The project covers construction of the sewage treatment plant in the municipality of Arafo on the island of Tenerife, including civil works, installation of equipment and facilities, commissioning and 6 months of operational tests.
According to Cadagua, treatment capacity upon completion of Stage I will be 7,000 m³/day, and this capacity will increase to 10,500 m3/day when Stage II is completed (though this is not part of the present contract). Cadagua further specified that the process to be used in the plant for treatment of activated sludge is an integrated ultrafiltration membrane bioreactor system. Essentially, the ultrafiltration system does away with the need to separate solids through the secondary clarifier and sand filters used in conventional activated sludge systems.
The ultrafiltration membrane bioreactor (MBR) technology effectively overcomes settlement issues associated with conventional activated sludge technology. This process is typically used for concentrations of mixed liquor suspended solids (MLSS) of between 8,000 mg/l and 10,000 mg/l. High concentrations of biomass allow for greater efficiency in the elimination of particulate soluble biodegradable matter from wastewater. The MBR process combines the operations of aeration, secondary clarification and filtration into a single process, resulting in high quality effluent which can be reused in irrigation for agriculture and in the watering of gardens, golf courses, etc., thereby simplifying operation and considerably reducing space requirements.