Meeting today’s water and wastewater challenges

Sabina Martyn, Philip Pedros, and John Scheri delivered insightful presentations at this year’s New England Water Environment Association conference, held in Boston from January 22 to 25.

Our three water and wastewater professionals addressed challenges that included engaging the public to prevent combined sewer overflows, treating wastewater sludge with pyrolysis, and optimizing the use of oxidation ditches.

Involving the public to stop sewer overflows

Senior Project Engineer Sabina Martyn focused on a public engagement toolkit used by the City of Elizabeth in New Jersey to control combined sewer overflows (CSO).

The City is working with the EPA and the New Jersey Department of Environmental Protection to reduce the number of CSO events and improve the water quality in receiving streams. Public outreach is needed to share information, obtain feedback, consider stakeholder values and priorities, and create a long-term collaborative relationship.

The City’s website offered notifications of public meetings, project updates, presentations, and information on CSOs and green infrastructure. The City’s Twitter and Facebook accounts provided quick bites of info and links for more in-depth information.

Signs explaining the function and purpose of green architecture were displayed in community rain gardens. A online CSO notification system was made available. Multilingual flyers provided information about CSOs, the Long Term Control Plan, and City projects to improve water quality.

Reducing sludge and removing PFAS with pyrolysis

CSO public engagement toolkit: Engaging a diverse and multigenerational urban community to craft an effective CSO Long Term Control Plan

Sabina Martyn

Senior Project Engineer

Dr. Philip Pedros, a Principal Process Engineer, joined Dr. Robert Brown of Iowa State University to discuss gasification and pyrolysis, two thermochemical processes that are experiencing a renewed interest in the wastewater treatment industry.

These processes are easier to permit than incineration systems and they achieve a similar reduction in sludge volume of 90% to 95%, reducing the cost of hauling. There is mounting evidence that when these processes are used at the right temperature, per- and polyfluoroalkyl substances (PFAS) are removed from the resulting char.

Either gasification or pyrolysis may be used to convert sewage sludge biosolids to energy. This energy is then used to dry to the biosolids to the required 10% moisture content. In this way, PFAS compounds are removed from the biochar and the facility’s energy consumption is reduced, decreasing its carbon footprint.

Philip Pedros and Robert Brown discussed autothermal pyrolysis, which removes the barrier to the use of pyrolysis at large wastewater treatment plants. Currently available pyrolyzers can be used at smaller wastewater treatment plants but cannot be easily scaled to large treatment plants. However, an autothermal pyrolyzer can be scaled up while remaining economical.

Optimizing oxidation ditches to control nitrates

John Scheri, our Wastewater Practice Leader for North America, focused on how nitrates were controlled at the Caldwell Wastewater Treatment Plant in New Jersey.

Under the National Pollutant Discharge Elimination System (NPDES), the plant’s permit imposed a future nitrate limit of 10 mg/L. The plant considered several options to reduce nitrate output, including extending the outfall extension to the Passaic River, using new anoxic tanks with internal recycle streams, and improving the operations of oxidation ditches.

Oxidation ditches were optimized in several ways, successfully reducing nitrate output. Existing aerators were replaced with a larger dual-impeller style aerator and a velocity baffle was installed. Variable frequency drive controls and dissolved oxygen probes were installed for process control. The plant also used preventative and remedial measures to reduce foaming issues.