NOVELTY - Treating water involves contacting organism flowing-down of the surface flowing water containing ammonia nitrogen, which is carried out on a porous body, in the first half part of a treatment tower; manipulating the oxygen concentration of an injection water, ammonia nitrogen is oxidized to nitrite-nitrogen and stabilized; the ammonia nitrogen containing natural water is reinjected in the nitrite-nitrogen containing water generated in the processing second half part; and denitrifying without passing through nitrate-nitrification.    USE - The methods, system, service, and mechanism are useful for treating water; for carrying out raw food catalytic oxidation/filtration removal of the soluble metals coexisted at the same time aiming at denitrifying by pouring ammonia nitrogen containing water again; for adsorbing viscous material generated from the somatic-cell surface of microorganisms; and for helping for biomass to gasify nitrogen or to capture other contaminant before and behind the treatment tower, and the tank containing the suspending type raw material which microorganisms coated (the slightly soluble electron donor mixture into which the customer itself can collect easily the biomass which captured nitrogen other contaminant adhering to the surface, and can discard it) do not decompose (all claimed).    ADVANTAGE - The method and system can made water containing various particle, such as soluble metals, or clay, a metal hydroxide with object the 3 component-containing water and also these containing water of ammonia nitrogen, a nitrite nitrogen, and a nitrate nitrogen, and these can be processed advantageously in terms of cost. Also, the biological treatment system can make the processing performance much more effective a circulation processing method aiming at promoting the improvement of its biological treatment performance biomass collection mechanism which a customer can collect and can be discarded at a field, by light-irradiating in a tank before and after passing the treatment tower.    DETAILED DESCRIPTION - Treating water involves contacting organism flowing-down of the surface flowing water containing ammonia nitrogen, such as underground water, subsoil water, a waste water, a hot spring, mineral water, and a river, which is carried out on a porous body, in the first half part of a treatment tower; manipulating the oxygen concentration of an injection water, ammonia nitrogen is oxidized to nitrite-nitrogen and stabilized; the ammonia nitrogen containing natural water is reinjected in the nitrite-nitrogen containing water generated in the processing second half part, by flowing down and adjusting the mixing conditions of ammonia nitrogen and nitrite-nitrogen containing water by making the microorganisms which have the capability to form nitrogen-gas with ammonia nitrogen:nitrite-nitrogen simultaneously dominate; and it denitrifies without passing through nitrate-nitrification. INDEPENDENT CLAIMS are:    (1) a method of carrying out raw food catalytic oxidation/filtration removal of the soluble metals coexisted at the same time aiming at denitrifying by pouring ammonia nitrogen containing water again; when making the porous body carry out raw food contact flowing-down of the water which coexists and contains iron and a manganese arsenic, and other soluble metals in ammonia nitrogen containing water, in the first half part of the treatment tower, by operating the oxygen concentration of the injection water, ammonia nitrogen is oxidized even to nitrite-nitrogenization and stabilized;    (2) a method of adsorbing viscous material generated from the somatic-cell surface of microorganisms, by filtering and removing, when making the porous body carry out raw food contact flowing-down of the water which coexists and contains iron and the manganese arsenic, and other soluble metals in ammonia nitrogen containing water, in the first half part of the treatment tower, by operating the oxygen concentration of the injection water, ammonia nitrogen is oxidized even to nitrite-nitrogenization and stabilized, by pouring ammonia nitrogen containing water again, it is the microorganisms catalytic oxidation filter-medium surface about various fine particle-like substances, such as clay, a metal hydroxide, coexisted at the same time it aims at denitrification;    (3) a biological treatment system which made the processing performance much more effective by equipping fine air, a micro-bubble, or a nano bubble injection apparatus, where it is air oxidation in a biological treatment tower;    (4) a circulation processing method aiming at promoting the improvement of its biological treatment performance, where natural water is circulated by an air lift;    (5) a biomass collection mechanism which a customer can collect and can be discarded at a field, by light-irradiating in a tank before and after passing the treatment tower given in the specification, the biomass which took in contaminant, such as nitrogen, according to a photosynthesis adheres; and    (6) a service which selects a treated water and especially the nitrogen removal microbial population suitable for the environment of the field among microbial populations, and is prepared as the nitrogen removal microbial population for inoculation.