I ask Leitrim County Council what specific parts of the proposed system for the Zero Discharge Pilot Scheme are not tried and tested already and need to be studied to see if it is a workable solution for sites which fail a T-Test.
Minutes:
To consider the following Notice of Motion submitted by Councillor Brendan Barry;
"I ask Leitrim County Council what specific parts of the proposed system for the Zero Discharge Pilot Scheme are not tried and tested already and need to be studied to see if it is a workable solution for sites which fail a T-Test."
Report by Director of Services for Economic Development, Planning, Environment and Transportation.
"On-site wastewater treatment systems, comprising standard septic tank/percolation area or some form of packaged wastewater treatment system, are reliant on the ground characteristics of any particular site. With such systems the ground receives the treated effluent, which still contains biological and chemical contaminants. These contaminants are subsequently ‘polished’ out as the effluent flows through the ground. This is an essential part of the treatment process and is required to ensure that such contaminants do not enter ground or surface water bodies in the area. In order for the ground to act as an integral part of the treatment process it must be capable of percolating the discharged effluent at within a specified range – i.e., the effluent must be able to ‘flow’ through the ground at a particular rate in order for the effluent to be ‘polished’. It is also necessary that the area where such polishing of the effluent takes place is separated by a minimum distance from the underlying water table to ensure that no un-polished effluent enters the underlying ground waters.
On-site wastewater treatment systems are problematic for large areas of county Leitrim due to either too high water tables or the soils are too dense and have percolation values that exceed the maximum values set out in the Environmental Protection Agency’s Code of Practice for Waste Water Systems for Domestic Waste Water Treatment Systems (Population Equivalent = 10) which provides guidance on domestic waste water treatment systems (DWWTSs) for single houses or equivalent developments with a population equivalent (PE) of less than or equal to 10. The Code sets out a methodology for site assessment and selection, installation, and maintenance of an appropriate DWWTS. The requirement to comply with the Code of Practice is further stipulated by Part H of the Building Regulations and the European Union Construction Products Regulations.
Where ground conditions permit, the use of standard on site wastewater treatment systems does not pose any problems and such systems and technologies are recognised as being ‘tried and tested’. (Assuming the particular system has been designed specifically for any particular site and correctly installed).
Where ground conditions do not permit the use of such standard systems, the possibility of using zero-discharge systems is being considered. Evapotranspiration (ET) is a method of onsite wastewater treatment and disposal that offers an alternative to conventional soil absorption systems for sites where protection of the surface water and groundwater is essential. An ET system disposes of wastewater into the atmosphere through evaporation from the soil surface and/or transpiration by plants, without discharging wastewater to the surface water or groundwater reservoir. Evapotranspiration is the net water loss caused by evaporation of moisture from the soil surface and transpiration by vegetation. The main components are a pre-treatment unit (usually a septic tank or an aerobic unit) used to remove settleable and floatable solids and an ET sand bed with wastewater distribution piping, a bed liner, fill material, monitoring wells and overflow protection. Vegetation must be planted on the surface of the bed to enhance the transpiration process. The septic tank effluent flows into the lower portion of a sealed ET bed equipped with continuous impermeable liners and carefully selected sands. Capillary action in the sand causes the wastewater to rise to the surface and escape through evaporation as water vapor. In addition, vegetation transports the wastewater from the root zone to the leaves, where it is transpired as a relatively clean condensate. This design allows for complete wastewater evaporation and transpiration with no discharge to nearby soil.
Whilst these zero-discharge systems have been found effective in other countries, the study aims to look at whether the evapotranspiration method is suitable for use in Ireland having regard to our climatic conditions.
There is need to have the testing and certification of such zero-disposal type facility that has the potential to have no (zero) discharge of effluent carried out. This process involves the design and operation of a system in the Irish context. In order to provide for testing and certification, of this identified process, the installation of a limited number such systems can be facilitated by Leitrim County Council as Planning Authority, subject to all other matters relating achieving a grant of planning permission in rural Leitrim, as required by the current Leitrim County Development Plan. The Council is working in collaboration with Trinity College Researchers in order to further the specific design and potential testing of systems subject to securing the financial resources to fund this research.
The successful testing of such a facility would be of obvious importance to the County."
Councillor Barry’s acknowledged the detailed reply to his Notice of Motion. A detailed discussion on the Zero Discharge Scheme ensued.
Councillor Ita Reynolds-Flynn thanked Councillor Barry and Councillor O’Rourke for their research into the subject. It was agreed that the matter should be raised at a Council meeting to have the full agreement of all the members on how to proceed.
As Councillor Gerry Dolan was absent from the meeting at this point, it was agreed that Councillor Enda McGloin would move Councillor Dolan’s Notices of Motion’s.