Mechanisms and Model Process Parameters in Bioelectrochemical Wet Phosphate Recovery from Iron Phosphate Sewage Sludge

Abstract

Phosphate recovery from sewage sludge is possible with a bioelectrochemical system (BES) also referred to as microbial fuel/ electrolysis cell (MFC, MEC). The investigated process is based on phosphate removal with iron salts, which is extensively used in wastewater treatment. The mechanisms and reaction parameters of the bioelectrochemical phosphate recovery process was examined by modeling and model reactions for future scale up works. The mechanistic analyses concerned the electron reduction process, the role of the pH as well as the observed metal removal capacity. Iron oxidation state analyses showed that the iron reduction mechanism was of negligible importance under microbial electrolysis cell conditions. The cathodic iron reduction was outperformed by fast iron precipitation and phosphate remobilization process depended largely on chemical base (OH − ). Fluid particle kinetics and shrinking core modeling determined the relevancy of the reaction parameters in order to accelerate phosphate remobilisation. Rate enhancements were possible at higher pH, increased temperature and faster stirring. With the elucidated mechanisms and reaction kinetics parameters, the scale-up of bioelectrochemical system based phosphate recovery was given a foundation for scale-up works.

Electrochemically mediated precipitation of phosphate minerals for phosphorus removal and recovery: Progress and perspective

“…The two studies proved the achievability of P removal and recovery in BES. In MEC, the P removal effectiveness and the P precipitation rate increased with current density (Blatter et al, 2019;Cusick and Logan, 2012;Lei et al, 2019a;Wang et al, 2019;Wang et al, 2020). Pepè Sciarria et al ( 2019) compared the P recovery effectiveness in a digestate by MEC and MFC, respectively.…”

Recovery of Nutrients from Residual Streams Using Ion-Exchange Membranes: Current State, Bottlenecks, Fundamentals and Innovations

“…An example of the use of energy generated in a microbial fuel cell to recover P V from sewage sludge digestate is presented in Ref. [ 117 ]. This energy is required to dissolve the precipitated iron phosphate, and then convert the phosphate anions to struvite.…”

New frontiers from removal to recycling of nitrogen and phosphorus from wastewater in the Circular Economy

“…Although P recovery has not been evaluated as much as N recovery, several authors have applied BES to recover P as struvite from different wastes, such as swine manure and urine (S. . P can also be recovered from iron phosphate sewage sludge (Blatter et al, 2019). In this case, the electricity produced in the microbial fuel cell is used to reduce the FePO3 present in the digested sludge, dissolving precipitated phosphate into soluble forms, which can be recovered in the form of struvite in a subsequent crystallization process.…”