A device is provided for increasing the pH of an acidic aqueous stream, which may result from commercial activity in petroleum, mining, metal finishing and food processing sectors, among others. A container defines an upright reactor portion with a cross-section that increases upwardly, along with inlet and outlet conduits connected to an inlet and an outlet between which the reactor portion is located. The conical portion contains a bed of substantially water-insoluble alkaline salt particulate, such as MgSO, the bed being such that, when the pH of the inflowing aqueous stream is below 7, contact between the particulate and the aqueous stream will raise the pH of the outflowing stream to a level above that of the inflowing stream.