The Use of Hydrophytes for Additional Treatmnet of Municipal Sewage

At the current stage of discharge and treatment of municipal sewage and other types of wastewater in the territory of Ukraine, traditional technologies of biological treatment in aero-tanks by the process of aerobic oxidation involving active silt characterized by low efficiency are largely used. It was established that biological treatment and additional treatment of sewage involving hydrophytes are efficient. The research on wastewater quality and the efficiency of sewage treatment was conducted in three phases: Phase 1 – “the quality before treatment”, Phase 2 – “the quality after mechanical-biological treatment” at the existing municipal treatment plants, Phase 3 – “the quality after additional treatment by hydrophytes”. In order to determine the efficiency of using hydrophytes additional treatment, Eichhornia crassipes (water hyacinth) and the perennial aquatic plant Lemna minor were planted in one treatment pond. The results of the experiment made it possible to determine high efficiency of using hydrophytes for additional sewage treatment. In particular, the efficiency of additional treatment in the treatment ponds removing the residue of suspended pollutants for 40 days was 32%, toxic salts – 13.0–23.0%, oil products – 30.0%, biogenic substances – 68.5–83.3%. It caused a drop in the values of chemical and biological oxygen demand for 5 days by 89.6% and 61.2%, respectively. The efficiency of sewage treatment removing toxic salts and oil products reached 97.7%, whereas in the case of mineral and organic pollutants – up to 99%. That contributed to a considerable increase in the wastewater quality by the criteria for fisheries. In particular, high nutritional value of Eichhornia crassipes and Lemna minor allowed obtaining 12.5 tons of hydrophyte wet mass that can be used as green manure, feeds for farm animals, poultry and fish.