Uodated June 2026
Sewage Treatment Systems
Manufactured in Killarney since 1973
EN 12566 & S.R. 66:2015 certified
Sewage Treatment Systems in Ireland
A sewage treatment system treats wastewater from a property that cannot connect to the public sewer. The correct system depends on your site assessment, population equivalent (PE), ground conditions, discharge route and required treatment level. This applies equally to rural homes, one-off houses, replacement systems and commercial sites.
1,200+
Septic tank inspections carried out each year under the National Inspection Plan
EPA, 2022–2026 plan
€12,000
Maximum grant for qualifying repairs, upgrades or replacement.
Grant scheme, from Jan 2024
€50
Once-off DWWTS registration fee — non-registration carries a fine of up to €5,000
Local authority requirement
QUICK RESPONSE
What is a sewage treatment system?
A sewage treatment system collects and treats wastewater from toilets, sinks, showers and washing machines. It then discharges the treated effluent through an approved route.
If your property connects to the public sewer, a central works treats your wastewater. If no mains connection is available, however, you need an off-mains system. This may be a septic tank, a packaged treatment plant, a secondary or tertiary system, a sand polishing filter or a pumping station.
Used where no mains sewer connection is available
Treats wastewater onsite before discharge
Selected from the site assessment and PE
May include primary, secondary or tertiary treatment
Common for rural homes, one-off houses and commercial sites
Connection types
Mains sewer or off-mains sewage treatment system?
A mains sewage system carries wastewater from the property to the public sewer network. From there, it flows to a central treatment works. An off-mains sewage treatment system, by contrast, treats wastewater on the property before discharge through an approved route.
Rural and unsewered sites often need an off-mains system. Therefore, the final design should follow the site assessment, soil conditions, treatment level and local approval requirements.
| Connection type | Where treatment happens | Typical use | Requirement |
|---|---|---|---|
| Mains sewer | Central treatment works | Urban or serviced areas | Public sewer connection |
| Off-mains system | Onsite at the property | Rural or unsewered sites | Site assessment and correct system design |
How it works
How does a sewage treatment system work?
Treatment happens in stages. The stages a site needs are set by the site assessment, not by preference.
Primary treatment
Primary treatment separates solids from liquid wastewater. Heavier solids settle as sludge, while lighter material forms a scum layer. Septic tanks provide this stage. As a result, they rely on suitable ground conditions and a percolation area for further treatment.
Secondary treatment
Secondary treatment uses bacteria to break down organic matter in the wastewater. Packaged sewage treatment plants provide this level of treatment. Installers often specify them where a septic tank alone is not suitable.
Tertiary treatment or polishing
Tertiary treatment adds a final polishing stage. Sensitive discharge routes, site conditions or local authority requirements can make it necessary. Options include a tertiary treatment unit or a sand polishing filter.
Decision guide
What is the difference between a septic tank and a sewage treatment plant?
A septic tank provides primary treatment only. It separates solids from wastewater inside the tank. However, the liquid effluent still needs further treatment in a suitable percolation area or ground disposal system.
A sewage treatment plant provides a higher level of treatment. It uses a biological process to treat wastewater before discharge. For this reason, it suits sites where a septic tank and percolation area are not suitable, or where the site assessment requires secondary treatment.
| System type | Treatment level | Best suited to | Key requirement |
|---|---|---|---|
| Septic tank | Primary treatment | Sites with suitable percolation and space | Suitable percolation area |
| Sewage treatment plant | Secondary treatment | Restricted or sensitive sites, or higher treatment requirements | Electricity, servicing and approved discharge route |
| Tertiary system | Final polishing | Sites requiring further effluent treatment | Used after primary or secondary treatment |
| Pumping station | Transfer, not treatment | Sites where gravity flow is not possible | Correct pump, chamber and level design |
Need help choosing the right system?
Our team can advise on the best solution for your site, your budget and your discharge route.
PE explained
What does PE mean in sewage treatment systems?
PE means Population Equivalent. Assessors use it to size a sewage treatment system according to the expected wastewater load from a property or project.
For domestic homes, PE usually depends on the number of bedrooms and expected occupancy. For commercial sites, however, PE depends on building use, users, flow, organic load and peak demand.
Do not guess the exact PE. Instead, confirm it through the site assessment, design guidance and the relevant regulatory requirements.
1 PE
represents the average daily wastewater load produced by one person. An undersized system may become overloaded; an oversized system may not operate as intended.
Learn how PE is calculatedSystem Options
Tricel sewage treatment options
Choosing the correct sewage treatment system depends on the site, the number of users, the available ground area, the percolation result, and whether primary, secondary, or tertiary treatment is required. Tricel supplies a range of wastewater and sewage treatment systems for domestic, light commercial, commercial, and sensitive-site applications across Ireland.
For a full overview of available wastewater systems, visit the Tricel wastewater systems page.
Tricel Vento septic tank
The Tricel Vento is a septic tank designed for primary treatment. It separates solids from wastewater before the liquid effluent moves to a suitable percolation area or approved disposal system. This option is generally suited to sites with good ground conditions, adequate space, and a site assessment confirming that a septic tank is appropriate. Tricel states that Vento septic tanks are tested to EN 12566-1.
Tricel Novo sewage treatment plant
The Tricel Novo is a packaged sewage treatment plant for domestic and light commercial projects up to 50 PE. It provides a higher level of treatment than a septic tank by treating wastewater through primary settlement, aeration, and final settlement stages. It is generally the preferred option where a septic tank and standard percolation area are not suitable, or where the site assessment requires secondary treatment.
Tricel Maxus commercial sewage treatment plant
For larger projects above 50 PE, the Tricel Maxus provides a commercial sewage treatment option using Submerged Aerated Filter technology. It is suitable for larger or semi-collective applications such as hotels, schools, caravan parks, nursing homes, housing estates, restaurants, retail units, and other off-mains commercial sites.
Tricel Tero tertiary treatment
The Tricel Tero provides tertiary treatment after a packaged treatment plant, including the Tricel Novo. It uses coconut coir media to further treat effluent before discharge to ground and is designed for projects where a higher treatment level is required, including sites with sensitive environmental conditions.
Tricel Sandcel sand polishing filter
The Tricel Sandcel is a sand polishing filter used to provide additional treatment after a secondary treatment unit. It can polish treated effluent and discharge it to groundwater, with the filter enclosed in GRP panels and designed around EPA Code of Practice requirements for single houses.
Tricel Puraflo packaged filter system
The Tricel Puraflo is a packaged filter system that can provide secondary treatment after a septic tank. It uses coconut fibre media and is suited to sites where higher treatment is required, including sensitive locations and intermittent-use properties such as holiday homes, campsites, and schools.
Not every system is suitable for every site. A qualified site assessment is required to confirm the correct wastewater treatment route, system size, discharge method, and whether secondary or tertiary treatment is needed. For help comparing the options, view all Tricel wastewater systems or contact Tricel for product advice.
Cost and maintenance
How much does a sewage treatment system cost?
The cost of a sewage treatment system depends on the system type, size and PE. Ground conditions, site access, discharge route, pumping needs and installation complexity also affect the price.
A septic tank unit may cost less than a packaged treatment plant. However, the full installed cost varies significantly once you include excavation, percolation, polishing filters, electrics and commissioning.
Note: Figures vary by site. Budget for the full installed cost, not the tank price, and obtain written, like-for-like quotations before committing.
Servicing and desludging
Sewage treatment systems need correct use and ongoing maintenance. Septic tanks require desludging. Packaged treatment plants, meanwhile, normally require scheduled servicing to maintain treatment performance.
Table of Contents
Case Study
Septic tank upgrade in an environmentally sensitive area
A homeowner needed to replace an existing septic tank close to a stream. Because of the ground conditions and the nearby watercourse, the site required a high level of effluent filtration before discharge.
Tricel supplied a pumped Tricel Novo 6 PE treatment plant paired with a Sandcel sand polishing filter. This combined secondary treatment with polishing, matched to the site’s discharge requirements. After installation, a Tricel technician returned to confirm the plant was operating correctly and to answer the owner’s questions.
Commissioning the tank followed the final installation.
Project Summary
| Project type | Replacement / septic tank upgrade |
|---|---|
| Site constraint | Sensitive site near a stream; high filtration required |
| System supplied | Pumped Tricel Novo 6 PE + Sandcel polishing filter |
| Aftercare | Post-installation technician check and handover |
Why choose Tricel?
Irish manufacturing. Nationwide support. Guaranteed compliance.
Tricel has manufactured wastewater treatment systems in Ireland since 1973, from its facility in Killarney, Co. Kerry. The Vento septic tank range and Novo treatment plant range are certified to EN 12566 for installations from single homes up to 50+ population equivalent.
A nationwide network of approved distributors and installers, backed by Tricel's own technical sales team, covers supply, installation, commissioning and servicing across every county.
Quality
Manufactured in Killarney, Co. Kerry. The Novo tank is built from compression-moulded SMC — a composite material proven over 50 years in harsh operating conditions.
- EN 12566-1 (septic tanks) & EN 12566-3 (treatment plants) certified
- Independently tested by PIA GmbH, Aachen, Germany
Efficiency
The Tricel Novo treats wastewater across three independent zones, reaching an average 95.9% BOD removal — a higher standard of treatment than a septic tank alone.
- No moving parts or pumps inside the tank
- Ceramic diffuser lasts twice as long as standard rubber equivalents
Support
A nationwide network of approved distributors and installers, with a dedicated technical sales team on hand for sizing, site queries and project support.
- County-based distributor network across Ireland
- Direct technical support from Tricel's own team
Maintenance
Servicing and technical advice available directly from Tricel's environmental team, for the lifetime of your system.
- 10-year warranty on the Vento septic tank
- Call 064 663 2421 for servicing or technical advice
Questions about sewage treatment systems
Your site, ground conditions, property type, PE and discharge route determine the right sewage treatment system. These FAQs explain the main differences between septic tanks, treatment plants, polishing filters and pumping stations.
What is a sewage treatment system?
A sewage treatment system treats wastewater from a property where a mains sewer connection is not available. It may include a septic tank, packaged treatment plant, secondary treatment, tertiary treatment, polishing filter or pumping station.
What is the difference between a septic tank and a sewage treatment plant?
A septic tank provides primary treatment by separating solids from wastewater. A sewage treatment plant provides a higher level of biological treatment before discharge. The correct choice depends on the site assessment and discharge route.
Do I need a sewage treatment system if I am connected to the public sewer?
No. If your property is connected to the public sewer, wastewater is normally carried away and treated centrally. An off-mains sewage treatment system is required where no public sewer connection is available.
What type of sewage treatment system is suitable for my site?
The suitable system depends on the site assessment, percolation results, ground conditions, PE, treatment level and discharge route. A septic tank may suit suitable ground, while restricted or sensitive sites may require a treatment plant or additional polishing
What does PE mean?
PE means Population Equivalent. It is used to size a sewage treatment system based on the expected wastewater load from the property or project.
Can a sewage treatment system be pumped?
Yes. A pumping station may be required where wastewater cannot flow by gravity to the treatment system or discharge point.
How often does a sewage treatment system need maintenance?
Maintenance depends on the system type, usage and manufacturer guidance. Septic tanks require desludging, while packaged treatment plants usually require scheduled servicing.
Is a sewage treatment system suitable for commercial sites?
Yes. Commercial sites can use sewage treatment systems, but they must be sized around project-specific PE, flow, organic load, peak use and discharge requirements.
Need help choosing a sewage treatment system?
Send Tricel your site location, project type, expected occupancy or PE, site assessment details and discharge route. The team can help identify the correct product route and advise whether your project requires a septic tank, sewage treatment plant, polishing filter, pumping station or commercial system.
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