Tsuno Hiroshi, Nishimura Fumitake, Somiya Isao
Doboku Gakkai Ronbunshu, 1994(503) 159-166, 1994
Biological nitrification can be inhibited by free NH3 in wastewater containing high concentrated ammonium. Bio-zeolite reactor is developed in this study. It is a combined physical and biological reactor, in which zeolite is used as both adsorbent of ammonia and attached growth medium for nitrifier. In this reactor, concentration of ammonium nitrogen is kept by ion-exchange under the threshold level which causes the inhibition, and the ammonium nitrogen is nitrified by bacteria grown on the medium (zeolite). It is experimentally shown that ion-exchange and biological nitrification mechanisms occur concurrently, and that adsorption of ammonium nitrogen prevails when its load is larger than the nitrification activity. However, adsorbed ammonium nitrogen is released and nitrified after sufficient growth of nitrifier on the medium, then ion-exchanging capacity of zeolite is regenerated. Thus, stable removal of high concentrated ammonium nitrogen can be obtained, and successful response to stepwise shock loading is also shown without any serious increase of concentration of ammonium nitrogen. Ammonium-nitrogen loading per unit weight of zeolite is shown to be an important design parameter of this reactor, and more than 90% removal of ammonium nitrogen can be accomplished until the loading is increased to 0.15mgN/(g-zeolite·h).