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

Control valves in controlled pneumatic aeration processes

Summary

Through the 2013–2019 program of the Ministry of Energy and Public Utilities of the Samara Area «Samarskie Kommunal’nye Sistemy» Company has developed and has been successfully implementing the project of upgrading the municipal wastewater treatment facilities. In order to improve the energy efficiency retrofitting the systems of aeration and air distribution, equipping with compressors with controlled air supply to the aeration tanks within 45–100% range is envisaged. The general concept of control has been substantiated that includes complex level of process control and a two-loop automation scheme «aeration tank gate valve control – air blower group». The method of selecting control valves for the air supply control system for pneumatic wastewater aeration has been developed and substantiated. The method is based on the dependence of compressed media flow through the control valve stated in IEC 60534-2-1 International Standard. Under full-scale conditions with the use of precision equipment the flow characteristics of IRIS (DN300) control valve manufactured by Egger were studied. The average percentage error of the method was 6.79%. The method error does not matter much for the automated control since PID-control provides for supplying the required air amount according to the condition of compliance to О₂, NH₄ set values and current measurements of the supplied air amount. The classification of control valves is presented based on the type of the dependence of K_v/K_vs valve capacity coefficients from the rate of valve opening. Technological modes were identified: comparison of the theoretical and experimental flow characteristics of the control valve, pressure difference at the control valve, pressure difference in the «control valve – aerators» system, aerial environment temperature before the valve. The suggested method of the control valve calculation is a part of the «Energy efficiency of the controlled air supply to the aeration tanks» comprehensive mathematical model.

Key words

energy efficiency , automated control system , membrane aerator , wastewater treatment facilities , pneumatic aeration system , control valves , flow coefficient , diaphragm gate valve

Energy-efficient principle of upgrading the air blower house at the Samara municipal wastewater treatment facilities

Summary

As a key and economically advantageous measure on energy efficiency and investment return in the field of wastewater disposal «Samarskie Kommunal’nye Sistemy» Company approves the processes of air supply regulation at the municipal wastewater treatment facilities. A big complex of the air blower house has been designed and successfully implemented by improving the typical design projects for the RF conditions developed by SoiuzvodokanalNIIproject Institute for the estimated supply of 132 144 Nm³/h. The specific features of building and assembly works when installing 15 ton units under the conditions of the limited capacity of the hoisting equipment (9 tons) are set. The mechanical rotary blade principle of fan regulation was adopted as a basis of the energy saving solution. At the first implementation stage under the conditions of the lack of an operating automated process control system 26.1% reduction of the specific power consumption was recorded at the average specific power consumption of 22.39 kW/1000 Nm³. The engineering design reflects possible 45–100% regulation of air supply to the aeration tanks as well as its relation to the consumed power of 1273.2–2674.2 kW (for 20 °C input temperature, 50% relative humidity). Two-loop scheme of the automated control system for «aeration tank gate valve control unit – blower unit group» is presented. The analysis of the fan testing at the manufacturer’s factory is given. The parameters of regulating centrifugal air blowers by two control actions: of regulated diffuser at the outlet and inlet guide vane unit are presented. The mathematical method of recalculating the characteristics of air blowers with the use of the «degree of control» basic concept was developed and experimentally verified. The use of the method proves the wide range of the running characteristics of regulated units for all the year seasons, the mode of combined operation of one non-regulated and three regulated air blower units for the experimental work period.

Key words

reconstruction , energy efficiency , simulation modeling , air-blowing house , wastewater treatment facilities , rotary blade regulation