Wastewater Treatment
Sandcel
Sand polishing filters from Tricel (Sandcel) are secondary or tertiary treatment systems that comply with the Environmental Protection Agency’s (EPA) Code of Practice.
Wastewater treatment
Guide to Tricel Sandcel sand polishing filters
Overview
Tricel Sandcel panels are made from a composite material known as Sheet Moulding Compound, or SMC, a type of glass-reinforced plastic.
They are strong, durable, chemical-resistant, and impact-resistant, and the material will not rot or deteriorate over time.
Where should a sand polishing filter be used?
A sand polishing filter is used after a septic tank or wastewater treatment unit to treat further the effluent (based on ground requirements).
- Sand polishing filter as a secondary treatment system
If placed after a septic tank (primary treatment), a Tricel Sandcel is described as a secondary treatment system.
- Tertiary treatment system
If it is placed after a wastewater treatment plant (secondary treatment), the Sandcel is then described as a tertiary system.
How does a Sandcel sand polishing filter work?
Sandcel is a pipework system designed to direct wastewater to stratified layers of certified sands according to current EPA guidelines for effluent treatment.
A service pod is used to access all of the pipework in these filters, whether installed above or below ground.
Drawing of Sandcel as a tertiary treatment (following a Tricel Novo)
Close up to a Sandcel pipe network completed before final gravel layer is laid.
Sandcel filters all come with a service pod allowing access to the entire pipe network. To maintain pressure within the network, the laterals terminate in the pod and are capped and sealed. As a result, service and rodding are possible through the pipe system.
What are the benefits of using a sand polishing filter, and why should you use it or recommend it?
Sandcel’s sand polishing filter is suitable for homeowners, site assessors, and engineers alike because it meets a wide range of requirements.
Homeowners
- Ideal for smaller sites (only 16 m2 for an application with six people, reducing the need for a large percolation area).
- The Sandcel sand polishing filter blends into any garden design, as it can be buried, covered with soil, and planted with grass.
- Suitable for sensitive sites with a high level of treatment.
- Low maintenance requirements, maintenance contract available.
Site Assessors and Engineers
- Reduces the size of the percolation area, which is ideal for tight sites.
- Reduces the soil depth in your rock bed (free-draining soil); 900 mm is usually required.
- Constructed from high-quality materials (GRP panels, certified sand, gravel).
- Designed for high effluent treatment (using a sand polishing filter bed to ensure an even distribution of effluent around the entire bed).
- Ideal for sensitive areas (e.g., near a river or in a conservation area) thanks to a high quality of effluent treatment, which helps preserve the environment. Sandcel reduces nutrients discharged into the environment.
How to build a sand filter?
Sand polishing filters made by Tricel are constructed as follows:
- GRP panels
- Certified sands
- 10mm pea gravel
- Servicing pods
- Pipes
- Geotextile cover (as a top layer to block the soil from clogging the pipework)
Sand polishing filters are installed after a packaged wastewater treatment system or septic tank.
GRP panels
Layers of pea gravel and sands
Network of pipes and servicing pod
How deep does a Sandcel sand polishing filter go?
Depending on how much soil exists on-site, the Sandcel sand polishing filter can be installed above or below ground.
We recommend leaving 100mm between the top of the panels and the ground level to ensure enough soil to cover the pipes and promote grass growth.
Can a sand polishing filter be buried?
Sandcel sand polishing filters can be buried, but they must be placed 400mm above the bedrock or water table, whichever is higher. This prevents contamination of groundwater.
Sandcel Sand Polishing Filter being installed
Sandcel Sand Polishing Filter installed
How large is the base?
EPA Code of Practice tertiary distribution area formula determines the base size.
0.125 x PE x T = Area in m2
Standard sizes and dimensions of Tricel’s Sandcel Sand Polishing Filters
| Details | Sandcel 900 | Sandcel 1200 | Sandcel 1500 |
|---|---|---|---|
| Capacity (litres per day) | 900 | 1200 | 1500 |
| Length (mm) | 4000 | 4000 | 6350 |
| Width (mm) | 3850 | 5000 | 4000 |
| Depth (mm) | 1000 | 1000 | 1000 |
| Footprint (m2) | 15.4 (165.77 sq/ft) | 20 (215.28 sq/ft) | 25.4 (269.10 sq/ft) |
Gravel calculator for Tricel’s Sandcel. How to calculate how much gravel is required?
Use the illustration below (Sandcel stratified layers) as a reference for the calculator.
Note: these calculations only apply to Tertiary systems, so they are not appropriate when Sandcel is used as a secondary treatment system.
Step 1: Area calculator
A gravel distribution bed is required to disperse the treated effluent from the Sandcel. A 300mm layer of 10mm gravel should be used as the distribution bed.
For calculating the area, you must have available:
- the population equivalent (PE) value
- and the surface/subsurface value
For subsoil with a Subsurface/surface the distribution area is calculated using the below table from EPA Code of Practice 2021.
For example with a 6PE with a subsurface/surface value of 3-20
For a range of 3 < PV < 20, looking at the column “tertiary infiltration area (option 6)”, select the correct area required per person based on the subsurface/surface value. In our example, the value is >3.75 m2.
Then take your PE value (6) x per the area required per person (3.75m2) = 22.50m2 total required area.
Step 2: Base gravel calculator for Sandcel sand polishing filter
Using the formula below, you can calculate how much gravel you need for your site once you have calculated its area. Please note two tonnes of 10mm pea gravel is required per m3.
Formula = Area in m2 (calculated above) x 0.3 (300mm depth) x 2 (2 tonnes / m3).
Step 3: Sandcel infill gravel calculator
350mm of pea gravel sprayed over different layers (see above sketch of the Sandcel stratified layers) is required to fill in the inside of the GRP panels.
Formula = 350mm x area in m2 x 2 (2 tonnes / m3).
Total sand required for Sandcel installation = results step 2 + results step 3 = tonnes of 10mm pea gravel required.
Gravel requirements for standard size Sandcel sand polishing filters
See below examples of standard Sandcel dimensions and gravel quantities in tonnes.
INFILL
NOTE: Dimensions add 150mm to the below dimensions to include the GRP panel enclosure
| Dimensions of the area | Sandcel 900 | Sandcel 1200 | Sandcel 1500 | Sandcel 1800 |
|---|---|---|---|---|
| 3850mm * 4000mm | 6.08m3 or 13 tonne | |||
| 5000mm * 4000mm | 8m3 or 16 tonne | |||
| 6350mm * 4000mm | 10.4m3 or 21 tonne | |||
| 7500mm * 4000mm | 12m3 or 24 tonne |
Who supplies the sands and gravel?
Builders and installers are responsible for pea gravel during a Tricel Sandcel installation, while Tricel is responsible for the sand. Sand used throughout has been certified compliant with the EPA Code of Practice, and these particles are washed and graded to ensure that little or no binding occurs during use.
Tricel is responsible for the delivery and installation of the Sandcel sand polishing filter.
The contractor carries out all other works, such as excavation, concrete surround, pumping main, etc.
Images of an installation
Base gravel & panels assembled & first Layer of Sand, Placed
First Layer of Pea Gravel, Placed
Second Layer of Sand, Placed
Second Layer of Pea Gravel, being placed
Final Layer of Sand, Placed
Base layer of gravel distribution layer and distribution pipework
Gravel capping layer & geotextile
Gravel capping layer & geotextile
Key Features
Reliable & long-lasting
SMC panels, strong & lightweight
Fast delivery
Manufactured in Ireland, short lead time
Certified
Designed to the EPA Code of Practice
Get in touch
HQ
Tricel (Killarney) Unlimited Company
Ballyspillane Industrial Estate, Killarney, Co. Kerry, V93 PN84, Ireland
Tel: 00353 (0)64 6632421