Learning Objective Describe how we produce and treat waste water To be able to: Describe how we produce and treat waste water Key Words: Sewage, effluent, microbes

Exam question Monday, 20 May 2019 Waste Water Treatment Date and title in books. You need a pen, pencil & ruler. Starter Activity – 5 minutes Exam question

Describe ways to treat waste water (F) Target 9-1 Identify ways we produce waste water (F/H) Target 4-9 Describe the problems with waste water (H) Target 5-9 Describe ways to treat waste water Extension: Application of Knowledge Target 8/9 Analyse data about different ways to treat water Learning Outcomes

Producing Waste Water Waste water is produced by humans, industrial processes and agriculture. For example, humans use toilets and showers. Farmers use water to wash animals and clean their shelters.

Screening and Grit Removal Screening removes objects such as rags, paper, plastics, and metals to prevent damage and clogging of equipment and pipes. Grit is the name given to sand, gravel, eggshells, bone chips, seeds, coffee grounds, and large organic particles, such as food waste

Effluent Effluent is liquid waste or sewage discharged into a river or the sea General water pollution, for example from a sewage treatment plant or industry

Sedimentation Sedimentation involves allowing water to slow down or not move, to remove any solid particles, like sand.

Glucose  carbon dioxide + methane Anaerobic Digestion Some microbes can break down organic material (material containing carbon) They do this when there is a lack of oxygen present, so they cannot undergo normal respiration. Glucose  carbon dioxide + methane C6H12O6 → 3CO2 + 3CH4

Anaerobic Digestion of Sludge The goal is to reduce the amount of sludge that needs to be disposed. The most widely employed method for sludge treatment is anaerobic digestion. In this process, a large fraction of the organic matter (cells) is broken down into carbon dioxide (CO2) and methane (CH4), and this is accomplished in the absence of oxygen. About half of the amount is then converted into gases, while the remainder is dried and becomes a residual soil-like material.

Aerobic Digestion of Effluent The microbes feed on undesired biological substances in the water, creating organic substances and microorganisms that settle to the bottom of the container. This sludge is stable and usually can be disposed of easily. Oxygen is present throughout.

Task Describe the advantages and disadvantages of each method of sewage treatment.