If your property is not connected to mains sewerage, choosing the right sewage treatment plant is an important decision. The correct system needs to be suitable for the number of people using the property, the site conditions, the proposed discharge arrangement and the requirements of the installation.
At AJ Gammond, we supply sewage treatment solutions for domestic applications, including Marsh ENCO sewage treatment plants in different capacities and outlet configurations.
This guide explains what sewage treatment plants are, how they work, what size you may need and the difference between gravity and pumped outlet systems.
What Is a Sewage Treatment Plant?
A sewage treatment plant is an underground system designed to treat domestic wastewater and sewage before the treated effluent is discharged from the property.
Unlike a simple holding tank, a sewage treatment plant uses a biological treatment process to break down organic matter within wastewater.
They are commonly used at properties where connection to a mains sewer is unavailable or impractical.
Sewage treatment plants can be suitable for a variety of properties, including:
- Rural homes
- New-build properties
- Renovated properties
- Residential developments
- Properties located away from mains drainage
- Other domestic applications requiring on-site wastewater treatment
The treatment plant must be correctly sized and installed for the individual property and site.
How Does a Sewage Treatment Plant Work?
A sewage treatment plant uses a biological process to treat wastewater.
Wastewater from toilets, sinks, showers and other domestic appliances enters the treatment system. Within the plant, microorganisms break down organic matter in the wastewater.
Many modern sewage treatment plants introduce oxygen into the wastewater using an aeration system. The oxygen encourages aerobic microorganisms to break down organic material.
Following treatment, the resulting effluent can be discharged through the approved outlet arrangement, subject to the requirements of the installation.
The exact treatment process varies between manufacturers and models, so always refer to the manufacturer’s technical information for the specific sewage treatment plant.
What Size Sewage Treatment Plant Do I Need?
One of the most important considerations when purchasing a sewage treatment plant is capacity.
Domestic sewage treatment plants are generally specified according to the number of people the system is designed to serve, often referred to as population equivalent or PE.
For example, AJ Gammond supplies Marsh ENCO sewage treatment plants for 6 and 8 people, providing options for different household sizes.
6 Person Sewage Treatment Plant
A 6 person sewage treatment plant can be suitable for a domestic property designed to accommodate up to six people, subject to the manufacturer’s specifications and the property’s expected wastewater production.
AJ Gammond supplies:
6 Person Marsh ENCO Sewage Treatment Plant – Gravity
6 Person Marsh ENCO Sewage Treatment Plant – Pumped Outlet
8 Person Sewage Treatment Plant
An 8 person sewage treatment plant provides additional capacity for domestic properties designed to accommodate up to eight people.
AJ Gammond supplies:
8 Person Marsh ENCO Sewage Treatment Plant – Gravity
8 Person Marsh ENCO Sewage Treatment Plant – Pumped Outlet
Always select the capacity based on the intended use of the property and the manufacturer’s recommendations.
Gravity vs Pumped Outlet Sewage Treatment Plants
One of the most important decisions when selecting a sewage treatment plant is whether you require a gravity or pumped outlet.
The correct choice depends largely on the levels of the treatment plant, drainage system and final discharge point.
Gravity Sewage Treatment Plants
A gravity outlet system allows treated effluent to flow naturally from the treatment plant towards the approved discharge point.
This can provide a straightforward installation where the site levels allow sufficient fall between the treatment plant outlet and the discharge location.
A gravity system may be appropriate where:
- The site has suitable natural levels
- The discharge point is lower than the treatment plant outlet
- There is sufficient fall for the effluent to flow naturally
- The drainage layout allows gravity discharge
AJ Gammond supplies:
6 Person Marsh ENCO Sewage Treatment Plant – Gravity
8 Person Marsh ENCO Sewage Treatment Plant – Gravity
Pumped Outlet Sewage Treatment Plants
A pumped outlet system is designed for situations where treated effluent cannot conveniently discharge by gravity.
This can occur where the final discharge point is at a higher level than the treatment plant outlet or where the site’s drainage layout makes gravity discharge impractical.
A pumping arrangement can provide greater flexibility when planning the route from the treatment plant to the approved discharge point.
AJ Gammond supplies:
6 Person Marsh ENCO Sewage Treatment Plant – Pumped Outlet
8 Person Marsh ENCO Sewage Treatment Plant – Pumped Outlet
Important
The choice between gravity and pumped outlet should be determined by the individual site’s levels and proposed drainage arrangement.
If you are unsure which configuration you require, speak to your drainage contractor or installer before ordering.
Where Can a Sewage Treatment Plant Be Installed?
The location of the treatment plant needs to be carefully considered before installation.
Factors may include:
- Ground conditions
- Groundwater levels
- Property location
- Inlet and outlet levels
- Access for installation
- Access for maintenance
- Position of the discharge point
- Electrical requirements where applicable
- Ventilation requirements
- Manufacturer installation requirements
The treatment plant should be installed according to the manufacturer’s instructions and any applicable requirements for the site.
Professional installation is strongly recommended.
Sewage Treatment Plant Installation
Installing a sewage treatment plant is not simply a case of placing the tank underground and connecting a pipe.
The installation needs to consider the complete drainage system, including the incoming sewage pipe, treatment plant, outlet arrangement and final discharge point.
Before installation, your installer should establish:
1. Required capacity
Determine the number of people the property is intended to accommodate.
2. Inlet level
The incoming drainage needs to connect correctly to the treatment plant.
3. Outlet level
The outlet needs to be compatible with the proposed discharge arrangement.
4. Gravity or pumped discharge
Establish whether the treated effluent can discharge by gravity or whether pumping is required.
5. Ground conditions
Ground conditions and groundwater levels can affect installation requirements.
6. Final discharge
The proposed discharge method must be suitable for the site and comply with applicable requirements.
What Is the Difference Between a Sewage Treatment Plant and a Septic Tank?
Although both systems are used for properties without mains sewerage, they operate differently.
A septic tank primarily separates solids and allows the liquid portion to leave the tank for further treatment or disposal as required.
A sewage treatment plant uses a biological treatment process to treat the wastewater within the system before the treated effluent is discharged.
The appropriate system depends on the property, site conditions, discharge arrangements and applicable requirements.
If you’re replacing an existing septic tank, don’t automatically assume that a sewage treatment plant is the correct replacement. Your installer should assess the complete installation.
Sewage Treatment Plant Maintenance
Like any wastewater treatment system, sewage treatment plants require appropriate maintenance.
Maintenance requirements depend on the manufacturer and model but may include:
- Regular servicing
- Checking mechanical components
- Inspecting the treatment system
- Removing accumulated sludge when required
- Checking aeration equipment
- Inspecting pumps on pumped systems
- Following the manufacturer’s maintenance schedule
Regular servicing can help maintain the performance of the system and identify potential problems before they become more serious.
Always follow the manufacturer’s maintenance instructions.
What Should I Consider Before Buying?
Before ordering a sewage treatment plant, we recommend considering the following:
Number of occupants
How many people is the property designed to accommodate?
Site levels
Can treated effluent flow naturally to the discharge point?
Discharge location
Where will the treated effluent be discharged?
Gravity or pumped outlet
Does the site require a gravity or pumped configuration?
Ground conditions
Are there any issues with groundwater, soil conditions or excavation?
Access
Can the treatment plant and installation equipment access the site?
Maintenance
How will the system be accessed for servicing and maintenance?
Installation
Who will install the system, and have they confirmed which model and configuration is appropriate?
Choosing a 6 Person or 8 Person Sewage Treatment Plant
If you’re choosing between the Marsh ENCO 6 person and 8 person systems, the key consideration is the intended occupancy of the property.
6 Person
Suitable for domestic applications designed for up to 6 people, subject to the manufacturer’s specifications.
Available from AJ Gammond:
8 Person
Suitable for domestic applications designed for up to 8 people, subject to the manufacturer’s specifications.
Available from AJ Gammond:
If you are uncertain which capacity or outlet configuration you require, speak to your installer before purchasing.
Frequently Asked Questions
What is a sewage treatment plant?
A sewage treatment plant is an underground system that treats domestic sewage and wastewater using a biological treatment process before the treated effluent is discharged.
Do I need a sewage treatment plant?
A sewage treatment plant may be suitable for a property that is not connected to mains sewerage. The correct solution depends on the individual property, site and discharge arrangements.
What size sewage treatment plant do I need?
The required capacity depends on the intended occupancy and the manufacturer’s specifications. AJ Gammond supplies Marsh ENCO systems for 6 and 8 people.
What is a gravity sewage treatment plant?
A gravity system allows treated effluent to flow naturally towards the discharge point where site levels permit.
What is a pumped outlet sewage treatment plant?
A pumped outlet system uses a pumping arrangement to move treated effluent towards the discharge point where gravity discharge is not practical.
Which is better – gravity or pumped?
Neither is universally better. The correct option depends on the levels and drainage layout of the individual site.
Can I install a sewage treatment plant myself?
Installation requirements can be complex and site-specific. Professional installation is recommended, and the manufacturer’s installation instructions should always be followed.
How often does a sewage treatment plant need servicing?
Maintenance and servicing requirements vary between systems. Always follow the manufacturer’s recommended servicing schedule.
Shop Sewage Treatment Plants at AJ Gammond
AJ Gammond supplies Marsh ENCO sewage treatment plants for domestic applications, with different capacities and outlet configurations available.
Our current range includes:
6 Person Marsh ENCO Sewage Treatment Plant – Gravity
For suitable domestic properties where treated effluent can discharge naturally by gravity.
6 Person Marsh ENCO Sewage Treatment Plant – Pumped Outlet
For suitable domestic applications where a pumped discharge arrangement is required.
8 Person Marsh ENCO Sewage Treatment Plant – Gravity
For domestic properties designed to accommodate up to eight people where gravity discharge is suitable.
8 Person Marsh ENCO Sewage Treatment Plant – Pumped Outlet
For domestic properties designed to accommodate up to eight people where a pumped outlet is required.
Need Help Choosing?
Sewage treatment plants are a significant purchase, and choosing the correct system is important.
If you’re unsure whether you need a 6 person or 8 person system, or whether gravity or pumped outlet is appropriate, contact the AJ Gammond team before ordering.
We can help you identify the key information you should confirm with your installer so you can select the appropriate product for your property.
AJ Gammond – supplying drainage, agricultural, building, plumbing and trade products across the UK.