The Influence of the Duration of Exposure to Direct Current on the Treatment Efficiency of Wastewater from Soilless Tomato Cultivation in a Bio-Electrochemical Reactor

Abstract

The management of wastewater from soilless tomato cultivation poses a technological and economic challenge. Given the above, the aim of this study was to determine the treatment efficiency of wastewater from soilless tomato cultivation in a bio-electrochemical reactor under conditions of direct electric current flow. The treatment efficiency was tested in three time variants of wastewater exposure to the electric current: V1—24 h exposure phase; V2—12 h exposure phase/12 h no exposure phase; and V3—12 h no exposure phase/12 h exposure phase. Experiments were conducted with two organic substrates, sodium acetate and acetic acid, at the C/N ratio of 1.25, with a direct current intensity of 1.25 A·m−2 and hydraulic retention time of 24 h. The study results show the feasibility of achieving a satisfactory technological effect in a bio-electrochemical reactor without the need for electric current flow throughout the 24 h treatment cycle. From the energy consumption and technological standpoints, the most viable approach, ensuring 90.4 ± 1.6% and 94.9 ± 0.7% efficiencies of nitrogen and phosphorus removal, respectively, turned out to be feeding the reactor with sodium acetate and wastewater exposure to the electric current flow only during the first 12 h of the treatment cycle. The scope of the conducted research justifies its continuation in order to determine the optimal time for supplying electricity to the bio-electrochemical reactor and the impact of the C/N value on the nitrogen and COD effluent concentrations.