First Report on Cyanotoxin (MC-LR) Removal from Surface Water by Multi-Soil-Layering (MSL) Eco-Technology: Preliminary Results

Abstract

Cyanobacteria blooms occur frequently in freshwaters around the world. Some can produce and release toxic compounds called cyanotoxins, which represent a danger to both the environment and human health. Microcystin-LR (MC-LR) is the most toxic variant reported all over the world. Conventional water treatment methods are expensive and require specialized personnel and equipment. Recently, a multi-soil-layering (MSL) system, a natural and low-cost technology, has been introduced as an attractive cost-effective, and environmentally friendly technology that is likely to be an alternative to conventional wastewater treatment methods. This study aims to evaluate, for the first time, the efficiency of MSL eco-technology to remove MC-LR on a laboratory scale using local materials. To this end, an MSL pilot plant was designed to treat distilled water contaminated with MC-LR. The pilot was composed of an alternation of permeable layers (pozzolan) and soil mixture layers (local sandy soil, sawdust, charcoal, and metallic iron on a dry weight ratio of 70, 10, 10, and 10%, respectively) arranged in a brick-layer-like pattern. MSL pilot was continuously fed with synthetic water containing distilled water contaminated with increasing concentrations of MC-LR (0.18–10 µg/L) at a hydraulic loading rate (HLR) of 200 L m−2 day−1. The early results showed MC-LR removal of above 99%. Based on these preliminary results, the multi-soil-layering eco-technology could be considered as a promising solution to treat water contaminated by MC-LR in order to produce quality water for irrigation or recreational activities.

Accumulation of Microcystin from Oscillatoria limnetica Lemmermann and Microcystis aeruginosa (Kützing) in Two Leafy Green Vegetable Crop Plants Lactuca sativa L. and Eruca sativa

“…Other studies have found a link between MC production in cyanobacterial blooms and the cell density of dominant species in the aquatic environment [28]. According to previous research on toxin production in cyanobacteria, MC-LR is the most toxic and commonly found cyanotoxin variant in freshwater sources around the world [29]. It is also a specific inhibitor of the protein phosphate enzymes 1 and 2 A, which regulate a variety of cellular functions in higher plants [30].…”

Multi-Soil-Layering Technology: A New Approach to Remove Microcystis aeruginosa and Microcystins from Water

“…Considering the preliminary results of cyanotoxin removal by the MSL system in the laboratory [60], this technology may be the most promising in this field.…”

“…The multi-soil-layering (MSL) approach is one of the eco-technologies that integrates multiple processes into a single system to achieve high performance. MSL technology can be implemented in vertical or horizontal infiltration-percolation mode, while promoting adsorption, filtration [60], and biodegradation as fundamental mechanisms operating in the filters during purification [125,172].…”

“…Implementing the MSL system requires considering two fundamental elements, which are permeable layers (PL) and soil mixture blocks (SMB) [125,170]. On the one hand, the PL can be made of material with small size and a uniform diameter of 1-5 mm, such as gravel, pumice, perlite, zeolite [170][171][172], or pozzolan [60]. The size of the material used plays a crucial role in the system's longevity, as it allows a balanced distribution of the effluent, and thus prevents clogging while harboring the microbial biofilm that carries out the treatment.…”

“…Thereafter, we highlight the untapped potential of multi-soil-layering technology (MSL) to clean up eutrophic waters. So far, only one report has been published showing preliminary results of the effectiveness of the MSL system to remove cyanotoxins from water [60]. Furthermore, we describe the fundamentals of MSL systems and compare their performance with other technologies, highlighting some of the advantages of MSL technology for removing MCs.…”