https://www.hitachi.com/businesses/infrastructure/product_site/water_environment/nitrification_control_system/index.html
Efficient Nitrification Control System Using ICT : Water Environment Solutions : Hitachi
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https://www.intechopen.com:443/books/5738
Nitrification and Denitrification | IntechOpen
Nitrification and Denitrification. Edited by: Ivan X. Zhu. ISBN 978-953-51-3299-8, eISBN 978-953-51-3300-1, PDF ISBN 978-953-51-4753-4, Published 2017-07-05
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