Abstract
The new paradigm in wastewater treatment involves the development of energy efficient technologies that allow for complete recovery of valuable nutrients and water reuse. In this study, a new bubble column electrolytic reactor configuration integrating ammonia scrubbing was developed and the influence of applied current, airflow rate, and different anode–cathode combinations (Mg-Mg, Mg-Al, Mg-Cu, and Mg-Ag) on the recovery efficiency of total ammonia nitrogen (TAN) and MgNH4PO4·6H2O (struvite) from anaerobic digested poultry litter supernatant was investigated. The experimental results showed that the removal and recovery efficiency of TAN is significantly dependent on the applied current, types of cathode material used and the airflow rate. Under constant current (4 A) and airflow rate (15 L/min) with Mg-Mg electrodes, up to 99.9 % and 98.4 % of total phosphorus and TAN were removed and recovered as struvite and ammonium sulphate solution after 30 mins of electrolytic treatment at room temperature. The space–time yield for struvite was 32 kg/m3·h and 7.85 kg/m3‧h, respectively, while the electrical energy used for electrolysis and air mixing/stripping was 18.4 kWh/m3, with the struvite purity of 90.5 %. These results indicated that the new integrated electrolytic struvite reactor is highly effective at removing and recovery nutrients from wastewater and suggests that the process could serve as a more suitable alternative to traditional processes that focus solely on struvite precipitation for nitrogen and phosphorus removal or air stripping for recovery of TAN only.