By J.R. Hitchmough, P.Eng., Lockerbie Stanley Inc.
Lockerbie Stanley has signed a contract to supply engineering services and all major mechanical, electrical, instrumentation and control system equipment, as well as installation for the first primary effluent treatment facility in China's most populous province of Jiangsu. The plant is located in the coastal city of Lianyungang, which has a population of 600,000 people. This is Lockerbie Stanley's ninth project in China over a period of five years.
Because of the fact that the province has committed itself to improve the environment for its people and that this facility is the first one to be installed in the province, the project has generated great interest. The plant will be built on the site of an existing fish farm that will be relocated in order to install the treatment plant. Typical ground elevations at the site are in the range of 2.7 to 3.5 m and the climate is considered subtropical.
Lockerbie Stanley has made numerous visits to China to pursue the project. After being selected from a short list of three, the contract was awarded in December 1999. A delegation from China recently came to Canada to verify the companies' capabilities and to visit several North American operating and manufacturing facilities. The delegation included technical personnel from the design institute and city as well as senior city and provincial government officials.
The first phase of the project will be a primary treatment facility designed to treat 100,000 m3/d of municipal effluent. The second phase of the project will add a secondary treatment facility, of equal capacity, after primary treatment. A future addition of a third phase is planned that will be a parallel, near identical primary and secondary facility, also with a design capacity of 100,000m3/d.
The North China Municipal Engineering Design and Research Institute with whom Lockerbie Stanley is working will design the sanitary sewer collection system. Lockerbie Stanley is supplying pumps and screens for five of the pump stations moving the sewage to the treatment plant.
At the treatment plant, the effluent from the various sources will come together in a single inlet pipe and pass through three climber type coarse screens of 325,000m3/d total hydraulic capacity. Debris will be removed mechanically from the face of the screens and discharged onto a common belt conveyor, which will convey the debris away for further processing. The screened water will pass into the sump of a lift pump station where four submersible pumps, three operating and one standby, will transfer the effluent up to an aerated grit chamber. The sump will also contain four, submersible type, by-pass pumps, of 200,000m3/d combined capacity, which will divert flows greater than the design treatment capacity of the plant to the river. The intake pump station and coarse screen structures will be designed for a hydraulic capacity of 325,000 m3/d.
The aerated grit chamber will remove grit and any oil and grease present from the effluent. Two identical rectangular chambers, each designed to handle 65,000 m3/d of effluent, will operate in parallel. Each chamber will be aerated. Floating solids will be removed from each chamber by a travelling skimmer and discharged from each chamber to a common scum collector screw conveyor. The scouring action generated by the aeration system will produce low detritus content grit. Settleable solids will be directed by the sloped side walls of the chambers to the bottom of each chamber from where they will be removed through the suction line of a grit pump. The grit pump will be mounted on a single travelling bridge spanning both chambers. Each chamber will have its own grit removal pump.
The grit pumps will transfer the grit to a single sand water separator. The grit will settle to the bottom and be dewatered on an inclined screw as it is removed from the separator by the inclined screw and discharged to a grit box for eventual disposal off-site.
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