abstract
BACKGROUND This work is focused on phosphorus (P) recovery from the anaerobically digested organic fraction of municipal solid waste (referred to as 'digestate') as a fertilizer. The main purpose was to propose and test modifications to the electrodialytic process that increase P extraction, improve the quality of the fertilizer by removing contaminants, and reduce hydraulic retention time to allow for smaller system footprints. Strategies tested were: (i) lowering the pH of the digestate suspension to <4.5 using the electrochemical reactions and enhance P solubilization from the waste; (ii) changing the configuration of the electrodialytic cell from three to two chambers; and (iii) stirring the sample to shorten the duration of the extraction. RESULTS Results show that the acidification of digestate by the electrochemical reactions was effective to enhance P extraction yield. Three-chamber electrodialytic experiments enabled the removal of heavy metals from the digestate, producing P-rich solutions with low metal concentrations. This resulted in the production of high-quality fertilizer which can be used for agricultural applications. The modification of the electrodialytic cell set-up from three- to two-chamber neither resulted in an increase of the P extraction yields, nor contributed to the removal of metals from the liquid phase of digestate. Reduction of the hydraulic retention time of electrodialytic extraction of P from 16 days to 9 days was attained by the use of stirring and by electrodialytic acidification. CONCLUSIONS An increase of P recovery was accomplished by modification of electrodialytic extraction, resulting in 90% of P being successfully extracted from the digestate and transformed into struvite. (c) 2019 Society of Chemical Industry
keywords
SEWAGE-SLUDGE; HEAVY-METALS; GASIFICATION; INCINERATION; EXTRACTION; ASH
subject category
Biotechnology & Applied Microbiology; Chemistry; Engineering
authors
Oliveira, V; Dias-Ferreira, C; Labrincha, J; Rocha, JL; Kirkelund, GM
our authors
Célia Maria Dias Ferreira
Post-Doc Fellowship
João António Labrincha Baptista
Full professor
Verónica Oliveira
PhD Studentacknowledgements
The authors would like to thank Sabrina Hvid for carrying out ICP analyses. This work was funded by Portuguese National Funds through FCT - Portuguese Foundation for Science and Technology under CERNAS (UID/AMB/00681/2013). Celia Dias-Ferreira and Veronica Oliveira were funded through FCT 'Fundacao para a Ciencia e para a Tecnologia' by POCH - Programa Operacional Capital Humano within ESF - European Social Fund and by national funds from MCTES (SFRH/BPD/100717/2014; SFRH/BD/115312/2016). Joana L. Rocha was funded by project 0340-SYMBIOSIS-3-E co-funded by FEDER 'Fundo Europeu de Desenvolvimento Regional' through Interreg V-A Espana-Portugal (POCTEP) 2014-2020.