Biological phosphorus removal in seawater-adapted aerobic granular sludge

de Graaff, D.R.; van Loosdrecht, Mark C.M.; Pronk, M.

doi:10.1016/j.watres.2020.115531

Biological phosphorus removal in seawater-adapted aerobic granular sludge

Title

Biological phosphorus removal in seawater-adapted aerobic granular sludge

Author

de Graaff, D.R. (TU Delft BT/Environmental Biotechnology)
van Loosdrecht, Mark C.M. (TU Delft BT/Environmental Biotechnology)
Pronk, M. (TU Delft BT/Environmental Biotechnology; Royal HaskoningDHV)

Date

2020

Abstract

Seawater can be introduced or intrude in sewer systems and can thereby negatively influence biological wastewater treatment processes. Here we studied the impact of artificial seawater on the enhanced biological phosphate removal (EBPR) process performance by aerobic granular sludge (AGS) with synthetic wastewater. Process performance, granule stability and characteristics as well as microbial community of a seawater-adapted AGS system were observed. In seawater conditions strong and stable granules formed with an SVI₅ of 20 mL/g and a lower abrasion coefficient than freshwater-adapted granules. Complete anaerobic uptake of acetate, anaerobic phosphate release of 59.5 ± 4.0 mg/L PO₄^3--P (0.35 mg P/mg HAc), and an aerobic P-uptake rate of 3.1 ± 0.2 mg P/g VSS/h were achieved. The dominant phosphate accumulating organisms (PAO) were the same as for freshwater-based aerobic granular sludge systems with a very high enrichment of Ca. Accumulibacter phosphatis clade I, and complete absence of glycogen accumulating organisms. The effect of osmotic downshocks was tested by replacing influent seawater-based medium by demineralized water-based medium. A temporary decrease of the salinity in the reactor led to a decreased phosphate removal activity, while it also induced a rapid release of COD by the sludge, up to 45.5 ± 1.7 mg COD/g VSS. This is most likely attributed to the release of osmolytes by the cells. Recovery of activity was immediately after restoring the seawater feeding. This work shows that functioning of aerobic granular sludge in seawater conditions is as stable as in freshwater conditions, while past research has shown a negative effect on operation of AGS processes with NaCl-based wastewater at the same salinity as seawater.

Subject

Accumulibacter phosphatis
Aerobic granular sludge
Biological phosphorus removal
Salinity
Seawater

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http://resolver.tudelft.nl/uuid:a21c570e-9f62-41df-a4ff-60266a444cc5

DOI

https://doi.org/10.1016/j.watres.2020.115531

ISSN

0043-1354

Source

Water Research, 172

Part of collection

Institutional Repository