phosphorous Removal systems. The phosphorus buildup is a biproduct of the plant’s anaerobic processes that can accumulate in piping and equipment. Over time, it can limit a plant’s operation capacity and cause unnecessary damage. The phosphorus precipitation system converts the excess phosphorous into struvite crystals via chemical conversion. These crystals can be harvested from the biosolids fertilizer, turning a biproduct of the Plant into a valuable resource.

Clark utilized a tandem pick to lift the AirPrex system’s 52-foot-tall, 25-ton reactor tank from Germany into position. Once the reactor tank was in place, the team installed the additional system equipment including two blowers, a progressive cavity pump, two chemical dosing skids, an 8,000-gallon insulated chemical tank, multiple process instruments, a chemical fill station, and all the interconnecting piping. With the process, Clark Civil’s Water Group became the first team in the United States to successfully start up an AirPrex phosphorous precipitation system.

Joshua Gliptis of Howard County’s Department of Public Works stated that “[it] is quite possible the Little Patuxent WRP will never again have such a major project upgrade incorporating improvements or additions of this magnitude. I am not exaggerating when I say nearly every inch of the existing biosolids facilities were touched in some way by this project. Maintenance of Plant Operations (MOPO) has always been a top priority of the Clark team and helped us maintain our operations without a permit violation and unplanned disruptions to the process operations.”

As part of the scope of the Little Patuxent Water Reclamation Plant project, Clark will also add direct heat drying, centrate treatment, enhanced odor control facilities, and other process and electrical upgrades to the facility. Once the upgrade is complete, biosolids leaving the Little Patuxent facility will meet EPA’s Class A, Exceptional Quality requirements and be suitable for use on local farmland, by soil and/or fertilizer blenders, and possibly even by the community residents the Plant serves.

The Little Patuxent Water Reclamation Plant project is scheduled to complete in 2020.