The Net Energy Neutral Wastewater Treatment Plant

From Stanford University - link.  The goal of energy reduction and even neutral energy requirements will be a significant focus for wastewater researchers and practitioners this decade. 

 

"A major goal of wastewater treatment is net energy neutral or net energy producing treatment processes that remove oxygen depleting forms of carbon and nitrogen. While the treatment of waste carbon via processes such as anaerobic digestion or gasification enable energy recovery, the treatment of waste nitrogen requires energy inputs. My research at Stanford has focused on the development of a a new wastewater treatment process that recovers energy from waste nitrogen by converting reactive nitrogen (i.e. ammonia) to nitrogen gas via a nitrous oxide intermediate. This process is termed the Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO) and involves 3 steps: (1) oxidation of ammonia to nitrite, (2) reduction of nitrite to nitrous oxide, (3) decomposition/combustion of nitrous oxide to nitrogen and oxygen gas with energy recovery. Step (1) of CANDO has been developed by European researches and is termed the Single reactor system for High activity Ammonia Removal Over Nitrite (SHARON) process. My research has focused on the development of a biological process that enables partial reduction of nitrite to nitrous oxide. My research has also focused on the development of devices that enable catalytic decomposition of nitrous oxide with a net energy output.

When coupled with anaerobic digestion, CANDO has the potential to enable net energy producing wastewater treatment by recovering significant amounts of energy through the combustion of biogas (i.e. methane) and nitrous oxide. The impact of energy recovery from wastewater is significant, considering that the treatment and transport of wastewater imposes a 3% load on U.S. energy supply and approximately 3-5% in most countries around the world. In principle, CANDO is applicable to any high concentration ammonia streams including landfill leachates and industrial manufacturing processes."