NOVELTY - A closed loop system comprising production unit(s) of nitrogen containing compounds and/or substances, suspended carrier bioreactor(s) for bacterial growth under anoxic conditions to cause anaerobic denitrification, with compartments, and suspended-carrier bioreactor(s) for bacterial growth under oxic conditions to cause aerobic nitrification, is new.    USE - The system is used for processing industrial and agricultural waste water to produce solid concentrated biological phosphorus sludge useful in agriculture as fertilizer, non-eutrophic mineral salts, fermented organic liquor and/or sediment, activated sludge for soil improvement or compost or reused within the system as biological oxygen demand to create anoxic conditions, sulfuric gas in the form of hydrogen sulfide for the production of sulfate, carbon dioxide, and inert dinitrogen.    ADVANTAGE - The invention is cost efficient, reliable for control, and easy to prepare, with high turn over rates for water in the industrial water treatment. It reduces the concentration of biological oxygen demand or organic materials, the concentration of inorganic or organic nitrogen, and the organic and inorganic phosphorus compounds by biological process.    DETAILED DESCRIPTION - A closed loop system for waste water treatment, comprising:    (a) production unit(s) of nitrogen containing compounds and/or substances and using continuous bioreactor technology for the biological treatment and removal of organic matter, nitrogen and phosphorus from the water at continuous flow;    (b) suspended carrier bioreactor(s) for bacterial growth under anoxic conditions to cause anaerobic denitrification, with compartments; and    (c) suspended-carrier bioreactor(s) for bacterial growth under oxic conditions to cause aerobic nitrification.    The denitrification takes place after the production unit (10) and the nitrification takes place prior to the production unit in a by-pass mode as part of the continuous flow. The water contains nitrogen containing compounds and/or substances.    DESCRIPTION OF DRAWING(S) - The drawing shows an integrated closed loop system.    Reactors (1a-1c)    Denitrification reactor (2a-2)    Biological oxygen demand oxidation reactor (4a-4c)    Bioreactor (7a)    Production unit (10)    By-pass system (12a).