Primary Treatment 2 : The first stage in waste-water treatment in which substantially all floating or settleable solids are mechanically removed by screening and sedimentation. (Bul D11)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}