Calcium addition to increase the production of phosphate granules in anaerobic treatment of black water. (1st March 2018)

• Record Type: Journal Article
• Authors: Cunha, Jorge Ricardo; Schott, Chris; van der Weijden, Renata D.; Leal, Lucía Hernández; Zeeman, Grietje; Buisman, Cees
• Is Part Of: Water research. Volume 130(2018)
• Page Start: 333
• Page End: 342
• Publication Date: 2018-03-01
• Subjects: Phosphate recovery -- Calcium phosphate -- Anaerobic treatment -- Black water -- UASB reactor; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2017.12.012
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Simultaneous recovery of calcium phosphate granules (CaP granules) and methane from vacuum collected black water (BW), using an upflow anaerobic sludge blanket (UASB) reactor was previously investigated. It was calculated that only 2% of the total phosphorus (P) fed was present as CaP granules whereas 51% of the P accumulated dispersed in the reactor, limiting the applicability of this process for recovery of phosphate. This study proposes adding calcium to increase the P accumulation in the reactor and the production of CaP granules. Calcium was added in a lab-scale UASB reactor fed with BW. An identical UASB reactor was used as reference, to which no calcium was added. The treatment performance was evaluated by weekly monitoring of influent, effluent and produced biogas. Sludge bed development and CaP granulation were assessed through particle size analysis. The composition and structure of CaP granules were chemically and optically assessed. Calcium addition increased accumulation of P in the reactor and formation and growth of granules with size > 0.4 mm diameter (CaP granules). Moreover, with calcium addition, CaP granules contained 5.6 ± 1.5 wt% of P, while without calcium a lower P content was observed (3.7 ± 0.3 wt%). By adding Ca, 89% of the incoming P from BW accumulated in the reactor and 31% was sampled as CaP granules (> 0.4 mm diameter). Addition of 250 mgCa L −1 of BW was the optimum loading found in this study. Furthermore, no significant reduction in CODTotal removal (> 80%) and CH4 production (0.47 ± 0.10 gCOD-CH4 g −1 CODTotal -BW) was observed. Therefore, adding calcium can significantly increase the CaP granulation without inhibiting the simultaneous CH4 recovery. This further indicates the potential of this process for phosphate recovery. Graphical abstract: Highlights: Ca 2+ addition up to 546 mg L −1 did not hindered the treatment performance. P content in granules >0.4 mm increased on average from 4 to 6 wt% by adding Ca 2+ . By adding Ca 2+, P recovered as granules >0.4 mm increased from 14 to 31%.