Choosing the right wastewater treatment plant is one of the most important investments for any property without access to a sewer network, whether it is a house, a holiday home, a hotel or a business. However, many owners make the mistake of choosing "by eye", without taking into account the real load, the frequency of use and the type of wastewater.
In this guide, ERMAX BG will show you how to go through the whole selection process step by step, so that you get a system that meets your needs exactly and will serve you without problems for years to come.
1. Define the profile of the site
The first step when choosing a treatment plant is to determine what type of site it will serve. Different sites have different loads and different requirements for the system:
| Site type | Characteristics | Load |
| Single-family house | Permanent residents, even consumption | Medium |
| Holiday home / seasonal property | Irregular use, peak loads | Variable |
| Hotel / resort complex | Many users, dynamic load | High |
| Business / workshop | Mixed or process wastewater | Individual |
Tip: If you have a seasonal site, choose a system with automatic load regulation, so that it does not lose efficiency at a low flow rate.
2. Calculate the required capacity
The next step is to determine the capacity of the system. It is based on the number of people who will use the installation and the average water consumption per person per day (about 150 – 200 litres).
Indicative table for choosing the capacity of a treatment plant
| Site type | Number of users / employees | Consumption rate | Recommended capacity (m³/day) | Suitable type of plant |
| Single-family house | 3 – 6 people | 150 l/day per person | 0.45 – 0.9 m³/day | Biological |
| Holiday home / guest house | 6 – 10 people | 150 l/day per person | 0.9 – 1.5 m³/day | Biological |
| Hotel (seaside region) | 15 – 50 people | 200 – 210 l/day per person | 3.0 – 10.5 m³/day | Mechanical-biological |
| Hotel (mountain region) | 15 – 50 people | 180 l/day per person | 2.7 – 9.0 m³/day | Mechanical-biological |
| Business without showers | 10 – 100 employees | 30 l/shift per person | 0.3 – 3.0 m³/day | Modular |
| Large industrial site | 100+ people / shifts | Depends on production | over 10 m³/day | Individually designed |
Choose a system with a reserve capacity of 10 – 20%, so that it is not overloaded at peak times and works more reliably in the long term.
3. Analyse the type of wastewater
The next step is to determine the nature of the wastewater. This determines which technology is suitable for you:
- Domestic wastewater (from the kitchen, bathroom, toilet): a standard biological plant;
- Mixed wastewater (domestic plus grease, cleaning agents): an additional grease trap needs to be installed;
- Process wastewater (from production processes): requires an individual solution with additional filters or tanks.
ERMAX BG offers different types of systems, including biological and modular plants, which can be configured according to the specific type of wastewater.
4. Choose the treatment technology
This is the point at which you choose the specific type of plant:
🔹 Biological wastewater treatment plant
It works through an active biological mass of microorganisms that break down organic substances.
Suitable for residential and tourist sites, with a capacity of up to 20 m³/day.
Advantages: quiet operation, low energy consumption, up to 98% treatment efficiency.
🔹 Mechanical-biological plant
It combines a mechanical stage, settling, biological treatment and filtration.
Ideal for larger sites with a less predictable load.
Advantages: stable operation, flexible configuration, potential for expansion.
🔹 Modular system
It allows gradual upgrading as the capacity of the site increases, and is a common solution for hotels, businesses and residential complexes.
ERMAX BG offers modular plants that can easily be adapted as a business grows or its needs change.
5. Consider the installation conditions
Even the best system will not work properly if it is not installed in suitable conditions.
Before choosing, clarify the following:
- Do you have enough space for the excavation and the placement of the module (tank)?
- What is the depth of the groundwater?
- Can machinery access the installation site?
- Will additional equipment be needed (pump, aerator, settling tank)?
The ERMAX BG team carries out a full technical on-site inspection in order to propose the most suitable solution before purchase.
6. Maintenance and long-term efficiency
The choice does not end with the purchase. It is important to also think about easy maintenance and affordable consumables.
The best plants are those that work automatically and without constant supervision, but it is advisable to:
- remove the sludge periodically (every 12 – 24 months);
- check the compressor and the aeration;
- carry out an annual technical inspection.
ERMAX BG offers servicing, consumables and warranty service, which ensures peace of mind and a long life for your treatment system.
7. Consult a specialist before buying
Even with the best research, consulting a specialist remains a key stage.
The engineers at ERMAX BG can provide:
- an individual hydraulic calculation based on the real load;
- a recommendation on the type of plant and technology;
- a quotation with installation and maintenance included.
This way you will avoid underestimating or overestimating the capacity and can be sure that the system works optimally.
Conclusion
Choosing a treatment plant is not simply a purchase, but a planning process that must take into account the needs, the capacity and the characteristics of the specific site.
With the right calculation and professional consultation, you will get a system that is economical, quiet and efficient in the long term.
Trust ERMAX BG, the specialists in building biological and modular treatment plants for all kinds of sites.
We will help you choose the exact solution for your real needs.