Simultaneous removal of harmful algal blooms and microcystins using microorganism- and chitosan-modified local soil

Abstract

Cyanobacterial harmful algal blooms (cyano-HAB) and microcystins (MCs) can cause potential threat to public health. Here, a method for simultaneous removal of cyano-HAB and MCs was developed using chitosan modified local soil (MLS) flocculation plus microorganism modified soil capping. The experiment was conducted in simulated columns containing algal water collected from Lake Taihu (China). More than 90% algal cells and intracellular MCs were flocculated and removed from water using chitosan-MLS and the sunk flocs were treated by different capping materials including Pseudomonas sp. An18 modified local soil. During 40 days’ incubation, dissolved MC-LR and MC-RR showed 10-fold increase in the flocculation only system. The increase of MC-LR and MC-RR in water was reduced by 30% and 70% in soil capping treatments, however, the total content of MCs in the sediment-water column remained similar with that in the control and flocculation only systems. In contrast, both dissolved MCs and total MCs were reduced by 90% in Pseudomonas sp. An18 modified soil capping treatment. The high performance of toxin decomposition was due to the combined effects of flocculation and MCs-degrading bacteria that embedded in the capping material, which prevents dilution of bacteria biomass, concentrates the algal cells, confines the released toxins, and enhances toxin biodegradation