Мелиорация и гидротехника (Aug 2023)
STUDY OF ENVIRONMENTAL AND AGROCHEMICALINDICATORS OF SEWAGE SLUDGE BY PHYTOTESTING
Abstract
Purpose: to assess environmental and agrochemical indicators of sewage sludge from municipal wastewater treatment plants through phytotesting. Materials and methods. Sewage sludge from municipal wastewater treatment plants with a three-year stay on the sludge map was studied. The examined sludge contains a high amount of sulfate ions (0.720 g/100 g) with a content of calcium ions of 0.350 g/100 g. The remaining salt ions and heavy metals are in small quantities. Phytotesting was carried out by studying the phytoresponse of the test plants seeds in contact with an aqueous extract and directly with precipitation. In the first variant, solutions of various concentrations were prepared: an aqueous extract of sediments, its two-fold dilution and four-and eight-fold dilution. To control the indicators, the distilled water and one-component model solutions of sodium sulfate with concentrations identical to the tested solutions were used. Testing was carried out on the seeds of oats and vetch. In the second variant, under laboratory conditions, seeds of oats, vetch, white mustard, radish and watercress were sown in vegetation vessels with sewage sludge. Results and discussion. Phytotesting allowed revealing the complex effect of precipitation due to their composition. In the variant of undiluted aqueous extract from sewage sludge, the inhibitory effect of sulfates on seed germination and biomass growth is revealed. In the variant with two-fold dilution, the stimulating effect of precipitation components on seed germination and biomass growth was noted. To clarify the effect of the stimulating effect of sewage sludge, an experiment on sowing test plants directly into the sludge was carried out. The best indicators were noted in the variants with oats sowing. Conclusions. The inhibitory effect of sewage sludge from municipal wastewater treatment plants in Novocherkassk is due to the content of sulfates in them. The best comparability of indicators in both variants was noted for oat seeds.
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