Rapid Gravity Filter Installed at New Desalination Facility in Fouka, Algeria

Severn Trent Services-Apliclor, in partnership with ACCIONA AGUA, has designed, constructed and installed the TETRA® LP Block dual parallel underdrain filters for pre-treatment of the Fouka SWRO desalination plant in Tipaza, Algeria. The plant will have a daily capacity of 120,000 m3/day (3.7mgd) and will provide water to more than 500,000 people. With the completion of construction expected during 2010, the Fouka SWRO plant is part of the Algerian government’s desalination program, which includes the construction of 12 desalination plants producing a total of 2.2 million m3/day.

The Fouka SWRO plant was built in partnership between ACCIONA AGUA and SCN-Lavalin, Canada. SCN-Lavalin also signed a joint venture agreement with ACCIONA AGUA to operate and maintain the plant for 25 years.

The underdrain filter is one of the most important factors contributing to a desalination pre-treatment system’s overall performance and operation. The TETRA LP Block dual parallel underdrain filters from Severn Trent Services are a proven design of underdrain filter offering superior distribution of both backwash air and water, either separately or concurrently.

In the Fouka SWRO plant installation, the LP Blocks cover the floor of the gravity filters supporting the filter media. The LP Blocks feature the unique Grout Grip design, which increases the adhesion of the filter base and eliminates buoyancy issues commonly found in competitive technologies. Air is distributed evenly across the entire filter bottom area to scour the media and to provide an air lift, which, with the water, removes the released solids from the filter. Effective media cleaning is the key requirement for a filter to function efficiently under all loading conditions. The backwash system ensures efficient cleaning for reduced operating costs.

An additional advantage of the LP Block is the block length and construction, which makes handling easy and ensures reduced installation cost. The block is durable and offers a low maintenance solution with no clogging nozzles and no moving parts to wear. The wide profile design of the TETRA LP block means that fewer blocks are required to cover the filter floor. Therefore, fewer joints and less grout are required than with other systems.

According to the general manager of Severn Trent Services-Apliclor, Rick Bacon, “the innovative TETRA LP Block is more compact than other solutions, ensuring lower civil costs for construction of the works. In addition, the solution supplied by Severn Trent Services–Apliclor allows greater power saving through process optimization of the plant. All these advantages ensure that TETRA LP Block underdrain filters require minimal maintenance and low operating costs.”