Removal of algae in a submerse biofilter system

ABSTRACT

This research proposed the development of a submerged biofilters system, modified based on the configuration of rock filters, aiming at the effluent post-treatment of stabilization lagoons, initially for algae removal. Two sets of submerged biofilters were implemented to collect treated sewage from two different depths of a maturation lagoon - at 60 cm (in a zone of this lagoon called superficial-SZ) and at 180 cm (in a zone of this lagoon called intermediary-IZ). It was used, as filling of submerged biofilters, gravel No. 3, at filtering layers heights of: 50, 100, 150 and 200 cm, aiming to evaluate the influence of this factor over algae removal efficiency toward chlorophyll a, and other 16 quality variables associated in this study. For SZ, efficiencies were obtained for COD in the range of 65 to 80%, and for IZ the efficiency results had a lot of variation, without stability, in a practical way, so the collection point in ZI was not recommended. For SZ efficiencies were obtained for chlorophyll a in the range of 65 to 99%, and for IZ the efficiency results were lower than those of SZ. It was concluded that the collecting from superficial zone of the maturation lagoon, and a layer depth between 150 and 200 cm, were the operational parameters that led to a better overall performance of the modified submerged biofilters, and more particularly to: COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand), chlorophyll a, and total solids.

Keywords:
biofilter; lagoon post treatment; algae removal