The experience of improving and evaluating the efficiency of aeration systems

Summary

The experience of improving and evaluating the efficiency of aeration systems of the new line of the Liuberetskie wastewater treatment facilities of the Moscow wastewater system is described. In the operation of the treatment line with a design capacity of 500,000 m3/day biological removal of nitrogen and phosphorus used. Upon five years of operation Austrian-manufactured AQUASTRIP membrane type plate aerators were replaced with Russian-manufactured АR-420Т disk membrane systems. This provided for significant increasing wastewater flow to the new line. In the course of studies two methods of evaluation of the aeration system efficiency were compared: the classical approach of direct «gas cap» measurement and the calculation method. In order to implement the calculation method a technique of evaluating the actual aeration efficiency of aeration tanks was developed based on the fundamental principles of the mass balance of the treatment processes. This technique allows calculating the actual efficiency of oxygen utilization supplied to the aeration system from the actual operation data for any time interval and with regard to any aeration tank number. In the course of the experiment about 9% divergence of the results of the two methods was obtained which corresponded to the measurement errors accepted as a basis of the calculations. The measurements and calculations showed that the specific efficiency of oxygen dissolution was around 6% per 1 meter of the aerator immersion depth which complied with the information submitted by the manufacturer («Ecopolymer-M» CJSC), and by 30% higher than shown by AQUASTRIP aerators. The developed method can be used both in evaluating the aeration system efficiency for the certain wastewater treatment facilities and in making the intra-sectoral analysis (benchmarking). The calculated values of the atmospheric oxygen actual dissolution efficiency and power consumption per 1 kilogram of the actually dissolved oxygen are recommended for being used as the target indicators of the wastewater treatment facilities’ improvement instead of the generally accepted air consumption (power consumption) per 1 m3 of wastewater.

Key words

wastewater biological treatment , nutrients removal , diffused-air aeration , oxygen dissolution efficiency , calculation method