Hazardous waste treatment technologies are designed to reduce the toxicity, volume, mobility, or environmental impact of hazardous wastes before their final disposal or recovery. Hazardous wastes may contain toxic chemicals, corrosive substances, flammable materials, reactive compounds, heavy metals, pesticides, solvents, and other harmful constituents. Proper treatment is therefore essential for protecting human health, soil, water, and air. The selection of treatment technology depends on the physical and chemical characteristics of the waste, its concentration, quantity, and the required disposal method. Physical treatment technologies alter the physical properties of waste without necessarily changing its chemical composition. Common methods include filtration, sedimentation, screening, centrifugation, evaporation, and adsorption. Filtration separates suspended solids from liquid wastes, while sedimentation allows heavier particles to settle. Evaporation can reduce the volume of liquid hazardous waste by removing water, although the concentrated residue requires further treatment. Adsorption, commonly using activated carbon, is useful for removing organic contaminants from liquids and gases. Chemical treatment technologies use chemical reactions to convert hazardous substances into less harmful or more stable forms. Neutralisation is widely used for acidic or alkaline wastes. Acids can be neutralised with alkaline substances, while alkaline wastes can be treated with suitable acids.