Tsang, Kwok-Wai

Dr. Tsang is a process specialist in the planning, design, and construction of residuals processing facilities. He has served on residuals and biosolids committees at the Water Environment Federation, American Water Works Association, American Society of Civil Engineers Environmental and Water Resources Institute, and is the current Chair of the International Water Association Sludge Management Specialist Group. He is a WEF Fellow and has done solids related projects around the world.

Titles from this speaker

Description: Navigating the PFAS Hype -- Biosolids Planning Through the Uncertain Regulatory...

Navigating the PFAS Hype -- Biosolids Planning Through the Uncertain Regulatory Climate

Abstract

In the past few years the concerns of the presence of PFAS compounds and how they may impact potential state and federal regulatory actions have dominated the narrative in the water industry. With the actions of Maine and more recently Connecticut, the threat of a ban on biosolids land application has prompted many municipalities to re-examine their biosolids management strategy. Many states have begun to collect data regarding the levels of PFAS in biosolids. Other such as Michigan has established a tiered standards based on extensive data collection to limit biosolids land application based on PFAS concentration. The majority of states are however, waiting for the results of the EPA risk assessment and pending actions before acting. In 2020 in anticipation of the above stated challenges, Pinellas County determined that they should become less dependent on using biosolids on land even though they have a successful history of marketing the thermally dried biosolids since 2013. The county has also set a goal to reduce the amount of wastes going to the landfill. With their waste to energy facility the volume of solid wastes to be landfilled have substantially been reduced. However, yard wastes and wastes tires continued to present challenges at times. There is also a desire to divert more organics from the landfill, thus the consideration of food wastes, and FOG wastes that cannot be handled by co-digestion at the South Cross Bayou Advanced Water Reclamation Facility (SCBAWRF) and the private haulers, also become part of the resource recovery targets. A concept to integrate resource recovery of these waste streams began to emerge. Furthermore, ten other wastewater facilities owned by various cities throughout Pinellas County still rely heavily on land application of biosolids and are facing similar challenges. Thus there is a desire to develop this into a regional facility. A request for proposal was subsequently issued to engage an engineering consultant to further develop this concept. CDM Smith was brought under contract in late 2022 to begin developing the regional resource recovery facility (RRRF) concept. The RRRF will accept a variety of feedstocks including FOG and yard wastes along with biosolids. The intent is that biosolids from Pinellas County, and several other local municipalities (estimated at 42 dry tons per day) will be transported to the RRRF for additional treatment and processing to produce a variety of market ready products such as biogas, biochar, compost, or others. Processing options to be considered include those of FOG and yard wastes for co-processing with biosolids or can synergistically contribute to efficient biosolids processing. After establishing the basic project information such as biosolids and other waste quantities, a number of treatment technologies were first reviewed and screened for applicability at the RRRF. Tables 1 and 2 provide a summary of the biosolids and other organic wastes streams available from Pinellas County and potential partners. The screened technologies are then utilized to develop processing alternatives at the proposed RRRF for evaluation. The screening and evaluation processes resulted in five treatment trains to be further evaluated. These shortlisted process alternatives include anaerobic digestion with potential pretreatment with thermal hydrolysis, thermal processes including drying, both thermal and solar, pyrolysis and gasification. FOG and food wastes codigestion are considered, with energy recovery through biogas generation. The woody portion of yard wastes are being considered as an alternative energy source to support the processes such as solar drying and thermal drying as well as power generation. One of the challenging aspects of the technology evaluation involves identifying technologies that can effectively eliminate PFAS, with a product that can be utilized independent of land application. Without a firm regulatory position, it is not known if complete destruction of PFAS compounds will be required, and whether it is even achievable with available technologies. While thermal technologies such as pyrolysis and gasification as well as advanced technologies such as supercritical water oxidation and hydrothermal liquefaction have been touted as technologies that can effectively destroy PFAS compounds, actual experience that can be pointed to are extremely limited, especially at the scale of the project being considered. Another challenging aspect of these technologies is the lack of available technical information. Since these technologies are mostly proprietary, technology providers are hesitant in sharing information. With little full-scale experience, basic engineering information such as general layout drawings, mass balance, energy balance, equipment costs, operating and maintenance requirements and costs are unavailable or difficult to come by. In order to overcome these challenges, CDM Smith spent much time reaching out to various technology providers and working with them closely to develop these details as part of our evaluation. Through the process, it became clear that most of these technologies are not deployment ready for the scale of facility we are considering. As such, we develop some alternative process trains that would allow us to use established technologies for the proposed facilities but at the same time accommodate some of these technologies at an acceptable scale. Figures 1 and 2 show two process trains with this concept. The final evaluation of these process trains includes the development of capital and operational and maintenance costs for each process train. This is followed by a business case analysis to establish the cost impacts to each municipality under each alternative. The County and partners are currently reviewing these cost impacts. The presentation will focus on the approach taken to develop a strategy that can address potential PFAS impacts as well as reducing the associated risks with new technologies.

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerTsang, Kwok-Wai

Presentation time

08:30:00

08:50:00

Session time

08:30:00

10:00:00

SessionTriple Bottom Line of Biosolids Master Planning

Session number21

Session locationBaltimore Convention Center, Baltimore, Maryland, USA