Phoenixville Borough Installs the First Hydrothermal Carbonization Wastewater Treatment System in North America
Winter 2023
Wastewater treatment is a hot topic in Phoenixville Borough! The Borough currently uses an anaerobic digestion system to treat its wastewater, which is already considered a more advanced type of treatment system than the average. Although it has many advantages, the anaerobic digestion process produces methane, a powerful greenhouse gas, and the process generates a byproduct that resembles compost that the Borough currently pays to have hauled away. This byproduct is used as a soil amendment for crops that are not used for human consumption (because trace amounts of pharmaceuticals and microplastics cannot be removed through the anaerobic digestion process). When the Borough needed to rebuild one of its two anaerobic digesters in 2018, it was faced with a decision: repair the existing plant, or re-think the entire system. Given the Borough’s culture of innovation, they decided to chart new territory.
In researching other types of wastewater treatment systems, they discovered a new type of system used in Europe called hydrothermal carbonization (HTC) that seemed superior to anaerobic digestion in a number of ways: first, HTC produces a byproduct called hydrochar that is more marketable than the current byproduct of the anaerobic system (it neutralizes pharmaceuticals and microplastics through the process of adding heat and pressure) and can be used as a soil amendment for some human-grade crops. Hydrochar also has potential applications as a "green" building material in that it can sequester carbon within the built environment. Phoenixville Borough is pursuing testing with national companies to use the product as an additive to replace sand in cement; as a green fuel source in lime manufacturing, and even in asphalt shingles and macadam. The system also can be designed to power itself through burning the hydrochar, which the Borough calls a "carbon neutral, clean biofuel", a major benefit since treating wastewater is typically an energy-intensive system. Additionally, switching to HTC would significantly expand the Borough’s wastewater treatment capacity, increasing the cost-benefit ratio and speeding up the payback period for the project (which is estimated to be only 8 years, though that could be reduced if they are able to accept and process food waste). For comparison, there is no payback period for their current anaerobic digestion system.
However, HTC is a relatively new process, and there are no HTC systems in North America, so despite the many benefits, the decision was not easy. Borough Council President Jon Ewald has been one of the major champions of the project and commented: "Phoenixville Borough Council, Staff and borough residents are committed to improving the environmental impacts of our municipal facilities. PXVNEO upends the current treatment-disposal model and creates a sustainable zero-waste system for future generations of Phoenixville residents. While some risks are inherent in adopting new technology, we thoroughly researched the HTC process and felt it represented the best path forward to meet our environmental commitments." The Borough's decision to transition to an HTC system launched a flurry of activity to onboard a consultant to help them through the process and obtain funding for the project, which included grants from Chester County and the Commonwealth of PA. Recognizing that they would be blazing the trail for others nation-wide looking to switch to this kind of system, the Borough launched a website to describe the HTC system and to provide project updates.
After three years of planning, teams from the equipment manufacturers arrived in early January and began calibrating and testing the system with water, pressure, and finally added heat. On Jan. 26, Phoenixville Borough completed a full test of the system and generated its first batch of hydrochar, officially making it the first operational system in North America after a close race with another system being installed in Mexico City. Now that the system has been successfully tested it must cool so it can be fully insulated. The Borough intends to begin using the system in March. Follow the progress at PXVNEO.com.