Countries in the Middle East face the constant challenge of providing sufficient water for their growing populations, both for drinking and agricultural irrigation.
The original 20 sand filter basins were converted to DynaSand filters (Image source: Sulzer Management AG)
In Bahrain, the country’s largest water treatment facility underwent a major redevelopment, with Sulzer brand Nordic Water refurbishing the original sand filtration tanks with Dynasand filters. This and a recent expansion of the filtration system means the factory can now handle 250,000 m3/day of irrigation, the equivalent of 100 Olympic swimming pools each day.
Wastewater treatment plants must meet strict quality standards for all water returned to the environment. This is to protect local flora and fauna and local people. However, as daily throughput increases, so does the strain on facilities. This means you often need to upgrade and expand your equipment without increasing your site footprint.
Reuse of filtration pond
In Bahrain, high demand for agricultural water has led to a major renovation of one of the country’s largest treatment facilities. The original sand filter was designed to remove suspended solids, biological matter, microplastics, and phosphorus and needed to be replaced. This first project was contracted to Nordic Water with an innovative solution that significantly increases efficiency and throughput.
Because of the need to maintain the existing footprint of the filters, the project removed the internals of the original equipment and installed 160 DynaSand filters in the original 20 concrete basins. Compared to traditional systems, new sand filters have several advantages, particularly the ability to operate continuously without backwashing.
DynaSand filters direct raw water to the bottom of the filter where solids are removed as the water flows up through the media bed. A small amount of the filtrate is used for washing and transferring waste solids. At the same time, an airlift pump draws media from the bottom of the filter into the wash box and into the sand washer, where debris is separated and ejected.
Extend your success
With such success, Nordic Water has re-engaged in an expansion project scheduled for completion in the first quarter of 2024. Essentially, the amount of water being treated each day has doubled since the last project, and the filtration equipment needed to do so has doubled. Handle this increase within the smallest possible footprint.
Considering these requirements, a purpose-built concrete basin was the perfect solution. By offering a large filter surface area within a small profile, the additional 160 filters now allow the treatment plant to recycle 250,000 m3 of wastewater each day. This simple but highly effective solution was provided as part of a planned expansion of the original site.
In addition to sand filtration, the problem of helminth eggs, which poses a significant risk to local residents, also had to be addressed. The World Health Organization (WHO) emphasizes the presence of helminth eggs in wastewater and considers these pathogens to be the greatest microbiological health risk associated with wastewater reuse. Nordic Water’s solutions exceed the recommended standard of less than 1 helminth egg/litre.
high quality solution
This 1989 WHO report recommended storing wastewater in stabilization ponds for 8 to 10 days. This obviously creates a bottleneck in the process and requires large amounts of land, both of which needed to be avoided in this project.
Nordic Water addressed this challenge by adding nine DynaDisc filters to be used as pre-filters in the new DynaSand equipment. This removes helminths such as hookworm larvae and roundworm eggs, which pose a particular risk to farm workers who come into contact with wastewater used for irrigation purposes.
The treatment plant now recycles the equivalent of 100 Olympic-sized swimming pools of water, which was previously released into the ocean every day, at a level high enough to be used for irrigation. The new filtration process has significantly lower operating costs than traditional systems. As a result of this major project, the surrounding land has been transformed over the past 13 years, and this will continue with the latest facility expansion.