6 february 2017


Innovation in storm water treatment.

Saint Jacques side
Veolia Water Technologies is the first in Europe to integrate the BioActifloTM process into a wastewater treatment plant in order to offer it the capacity to treat excess flows ofstorm water as well as to provide additional biological treatment capacity in dry weather (when necessary).
Like many Mediterranean countries, Spain is increasingly affected by intense and sudden precipitation: in March 2016, Corunna (Northwest) suffered torrential rains that caused the rivers to overflow their beds. Beyond the most spectacular fallout (flooded cellars, torrents of water in streets), heavy rains of this sort can have very negative consequences for the environment. In fact, the flow of water entering a wastewater treatment plant during heavy rains can exceed its maximum capacity for treatment in wet weather. The plant is thus unable to achieve the levels of quality of discharge imposed by the legislation. Such pollution peaks can cause loss of purification efficiency and major damage to the receiving environment.
In this context, the European Union regularly draws the attention of the Member States to the need to better treat storm water and to preserve both the ecosystem and the well-being of the population. This is what the city of Saint Jacques de Compostelle will do by choosing the BioActiflo ™ technology developed by Veolia Water Technologies to modernize its wastewater treatment plant.
For more than thirty years, this city in the northwest of Spain has made wastewater treatment a priority. For this reason, the Estación Depuradora de Aguas Residuales (EDAR) of Silvouta was built 10km from the town center in 1982. By 2016, the EDAR had reached the limits of its capacity. The maximum flows that can be treated each day are often exceeded in dry weather and in the event of heavy rains the installations may overflow.
The Veolia Water Technologies BioActiflo process quickly established itself as the best solution because of its many advantages. Thanks to its high decantation speed (about 100 m / h), BioActiflo is very compact. This suited the community as there was no land available to expand and furthermore, the work could be carried out without disrupting plant operation.
Developed and widely used in North America, BioActiflo is specially designed to deal with problems of excess stormwater and to avoid hydraulic rinsing of biological treatment facilities. It also offers additional capacity for biological treatment in dry weather when needed.
The technology consists of a contact tank where organic matter is first adsorbed / absorbed by microorganisms present in the activated sludge of the plant.
In a second stage, the purified water passes through the high-performance Actiflo® settling tank where suspended matter is ballasted by microsand and thus separated from the water.
Designed for a treatment capacity of 20,065 m3 / day, BioActiflo will enable the Saint Jacques de Compostelle plant to generate better quality effluents (BOD less than 25 ppm and suspended solids less than 35 ppm).
Co-financed by the European Union, the Spanish Ministry of Agriculture and the Galicia region, the works will last eight months, followed by two months of tests.