Class B biosolids are sewage sludges that have been treated to contain fewer than 2.0 x 106 fecal coliforms/dry gram. The USEPA estimates that 6.3 million tonnes of Class B biosolids are generated in the United States each year, and that by 2010, the amount generated per year will increase to 7.4 million tonnes.

Amid growing water shortages in parts of the United States, more communities are considering tapping their sewage treatment plants as a new source of drinking water.

A question arises whenever olive oil is obtained: what can we do with its agricultural residues, such as olive vegetable water, browse leaves, or the solid waste known as 'alperujo'?