Novel method to immobilize phosphate in lakes using sediment microbial fuel cells

Phosphate pollution in lakes poses an intractable remediation challenge. Accumulated stocks of phosphorus in sediments cause high concentrations in the overlying water despite elimination of external sources. We propose to use sediment microbial fuel cells (SMFCs) for lake remediation by sediment phosphorus immobilization. The hypothesis is that SMFCs can increase sediment redox potential at the top layer, and that such changes will allow the sediment to retain phosphorus as immobile species. This study placed an emphasis on scalability, practicality, and use of low-cost materials. Stainless steel net was selected as electrode material, and modifications were tested: (i) chronoamperometric operation with anode poised at + 399 mV (versus standard hydrogen potential); (ii) injection of graphite slurry; and (iii) coating with nickel-carbon matrix. Stainless steel electrodes were implemented in laboratory microcosms (1.3 L) and at field scale in a eutrophic freshwater lake. All tests were carried out in untreated sediment and water from Lake Sollerod, Denmark. Phosphate immobilization was shown at lab scale, with 85% decrease in overlying water using steel electrodes. At field scale maximum phosphate decrease of 94% was achieved in the water body above a 16 m2 stainless steel SMFC electrode. Results are promising and warrant further study, including remediation trials at full scale. Added benefits include degradation of sediment organic matter and pollutants, inhibition of methane and sulfide emission and production of electricity. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study suggests using SMFCs for lake phosphorus pollution control by immobilizing phosphorus in sediments to reduce phosphorus concentration in water. Results show significant phosphate immobilization using stainless steel electrodes, indicating promising potential for application.