Determination of substrates phytotoxicity based on waste activated sludge in vegetation experiments

The aim of the study is to determine the phytotoxicity of components and substrates using waste from the treatment facilities of the Arkhangelsk Pulp and Paper Mill. The substrates were made on the basis of high-moor peat with a decomposition degree of 15 %, with the addition of Biohumus Arkhangelsky, which is composted residual activated sludge from treatment facilities (RAS). To test extracts from materials used to prepare experimental substrates, oats (Avena sativa L.) and watercress (Lepidium sativum L.) were used. Comparison was carried out with distilled water and Knop's mixture. To select the optimal ratio of residual activated sludge and peat for plant growth, a model experiment was conducted with growing oats. The substrates prepared by the volume of fractions with a gradation of activated sludge of 10 % were studied. It was found that composted activated sludge does not have phytotoxicity in relation to the test objects. The extract based on dewatered activated sludge of the treatment facilities of the Arkhangelsk Pulp and Paper Mill does not have a depressing effect on the germination of test objects - oat and watercress seeds, and according to the indicators of the length of the root and coleoptile of oats, it has a stimulating effect comparable to or exceeding the effect of the Knop mixture. Phytostimulating effect of peat extract was not detected. The addition of OAI to high-moor peat during the preparation of substrates has a positive effect on growth indicators. An increase in the length of the stem and root, the mass of the underground and aboveground parts of plants is noted. The optimal addition to the substrate for growing oats is composted activated sludge in the amount of 10-20 %. With large proportions of composted activated sludge waste (more than 40 %), oat growth decreases, but the mass of stems and roots increases.