BACKGROUND: A preliminary study concerning water electrolysis for the onsite production of hydroxyl ions (OH-) was carried out in a 2-chambered electrochemical system equipped with a cation exchange membrane and running in batch mode. A swine denitrified effluent (1) (46 ± 6 mg PO4-P L-1) was treated to achieve reagent-free phosphorus (P) precipitation. The influence of the current density (CD) applied (0.4 - 1.2 A m-2) and the effluent strength (dilution 1:4 and 1:1) on the pH profile and P precipitation was studied considering two final pH values (10.5 and 11.5). RESULTS & DISCUSSION: The maximum P-removal rate (PRR) (4.5 mM d-1) was achieved at pH 11.5 for the highest CD tested (1.2 A m-2) and it was not affected by the effluent strength (Fig. 1). This CD allowed optimizing the time needed to reach pH 11.5 with the specific energy consumption. X-ray diffraction (XRD) revealed that cattiite (Mg3(PO4)2·22H2O) was the main mineral formed in the bulk liquid (Fig. 1). Ohmic resistance in the batch system was measured by Electrical Impedance Spectroscopy, showing a slight increase from the start to the end of the experimental tests (increment: 0.79 and 0.23 ? m-2 for tests with 2 and 3 electrodes, respectively) which suggests limited mineral deposition on the cathode and membrane surface. On the membrane, carbonate compounds were detected through XRD analysis (Fig. 1). CONCLUSION: Electrolysis for OH- production is a promising alternative to NaOH dosage to raise the pH, as it can reduce the operational costs (0.40 EUR m-3 for NaOH dosage vs. 0.23 EUR m-3 for electrolysis with non-diluted effluent considering CD as 1.2 A m-2 and final pH as 11.5). Moreover, low CD values enabled P precipitation while simultaneously limiting the deposition on surfaces.
Reagent-free phosphorus recovery from a swine denitrified effluent in an electrochemical batch system
Milia S;Carucci A;
2023
Abstract
BACKGROUND: A preliminary study concerning water electrolysis for the onsite production of hydroxyl ions (OH-) was carried out in a 2-chambered electrochemical system equipped with a cation exchange membrane and running in batch mode. A swine denitrified effluent (1) (46 ± 6 mg PO4-P L-1) was treated to achieve reagent-free phosphorus (P) precipitation. The influence of the current density (CD) applied (0.4 - 1.2 A m-2) and the effluent strength (dilution 1:4 and 1:1) on the pH profile and P precipitation was studied considering two final pH values (10.5 and 11.5). RESULTS & DISCUSSION: The maximum P-removal rate (PRR) (4.5 mM d-1) was achieved at pH 11.5 for the highest CD tested (1.2 A m-2) and it was not affected by the effluent strength (Fig. 1). This CD allowed optimizing the time needed to reach pH 11.5 with the specific energy consumption. X-ray diffraction (XRD) revealed that cattiite (Mg3(PO4)2·22H2O) was the main mineral formed in the bulk liquid (Fig. 1). Ohmic resistance in the batch system was measured by Electrical Impedance Spectroscopy, showing a slight increase from the start to the end of the experimental tests (increment: 0.79 and 0.23 ? m-2 for tests with 2 and 3 electrodes, respectively) which suggests limited mineral deposition on the cathode and membrane surface. On the membrane, carbonate compounds were detected through XRD analysis (Fig. 1). CONCLUSION: Electrolysis for OH- production is a promising alternative to NaOH dosage to raise the pH, as it can reduce the operational costs (0.40 EUR m-3 for NaOH dosage vs. 0.23 EUR m-3 for electrolysis with non-diluted effluent considering CD as 1.2 A m-2 and final pH as 11.5). Moreover, low CD values enabled P precipitation while simultaneously limiting the deposition on surfaces.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
