How do sewage treatment plants clean water?
Every day, human activity produces millions of gallons of wastewater that makes its way into our municipal sewage systems. This runoff can come from a variety of sources, from the lavatory, to industrial factories and excess storm water.
As you might imagine, much of this wastewater is not suitable to dump into nearby rivers and waterways. Untreated wastewater can end up polluting drinking water sources or natural habitats that plant and aquatic life reside in.
Therefore, this often highly hazardous runoff must be treated before it can be safely recycled back into our natural environment.
Why Do People Want or Need Sewage Treatment Plants?
Unfortunately, homes and commercial properties in isolated, rural areas that do not have a convenient connection to centralised sewer systems have to find alternative options to dispose of their polluted wastewater. This is where smaller-scale, sewage treatment plants and septic tanks come into play.
These ingenious self-contained systems are both cost-efficient, green, and long-term solutions for any property’s wastewater needs. Domestic and commercial sewage treatment plants act like miniature versions of a municipal treatment plant by performing the entire filtration and effluent purification process all on the grounds of the property.
Wastewater that a home or business produces becomes water that is free of pollutants and can then be safely dispersed into nearby drainage ditches or other natural waterways.
What Are the Benefits?
The benefits of sewage treatment plants to property owners are varied and numerous.
First, as previously mentioned, if you are located in a rural area where centralised sewers are not available, these systems are convenient solutions to drainage disposal problems.
Second, domestic sewage treatment systems are efficient and eco-friendly. Unlike septic tanks, sewage treatment plants clean water to a much higher degree of purification.
Cleaning water with a septic tank requires dispersing the still toxic effluent into a large drainage field on a property for the soil to finalise the bacteria treatment process. A sewage treatment plant’s end product is pure and can be safely discharged into a nearby ditch or waterway.
Third, by artificially introducing oxygen into the wastewater collection tank, naturally occurring bacteria will start to degrade organic matter present in the sewage. This in turn both reduces noxious odours in the wastewater, as well as separating more solid sludge that will settle out at the bottom of the tanks.
Fourth, since sewage treatment plants perform the wastewater purification process entirely ‘in-house’ the property owner does not owe a costly sewage bill to the local council at the end of the month.
Though of course a treatment plant costs money to first install, the savings over time more than pay for themselves. Only periodic inspection and a yearly cleaning by a professional are needed to keep a sewage treatment plant entirely self-sufficient.
How Does the Process Work?
A property’s dirty water goes through a three-part process that both breaks down organic solids and, through bacterial treatment, purifies what remains so it is eventually fit to be released into the natural environment once more.
Sewage treatment plants clean water by first routing the entire property’s runoff into one final pipe. This pipe terminates into a primary pre-treatment tank.
In this first phase, naturally occurring processes start to separate the wastewater into three separate components.
Simple gravity causes heavier sediment to descend to the bottom as sludge – this will need to be collected and removed later down the road. Fats, grease and oils found in the runoff will naturally start to rise to the surface.
Finally, naturally present anaerobic bacteria (bacteria that do not need oxygen to consume waste) start to break down the wastewater between the oil and the sludge into a liquid known as effluent. This effluent is now almost free of any solids, but it is not yet suitable to be released back into the environment.
The separated effluent then makes it way to a secondary chamber where oxygen is introduced to induce aerobic bacteria (bacteria that thrives in an oxygen rich environment) to consume pollutants further.
Aerobic bacteria are adept at removing odours, and purify the effluent to a much higher degree than anaerobic bacteria. As the aerobic bacteria consume the unwanted bacteria, more sludge is produced. This continues to settle at the bottom of the tank.
Most sewage treatment plants clean water at this stage by mechanically aerating the wastewater. This forcefully introduced oxygen aids the bacteria’s digestion of any remaining biodegradable material still present.
However, non-electric technology is also now available that uses natural air currents to power this process.
In the final step, the aerated and now almost pure effluent makes it way to a clarification tank.
The liquid is left to remain for any remaining silt to settle. These solids are then returned back to the previous aerobic tank for further processing.
The finalised and clarified water is now purified, and can be safely pumped out into a nearby waterway or drainage channel.
The leftover sludge that is separated from the effluent water does accumulate over time and must be cleaned out and removed via lorry by a professional service every two years.
If a sewage treatment plant is not inspected and pumped out periodically, the solid sludge can eventually cause blockages in the pipes and costly repairs to the entire system.
How Long Does It Take?
The process in sewage treatment plants described above takes around 24 hours from when your wastewater reaches the system and when it can then be safely reintroduced back into surrounding natural waterways. Larger sewage treatment plants clean water at a capacity that can handle up to hundreds of gallons per day. Keep in mind that most plants work round the clock, as bacteria are continually digesting pollutants in its receiving tank.
OMDI are specialists in the sewage treatment systems. We are a family-run business with over 20 years of experience in the installation, servicing, and maintenance of small-scale sewage treatment plants for both domestic and commercial properties throughout the UK.
Give us a ring: our experts are on call to answer any questions you may have. We will be happy to discuss your sewage treatment plant needs in-depth, and provide you with a free, no-obligation quote. Contact OMDI today.