Phosphorus Recovery Essay

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3.2. Phosphorus recovery in MEC
When the pH of the cathode chamber reached 8, P started to precipitate as struvite. The reactor accomplished a peak precipitation efficiency of 94%. Recovery of P was in the cathode chamber, where the neutral solution was converted to alkaline by proton consumption. Previous studies reported similar results, like Cusick et al. (2014) and You et al. (2016), where high P removal was carried out by MEC (85%) and MFC (82%), respectively. Cathode pH was affected by applied voltage, where an increase in applied voltage from 0.4 to 0.8 V caused increased the average cathode pH from 8 to 9.1. However, increasing the applied voltage to 1.2 resulted a decrease in the average cathode pH, down to 8.5. Using high voltage may inhibit bacteria activity and impact the oxidation process in the anode compartment, with the result that low protons are
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To realize the role of the current on P recovery and cathode pH, the system was shifted to an open circuit system (OCV), where no resistance was used in the circuit, and MECs were operated for at least three cycles. Cathode pH remained at 7 without any increasing. These outcomes show the importance of defining the ideal applied voltage to obtain high pH in the cathode. Efficacy of precipitation in OCV was less than 1%, while when the circuit closed and 0.4 V was applied, the MEC attained 45 % precipitation efficiency as it shown at Fig. 3. Moreover, precipitation efficiency enhanced and reached 90 % when the applied voltage increased to 0.8 V. At 1.2 V, precipitation efficiency reached 92%. Precipitation of P was on the cathode electrode, suspended on the

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