Abstract
Aquatic nitrogen pollution is one of the most urgent environmental issues requiring prevention and mitigation. Large quantities of high-ammonium wastewaters are generated by several industrial sectors, such as fertilizer and anaerobic-digestion plants. Nitrification of these wastewaters is commonly carried out, either to remove nitrogen or produce liquid fertilizers. Standard control methodologies for the efficient nitrification of high-ammonium wastewaters to produce liquid fertilizers have not yet been established and are still within their early stages of development. In this paper, novel pH-based control algorithms are presented that maintain operation at the microbial maximum reaction rate (υmax) in batch and continuous reactors. Complete conversion of ammonium to nitrate was achieved in a batch setup, and a conversion of 93% (±1%) was achieved in a continuously-stirred-tank-reactor. The unparalleled performance and affordability of the control schemes proposed offer a steppingstone to the future of sustainable fertilizer production.
Highlights
Fermentation 2021, 7, 319. https://The explosion of the world-population in the 20th century was made possible by the advent of the Haber–Bosch process
At lower pH levels, ammonia will predominantly exist in its protonated form, ammonium
Effectively 2 mols of protons are released per mol of ammonium oxidized
Summary
Fermentation 2021, 7, 319. https://The explosion of the world-population in the 20th century was made possible by the advent of the Haber–Bosch process. Nitrogen fertilizer (ammonia) could be produced at relatively low cost, allowing a several-fold increase in agricultural food production [1]. This high input of synthetic nitrogen has caused extensive environmental damage. Nitrogen is the limiting nutrient in most ecosystems and excess nitrogen results in far-reaching consequences. These include eutrophication, air pollution, biodiversity loss, climate change, and stratospheric ozone depletion [2]. Numerous investigations and regulations have since aimed to reduce this hazardous use of nitrogen [3,4,5,6,7]
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