BANK FILTRATION AS A WATER TREATMENT ALTERNATIVE FOR THE REMOVAL OF CYANOBACTERIA AND CYANOTOXINS

Removal of cyanobacteria from water requires the water treatment systems to prevent the breakage of the cells, so as to avoid the possible increase of cyanotoxin concentration. The effective removal of cyanobacteria and cyanotoxins normally requires systems with several stages. Bank filtration (BF) is presented as an effective alternative to eliminate or reduce those pollutants. BF involves pumping water from wells or infiltration galleries located on the banks of the superficial water bodies. It can operate as a sole treatment or as a rather effective pre-treatment. Some of the parameters that determine the removal of algae and cyanobacteria include the shape and size of the cells, the type of material from the aquifer and the bottom of the water source, and the distance/travel time of the water to the wells. Removal of cyanotoxins can occur by adsorption and biodegradation mechanisms; both of them depend on the type of water body bottom and aquifer materials, and on the physicochemical characteristics of the cyanotoxins. In general, for the successful implementation of BF, a hydraulic connection between the bed of the water source and the local groundwater must exist. It is also necessary to study local conditions such as temperature, type and amount of organic matter in the water, redox conditions and changes in the level of rivers and lakes in extreme conditions (dry and rainy seasons).