Field Study IV: Arsenic Removal from Groundwater by Ferrate with the Concurrent Disinfecting Effect: Semi-Pilot On-site Application

Abstract

The effect of ferrates on arsenic removal from groundwater was initially observed using laboratory tests. Two different sources of groundwater containing an elevated concentration of As (ca 100 μg/L) were used for the semi-pilot scale testing, both possessing the potential for drinking water production. Groundwater treated by ferrates under laboratory conditions proved to meet the requirements for As limits in drinking water, i.e., 10 μg/L (according to Czech legislation—Public notice No. 252/2004 Sb.). A prototype of a portable technological unit for an on-site ferrate application (Fe(IV), Fe(V)) has been constructed to prove on a semi-pilot scale that ferrates are applicable for production of drinking water. Water flow of 100 L/h, two sources of groundwater containing arsenic in concentrations ten times exceeding the limit for drinking water, and ferrates (in the form of commercial ferrate, dosed in different amounts—5 mg/L, 10 mg/L, 15 mg/L, and 20 mg/L) were used. The quality of the treated water from both sites was in compliance with the requirements for drinking water. The minimal dose of commercial ferrates to reach the As limit for potable water was set to 10 mg/L for the first water source and 15 mg/L for the second one. Elimination of microbial organisms was achieved even with a lower dose of commercial ferrates—10 mg/L. The main advantages of the tested technology over the existing ones are minimal reagent consumption, minimal sludge production with As (hazardous waste), and disinfecting effect.