NITROGEN REMOVAL SYSTEM AND NITROGEN REMOVAL METHOD FOR DEHYDRATION FILTRATE

PROBLEM TO BE SOLVED: To provide a nitrogen removal system and a nitrogen removal method for dehydration filtrate that reduces a nitrogen load in a water treatment process for treating anaerobic digested sludge.SOLUTION: A nitrification tank 13 includes an intermittent aeration 11 and an agitator 12. A fixed amount A of dehydration filtrate is supplied to the nitrification tank 13 to perform intermittent aeration with agitation. After a lapse of time required for nitrification treatment, agitation and aeration of the nitrification tank 13 are stopped, and the fixed amount A of supernatant liquid of nitrified liquid is returned to the oxygen-free tank 1. After nitrification treatment, waste water in the nitrification tank 13 and waste water in the oxygen-free tank 1 constituting a reaction tank 3 are alternately exchanged to prevent decomposition of a sludge floc while maintaining proper organic matter concentration of nitrified sludge in the nitrification tank 13. An environment suitable for culturing nitrification bacteria and denitrification bacteria is obtained by intermittent aeration and proper hydrogen ion concentration while maintaining low dissolved oxygen level, and breeding of actinomycetes is prevented by oxygen-free conditions to improve sludge settleability.