Iron deficiency and bioavailability in anaerobic batch and submerged membrane bioreactors (SAMBR) during organic shock loads. (July 2016) - Ketheesan, Balachandran
Highlights: Speciation and bioavailability of Fe during organic shock loads was studied. Effects of Fe 2+ on the degradation of VFAs during organic shock loads was examined. The implications of Fe accumulation in the seed sludge was demonstrated. Fe existing as sulphide salts appeared to be bioavailable to the methanogens. Fe addition during organic shock loads enabled rapid removal of acetate in SAMBR. Abstract: This study examined the effects of Fe 2+ and its bioavailability for controlling VFAs during organic shock loads in batch reactors and a submerged anaerobic membrane bioreactor (SAMBR). When seed grown under Fe-sufficient conditions (7.95 ± 0.05 mg Fe/g-TSS), an organic shock resulted in leaching of Fe from the residual to organically bound and soluble forms. Under Fe-deficient seed conditions (0.1 ± 0.002 mg Fe/g TSS), Fe 2+ supplementation (3.34 mg Fe 2+ /g-TSS) with acetate resulted in a 2.1–3.9 fold increase in the rate of methane production, while with propionate it increased by 1.2–1.5 fold compared to non-Fe 2+ supplemented reactors. Precipitation of Fe 2+ as sulphides and organically bound Fe were bioavailable to methanogens for acetate assimilation. The results confirmed that the transitory/long term limitations of Fe play a significant role in controlling the degradation of VFAs during organic shock loads due to their varying physical/chemical states, and bioavailability.