Energy balance performance of municipal wastewater treatment systems considering sludge anaerobic biodegradability and biogas utilisation routes
Number of Authors: 3
2016 (English)In: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437Article in journal (Refereed) Epub ahead of print
The energy balance of a municipal wastewater treatment (WWT) system was evaluated considering the influence of excess biological sludge anaerobic biodegradability (BDAn) and of biogas utilisation as either fuel for co-generation of heat and power (CHP) or for vehicle transport. Sludge thermal pre-treatment prior to anaerobic digestion and high-rate carbon removal were considered as modifications of a reference municipal WWT system to impact the sludge BDAn. Both thermal pre-treatment and a high-rate process with a short sludge retention time (SRT = 1-3d) led to ∼30% higher sludge BDAn than that of untreated sludge from a low-rate WWT system with long SRT ( > 8d), which enhanced methane yields and energy production correspondingly. An efficient separation (40% of CODin) of primary solids promoted biogas production by capturing a significant part of the incoming COD, and lowered aeration energy demands for carbon oxidation due to lower loads of particulate organics into the biological treatment. Thermal pre-treatment can most effectively increase the biodegradability of sludge originating from a low-rate WWT system with a long SRT. Sludge solubilization alone as an indicator of increase biodegradability by a pre-treatment is inadequate for sludge types with inherently high biodegradability. A WWT system with primary separation, sludge pre-treatment, and CHP from biogas can be a net electricity producer and self-sufficient in thermal energy, provided the thermal energy from CHP is available for the pre-treatment. With other types of energy carriers as inputs and outputs, the WWT performance also needs evaluation with respect to the energy economic and environmental value.
Place, publisher, year, edition, pages
Other Environmental Engineering
Research subject Waste Science and Technology
IdentifiersURN: urn:nbn:se:ltu:diva-60053DOI: 10.1016/j.jece.2016.10.030OAI: oai:DiVA.org:ltu-60053DiVA: diva2:1043686