Active elements based on composite material with additives of biogenic substances for biological treatment systems of seawater

Abstract

The increasing anthropogenic pollution of the Black Sea is one of the urgent environmental problems. The currently proposed seawater biological treatment systems using attached hydrobionts (the main part of which are various types of algae) cultivated on the surface of artificial reefs have a number of limitations related to the complexity of maintenance of such reefs and the variability of the concentration of nutrients necessary to ensure the vital activity of hydrobionts. The objectives of the study were to develop a composite material containing additives of biogenic substances of prolonged action and compact active elements based on it, from which seawater biological treatment systems can be formed in certain water areas characterized by increased intake of anthropogenic pollutants (marinas, bays, ports). The results of the experiments have shown that the synthesized highly porous composite material based on an environmentally friendly thermoplastic polymer (polyethylene) and additives of a number of biogenic substances of inorganic origin embedded in its structure can be considered as a promising artificial carrier that provides optimal conditions for the cultivation of marine microalgae. Due to the high concentration of microalgae in the biofilm, which is formed on its porous surface, this carrier is able to effectively purify seawater from ammonium ions at four times their maximum permissible concentration (hereinafter referred to as MPC): the degree of purification was 1.5–2 times higher than the same indicator of the seawater self-purification process; at the same time, the self-purification process during the experiment it did not provide a decrease in the concentration of ammonium ions to the MPC. The developed composite material can be recommended as a basis for the production of block-type active elements having the shape of a cube with dimensions of 0.5x0.5x0.5 m and a relatively small mass (about 35 kg). Seawater biological treatment systems can be organized by installing the required number of such elements in selected areas of the water area; maintenance of such systems (cleaning, replacement of elements) should not be problematic due to the compactness and small weight of the elements.