… For the first paper, published in June in the journal Energy & Environmental Science, William Tarpeh and his co-authors – including first author Dean Miller, a Stanford PhD candidate in chemical engineering – used wastewater from a Palo Alto treatment plant to test a process for converting nitrate into ammonia. For the second paper, published in October in the same journal, Tarpeh’s team tested another process that produces high-purity ammonia from agricultural runoff. … Tarpeh and his colleagues created an “electrocatalyst-in-a-box” – an electrically driven process that both extracts nitrate from wastewater and converts that nitrate into ammonia. For the second paper, Tarpeh’s team used a two-step process of electrodialysis and nitrate reduction to take nitrate and ammonia from wastewater and convert them together into high-purity ammonia. They successfully concentrated ammonia about 12 times compared to the nitrate and ammonia in the original wastewater, Tarpeh said.