Temperature phased anaerobic digestion with side-stream archaea enrichment for Lulu Island wastewater treatment plant digester upgrade

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Waste sludge processing at wastewater treatment plants (WWTPs) represents one of the major challenges, often costing more than the treatment and discharge of the liquid stream. Among several waste sludge treatment options, anaerobic digestion (AD) has proven to be an effective technology. AD is essentially a bioreactor that induces microorganisms to form volatile fatty acids and methane, supplied through the introduction of organic matter such as sewage sludge or manure. In addition to generating methane (which can be converted to heat/electricity), the other benefits of AD are the diversion of organic waste from landfills, reduction of solids, pathogens, production of organic fertilizer as well as reduction of GHG emissions. Lulu Island WWTP (Richmond, BC) has been operating two single-stage AD in parallel. Although the process achieves 63% solids reduction, the current configuration does not provide process redundancy when one of the digesters needs to be shut down for maintenance/repair. Moreover, the dewatered digestate qualifies as Class B biosolids with restrictions for land application. For reducing operational risks and intensifying resource recovery, Metro Vancouver is interested in developing next generation AD technologies at their WWTPs. In this project, a dual-stage AD tandem with a side-stream bioaugmentor is proposed as an advanced AD option for increasing solids reduction, upgrading biogas methane composition from the typical 60% to 90% or higher, enhancing digestate dewaterability, and upgrading biosolids from Class B to Class A. The project will also include microbial profiling combined with select multi-omic (DNA and RNA) analyses to gain insight to community structure, activity and function in both conventional and advanced AD configurations. Metro Vancouver has budgeted $1M to integrate and operationalize a pilot-scale AD at Lulu Island Water Resource Recovery Facility and $13M for a plant upgrade to feed biogas into the power grid. Lab-scale results obtained from this project will provide clear direction for the pilot-plant design/built/operation, which will enable the evaluation of advanced AD processes "offline" without risking ongoing operations.