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Datong Lake Sewage Treatment Plant is located in Datong Lake, Yiyang City, Hunan Province. It is a sewage treatment plant which mainly treats municipal domestic sewage. In order to further improve the local environmental quality and consolidate the achievements of ecological civilization construction, in combination with relevant requirements, Beijing Huiheng Environmental Protection Engineering Co., LTD. (hereinafter referred to as "Huiheng Environmental Protection"), a subsidiary of Willy Environmental Protection Group, undertook the quality improvement and expansion renovation project of Datong Lake sewage Treatment Plant.

Project background

The original design process of Datong Lake sewage treatment plant is shown in the figure below. The original design treatment scale is 5000m3/d, and the effluent is subject to Class B discharge standard. The original design process has many problems, such as overload operation of the grid, lack of sand settling pretreatment, insufficient capacity of the biochemical system, inability of the existing pool to meet the expansion demand, and inability of the effluent to meet the first-class A standard.

After the quality improvement and upgrading by Huiheng Environmental Protection, the effluent standard was upgraded from the original Grade B standard in the "Urban Sewage Plant Pollutant Discharge Standard" (GB18918-2002) to the grade A standard, and the daily treated water volume was expanded from the original 5000m3/d to 10000m3/d.

  Solution

In response to the above transformation problems, Huiheng environmental design team has fully considered the actual operation of the water plant, advanced and reliable technology, reasonable economic cost, and full use of existing facilities and other factors. By installing mechanical gratings, adding cyclone sand settler, adding EBIS (improved A2O) tank, adopting "flocculation tank + advection sedimentation tank + artificial fast infiltration tank" for in-depth treatment, adding ultraviolet disinfection facilities and other solutions, greatly improving the nitrogen and phosphorus removal performance of the system, and achieving the needs of system expansion, and the effluent water quality has reached the first-class A standard.

Grade A and Grade B effluent quality comparison table

Transformation process description：

Transformation plan process flow chart

Municipal sewage first through the thickness of the grate to remove the large particle size of the float and solid particles, and then under the action of lifting pump, lift the cyclone sand sink for sand removal.

After sand removal treatment, the sewage enters the anoxic tank for denitrification and nitrogen removal, removing part of organic matter, and decomposes large molecular pollutants into small molecular pollutants.

The effluent from the anoxic pool enters the EBIS pool, where effective phosphorus release is carried out in the anaerobic section of the pool, and then excessive phosphorus enrichment is carried out in the low oxygen section (EBIS- aeration pool), and simultaneous nitrification and denitrification reaction is carried out to fully degrade organic matter. The mixed liquid in this section is returned to the anoxic pool to further strengthen the nitrogen removal effect.

Sewage is separated from solid and liquid in the clarifying section of EBIS tank, and then enters the flocculating tank for flocculation by adding flocculant, and settles in the sedimentation tank. The settled sludge enters the sludge thickening tank, and the final sludge is dehydrated and transported for external treatment.

The effluent from the sedimentation tank enters the artificial fast infiltration tank to further remove the residual organic matter and total nitrogen in the sewage. Finally, after ultraviolet disinfection treatment, the effluent is discharged up to the standard.

Project experience

The core biochemical process of this transformation scheme is EBIS (Improved A2O) process, which is the advanced sewage treatment technology in China at present. Datong Lake Sewage Treatment Plant quality expansion and renovation project is a successful example of Huiheng Environmental Protection to provide customers with EBIS sewage treatment solutions.

EBIS process is an efficient integrated activated sludge biological treatment system based on simultaneous nitrification, denitrification and nitrogen removal theory. On the basis of ensuring the treatment effect, the system realizes the highlights of high efficiency, energy saving and consumption reduction, land saving and easy operation and maintenance of biological treatment in a real sense, which is a huge innovation in the control and operation mode of the existing biological sewage treatment system.

Dissolved oxygen control is a highlight of the EBIS system of this project. In order to achieve effective control of dissolved oxygen, the EBIS system of this project applies a number of proprietary and patented technologies, such as new air lifting push system, high efficiency aeration system and intelligent control system, to stably control dissolved oxygen in the aeration tank and achieve the system environment required by the process, accumulating valuable experience in the design and practice of low dissolved oxygen control system for sewage treatment.

Project significance

The quality improvement and expansion renovation project of Datong Lake sewage Treatment Plant was completed in October 2019. Due to the impact of epidemic factors since the Spring Festival, relevant approval work has been delayed. On March 28, 2020, the project successfully passed the operation acceptance. At present, the arrangement, archiving and filing of all project materials, as well as project audit and completion settlement and other work have been completed, and the project has been smoothly handed over, and has been unanimously recognized by the owner and relevant departments.

At present, Datong Lake sewage treatment plant has entered normal operation, receiving municipal sewage from 4 towns and 1 office of Datong Lake District, Yiyang City, the daily treatment capacity reaches the designed 10000t/d, and the effluent quality meets the "Urban sewage Plant Pollutant Discharge Standard" (GB18918-2002) in the Grade A standard.

Datong Lake Sewage Treatment Plant quality expansion and renovation project is an important infrastructure to maintain and promote local economic development, and is of great significance to the improvement of local ecological environment and living environment quality. At the same time, the successful completion of the project has also laid the foundation for the extensive application and promotion of Huiheng Environmental Protection EBIS process, which will greatly enhance the company's market share in the field of municipal sewage treatment.