C14

• SEWAGE TREATMENT STEPS: screening, sedimentation and aerobic biological treatment
• screening removes large solid objects and grit from waste water
• sedimentation is when sludge settles out of mixture. The watery liquid above sludge is called effluent which contains many potentially harmful microorganisms
• aerobic biological treatment is the useful bacteria in effluent feed on remaining organic matter and harmful microorganism. This breaks them down aerobically
• Potable water is water that is safe to drink and isn't pure as it contains dissolved substances
• potable water has pH between 6.5 & 8.5, dissolved susbtances will be in small quantites and free of bacteria
• Difference between potable and pure water is that pure water is solely made up of H2O molecules, whereas potable water may contain different substances usually dissolved minerals and salts
• sewage is the general name for waste water from homes, businesses and industry
• sewage treatment removes organic matter and harmful microoganisms from sewage and agricultural waste water.
• industrial waste water may also need harmful chemicals removes to make the sewage safe to return to environment
• finite resources are being used up at faster rate than they can be replaced and will eventually run out
• renewable resources are those that can be replaced at same rate as they are used up
• sustainability is developments that meet needs of society now without endangering ability of future generations to meet their needs
• in plastics industries to increase sustainability, polymers are produced from ethene which can be made from ethanol from sugar cane
• Natural resources are used to provide food, warmth, shelter and transport and are found in earth's crust, oceans and atmosphere
• examples of natural products replaced by synthetic ones, rubber from sap of trees with polymers
• most copper is extracted from copper-rich ores
• scrap iron can be added to solutions of copper compounds to displace copper