Wastewater Treatment

Pressurised percolation

A pressurised system distributes treated wastewater by discharging it through a system of small diameter pipes. The distribution network is made up of a supply manifold and specially designed and drilled distribution pipes. The wastewater is pumped at pressure from the treatment tank, ensuring it flows to all points of the network. This pipe network is laid out on a bed of stone and subsoil, covered with a geo-textile membrane and covered with topsoil.

Pressurised systems are particularly useful in raised percolation beds. Raised beds are constructed by creating a mound on top of the normal ground level using imported soil of suitable percolation characteristics. They are installed where difficult site conditions such as high water table, insufficient subsoil depth or poor percolation characteristics are encountered.

Pressurised percolation

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Pressurised kits supplied by Molloy include:

Manifold

Specially drilled 32mm distribution pipes

Geo-textile membrane cover

Installation and best practice manual

Delivery and/or installation of pressurised kits is available throughout the country.

These kits are normally used in conjunction with secondary treatment systems. Usually the pump included in our AswaFlow treatment system can be used to feed the pipe network, however, distance from the system, height above the system and size of the pipe network may prevent this. In these circumstances we recommend the installation of a larger pump fitted inside a separate pump chamber which can also be supplied by Molloy Precast.


Sizes

Each system is designed to be site specific. Size and layouts are dependent on the occupancy of the dwelling and the permeability of the soil. The following table outlines the minimum required bed sizes (EPA CoP, 2009).

P-T Values Loading rate on plan area (l/sq. m/day) Area required per PE (sq. m)
    4 5 6 7 8 10 12
3-20 ≤20 30 37.5 45 52.5 60 75 90
21-40 ≤10 60 75 90 105 120 150 180
41-50 ≤5 120 150 180 210 240 300 360
51-75 ≤3 200 250 300 350 400 500 600
(EPA, CoP, 2009)

Further Information

Generic drawings are available. Site specific drawings can also be prepared on request. For further information do not hesitate to contact our design team. We would also strongly recommend a visit to our interactive training and display facility where you can see exactly how a pressurised system is constructed and operates.

Trench percolation

A trench percolation system uses a series of specially designed 4" perforated pipes in stone lined trenches to distribute treated effluent to the subsoil, where it undergoes further treatment. Each pipe is connected to a single distribution box which evenly distributes the wastewater between each trench. A permeable geo-textile membrane covers the stone trench, preventing clay from the top soil from washing down and sealing drainage paths.

Distribution of water along the trench relies on gravity, therefore accurate levels are critical. As this can be difficult to achieve in long trenches, Molloy Precast recommend that a gravity system and hence a trench system is not installed for trench lengths greater than 100m.

Trench percolation

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Trench kits supplied by Molloy include:

Distribution box and accessories

Specially designed 4” distribution pipes

Geo-textile membrane cover

Installation and best practice manual


Sizing

The design of a percolation area will vary with both the site characteristics and method of wastewater treatment. The minimum design requirements are stated in the following tables, as per EPA Code of Practice for Wastewater Treatment and Disposal Systems Serving Single Houses, 2009. For this reason, each design should be site specific.

Minimum Percolation Trench Length Required with Secondary Treatment Input
P-T Values Percolation Trench Discharge Trench Length Required per no. of People (m)
    4 5 6 7 8 10 12
3-21 ≤50 24 30 36 42 48 60 72
21-40 ≤25 48 60 72 84 96 120 144
41-50 ≤25 48 60 72 84 96 120 144
51-75 ≤16 75 94 113 131 150 188 225
10m Maximum Trench Length (EPA, CoP, 2009)

Further Information

For further information do not hesitate to contact our design team. We would also strongly recommend a visit to our interactive training and display facility where you can see exactly how a trench system is constructed and operates.

Tertiary Treatment Systems

Chieftain® Coco Filter

Local Authorities may specify higher effluent quality levels in specific circumstances. Tertiary treatment is used as a means to treat wastewater to high quality prior to discharge to a sensitive area or water course. We at Molloy Precast are delighted to design, manufacture and install solutions for such circumstances. We have developed a range of design solutions.

Chieftain® Coco Filter

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Why a Chieftain Coco Filter?

Off-the-shelf design - a ready to install packaged tertiary treatment system

Easy to install - no high skilled installation procedures required

Ready to go design - just place on the infiltration/dispersal pad and connect the inlet pipe

Compact - this system has a reduced footprint compared to a sand polishing filter

Available in 8PE and 15PE modules

You should consider if...

You are in need of a tertiary treatment filter

You want to reduce the footprint from a soil polishing filter

You have a small site

Your site has a high water table or bedrock. This system could potentially eliminate the need for a raised bed.

Available in 8PE and 15PE modules

Achieveable results

Parameters BOD5 TSS Ammonia
Influent mg/l 50 ± 14 40 ± 10 20 ± 2
Treated effluent mg/l 7 ± 1 3 ± 1 3 ± 2
Parameters E.coli Enterococci
% Reduction 97.35% 98.22%
Third party testing of the Chieftain® Coco Filter for Tertiary Treatment by the National University of Ireland Galway NUIG

Downloads

System Type PE ID PDF drawing
8PE Coco Chieftain Coco filter 8 Coco_8PE_01_211119 Download
8PE Coco Chieftain Coco filter 8 Coco_8PE_02_211119 Download
15PE Coco Chieftain Coco filter 15 Coco_15PE_02_211119 Download
15PE Coco Chieftain Coco filter 15 Coco_15PE_01_211119 Download

Other Tertiary Systems

Local Authorities may specify higher effluent quality levels in specific circumstances. Tertiary treatment is used as a means to treat wastewater to high quality prior to discharge to a sensitive area or water course. We at Molloy Precast are delighted to design, manufacture and install solutions for such circumstances. We have developed a range of design solutions.

Sand Filters

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A sand filter consists of several layers of graded sand. Wastewater is distributed evenly over the filter's surface. It then percolates through the sand, where it is treated by a biofilm within the system. The effluent from the system will be clarified to the required standard. Molloy Precast provide the following services:

A system designed to suit your needs

Systems can be housed in one of our precast tanks or in an in-situ built tank

Specially designed 4” distribution pipes

Sand filters can be used in conjunction with the Aswaflow wastewater treatment system

Delivery and/or installation of sand filters is available throughout the country.


Sizing

Each system is designed to be site specific. Size and layouts are dependent on the occupancy of the dwelling and the effluent quality. We have standard systems for different sizes; however, our team would be happy to design and manufacture kits to suit your site with regard to size and layout. We also offer an installation service.

Further Information

Generic drawings are available. Site specific drawings can also be prepared on request. For further information do not hesitate to contact our design team. We would also strongly recommend a visit to our interactive training and display facility where you can see exactly how a tertiary treatment unit is constructed and operates.


Questions about percolation and tertiary treatment?

Get in touch and we can help.