TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: Oxygen consumption reactor(s) preceding the denitrification reactor can be arranged to generate anoxic conditions for denitrification. Particulate removal devices are arranged to generate particulate free water in different parts of the system. The separated organic material is recycled directly to the oxygen consumption reactor, to a fermentation reactor or to the denitrification reactor (2a-2). The closed loop system further contains biological phosphate removal bioreactor(s) (7a) containing activated sludge or suspended carrier system. A by-pass system (12a) for a removal of phosphorus is arranged to use biological activated sludge or a suspended carrier system in anaerobic and aerobic compartment systems. A sedimentation tank for the final polish of water by chemical precipitation of phosphorus is placed between the system and the recipient. The production unit is a production unit for industrial nitrogen containing water, food industry production unit, or culturing vessels for agriculture or aquaculture. A sterilization unit using UV and/or ozone is placed as the very last constituent of the system. The organic material is arranged to become fermented to fermentation products, e.g. acetic acid or 0-4C carboxylic acid, aldehyde, ketones, acetone, or other compounds as carbon sources for the reactors (1a-1c), e.g. methanol, ethanol, glycerol, pyruvate. Carbon dioxide is preserved by introducing oxygen or pressurized air in a closed biological oxygen demand oxidation reactor (4a-4c) prior to the nitrification bioreactor. The nitrification reactor is supersaturated with carbon dioxide by omitting air-and carbon dioxide stripping. Biogas is produced by fermentation of waste material of the system. Oxygen is provided to the system using air, molecular oxygen in gas phase or liquid phase for any of the aerobic reactors. The organism is a fish species, shellfish species, or crustacean.Preferred Property: The system comprises a plant and/or algal production system used in a green house or building in upper, second level basin having a depth of 1-10 cm (preferably up to 1 m) and a weight of 10-2000 kg/m2 for deeper applications of 20-300 kg/m2. It has plants or algal growth systems that filter off red and blue sunlight reducing algae growth in underlying aquaculture vessels, filtering off red and blue wavelengths of 420-600 nm and 650-720 mm, particularly absorbing light in the wavelengths of 420-550 and 670-720 nm. It may comprise plastic film for coverage of the light transfer through the windows of, e.g. the greenhouse, filtering off the red and blue wavelengths.