Application of Hydrocyclones to Improve Membrane Technologies for Urban Wastewater Treatment

The technologies associated with the use of a membrane bioreactor (MBR) are becoming one of the dynamically developing directions in the wastewater disposal system. However, a certain part of the used design of membrane units are exposed to mechanical contamination, which significantly impairs their performance. This is especially noticeable when working at wastewater treatment plants, where the required degree of preliminary cleaning from solid mechanical particles and suspended solids is not provided. The purpose of the work was to improve the process of post-treatment of urban wastewater and protect the membrane element of the installation from clogging with coarse impurities and wear, with an overestimated concentration of suspended solids. The essence of the improved membrane technology of wastewater treatment consists in the preliminary capture of heavy and suspended particles with a size of more than 0.03 microns in a hydrocyclone, followed by water treatment in a chamber of a membrane bioreactor of modern design. The operating conditions of the membranes were determined by the operating modes and parameters of the bioreactor, in particular, by the degree of formation of colloidal compounds in it, which adversely affect the permeability. The density of the initial water varied within 1.059–1.078 g/cm3, and the content of solid particles was up to 0.3 mm. The activated sludge was filtered under vacuum on a Buchner funnel through a thin layer of cotton wool and gauze. During the tests, the indicators for capturing suspended solids were 5.0–9.0 mg/dm3, whereas, when working without a hydrocyclone, they were equal to 27–30 mg/dm3. The maximum performance of the hydrocyclone is provided at an inlet pressure of 225–300 kPa, and the pressure loss in the hydrocyclone chamber is 7.9–9.0 kPa. It was established that additional preparation of waste water for the post-treatment process using a hydrocyclone increases the cleaning capacity of membrane elements by reducing the load of accumulation of coarse impurities on the membrane surface