METHOD FOR CLEANING WASTEWATER USING A WASTEWATER TREATMENT PLANT HAVING TWO LEVELS OF ACTIVATION

摘要

A waste water purificn. process, in which intermediate clarification is effected between first and second activation stages and post-clarification is effected between the second activation stage and the sludge circuit, involves (a) operating the first activation stage aerobically or facultatively anaerobically mainly with prokaroytes in the functional biomass as an adsorption stage with a sludge loading of at least 2kg 'BSB5' per kg. dry matter per day; (b) operating the second activation stage as an aeration stage with a sludge loading of less than 0.15 kg. 'BSB5' per kg. dry matter per day; (c) returning at least part of the sludge from the post-clarification to the adsorption stage in an amount which does not deleteriously affect its operation as an adsorption stage; (d) returning sludge from the intermediate clarification to the adsorption stage as recycle sludge or discharging it as excess sludge; (e) returning the rest of the sludge from post-clarification to the second activation stage as recycle sludge and, if necessary, discharging excess sludge from post-clarification. ADVANTAGE - The amount of excess sludge, requiring expensive dewatering, is reduced.