A Guide to Sewage Treatment Plants
Posted: Jun 08, 2019
How a sewage treatment plant works
The process of a working sewage treatment plant is quite similar on the surface to the way a septic tank works, however the sewage treatment plant involves the incorporation of some extra mechanical components providing some additional processes whose job it is to break down solids, yielding a cleaner and greener effluent.
The way a sewage treatment plant works is as follows. Waste from the connected properties is directed into a primary settlement tanks, wherein waste flows into the biozone chamber. Inside this chamber the pump aerates the waste, encouraging the "good" bacteria to digest the organic matter. This is how it is purified. Upon leaving the final chamber, which is commonly referred to as the humus chamber (sorry if you’re eating hummus and pita bread right now), the effluent is now usually 95% clean and ready to be discharged into local watercourses, land drainage systems and ditches.
The Environment Agency has created new general binding rules concerning septic tanks. If you are in charge of one that discharges directly to surface water (ditches or rivers etc.) then it must be upgraded to a full sewage treatment plant by 1st Jan 2020.
The options are as follows:
You can connect to the mains sewer – where applicable
You may install a drainage field (also known as an infiltration system) so the septic tank can discharge to ground instead of surface water
Or, ideally you should replace your septic tank with a small, independent sewage treatment plant
If you are in charge of a sewage treatment plant then you should be aware of some little titbits of advice…
Inside the property you should use biologically friendly cleaning products
Make sure no medicines, harsh chemicals or other such products enter the system as they can stop the good bacteria from working as efficiently
Make sure you have the tank de-sludged every year to prevent excessive build-up
Beware that too much bleach or biological cleaning agents can also stop the good bacteria from flourishing
The key distinction between septic tanks and sewage treatment systems
Septic tanks rely entirely on anaerobic bacteria digestion, which yields lots of carbon dioxide and methane, which leads to unpleasant smells. Instead, sewage treatment plants use aerobic processes by forcing oxygen into the system. In this manner, aerobic bacteria digest the sewage, yielding carbon dioxide, water and biomass.
The aerobic process in a sewage treatment plant is much more efficient, it works quicker and yields a higher quality effluent.
Unlike a septic tank, the outfall of a sewage treatment plant can be legally discharged to surface waters.
Buying a sewage treatment plant
If you are thinking of purchasing and installing a sewage treatment plant you will need a comprehensive site visit from a professional company to assess your needs. Depending on the size and scale of the plant needed you could be looking at costs anywhere between £1500 and £8000 for purchase and installation of the plant. Shop around and use a reputable company preferably one that has great online reviews.
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