ABSTRACT
Deposition can become very extensive and is determined primarily by the environment created for biological growth and subsequent mineral oxidation. River-connected collector wells tend to have ideal growth environments and can experience extensive buildup of deposits. Certain radial screens in radial wells feeding into a central cistern will have more deposited material than others, due to the creation of different environments in the same collector well. The size of the zone of fouling is determined primarily by the availability of oxygen. A biologically active zone often takes years to filter enough material from the groundwater to significantly affect capacity and warrant rehabilitation. During rehabilitation it is difficult to remove 100% of that deposited mass which is in the well. It is possible to look at rehabilitation of a well just to keep the efficiency up and the pumping costs down and nothing else. The loss of efficiency of a well can involve plugging.
