Conference Agenda

The past decade has seen a wave of research and development of new technologies that allow for “process intensification” – those technologies developed to increase wastewater treatment capacity using less site footprint and/or tankage volume. These intensification technologies will be instrumental in addressing nutrient limitations from treatment facilities discharging to the Puget Sound. Such newer breakthrough technologies include aerobic granular sludge (AGS), mixed liquor densification, membrane aerated biofilm reactors (MABR), and mobile organic biofilm (MOB) technologies. Compared to these technologies, the Integrated Fixed-film Activated Sludge (IFAS) process, considered one of the original process intensification technologies, is now well proven and fully established, having been developed and applied since the 1990s. With the fervor at which these newer technologies are being embraced, the question that has arisen in the industry is this: Is the IFAS process still a viable technology?

This purpose of this presentation is to examine through performance of full-scale IFAS implementations whether the known benefits of IFAS technology (e.g., process robustness, ammonia-nitrogen removal for cold wastewater) outweigh the known drawbacks (e.g., higher aeration demands). Case studies of IFAS facilities are presented, highlighting the advantages and challenges of implementing this technology at four facilities: 1) Bend Water Reclamation Facility in Oregon/USA; 2) Field’s Point Wastewater Treatment Facility in Rhode Island/USA; 3) Twin Falls Wastewater Treatment Plant in Idaho/USA; and 4) Ellesmere Port Wastewater Treatment Works in the United Kingdom. The facilities have all been operating with the IFAS technology for a number of years, allowing investigation into the long-term benefits and limitations of the process. All of the facilities are able to meet their respective nutrient removal goals, providing the warranted capacity and performance requirements. Some of the facilities; however, have experienced higher than expected energy demands – specifically with respect to the seasonal air demand anticipated with the system. The viability of the IFAS intensification technology will be proven, specifically for site-constrained facilities that require improved total inorganic nitrogen removal, in documenting the success of these facilities. The shortcomings, and warranted improvements to the IFAS technology, will also be discussed – using lessons-learned from these projects.

The City of Peterborough Wastewater Treatment Plant (WWTP) is an 18 MGD conventional activated sludge plant in Southern Ontario, Canada. The plant consists of 4 aeration trains, originally designed for conventional suspended growth. The trains were converted to a moving media Integrated Fixed Film Activated Sludge (IFAS) system in 2006 (Plant 1) and 2011 (Plant 2). The system consisted of non-engineered plastic matrix material within metal media retention cages in the first pass of each tank. The moving media system had several operational challenges including media loss, non-uniform dispersion of media, increased hydraulic head loss, screen and diffuser maintenance difficulties.

The City of Peterborough retained R.V. Anderson Associates Limited (RVA) to implement an alternate IFAS system that would address problems with the existing configuration. Various alternatives were evaluated in terms of retrofit requirements, Operations and Maintenance (O&M) obligations, life cycle costs, Environmental Compliance Approval (ECA) requirements and other criteria. The selected fixed media IFAS system was the WavTex^TM woven media system by Entex Technologies Inc. (Entex). It included a total of 32 modules, each having buoyant media sheets tethered to 304L stainless steel support frames with integral coarse bubble aeration. This paper/presentation will go into details of the evaluation/selection and operation of the new IFAS system.

The final aeration tank with the new IFAS system was put in service in December 2021. To validate the system performance, testing during cold weather winter, high flow spring, and high temperature summer was required. The performance was monitored for Total Ammonia Nitrogen (TAN) removal at the rated capacity. The new Entex system was able to consistently meet TAN limits of 6 mg/L (summer) and 10mg/L (winter).

Based on the TAN results, ease of operation, and reduced O&M costs the new system proved to be able to meet the plant’s needs. Further details including testing methods, other parameters tracked, and plant performance will be discussed in this paper/presentation. At the end of this project, the City of Peterborough WWTP was able to install and validate an alternative IFAS system to address O&M issues which also met effluent requirements for the full rated capacity.