Features of wastewater composition at small-scale treatment facilities

Summary

The composition of wastewater at small-scale treatment facilities differs significantly from the composition of municipal wastewater both in terms of pollution concentrations and their proportions. Information is presented on the collection and analysis of data from long-term observations of the composition and temperature of wastewater from small settlements at 31 treatment facilities. It has been revealed that an increased concentration of nitrogen at medium concentrations of organic substances is typical for these facilities. Such a disproportion results in a shortage of substrate for biological treatment – denitrification; consequently, dosing an external source of organic matter is required. Wastewater supplied to the treatment facilities has a very low N–NH₄/N_total ratio, which indicates incomplete ammonification and the need to take into account total nitrogen during laboratory control. At some facilities, the temperature of incoming wastewater is below 10–12°C during most of the year, which significantly reduces the efficiency of biochemical treatment processes.

Key words

domestic wastewater , sewerage treatment facilities , temperature , wastewater composition , denitrifying potential

Reconstruction of the right-bank wastewater treatment facilities
of Irkutsk

Summary

Practically in all Russian cities the deterioration of the water and wastewater networks and facilities averages about 70%. Many of the facilities have been not only worn but also outmoded and do not meet the current technical and environmental requirements. The right-bank and left-bank wastewater treatment facilities of Irkutsk for many years have been overloaded: at the design capacity of 300 thousand m³/day the actual incoming wastewater flow has been 360 thousand m3/day. Lately, due to the significant reduction of the specific water consumption the incoming wastewater flow has reached 295 thousand m³/day. However the composition of the wastewater in relation to many parameters changed significantly; whereas the treatment efficiency lowered. As a result of the long time operation without heavy overhaul under the conditions of the corrosive wastewater a great number of reinforced concrete storage tanks, pipelines and equipment have been in poor state and need dismantling, repair, replacement and upgrade. In order to improve the efficiency of wastewater treatment the following basic process stages have been proposed: primary mechanical treatment; grit removal; biological treatment with nitrogen removal in the processes of nitrification-denitrification; chemical phosphorus removal by sedimentation method; enhanced treatment (organics and ammonia nitrogen removal) in a moving-bed bioreactor; suspended substances removal by enhanced tertiary treatment in sand filters; UV-disinfection. Upon complete reconstruction the required wastewater treatment level will meet the sanitary standards of the effluent quality to be discharged into water bodies.

Key words

reconstruction , sewerage treatment facilities , efficiency of treatment , wastewater composition

Advanced methods of designing biological treatment facilities

Summary

The data of the analytical reviews and practical results of calculating and designing advanced wastewater treatment facilities are presented. The analysis of the methods of designing biological wastewater treatment facilities (construction rules and regulations SNiP, ATV) and the software for mathematical simulation of the facilities operation («EcoSim», GPS-X etc.) is made together with the hydrodynamic continuum mechanics software as applied to calculating the flow conditions at the treatment facilities. The mathematical model of biological wastewater treatment process is based on the analysis of the relationships of enzyme kinetics of the wastewater pollutant transformation and makes a connection between the parameters of the raw waste and effluent, dissolved oxygen concentration and activated sludge. The principles of designing and calculating the facilities for biological treatment of municipal and industrial wastewater including the use of nitri-denitrification and biological phosphorus removal processes have been developed. The practical experience of using the mentioned methods in front end and design works.

Key words

biological treatment , nitri-denitrification , mathematic modelling , energy efficiency of equipment , wastewater composition , biological phosphorus removal