The paper presents studies of the state of biologically active filtering material - vermicompost in the working area of ​​the aeration station at closed sewage treatment plants with an increased concentration of sulfur dioxide. The assessment of the filtering sorption properties was carried out using bioindication methods, namely, germination of test seeds under conditions of an increased content of sulfur dioxide. The bioindication method is considered fast and accurate, it allows to obtain reproducible results.Oat seeds, wheat seeds - representatives of monocotyledonous plants, as well as radish seeds - a dicotyledonous plant, were used as test seeds, as they are highly sensitive to harmful effects. The experiment took place in four stages with different time intervals. The indicator is the average length of development of the root system in the tested water compared to the control. The results showed that 60% of normal germination was recorded in monocotyledonous seeds, and 90% of normally germinated seeds were recorded in dicotyledons. According to the well-known method, the non-toxic properties of vermicompost was assessed based on the lengths of shoots and seed roots, which can be used as a load in installations for the biochemical purification of gases emitted into the air of the working area from closed wastewater treatment facilities. Such an installation can be a biofilter. Thus, the thickness of the load, the height of each of its constituent layers, affects the degree of its efficiency.

Keywords: sulfur dioxide, bioindication, closed treatment facilities, waste water, test seeds, germination of seeds, vermicompost