Soil Aquifer treatment (SAT) facilities are constructed in a similar fashion as infiltration ponds, but are using reclaimed water as the source water. During SAT, it is required to ensure that unsaturated conditions prevail below the infiltration area. SAT systems are often operated in a dry/wet cycle in order to maintain aerobic conditions in the soil and allow for regular maintanence (e.g. clogging layer removal). Reclaimed water percolates through the unsaturated zone, which is often several tens of meters thick. Residence times (usually several months) in the sub-surface improves chemical and biological quality significantly. Examples of SAT can be found in Israel.