The project of Associate Professor Chul Park of the Civil and Environmental Engineering Department was one of four UMass Amherst projects to receive $25,000 Technology Development Grants from UMass President Marty Meehan’s office. The name of Park’s project is “Promoting the co-op anaerobic digestion for communities in New England using the UMass Anaerobic Side-stream Reactor Process.” His project aims to implement a system to minimize the production of sludge—a byproduct generated from wastewater treatment—using anaerobic side-stream reactor treatment and anaerobic digestion.
The well-proven anaerobic digestion process breaks down organic matter anaerobically (in the absence of oxygen) from municipal sewage sludge under operational control.
As Professor Park describes his up-and-coming new project, “The anaerobic side-stream reactor (ASSR) process developed in our laboratory has demonstrated the ability to minimize sludge production at wastewater treatment plants. The new idea of using the ASSR process is proposed to enhance anaerobic digestion of waste sludge and promote a co-op anaerobic digestion facility built for multiple towns in Western Massachusetts facing increasing challenges associated with handling and disposal of their waste sludge.”
In his proposal to the UMass president’s office, Park explains that, when wastewater is treated, approximately 70 percent of organic matter in wastewater is removed as sludge. The majority of wastewater treatment plants in New England and the U.S. use thickening and hauling processes to remove waste sludge. At the offsite facility, sludge is further dewatered with the addition of chemicals, and then it is incinerated and/or landfilled. All these processes could cause more than 50 percent of any operational budget at wastewater treatment plants. The issue is that handling and disposing of sludge is becoming increasingly expensive and difficult, as landfills and incinerators are decommissioned and regulation associated with sludge disposal becomes more stringent.
“Consequently,” as Park explains, “minimizing sludge production has become an urgent issue in the wastewater industry.”
Park continues to explain that anaerobic digestion is one possible way to reduce the amount of sludge at wastewater treatment plants, while also harvesting bioenergy methane as a beneficial byproduct out of waste sludge. The challenge is that anaerobic digestion is a very slow bioprocess and sensitive to perturbations and, once upset, it is difficult to recover. These are the primary reasons why conventional anaerobic digestion requires a long retention time of about a month to stabilize and effectively digest waste sludge. The long retention time, however, necessitates large anaerobic digesters and significant capital investment. Many small- to medium-sized towns lack the finances and land space to build an anaerobic digestion facility.
This factor of large capital investment has created the idea for a co-operative anaerobic digestion facility built and operated by multiple communities. Indeed, as Park notes, several towns in Western Massachusetts are looking to create a co-op anaerobic digestion facility, which they believe is a much more cost-effective approach than disposing of sludge offsite. Nonetheless, the challenges associated with anaerobic digestion are still inherent in this co-op setup.
But Park has a very promising solution for this problem. “The UMass patented ASSR not only substantially decreases the production of waste sludge but creates useful sludge that can boost up the slow anaerobic digestion process due to the unique flow scheme included in the ASSR system,” says Park. “By using a combination of ASSR and anaerobic digestion, we expect to be able to significantly increase the speed of digestion, thus decreasing the size of digesters.”
Park adds that “Furthermore, we can increase the stability of the anaerobic digestion process by adding ASSR-sludge to anaerobic digesters. All these [innovations] could significantly decrease the burden of the communities that wish to build and operate anaerobic digesters to remove waste sludge. During this project, we would like to prove this concept and establish the prototype of ASSR + anaerobic digestion by working with local municipalities and conducting pilot/full-scale ASSR + anaerobic digestion systems.”
The Technology Development Fund is overseen by the Office of Technology Commercialization and Ventures (OTCV), based at the President’s Office in Boston. This year’s recipients, selected from a field of 35 applicants, were chosen for their projects’ commercial viability in hopes that development of the technology will lead to a startup company or licensing agreement, according to Abigail Barrow, interim executive director of OTCV. (May 2018)