waste water treatment

• agriculture produces water waste including nutrient run off from fields and slurry from animals
• sewage from domestic or agriculture sources has been treated to remove any organic matter and harmful microbes before it can be put into fresh water sources like rivers
• industrial processes produce lots of waste needed to be collected and treated
• industrial water can also contain harmful chemicals- has to undergo additional stages of treatment before it is safe to release into the environment
• before being treated the sewage is screened - this removes any large bits of material as well as any grit
• 2 - then it's allowed to stand in a settlement tank and undergoes sedimentation - the heavier suspended solids sink to the bottom to produce sludge while the lighter effluent floats to the top
• 3 - the effluent is removed and treated by biological aerobic digestion, where air is pumped through the water to encourage aerobic bacteria to break down any organic matter and microbes
• 4 - the sludge from the bottom is also removed and transferred into large tanks and gets broken down by bacteria in a process called anaerobic digestion
• 5 - anaerobic digestion breaks down organic matter in the sludge releasing methane gas in the process. methane gas can be used as an energy source and the digested waste as fertiliser
• 6 - the water containing toxic substances, additional stages of treatment may involve adding chemicals, UV radiation or using membranes