COMPARATIVE ENERGY- AND CARBON- FOOTPRINTS FOR ACTIVATED SLUDGE LAYOUTS

There are opportunities for direct and indirect carbon sequestration and emission offset in wastewater treatment. Biological processes partially convert oxygen demand to biomass, which can be digested, thus producing biogas and biosolids. Biogas can be used to offset carbon emissions by recovering its energy in a co-generation plant, energy that otherwise could be produced using a fossil fuel. Biosolids may be incinerated (i.e., immediate return of the carbon to the atmosphere), applied to land as soil amendment (i.e., retarded carbon return to the atmosphere), or buried in properly managed landfills (i.e., long-term carbon sequestration). The choice of biological treatment layouts affects the quantity of biomass produced and the process energy demand. In this paper we present the effects of biological process layout on the treatment's carbon and energy footprints. We also introduce our results on the effects of landfill distance on overall treatment footprint.