How does a domestic wastewater treatment plant work?

Domestic wastewater treatment plants play a key role in protecting the environment and maintaining sanitary conditions in residential and business properties. They are extremely important for every kind of house, holiday home and business that is not connected to the central sewer network. In this article we will look in detail at how such a system works, what its main components are and why its maintenance is important for long-term operation.

What is a domestic wastewater treatment plant?

A wastewater treatment plant for domestic wastewater is a technological facility that processes wastewater from households, such as water from kitchens, bathrooms, toilets and washing machines. The aim is for the water to be treated to a level that allows it to be safely released into the environment or used for technical purposes (for example irrigation). Such facilities reduce the environmental footprint of the site and allow more sustainable management of resources.

Main components of a wastewater treatment plant

1. Primary settling tank - initial separation of larger solid particles and dissolved grease by gravity.
2. Aeration chamber - supplies the oxygen needed to sustain the aerobic microorganisms.
3. Secondary settling tank - this is where the excess activated sludge is separated from the treated water by gravity.

How the treatment process works: step by step

1. Primary mechanical treatment: The wastewater enters the treatment facility and passes through a coarse screen that retains large, hard-to-degrade particles, after which it enters the primary settling tank, where the biological solid fraction and grease are separated by gravity.
2. Aeration: Air is supplied to this chamber by a compressor, which supports the biochemical processes.
3. Settling: takes place in the secondary settling tank: here the excess activated sludge is separated from the treated water by gravity.

The process in the facilities is fully automated and requires minimal human intervention, which is an advantage for owners.

Types of treatment plants: which is right for you?

1. Compact plants - suitable for single-family houses or holiday homes. They are easy to install and operate.
2. Higher-capacity plants - used for small hotels, guest houses or groups of properties.

It is important to assess your needs in advance in order to choose the right facility.

Maintaining a treatment plant: what you need to know

1. Checks: Monthly visual monitoring of the compressor's operation and, if necessary, cleaning of the filter. Once a year, a check of the tightness and the sludge level.
2. Cleaning: Carried out according to the load; it is recommended every 2 years.
3. Servicing: Some parts (filters, membranes, coils) need to be replaced periodically.

Regular maintenance guarantees a long life for the system and keeps the treatment efficiency above 95%.

Legal requirements in Bulgaria

1. Regulation: Depending on the capacity of the plant, a permit from the RIVER BASIN DIRECTORATE or the Ministry of Environment and Water may be required.
2. Design: required only for facilities with a capacity of over 100 population equivalents (PE) or at the express request of the RIVER BASIN DIRECTORATE.
3. Documentation: Every facility manufactured by us comes with the necessary documentation.

Consultation with a specialist is recommended before purchasing and installing the relevant facility.

Frequently asked questions (FAQ)

What is the difference between a septic tank and a treatment plant?

A septic tank stores the waste, while a treatment plant processes and purifies it.

What happens to the sludge?

It is collected periodically and removed by a licensed company.

How much electricity does a plant use?

About 1 – 3 kWh per day, depending on the model and the intensity of use.

Can the treated water be reused?

Yes, for watering or technical purposes, provided additional control is in place.

For a complete solution when building treatment facilities, we recommend that you also read our guides on the following topics: "How to choose a wastewater treatment plant according to the capacity and needs of the site" and "Designing water tanks: materials, technologies and regulatory requirements in Bulgaria".

Conclusion

A domestic wastewater treatment plant is a practical, environmentally friendly and long-term solution for properties without access to a central sewer system. It provides autonomy, reduces costs and helps with the sustainable management of water resources.

If you need professional advice or want to find out which system is most suitable for your property:

👉 Contact us for a free consultation or browse our solutions for wastewater treatment plants.