Phosphorus Removal Rate and Efficiency in an Electrochemical Sequencing Reactor for the Treatment of Wastewater with Low Organic Carbon Content

Abstract

Energy is essential for the operation of wastewater treatment systems. Simultaneously, it can be a factor facilitating the electrochemical purification processes. Previous studies have shown that under specific conditions, there is no technological justification for using bio-electrochemical reactors designed for the simultaneous removal of both phosphorus and nitrogen compounds. This is because similar dephosphatation process effects can be achieved in an electrochemical reactor. Additionally, in a bio-electrochemical reactor, a portion of the organic substrate introduced for biological treatment is lost due to the electrocoagulation process. The aim of the research was to determine the influence of low direct current densities (0.4–2.0 A/m2) on the rate and efficiency of phosphorus and other compound removal in a sequencing electrochemical reactor treating real wastewater from a greenhouse with low organic compound content. In the conducted studies, an increase in electric current density resulted in an increase in the removal rates of phosphorus from 26.45 to 34.79 mg/L·h, nitrogen from 2.07 to 6.58 mg/L·h, and organic compounds from 0.44 to 1.50 mg/L·h. This corresponded to maximum removal efficiencies of 88.6 ± 2.5% for phosphorus, 7.4 ± 2.5% for nitrogen, and 51.1 ± 8.3% for organic compounds. As a result of electrocoagulation, sludge rich in phosphorus was obtained, ranging from 347 ± 38 mg/L (18.1% P) to 665 ± 36 mg/L (11.7% P). The obtained results can be utilized in the future for the development of two-stage systems for wastewater treatment with a low content of organic compounds, aiming at the removal of phosphorus and nitrogen.