sludge mixture, sludge index, vacuuming of sludge mixture, vacuum value, vacuuming duration, efficiency of the vacuuming process
Abstract
The ability of activated sludge to settle and compact is characterized by the sludge index – the ratio of the volume of activated sludge in cubic centimeters after settling for 30 minutes in cylinders with a volume of 1 liter to 1 g of dry matter of activated sludge. The main factor that determines the value of the sludge index is the load on the sludge. In addition to the load, thesludge index is affected by the sufficiency of dissolved oxygen in the sludge mixture, the presence of toxic elements in wastewater, and easily oxidizable organic substances (sugar, glucose, alcohol). It has been established that when wastewater is treated in deep shaft aeration tanks and in oxytanks, the value of the sludge index is significantly reduced. In turn, the sludge index determines the dose of sludge in the aeration tank, the activated sludge recirculation coefficient, and the efficiency of secondary settling tanks. In recent years, a method of reducing the value of the sludge index by vacuuming the sludge mixture before secondary settling tanks has attracted great interest. It is obvious that as a result of the removal of gases during the vacuuming of the sludge mixture, the structure of the activated sludge flakes changes, which leads to an improvement in its settleability. The aim of the work is to experimentally verify the effectiveness of the method of vacuum degassing of the sludge mixture of urban sewage treatment plants. The research was carried out on an experimental installation, which is a chamber made of organic glass, in the upper part there is a fitting for supplying the sludge mixture and connecting it to a vacuum pump, at the bottom there is a valve for releasing the vacuumed sludge mixture into a cylinder. After the vacuuming was completed, the outlet valve was opened and the sludge mixture was slowly drained into a glass measuring cylinder with a volume of 1 l, after which the volume of the sludge was determined at different time intervals. At the first stage, the research was carried out at different vacuum values – 0,02, 0,04, 0,06 and 0,07 MPa. The working vacuum value was taken to be 0.04 MPa. At the second stage, the optimal duration of vacuuming was established – 3 minutes. Simple calculations showed that the dose of activated sludge in the aeration tank can increase by 1,39 times, which indicates the prospects and feasibility of using the process of vacuuming the sludge mixture in sewage treatment plants.
Author Biographies
V. A. Kovalchuk, National University of Water and Environmental Engineering, Rivne
Doctor of Engineering, Professor
S. V. Kohut, National University of Water and Environmental Engineering, Rivne
