Technologies and Processes for Pretreatment and Management of Source Separated Organics

Introduction: Source Separated Organics (SSO) co-digestion with wastewater solids at Water Resource Recovery Facilities (WRRFs) offers promise to advance sustainability through beneficial reuse of the organic fraction of pre- and post-consumer waste streams (source separated organics), which would typically otherwise be disposed in landfills. Currently, several states have started implementing regulations restricting organics disposal to landfills to reduce green house gas emissions. A major outlet for SSO's has identified as anaerobic digesters already built-in water resource recovery facilities however most of the time SSO's cannot be accepted as they generated and requires pretreatment. The pretreatment could be conducted on-site at WRRFs, in centralized facilities and in some cases at decentralized sites. Objectives: This paper will present the findings from a recent project funded by the Water Research Foundation. The objective of this presentation is to comprehensively evaluate SSO pretreatment technologies and existing operational facilities and produce information that utilities with interest in SSO pre-treatment can use as guidance. The utilities could use the findings from this research for several important purposes: - successfully building or enhancing existing SSO pretreatment and co-digestion programs, - addressing challenges and opportunities involved with SSO pretreatment, - identifying SSO pretreatment requirements based on SSO feedstock quality and quantity, - and determining capital and O&M costs and potential impacts on WRRFs. Methodology: A systematic approach was developed for conducting global literature review and also to gather information from existing facilities and case studies. This approach was successfully used to draw the borders of the research and stay focused on the main objectives of the project. Fact sheets were developed for each case study to provide detailed information. Finally, all the results were transferred into Microsoft Power BI platform to visualize the results and generate dash boards. This presentation will provide an overview of the project, goals and anticipated outcome of the project, and an update on progress made to date. Findings: The literature review showed that the physical SSO pretreatment technologies are preferred around the globe in full scale applications. Considering high variable nature of SSO, the pretreatment processes are found to be mostly site specific. However, in majority of the facilities SSO pretreatment starts with initial Unit Operating Processes (UOP's), that generally includes separation technologies such as trommel screens, magnetic belts, and rock traps. After an initial process the core of the process includes pulping/mixing/blending technologies. Hydropulper, depacking equipment, extrusion units are generally used as the core of the pretreatment process to generate homogenized slurry. As a last polishing step, mixers, blending/mixing tanks and also separation technologies are also included in the process. Our results indicated that the SSO pretreatment can be performed on-site at the WRRFs or off site as a stand alone facility. Several facilities were selected around the globe to evaluate. Figure 1 shows the different type of SSO Pretreatment/Processing applied in facilities and also lists the Utilities that adopted these management strategies. Figure 1. Four Types of SSO Pre-treatment/ Processing by Utility A fact sheet was prepared for each facility listed in Figure 1 and the type of SSO pretreatment and processes were evaluated in detail. The fact sheets include information on type of SSO received, types of processes and technologies applied along with key O&M lessons learned. Furthermore, seven case studies (selected WRRFs have successfully implemented SSO feedstock pretreatment systems) were included to include more detailed information especially on costs and maintenance requirements.