ABSTRACT
A deep well injection experiment was conducted at the DIZON pilot plant in the Southern Netherlands, using pretreated canal water. It consisted of 2 phases: (a) a flushing phase during the first 938 days, with continuous injection by one well and continuous pumping by a 98 m distant well; and (b) an aquifer storage phase during the next 106 days (no injection, no pumping). The oxidized zone around the injection well, which developed during the flushing phase, vanished during the aquifer storage phase by slowly reacting pyrite and organic material (OM). Subsequently iron, manganese and ammonium dissolved from the aquifer. Analyses of water pumped out of the injection well demonstrate that significant amounts of iron(hydr)oxide and OM accumulated around the injection well (< 5m). The iron(hydr)oxides were, partly, residues from the coagulation process in the pretreatment, and OM was composed of biological inputs from the activated carbon filtration step in the pretreatment.
