Conclusions
Chitosan is a promising biopolymer that can be used as
an alternative biofilter media for nitrite oxidizing bacteria
(NOB). The immobilization of NOB on the surface
of chitosan flakes depends on immobilization time, pH
pretreatment, particle size and degree of the deacetylation
of chitosan. On the other hand, the molecular weight of
chitosan did not affect nitrite removal efficiency. With
this study, the optimal immobilizing process was the use
of chitosan flakes with a size between 1–5 mm with a
degree of deacetylation higher than 80% and the chitosan
pretreated with a buffer at pH 6.5 to modify surface
charges. An optimal immobilization period of 24 hr is
required. The NOB immobilized on chitosan flakes has
a high potential to remove excess nitrite from wastewater
and aquaculture ponds.