DHV BEEC's Largest Carrousel® Oxidation Ditch Project (the first phase) Officially Start
Author: BEEC Update: 2023-06-21
In May 2023, as the multiple paper machine production lines successfully launched at Liansheng Pulp&Paper (Zhangzhou) Co., Ltd.'s annual output of 3.9 million tons of forest pulp & paper integration project in Chihu Industrial Park, Zhangpu County, Fujian Province, another large-scale Carrousel® system is also put into operation and enter the commissioning stage, where the core biochemical treatment process design and main equipment are provided by DHV BEEC.
The main products of the Liansheng Pulp&Paper project include white cardboard, high-grade cultural paper, household paper, chemical pulp, chemical-mechanical pulp, etc. It is planned to build an annual capacity of 1.2 million tons/year chemical pulp (for self-use), 1.06 million tons/year chemical mechanical pulp (for self-use), 2 million tons/year of high-grade coated white cardboard, 400,000 tons/year of high-grade cultural paper, and 300,000 tons/year of household base paper. The project covers a total area of 4,600 Chinese mu (or 306.7 hectares), with a total investment of about 20 billion yuan. The wastewater to be treated in this project is mainly bleaching wastewater, papermaking wastewater and other sporadic wastewater produced in various production sections such as chemical-mechanical pulp workshop, chemical pulp workshop, alkali recovery workshop, and papermaking. As one of the largest Carrousel® WWTP in the national pulp and paper industry, the system has an average treatment capacity of 146,000 m3/d in the near term and 194,000 m3/d in the long term. Currently, the Carousel® system mainly receives pulping & papermaking wastewater from chemical pulp, white cardboard, cultural paper, and household paper, as well as other miscellaneous streams such as power plant wastewater and domestic wastewater. After further tertiary treatment and reaching the standard, the wastewater is discharged into the sea.
The core of the biochemical treatment section and even the entire sewage treatment plant is the Carrousel® oxidation ditch system, whose operating status largely determines the final effluent quality of the treatment plant. DHV BEEC company has made a special process design for the volume and layout of the oxidation ditch system of this project. A total of 8 Carrousel® oxidation ditches have been built. For the aeration equipment, the latest generation of OXYRATOR®-Star surface aerators are used. In addition to remain the simple, efficient, powerful, reliable operation, and minimal maintenance workload of the OXYRATOR® series equipment, OXYRATOR®-Star also has higher oxygenation power efficiency, mixing and propelling capabilities.
Currently, the Carousel® system start up smoothly and all equipment are running normally.
After the completion of the first and second phases of the project, the influent water quality of the oxidation ditch in the integrated water treatment system project is as follows:
|
parameter |
units |
short-term influent |
long-term influent |
|
BOD5 |
mg/l |
≤ 450 |
≤ 350 |
|
SCOD |
mg/l |
≤ 1350 |
≤ 1050 |
|
SS |
mg/l |
≤ 350 |
≤ 300 |
|
pH |
- |
6 - 9 |
6 - 9 |
The main water quality requirements for the secondary sedimentation tank(SST) and final effluent of WWTP are as follows:
|
units |
designed SST effluent |
designed final effluent *[BL1] |
|
|
BOD5 |
mg/l |
≤ 20 |
≤ 20 |
|
SCOD |
mg/l |
≤ 250 |
≤ 90 |
|
SS |
mg/l |
≤ 80 |
≤ 30 |
|
pH |
- |
6 - 9 |
6 - 9 |
*The discharge standard shall comply with the local standard " Discharge Standard of Water Pollutants for Pulp & Paper Industry" in Fujian Province (DB35/1310-2013, Table 1, Standards for Other Pulp & Paper Enterprises).