Impact of natural and climatic factors on the efficiency
of open wastewater treatment facilities operation

Summary

The problem associated with the impact of natural and climatic factors on the efficiency of wastewater treatment in open treatment facilities is considered. The analysis of methods for calculating the basic units for mechanical treatment (primary settling tanks) and biological treatment (aeration tanks and secondary settling tanks) of municipal wastewater is presented. It is indicated that at the design stage of the complexes it is important to calculate correctly the temperature of the incoming wastewater. The long-term practice of operating municipal wastewater treatment facilities has shown that with a long retention time in open facilities waste liquid can be cooled during the cold period of the year and heat up to about 1.5–6 °C during the warm one. In the first case this negatively affects the processes of sedimentation of suspended solids in settling tanks and oxidation of organic substances in aeration tanks; whereas in the second case this negatively affects the saturation of mixed liquor in aeration tanks with oxygen resulting in a reduced treatment level. The purpose of the work was to develop recommendations that allow at the design stage of wastewater treatment facilities to correctly calculate the temperature of waste liquid in open structures for a certain project that has specific climatic conditions. To achieve this goal the data of laboratory and in-process control of the operating wastewater treatment complexes were analyzed. A theoretical analysis of the currently used methods for designing wastewater treatment facilities has been made; research has been carried out at the operating facilities. Mathematical models widely used in heat engineering have been studied to determine heat losses from the open surface and through enclosing structures as well as the heat input from solar energy and exothermic reactions.

Key words

aeration tank , sewerage treatment facilities , evaporation , primary and secondary settling tanks , wastewater temperature , cooling , evaporation , convection heat exchange

The main innovations introduced by Amendment No. 2 to the Code of Practice CP 32.13330.2018 «Sewerage. Pipelines and Wastewater Treatment Plants»

Summary

The main prerequisites for the development of Amendment No. 2 to CP 32.13330.2018, and the tasks facing this work are described. The main innovations introduced by Amendment No. 2 are considered. The principles of synchronization of the system of engineering regulation of wastewater treatment processes with environmental regulation of discharges; clarification of the provisions for determining the estimated wastewater inflows; additions to the subsection on drain stations are described. The main additions and clarifications in terms of wastewater and sludge treatment technologies are described and justified (Chapter 9 of the Code of Practice), namely: updated requirements for intrahour safety factors while calculating channels and flumes; supplemented requirements for reliability in the design of channels of bar screen buildings and the data for calculating the amount of screenings depending on bar spacing; specified conditions for the use of sewage regulators; requirements for the calculation of primary settling tanks, aeration tanks, secondary settling tanks; recommendations for the removal of phosphorus; requirements for the redundancy of sludge dewatering equipment in case of the lack of spare sludge beds; introduced formulas for calculating the pollution of primary effluent; recommendations for sludge acidification from primary settling tanks; requirements for the redundancy of submersible electromechanical equipment of aeration tanks and for the regulation of sludge discharge from secondary settling tanks; detailed recommendations on the use of filtration beds for receiving effluents; the limits of applying mandatory dechlorination while using chlorine and the allowability of using prefabricated units.

Key words

treatment facilities , sewerage , screens , phosphorus elimination , set of rules , dechlorination , primary and secondary settling tanks , pipelines and wastewater treatment plants , municipal (mixed) wastewater , estimated inflow , sewage regulators , drain stations , calculations , aeration tanks , equipment redundancy , sludge acidification , filtration beds , prefabricated units