Patent DE-102008028003-A1 (DE)
Title: Process for continuous cleaning of process water in the paper industry, comprises contacting the process water to be cleaned in an anaerobic reactor with anaerobic microorganisms in order to reduce impurities in waste water
Inventor: TROUBOUNIS GEORGE
IPC: C02F9/14
Filed: 2008-06-12
Abstract: The process comprises contacting process water to be cleaned in an anaerobic reactor (125a, 125b, 225)with anaerobic microorganisms in order to reduce impurities contained in waste water in an anaerobic cleaning step, separating the process water received from the anaerobic cleaning step selectively from the gas contained in the process water in a first separation step, and separating the process water received from the first separation step from the slid materials contained in the process water in a second separation step. The process comprises contacting process water to be cleaned in an anaerobic reactor (125a, 125b, 225)with anaerobic microorganisms in order to reduce impurities contained in waste water in an anaerobic cleaning step, separating the process water received from the anaerobic cleaning step selectively from the gas contained in the process water in a first separation step, and separating the process water received from the first separation step from the slid materials contained in the process water in a second separation step. The first separation step is carried out in a strip container in which the process water is led in the direct current or in the counter current with air through the strip container. The process water is led from top towards bottom through the strip container, the air is led in the counter current from bottom towards top through the strip container and the gas is drawn off in the upper area of the strip container. A low pressure of 20 mbar is designed in the strip container during carrying out the process water and the air. The process water and the air are mixed to each other in the strip container by an agitating device, which is a dynamic or static mixer. The process water in the first separation section is led from bottom towards top through the strip container and the air is supplied into the strip container in its lower area in such a way that the air spurges in the form of air bubbles through the process water. The process water and the air bubbles are mixed to each other in the strip container by the agitating device. The air is guided into the strip container in such a way that the air bubbles have an average size of 150-600 mu m. The pH value of the process water is adjusted to 7.2 to 8.2 in the first separation step. The precipitant and/or precipitating agent is added to the process water during the first separation step. The precipitant is sodium hydroxide or aqueous sodium hydroxide solution, an aluminum sulfate, iron sulfate, polyaluminum chloride or sodium aluminate and/or the precipitating agent is polyacrylamide. The solid material is separated from the process water by filtration and/or floatation in the second separation step. The floatation is carried out as disperse floatation or as pressure-release floatation. A partial flow is received after the second separation step and is mixed with the process water after the anaerobic cleaning step. The process water supplied to the process water processing step comes from a wastepaper processing device (100) and/or from a paper machine (200). An INDEPENDENT CLAIM is included for a plant for continuous cleaning of process water in the paper industry.