Role of phosphate and humic substances in controlling calcium carbonate scaling in a groundwater reverse osmosis system

Role of phosphate and humic substances in controlling calcium carbonate scaling in a groundwater reverse osmosis system

Mangal, M. Nasir (IHE Delft Institute for Water Education; University of Twente)
Salinas-Rodriguez, Sergio G. (IHE Delft Institute for Water Education)
Blankert, Bastiaan (Oasen; King Abdullah University of Science and Technology)
Yangali-Quintanilla, Victor A. (Grundfos Holding A/S)
Schippers, Jan C. (IHE Delft Institute for Water Education)
Van Der Meer, Walter G.J. (University of Twente; Oasen)
Kennedy, M.D. (TU Delft Sanitary Engineering; IHE Delft Institute for Water Education)

2021

The role of phosphate and humic substances (HS) in preventing calcium carbonate scaling and their impact on antiscalant dose was investigated for a reverse osmosis (RO) system treating anaerobic groundwater (GW) (containing 2.1 mg/L orthophosphate and 6-8 mg/L HS). Experiments were conducted with the RO unit (treating anaerobic GW), and with a once-through lab-scale RO system (operating with artificial feedwater). Additionally, (batch) induction time (IT) measurements were performed with, i) real RO concentrate, and ii) artificial RO concentrates in the presence and absence of phosphate and HS. It was found that at 80% recovery (Langelier saturation index (LSI) 1.7), calcium carbonate scaling did not occur in the RO unit when the antiscalant dose was lowered from 2.2 mg/L (supplier's recommended dose) to 0 mg/L. The IT of the real RO concentrate, without antiscalant, was longer than 168 h, while, at the same supersaturation level, the IT of the artificial concentrate was approximately 1 h. The IT of the artificial concentrate increased to 168 h with the addition of 10 mg/L of phosphate, humic acid (HA), and fulvic acid (FA). Furthermore, in the lab-scale RO tests, the normalized permeability (Kw) of the membrane decreased by 20% in 2 h period when fed with artificial concentrate of 80% recovery containing no phosphate, whereas, with phosphate, no decrease in Kw was observed in 10 h period. These results indicate that phosphate and HS present in the GW prevented calcium carbonate scaling in the RO unit and reduced the use of commercial (synthetic) antiscalants.

Antiscalant
Brackish anaerobic groundwater RO
Calcium carbonate scaling
Humic substances
Phosphate

http://resolver.tudelft.nl/uuid:6f267992-fa3b-440a-9aa9-a1f0587009a0

https://doi.org/10.1016/j.jece.2021.105651

Journal of Environmental Chemical Engineering, 9 (4), 1-12

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journal article

© 2021 M. Nasir Mangal, Sergio G. Salinas-Rodriguez, Bastiaan Blankert, Victor A. Yangali-Quintanilla, Jan C. Schippers, Walter G.J. Van Der Meer, M.D. Kennedy