The Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO) is a new wastewater treatment process that removes and recovers renewable energy from reactive nitrogen (NH 4 + ). The process consists of three principal steps: (1) NH 4 + oxidation to NO 2 -(2) NO 2 -reduction to N 2 O, and (3) N 2 O conversion to N 2 with energy recovery by using N 2 O as an oxidant in biogas combustion. Stanford University and Delta Diablo (Antioch, CA) partnered in 2012 to demonstrate CANDO at the bench-and pilot-scales. A bench-scale, the CANDO system treated anaerobic digester centrate where 75-80% of the influent NH 4 + converted to N 2 O with >95% nitrogen removal. Some organisms stored phosphorus as polyphosphate granules, possibly enabling simultaneous biological phosphorus removal. Operation of a pilot-scale CANDO system (~1/200 th of full-scale) is under way. Preliminary results show N 2 O production over repeating cycles, but the operation is not yet optimized. We demonstrated power gains in a fullscale biogas-fed internal combustion engine subjected to injections of N 2 O at flows that are expected from a full-scale CANDO system. Increases in power output ranged from 5.7-7.3%, depending on the ratio of biogas to N 2 O. We also describe the academic-utility partnership as a successful model for development of innovative wastewater technology. If successfully scaled up, CANDO can be an attractive option for nitrogen removal by decreasing oxygen requirements, reducing biosolids production, enabling greater diversion of organic matter to methane production, and recovering energy from nitrogen.

By a new synthetic technique, macroporous crosslinked polystyrene resin was functionalized with ligands containing sulfur, nitrogen, and/or oxygen atoms. Preliminary studies indicate that when added to a synthetic acid mine drainage (AMD) solution, some of these functional polymers were capable of selectively binding zinc without becoming "fouled" by iron. Elution of the loaded resins with acid to recover the zinc was also possible. The greatest selectivity for zinc was obtained with functional groups that contained only electronically "soft" nucleophilic centers such as sulfur and nitrogen, and not oxygen atoms, which are electronically "hard" (and prefer such "hard" electrophiles as magnesium, aluminum, or iron cations). The perfo1mance of some of these new materials exceeded that of the commercial ion-exchange resins tested with respect to capacity and selectivity.