TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

**Definition:** This place covers:

The physical, chemical and biological treatment of water, waste water or sewage, e.g. by distillation or evaporation, by degassing, by centrifugal separation, by flocculation of suspended impurities or by using plants such as algae.

Selection or use of compositions for such treatments.

Compositions (per se) specially adapted for water treatment.

Softening water and preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents.

Aeration of stretches of water.

Multistage treatment of water, waste water or sewage.

Treatment of sludge and devices therefore, e.g. bioreactors. Sludge treatment covered in this subclass is usually restricted to the treatment of sludge obtained from a water treatment process.

Devices for the treatment of water, waste water or sewage, e.g. devices for separating or removing fatty or oily substances or similar floating material.

**Limiting references (this place does not cover):** - Processes for making harmful chemical substances harmless, or less harmful, by effecting a chemical change in the substances -> A62D3/00 - Settling tanks and filter devices in general -> B01D - Adding materials to water to prevent corrosion -> C23F - Cleaning or keeping clear the surface of open water, e.g. the sea -> E02B15/00 - Devices for cleaning or keeping clear the surface of open water -> E02B15/04 - Methods for obtaining or collecting drinking water or tap water -> E03B3/00 - Treating radioactively-contaminated liquids -> G21F9/04

**Glossary:** - Sludge: Solids that remain after wastewater treatment. This material may be separated, treated and composted into fertiliser. Aqueous suspension of solids resulting from water treatment processes and having a solids concentration of typically more than 2 g/L.