Circular production – Evaluation of membrane technologies for nutrient recycling from a microbial fermentation effluent

Abstract

The present study demonstrates a detailed analysis of nutrient recovery from the spent fermentation broth of S. acidocaldarius, an archaeon with high industrial and pharmaceutical potential. The pathways of the resource recovery by the lately recognized environmental-friendly and cost-effective technologies nanofiltration (NF), electrodialysis (ED), and electrodialysis with bipolar membranes (EDBM) were assessed. In contrast to previous research, this study treated real wastewater and tested the reuse of recovered products in the subsequent batch fermentations. Ions were separated from the rest of the medium by NF, with 78–85% DOC removal and 0.74 kWh/m3. ED achieved a 1.7 concentration factor for ions, 96% DOC removal and 0.51–0.74 kWh/kg of removed salts. EDBM coupled with NF removed 94.8–98.1% DOC while recovering 0.11–0.15 M sulfuric acid from the feed containing 6.1–16.7 g/l of SO42− with energy consumption of 2.7–3 kWh/kgH2SO4. Recovered media were successfully applied for control fermentations. While NF was less energy-consuming, ED/EDBM offered a selective ion recovery, higher concentration factors and reuse-specific streams. The discharges of NF/ED/EDBM showed reduced negative environmental impacts due to the nutrient removal from the waste fermentation effluent. All applied technologies require a post-treatment to remove organic substances from side streams and close the production loop with a near-to-zero liquid and waste discharge.