Energy Sustainability and Nutrient Removal from Municipal Wastewater
Abstract:The state of energy sustainability in wastewater treatment and especially nutrient removal has improved rapidly with development of new technologies and increased concerns for the environment. The ultimate goal of the wastewater treatment industry could be achieving energy self-sufficiency within a facility. The progress that has been made toward this goal with nutrient removal technologies was investigated and the challenges and opportunities facing our industry are identified in this paper.
A benchmark for energy sustainability was recently achieved in Strass, Austria, where the energy usage of 1000 kwh/million gallons (MG) treated was achieved, which was actually less than the energy generated by digester gas, . This paper presents a comparison between the U.S. and Austria of potential energy use and generation, and offer approaches that could lead to similar U.S. success in the future.
The selection of technologies and their operation impact the sustainability of facilities in two ways; energy management and carbon management. On energy management, the current U.S. energy usage ranges between 600 and 2,600 kwh/MG treated when operated with internal carbon sources. When carbon is imported, the energy usage increases by approximately 600 kwh/MG treated or more, which needs to be either reduced or supplied from the outside sources. For the purpose of energy generation, , key factors include, in-plant generation of volatile fatty acids(VFA), increased biogas yield from both enhanced primary settling with chemical addition and conditioning of feed sludge and co-digestion, where feasible . For the purpose of energy conservation, key factors included ability to operate the swing zone, step feed mode of activated sludge , sidestream treatment of recycle loads, and automation with on-line sensors.
A list of challenges and opportunities are suggested for reaching a long term goal of energy self-sufficiency.
Document Type: Research Article
Publication date: January 1, 2009
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