Abstract: An apparatus and method are described for treating a flowing water stream with a chemical treatment agent. In particular, the apparatus includes a hopper for containing the chemical treatment agent, an auger for discharging the chemical treatment agent from the hopper into the flowing water stream, and a water wheel which provides an adjustable amount of mechanical energy for driving the auger to discharge the chemical agent into the flowing water stream at a rate proportional to the amount of mechanical energy provided by the water wheel. The apparatus is relatively light in weight with minimal dimensions to provide portability for locating the apparatus in remote locations. Further, the apparatus requires minimal human supervision because it uses the flowing water stream as an energy source and is mechanically simple.