Integrated upgrade of the Samara municipal wastewater treatment facilities

Summary

The experience of «Samarskie Kommunal’nye Sistemy» LLC in designing, constructing and upgrading the municipal wastewater treatment facilities with a capacity of 450–750 thousand m³/day is presented. Considering the adverse ecological state of the midstream and downstream of the Volga River the task of improving the efficiency of wastewater treatment is of top priority that has been approved by the Program adopted by the Department of Energy and Public Utilities of the Samara Area for 2013–2019. The results of retrofitting wastewater biological treatment technology on the basis of UCT Process with unique zone and recycling layout barrangement by modifying the existing capacities of four-corridor aeration tanks are presented. The justified technical solutions of the key facilities that determine the energy and structural efficiency of the project of upgrading the air blower house with the use of mechanically regulated air blowers (the capacity range of each 59.4–132.1 thousand Nm³/h) and constructing two sludge pumping stations with 15000–27360 m³/h regulated wastewater flow are set. The process automated control system has been introduced. The tied to time design works required fast and efficiency calculation methods with the use of process simulation modeling in GPS-X environment (ASM2d model), computerized fluid dynamics – in ANSYS Fluent environment. The prediction of the dynamics of the treatment efficiency changing within 24 hours while ensuring average daily concentrations in mg/l – suspended solids – 15.5; BOD5 – 5.7; COD – 34.9;
N–NH₄ – 0.25; N–NO₂, N–NO₃ – 7.02; P–PO₄ – 0.68 is given. Relatively high washout of suspended solids is caused by the significant design value of sludge index 150 сm3/g. In the implementation phase of the environmentally efficient measures the construction of tertiary treatment facilities valued at 400 million rubles (about 30% of the total cost of the upgrade of the entire facilities) was rendered economically unviable. Before commissioning the actual energy saving of 13 mln kW·h/year including 8.8 mln kW·h/year owing to the replaced air blowers, 4.2 mln kW·h/year owing to the sludge pumping stations with submerged pumps that replaced airlift was achieved. The performance targets of the projects and the technical solutions applied measure up to the best available technologies.

Key words

reconstruction , energy efficiency , best available techniques , aeration tank , simulation modeling , wastewater treatment facilities , UCT process , GPS-X

Distribution of oxygen consumption in an aeration tank:
comparison of engineering approaches and computerized simulation

Summary

A review of engineering and numerical approaches to describing the distribution of oxygen consumption in the aerobic zone of an aeration tank, a key element of biological wastewater treatment systems is presented. The schemes indicated in the engineering literature (EPA Design Manual, S. Jeyanagam, R. Venner, J. Tchobanoglos, D. Rosso, D. A. Danilovich, and A. N. Epov) are considered. The listed approaches are compared with the results of the computerized simulation performed in the GPS-X software environment using the ASM3 model and the series-connected reactor model. The simulation was carried out for different temperature conditions reflecting seasonal variation. It is shown that the oxygen distribution schemes adopted in engineering practice do not take into account the effect of temperature, flow velocity and longitudinal dispersion, what can lead to significant deviations in the design of aeration tanks. A unified approach to comparing oxygen distribution processes is proposed. Practical recommendations for the use of computerized simulation to specify design solutions are presented.

Key words

biological treatment , aeration tank , GPS-X , series-connected reactor model , ASM3 , temperature conditions , oxygen consumption