Formation and use of biogenic jarosite carrier for high-rate iron oxidising biofilms

• Published in: Research in microbiology 2020-10, Vol.171 (7), p.243-251
• Main Authors: Ahoranta, Sarita, Hulkkonen, Hanna, Salminen, Turkka, Kuula, Pirjo, Puhakka, Jaakko A., Lakaniemi, Aino-Maija
• Format: Article
• Language: English
• Subjects: Biogenic carrier; Biomass retainment; Expanded-bed bioreactor; Fluidised-bed bioreactor; Iron oxidation; Jarosite
• ISSN: 0923-2508; 1769-7123
• DOI: 10.1016/j.resmic.2020.06.004

Jarosite precipitates formed in iron oxidising bioreactors have been shown to harbour iron-oxidisers. The aim of this study was to develop an iron oxidising bioprocess where microorganisms are retained solely on biogenic jarosite particles. Based on preliminary experiments using a fluidised-bed bioreactor (FBR), the formed jarosite particles started to disintegrate and wash out at upflow velocities of ≥0.21 cm/s. Therefore, the generation and use of biogenic jarosite carrier was studied in an expanded-bed bioreactor (J-EBR) with an upflow velocity of 0.19 cm/s. Inside J-EBR, the jarosite particles formed granules of 0.5–3 mm containing 200–460 mg/g of attached biomass. The performance of J-EBR was compared with an activated carbon biofilm FBR at 0.82 cm/s upflow velocity (AC-FBR). At 35 ± 2 °C with a feed ferrous iron concentration of 10 g/l, the highest obtained iron oxidation rate of J-EBR (6.8 g/l/h) was 33% lower than that of AC-FBR (10.1 g/l/h). This was likely due to the 80% lower recirculation rate and subsequently higher oxygen mass transfer limitation in J-EBR compared to AC-FBR. The present study demonstrates that biogenic jarosite can be used for retainment of iron oxidising biofilms in expanded-bed bioreactors that oxidise iron at high rates.