The supply of clean drinking water is a technological and logistical challenge in the Canary Islands. Drinking water is either produced by means of complex and expensive reverse osmosis plants and delivered in pump lines to all regions, or transported onto the Islands from the mainland by huge tankers. Extensive secondary treatment steps (sandfiltration and disinfection) have been necessary to recycle the wastewater so that it can be reused as service water. These treatment facilities could not be established in all the necessary locations.
This is now possible, however, as membrane-activated sludge systems are now available which combine the well-known activated sludge process with separation of the clarified wastewater by means of submerged ultrafiltration membranes. Activated sludge plants, which are very common in the Canaries, can now be upgraded by adding membrane filtration. The resulting effluent can be used for irrigation or even as drinking water after additional treatment in a reverse osmosis plant. The space required for existing plants is likely to be reduced.
The VRM® 14/24 pilot plant was operated on Gran Canaria and Tenerife for almost a year, which demonstrated to the local authorities the efficiency of the HUBER product. The authority eventually decided in favour of innovation rather than the planned conventional refurbishment. The plants will now be equipped with an activated sludge plant (preceding denitrification and aerobic sludge stabilisation) and two subsequent stainless steel filtration chambers each with one VRM® 20/240 membrane unit. The total available membrane surface will be 1440 m2. The effluent of the new plant will be introduced into the local service water network on Lanzarote.
The plant is scheduled for delivery in late November for start-up early next year. The produced bacteria and germ-free clarified water will be introduced into the local service water network and used for irrigation.
Membrane filtration after wastewater ponds – A chance for arid and semi-arid countries
In arid and semi-arid countries wastewater treatment is often accomplished by means of simple aerated or unaerated wastewater ponds.
The clarification efficiency of such plants is frequently insufficient, resulting in heavy pollution of receiving water courses (e.g. the Nile in Egypt). Bathing or diving in such waters can endanger life. The wastewater scarcity in such countries means that the effluent from wastewater treatment plants is frequently used for irrigation of the land. Faecal bacteria and germs are returned into the food chain in this way via unwashed field crops which adversely affects the public health.
The Technical University of Berlin has started a research project for upgrading of wastewater pond systems through the addition of membrane filtration plants. The aim is to separate bacteria and germs from the partly clarified wastewater (nutrients such as nitrogen and phosphorus should remain in the water as they have a fertilising effect) and produce water that is suitable for irrigation.
HUBER is the industrial partner in this project supplying the complete mechanical technology for the membrane plant in Ankara/Turkey, comprising an Ro 9 Micro Strainer (3 mm perforated screen) for preliminary treatment, a VRM® 20/180 membrane plant with 540 m2 membrane surface including all aggregates and electrical controls necessary. The equipment will be installed on a disused pond plant. The German Federal Ministry of Education and Research have approved the project and allocated the aid money in July 2004 with the new plant scheduled to be supplied and commissioned at the end of the year.
A second installation in Germany was recently put into operation at WWTP Wildberg near Berlin, where a VRM® pilot plant is operating in conjunction with the customer's wastewater pond. The results obtained will be compared with those achieved from the pilot plant in Turkey.