Modified biochars present an economic challenge to phosphate management in wastewater treatment plants

In order to reduce phosphorus (P) discharge into aqueous systems, wastewater treatment plants usually precipitate sludge water with iron or aluminum salts and produce slow–release P fertilizer (struvite). Continued tightening of P discharge limits require additional equipment and larger doses of these salts which increase wastewater treatment cost. Many research teams are involved in P recovery and theoretical knowledge is rapidly increasing. However, most new proposals are only economically viable with the support of public funds. Novel and technically undemanding concepts are designed and techno–economically assessed on a pilot scale. The cheapest biochar derived from fermentation residues that are pyrolyzed by waste heat, was used as sorbent. Multiple austerity measures have been designed to modify the sorbent by ferric (Fe3+) and calcium (Ca2+) chemisorption. It is firstly reported that over 2.5 kg of P per 100 kg of modified biochar from the 80 mg P L−1 environment can be obtained, whereas the P forms are more readily available to plant nutrition than struvite. Provided that a majority of used reactants are recovered from waste, or their price is irrelevant (subsequently used for their original purpose), there are indications that the newly proposed technology is one of the few environmentally friendly measures that can swiftly become widespread in the wastewater industry for economic reasons. [Display omitted] •Biowaste is charred via waste heat to provide biochar of low production cost.•Inexpensive Ca and Fe sorbents are fixed on biochar and subjected to wastewater.•Captured P is present in readily available forms with no sign of phytotoxicity.•Pilot scale assessment indicates spread of technology to commercial scale.