Abstract
Phosphate rock is a depleting resource and wastewater a sustainable long-term alternative for phosphorous mining. In modern wastewater treatment phosphate is concentrated 7500 times from wastewater into sludge as iron phosphate (FeP). Recently developed bioelectrochemical reactors enabled phosphate recovery from sewage sludge containing FeP. The integrated bioelectric process was found of much broader utility than initially elaborated. It refines all principle components of wastewater. The implementation is confronted to a number of challenges. Three pilot microbial electrolysis cells (MECs) of 168 L each were constructed and installed in different municipal wastewater treatment plants (WWTPs). The scale-up MECs generated renewable chemical base and co-extracted abundant species such as Na+, K+, Ca2+, Mg2+ and NH4+ from wastewater. The chemical base remobilized phosphate quantitatively from iron phosphates contained in digested sewage sludge. Phosphate extracts contained ammonia and upon magnesium (Mg2+) addition struvite crystalized. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) on heavy metals, Direct Mercury Analysis (DMA), Liquid Chromatography Mass Spectroscopy (LC-MS/MS) on organic micropollutants, metagenomics sequencing, Scanning Electron Microscopy (SEM-EDS), and X-Ray Diffraction (XRD) indicated that a highly pure struvite-fertilizer was produced. Microbial electricity co-generation was verified by electrochemical characterisation and microbiome analysis using 16S rRNA V4-V5 methodology. Geobacter, Dechloromonas, Desulfobulbus and cyanobacteria were the principal electrogens found. All in all, renewable chemical base as well as phosphate were obtained in high quantities and other renewables became accessible such as the critical material magnesium and other compounds of importance like ammonia, potassium, calcium, solid P-free sludge useful as biofuel and purified water. In general, the process recycles important compounds from waste, in a close to traceless manner while purifying wastewater.
Highlights
Phosphate rock is a depleting resource and wastewater a sustainable long-term alternative for phosphorous mining
The phosphate recovery with the Pilot-microbial electrolysis cells (MECs) had in quint essence to overcome Ca2+ interferences
Calcium was abundantly contained in wastewater and just scarcely released from digested sewage sludge
Summary
Phosphate rock is a depleting resource and wastewater a sustainable long-term alternative for phosphorous mining. From today’s perspective, the best alternative for renewable phosphate supply is digested sewage sludge containing 3–4% elemental phosphorous. This accumulation in WWTPs is the result of iron salt addition to wastewater during treatment to remove phosphate and avoid eutrophication of rivers, lakes and sea shores receiving treated effluents. Due to the future legal obligation in Switzerland, Germany and other countries to recover phosphate from waste, mono-incineration furnaces become more and more installed as municipal waste incineration plants are no longer feasible as phosphate is much harder to recover from those ashes For this reason wet basic phosphate recovery, before incineration, is preferable for better phosphate recovery free of toxic metals as discussed in this paper. A breakthrough is seeked where, in the most ideal process, the potential energy contained in wastewater is used to propel intended wastewater refining to recover phosphate and other compounds
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
