Conference Agenda

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Session Overview
Session 26B: Wastewater Process: Solids
Wednesday, 15/Sept/2021:
10:30am - 12:00pm

Location: Room 410ABC
West Building

10:30am - 11:15am

Effect of Fat, Oil and Grease (FOG) on Digested Sludge Dewaterability

Ornella Sosa-Hernandez, Peter Schauer

Clean Water Services, United States of America;

VIrtual Speakers

Clean Water Services investigated the impact that co-digestion with Fat, Oil and Grease (FOG) has on the dewaterability of digested sludge. Over the past 4 years, a deterioration of the dewatering performance has been observed while the volume of FOG that is handled has increased at the Durham Advanced Waste Water Treatment Facility (AWWTF). In addition to a possible decline in centrifuge performance from equipment age, the FOG load and its variable composition had been suspected to cause dewatering issues as the cake solids dryness and solids capture have steadily decreased despite little change to the polymer dosing.

The anaerobic digesters at the Durham AWWTF have independent FOG feed lines allowing for different loadings to either digester. During this 4-month evaluation, more FOG was fed to one of the two anaerobic digesters while both received equivalent indigenous sludge loading which is composed of thickened primary and secondary sludge. The digester feed, FOG stream and digested sludge were characterized by measuring parameters such as proteins, lipids and carbohydrates, orthophosphate, and cations concentrations. Dewaterability was assessed through analysis conducted by Dr. Matthew Higgins at Bucknell University.

This presentation will include an analysis approach that can help recommend FOG management strategies whereas the lessons learned from this evaluation are:

  • FOG addition had no negative impact on digested sludge dewaterability.
  • The polymer demand was more affected by indigenous sludge VS loads than FOG loading.
  • The presence of charged compounds in the digestate such as phosphate and cations impacted some of the dewatering characteristics.
  • Although VS loads above 0.25 lbs/ft3/d and up to 50% FOG were fed for a short period of time, digestion stability was maintained. The time to perceive instability and the impact to other parameters such as alkalinity should be investigated.

11:15am - 12:00pm

The Future of Biosolids Handling

Tanner Hartsock

Biolynceus LLC, United States of America;

Sustainable biosolids handling strategies are becoming increasingly difficult to develop. For land applications, the most common biosolid disposal technique, wastewater facilities (WRRFs) must produce either Class A or Class B biosolids. Even if these requirements are met, some WRRFs are faced with local pressure, forcing them to alter the course of their biosolids handling program. Biosolids regulations have seen little change since the first regulations were established in 1993, and mounting pressure on the Environmental Protection Agency make future changes both likely and imminent. Additionally, contaminants such as per-polyfluoroalkyl substances (PFAS) are sure to complicate regulations moving forward. Even landfill applications are uncertain: recently, the state of California banned the use of biosolids as an alternative landfill cover. Now more than ever, WRRFs are considering innovative, even novel technologies for managing their biosolids. Bioaugmentation can be used to degrade volatile biosolids and should be viewed as a viable approach to reduce the amount of biosolids at WRRFs. Research has shown that microbes capable of producing amylase enzymes can hydrolyze cellulose, a primary component of wastewater sludge, and convert it to glucose, a form of soluble carbonaceous biochemical oxygen demand (cBOD). This soluble glucose is readily available as a food source to both the added microbiology and the existing sludge biomass, reducing sludge volumes by up to 40%. Probiotic additions are common in lagoon systems, reducing costs associated with dredging, dewatering and hauling and recently, biological sludge reduction at mechanical wastewater facilities has received attention as an alternative means to reduce costs associated with dewatering and hauling. As regulations become more stringent, the time to consider new technologies for biosolids reduction is now.