Silicon Valley Clean Water

Energy consumption and biosolids management are major operating expenses for municipal wastewater treatment plants. Energy-positive anaerobic secondary treatment was demonstrated by Silicon Valley Clean Water (SVCW), Stanford University and others. With funding from the California Energy Commission, SVCW built a demonstration-scale Staged Anaerobic Fluidized Bed Membrane Bioreactor (SAF-MBR) processing 24,000 gpd to test the potential to replace conventional aerobic secondary treatment. The system achieved secondary effluent standards for COD, BOD, and TSS in a treatment volume competitive with conventional aerobic systems. Biogas production and calculations of energy consumption at full scale indicate the process would produce a surplus of renewable power, allowing wastewater plants to be net energy positive without having to import high-strength organic wastes. Production of secondary biosolids was reduced by more than 90%. Operations continue, beginning Phase II to test integrated treatment trains to achieve California non-potable and potable water reuse standards.