Dewatering in Saudi Arabia –
10 Decanters for Upgrading two Waste Water Treatment Plants
Saudi Arabia is modernising its infrastructure. Specifically in the context of evidence of a shortage of drinking water, which is becoming apparent, the waste-water treatment processes in several cities of the country are now being modernised to bring them into line with state-of-the-art technology. The National Water Company, which acts on behalf of the Saudi Arabian Ministry for water and electricity, is now presenting plans for restructuring waste-water treatment in various cities.
Contents
For Jeddah, the main port of Saudi Arabia on the Red Sea, the National Water Company has modernised two existing waste-water treatment plants, and simultaneously increased their capacities. Jeddah, with its more than three million inhabitants, is considered to be the gateway to Mecca, which is situated approximately 70 km to the East in the centre of the country. Accordingly, many pilgrims pass through the city every year.
Complete process lines with complete engineering
For this project, the National Water Company has engaged GEA Westfalia Separator Group to equip the Al Bilad and Ruwais waste-water treatment plants with five decanters in each case for sludge dewatering. For GEA Westfalia Separator Group, this was the first environmental order worth a seven-digit figure in Saudi Arabia. It also comprises the polymer processing and feed system, the solids conveyance arrangement as well as the complete switching and control system. It also included an engineering package with the pipework and cable installation plan for the existing building. The challenge was to install the decanters in the small amount of space available in such a way that the machines were still readily accessible for maintenance and repair work, and also to ensure that the legal regulations regarding accident prevention were complied with. This is because the installations had to be extended and modernised during ongoing operation. The existing belt filter presses were only shut down after the decanters had been commissioned. Accordingly, GEA Westfalia Separator Group supplied an all-round package with which the customer was entirely satisfied.
The assured performance figures were attained reliably, and the engineering as well as the components were supplied on time. GEA Westfalia Separator Group used the decanter types UCD 346 for this project. The machines are installed in such a way that four of them operate in parallel in each installation, and one decanter is available as a reserve. The Al Bilad plant was the first to commence operation in March 2010, with five decanters, followed by the Ruwais plant in August / September 2010. As the design of the first plant was so successful, the customer used the identical planning for the second plant. Both plants have to handle purely aerobically stabilised clarified sludge which has to be dewatered. There are no sludge digestion tanks in the waste-water treatment plants, and there is accordingly no thickening system.
The National Water Company awarded GEA Westfalia Separator Group the contract to provide the Al Bilad and Ruwais waste-water treatment plants each with five decanters for sludge dewatering.
Frequency conversion necessary
The UCD 346 decanters are each equipped with two frequency converters with which the bowl speed can be adjusted to the process conditions, for instance, to enable energy savings to be achieved with a lower bowl speed with the same result in line with environmental considerations. However, in this case, the frequency converters also provided an entirely different benefit. In Saudi Arabia, the power grid operates at 60 Hz, whereas the machines are designed for 50 Hz. The frequency transformers are therefore used to convert the Saudi Arabian 60 Hz grid into a 50 Hz power supply for the decanters. This is a much less expensive solution than would be the case if the machines had been equipped with special motors. Nevertheless, it is also possible for the decanters to be optimised by a lower bowl speed or a lower frequency. This is because of following reason: If the product introduced into the decanters does not have to be accelerated so significantly, this results in huge energy savings.
Tropical conditions
A further contractual requirement was that the equipment had to be designed for the tropical conditions with up to 50 degrees Celsius ambient temperature on a permanent basis; this was possible without any problem as a result of the many years of experience of GEA Westfalia Separator Group.
All requirements met
In Jeddah, GEA Westfalia Separator Group has again demonstrated that it is able to supply a complete process line with complete engineering upon request, and to design a functional installation in extremely small spaces which complies with all requirements regarding accessibility, maintenance and repair work. Further waste-water treatment plant projects in Saudi Arabia are already in the planning stage. The National Water Company has currently been engaged to handle waste water processing for seven cities, and will further expand these arrangements.