As(III) removal in rapid filters: Effect of pH, Fe(II)/Fe(III), filtration velocity and media size

Gude, J.C.J.; Rietveld, L.C.; van Halem, D.

doi:10.1016/j.watres.2018.10.005

As(III) removal in rapid filters

Title

As(III) removal in rapid filters: Effect of pH, Fe(II)/Fe(III), filtration velocity and media size

Author

Gude, J.C.J. (TU Delft Sanitary Engineering)
Rietveld, L.C. (TU Delft Sanitary Engineering)
van Halem, D. (TU Delft Sanitary Engineering)

Date

2018-12-15

Abstract

In the top layer of aerated rapid sand filtration systems, uncharged As(III) is biologically converted to charged As(V). Subsequently, the main removal mechanism for As(V) is adsorption onto oxidised, flocculated Fe(III) (hydrous ferric hydroxides; HFO). The aim of this research was to understand the interactions between As and Fe in biologically active rapid filter columns and investigate the effect of different operational modes on Fe removal to subsequently promote As removal. For this purpose, different filter media column experiments were performed using natural, aerated groundwater containing 3.4 μg/l As(III). Results show that independent of the filter media size, complete (biological) conversion of As(III), manganese, ammonium and nitrite was achieved in approximately 70 days. After ripening, enhanced As removal was achieved with a top layer of coarse media or by dosing additional Fe(III). Addition of Fe(II) did not have the same effect on As removal, potentially due to heterogeneous Fe(II) oxidation in the upper layer of the filter, attaching rapidly to the filter grain surface and thereby preventing HFO flocs to penetrate deeper into the bed. Increasing the flow rate from 1 to 4 m/h did not improve As removal and lowering the pH from 8 to 7.4, resulted in an 55% increased removal of dissolved As. Altogether it is concluded that As removal in biologically active rapid sand filters can be improved by applying coarser filter media on top, in combination with dosing Fe(III) and/or pH correction.

Subject

Arsenite oxidation and arsenic adsorption
Groundwater treatment
Rapid filtration

To reference this document use:

http://resolver.tudelft.nl/uuid:60f48b27-3b14-43bb-890e-fcc6423fe014

DOI

https://doi.org/10.1016/j.watres.2018.10.005

ISSN

0043-1354

Source

Water Research, 147, 342-349

Part of collection

Institutional Repository