Do energy free sewage treatment plants work?
Energy free sewage treatment plants have been around for a long time. They can work very effectively for the treatment of domestic wastewater. If you understand how a sewage treatment plant works then you will understand that bacteria perform the main role in the treatment of waste. This is no different in an energy free sewage plant.
As you may already know, bacteria need oxygen to live. In a normal sewage treatment plant this oxygen is provided by a small air blower. For the purposes of this article we will call this “active aeration” as it is actively forced into the water.
How does an energy free sewage treatment plant work?
An energy free sewage treatment plant uses the same core process as a normal treatment plant, except the bacteria live on filter material and water trickles down through the filter material. The bacteria get oxygen from the air. Water produced from these trickle filter systems can be very good.
So, it all sounds great, good treatment, no energy, why wouldn’t I go for one?
We are fans of energy free treatment plants however we vary rarely install one, let’s have a look why:
- These systems always have deep outlets. Water has to trickle down through the filter material. Normally these systems will have an outlet around 2m below ground. And unless you live on a steep hill, you will require a pump to lift the water back to a more manageable level
- Oxygen – whilst manufactures try to hide the fact that lots of air is needed, it is well known that you require really good air flow to get the energy free systems to work well. Often a high vent pipe will be needed close to the system to allow fresh air to be pulled up through it. We have seen some that have had to have fans installed to help them treat the water
- Cost, most of the good ones are twice the price of a normal treatment plant
- Space, they all require a primary septic tank to be installed which takes up more space.
Take Home Message
Treatment plants use very little power (sometimes only £40 per household per year), and in most cases the energy free treatment plants need energy to pump the water. We see very few sites that allow the use of them without the need to pump the water. If you are looking at installing one and like what you’ve read about the product, turn your attention to the detail in the drawings and see if you have the fall on your site to make one work without using a pump. Don’t buy an energy free treatment plant before checking if you will need a pump (and energy).
Last Update: June 7, 2019