Every day and every minute, toilets are flushing, showers are running and sinks are draining in our homes and businesses. As a result, a lot of sewage is created. Sewage is 99% dirty water. The rest of it is made up of solids, chemicals, fats, nutrients and trash. No new water is ever made. The same water keeps being used, cleaned, treated and then used all over again. The urban water system is the modern way of treating water for public use. It all begins when it rains. Water is captured in huge dams and treated before it is ready for you to use.
When sewage is flushed or drained away from your house, it enters a huge system of pipes that connect your house to the sewerage network. The sewerage network is all the pipes, pumps and treatment plants used to remove and treat the sewage. The following is an overview of how the waste water systems process works.
The Inlet supply
When sewage arrives at a treatment plant, engineers screen it to remove all the unwanted objects, mainly large objects and grit. This could include jewellery, clothing, cooking oils etc.
Once the sewage is screened, it is placed in special tanks that control how much sewage enters the treatment plant at any one time. This helps to ensure the treatment of the water is always consistent.
When the sewage is removed from the holding tanks, the treatment process begins. Bacteria are introduced to the sewage to consume the organic material and reduce nutrient levels. This occurs within machines called bioreactors. The bioreactors are filled with oxygen, which allows bacteria to breathe, reproduce and consume all the carbon in the sewage, while reducing the amount of phosphorous and nitrogen in the sewage that could affect waterways.
When the nutrients have all been consumed, the sewage is moved to special clarifiers that separate the solids from the liquid. The solids are called sludge or bio solids. They are drained out and sent off to fertilize crops for animal food. The remaining water is the treated sewage, which is sent to be cleaned and filtered.
The disinfection stage is where the water is filtered and disinfected by using ultra-violet rays or chlorine. This removes all microorganisms or hidden germs that might still be in the water.
After all these processes are completed, the water is tested to make sure it meets strict guidelines. The water quality is measured by directly sampling it, and instruments such as Secchi disks, nets, probes and metres are used to determine water clarity and any contaminants that might be present.