Land treatment is defined as the application of partially treated wastewater or biosolids to the land at a controlled rate in a designed and engineered setting. The purpose of the activity is to obtain beneficial use of these materials, to improve environmental quality, and to achieve treatment and disposal goals in a cost-effective manner. In many cases the production and sale of crops can partially offset at least part of the cost of treatment. In arid climates the practice allows the use of wastewaters for irrigation and preserves higher-quality water sources for other purposes.

Disposal of wastes to the land has been an accepted and recognized cultural practice since time began. Stabilization and assimilation of body wastes in the soil are complete, and problems do not occur with low-density migratory populations of people or animals. The higher-density conditions that can cause problems have been documented since biblical times,1 and these problems require a technique for management rather than random disposal. Controlled application of the wastes to the land emerged as a technology with the centralization of people in towns and cities. The earliest land application system documented in the literature was in Bunzlau, Germany,2 where a sewage irrigation project was in operation for over 300 years, commencing in 1531. A system in the vicinity of Edinburgh, Scotland, began operation about 1650.2 The value of the wastewater as a fertilizer for vegetables and other crop production was well recognized.