Desalination solution for freight harbour
A substantial increase in iron ore imports for the rapidly expanding Chinese steel industry was putting pressure on water resources at Dalian freight harbour. Project manager, Bernhard Baumgärtner, and UK sales manager, Andrew Armytage, of German manufacturer ProMinent report on a reverse osmosis (RO) desalination system that provides potable water and has reduced dependence on the public supply.
In excess of 1000m3 water is required each day for workers' drinking and washing, and to ensure that the iron ore can be unloaded dust-free. With seawater readily available, the use of a desalination system prevented placing heavy demands on the local public drinking water network and the associated costs of such a complex undertaking.
This project was handled in its entirety by a special project team from ProMinent Fluid Controls Dalian. The primary treatment process is RO. The water passes through sand and activated carbon filters with fully automatic backwashing and chemical pre-treatment prior to RO treatment.
The RO unit removes 99% of dissolved salts and organic compounds. The electrical energy used for the RO is recovered to reduce the overall energy consumption of the system to a low level of 2.97kW/h.
Some of the water, which is used for drinking, is further treated with a second RO. The bypass adjustment allows the salt level to be set to achieve good tasting drinking water. Ozone is used as a further treatment step, before bottling, to prevent any biofilm growing in the pipework on the permeate side.
This also optimises the hygienic conditions for the filling process. After a few minutes, disinfection is complete, and the ozone decomposes to oxygen, leaving 100% germ-free drinking water with an excellent taste. The water is bottled into 19L containers for use in numerous hot/cold water stations throughout the harbour.
To ensure optimum performance of the system at each stage of the process, sensors are used to monitor the water quality. About 11 controllers monitor parameters such as turbidity, pH, ORP and conductivity. A process visualisation system was designed which integrates all sensor data as well as the automatic backwashing of the filters and the overall function of the water treatment system.
The quality of the final water exceeds World Health Organisation standards for drinking water. The plant was commissioned in September 2004 and is manned by seven technicians from ProMinent, who keep it running 24 hours a day.
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