Closed-loop Technology for Counteracting Cyanobacterial Contamination of Water Bodies Using Macrophytes

The results of a study of the process of suppressing cyanobacterial contamination of water bodies using higher aquatic plants (macrophytes) with subsequent anaerobic digestion of the spent macrophyte biomass to produce biogas with a high methane content are presented. The studies were conducted in the water area of the Spassky backwater of the Moskva River. A quantitative and qualitative assessment of the effectiveness of using the following macrophyte species is given: narrowleaf cattail (Typha angustifolia), yellow iris (Iris pseudacorus), yellow water-lily (Nuphar lutea), common reed (Phragmites australis), lake bulrush (Scirpus lac. Albescens), water hyacinth (Eichhornia crassipes), and water lettuce (Pistia stratiotes) to reduce the amount of cyanobacteria in a water body (efficiency calculated based on the phycocyanin indicator). It was established that the phycocyanin concentration decreased from 7,490 to 1,250 cells/mL (by 83%) over four months. Experiments were carried out to study the anaerobic digestion process of macrophyte biomass collected in the water body. It was determined that during anaerobic digestion of biomass under mesophilic conditions, the most effective ratio is 75% biomass of higher aquatic plants to 25% inoculum, at which 0.453 L of biogas (58.2% methane) was released on day 27 of the experiment.