WATER ENVIRONMENT RESEARCH FOUNDATION (WERF) A ROADMAP TO REDUCE BIOSOLIDS CAKE ODOR REDUCTION

A roadmap to reduce biosolids cake odors was developed under the WERF Phase 3 Project 03-
CTS-9T entitled “Biosolids Processing Modifications for Cake Odor Reduction” encompasses
nine research agenda items developed from the results of Phase 2, which was completed under
WERF Project No. 00-HHE-5T (Adams et al, 2003). Phase 3 has been a 3-year project dedicated
to testing hypotheses in the laboratory as well as on pilot-scale and full-scale bases, to determine
the causes and biosolids odors and find ways to remediate them. The Phase 3 project has
concluded and the Final Report was published in late 2007.
Laboratory and full-scale investigations conducted in Phase 3 that helped develop a biosolids
cake odor reductions roadmap included:
1. The role of cations in odor production from anaerobically-digested biosolids
2. The effect of anaerobic digestion parameters such as mixing, detention time, temperature,
and phasing on cake odor production.
3. Effects of dewatering processes and their control parameters on cake odors
4. Effects of chemical addition on cake odors
Demonstration of promising research findings at full-scale biosolids digestion and dewatering
facilities were undertaken in Phase 3. The main goal of this last phase of the project was to
develop a biosolids cake odor reduction roadmap. This roadmap matches wastewater or
biosolids facilities that need to reduce biosolids odors with specific technology solutions,
potential changes in operational practices, and/or chemicals, or biological agents additions. Each
biosolids processing facility or wastewater treatment plant (WWTP) will need to determine their
own biosolids cake odor reduction goal, which is typically determined by either
reducing/eliminating surrounding site or application location odor complaints or set using odor
dispersion modeling to demonstrate that the odor threshold goal is met at the sites property line.
The roadmap provides several approaches to meet any level of biosolids cake odor reduction
needed to meet reduction goals. Typically a combination of roadmap approaches, such as
technology, operational, and/or chemical strategies are needed to meet higher cake odor
reduction requirements. Whereas, for smaller cake odor reduction needs, only one or several
roadmap approaches are needed. All roadmap approaches are independently viable and have
shown cake odor reductions. Several WWTPs are currently looking at the roadmap concept to
meet needed biosolids cake odor reduction needs. WERF is considering adding another phase to
this project to roll-out and fine-tune the roadmap concept at a WWTP. To date, parts of the
roadmap have been used by WWTP to meet their biosolids cake odor reduction needs.