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 (umax) 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.
