Effect of Electrical Current Density and Type and Dose of the External Source of Carbon on the Quantitative and Qualitative Characteristics of Sludge Formed During Wastewater Treatment in the Sequencing Batch Biofilm Reactors

• Main Authors: Izabella Kłodowska, Joanna Rodziewicz, Wojciech Janczukowicz
• Format: Article
• Language: English
• Published: Polish Society of Ecological Engineering (PTIE) 2018-07-01
• Series: Journal of Ecological Engineering
• Subjects: bio-electrochemical reactor; denitrification; electrocoagulation; citric acid; potassium bicarbonate; characteristics of sludge
• Online Access: http://www.journalssystem.com/jeeng/Effect-of-electrical-current-density-and-type-and-dose-of-the-external-source-of,89656,0,2.html

This work presents results of an experiment on the effect of electrical current density (53, 105, 158 and 210 mA/m2), type of an external source of carbon (citric acid, potassium bicarbonate) and C/NNO3 ratio (0.5, 1.0 and 1.5) on the quantity and quality of formed sludge. The experiment was conducted in sequencing batch biofilm reactors (SBBRs), under anaerobic conditions without and with the passage of electrical current, under controlled pH of 7.5 – 8.0. The study demonstrated that in the reactors with electrical current passage and external source of carbon, the volume of sludge increased along with current density increase from 53 to 158 mA/m2. At its highest density (210 mA/m2), the concentration of sludge was insignificantly lower. For all densities of electrical current and C/NNO3 values, concentrations of sludge formed in the reactors with potassium bicarbonate (1.00 to 1.26 g d. m./L) were lower than in the reactors with citric acid (1.26 to 1.30 g d. m./L). The concentration of organic matter was higher in the sludge from reactors with electrical current passage and potassium bicarbonate, compared to the sludge from the reactors with citric acid. In the reactors with electrical current passage and external source of carbon, the total nitrogen content in the sludge decreased along with C/NNO3 ratio increase for current densities of 53 and 105 mA/m2. For higher electrical current density nitrogen content in the sludge was similar. Irrespectively of current density, nitrogen content in the sludge from the reactors with citric acid was higher than in the sludge from the reactors with potassium bicarbonate. For higher current densities (158 and 210 mA/m2) the increase in the C/NNO3 value caused an increase in P content in the sludge. Electrical current density increase contributed to increasing content of phosphorus in the sludge. Phosphorus content in the sludge from the reactors with citric acid was lower than in the sludge from the reactors with potassium bicarbonate. CST values prove that sludge formed during wastewater treatment in electrobiological SBBR was characterized by very high dewaterability. Capillary suction time decreased along with increasing the electrical current density but was not significantly affected by the type of carbon source.