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The Shannon
Regional Fisheries Board
Aquatic
Environment - Living in the Shannon Catchment
Septic
Tanks and the Environment
 The river Shannon together with its lakes and
tributaries, is an important part of Ireland's wonderful natural
heritage. Those of us who live and work in the catchment of the river
have a special duty to protect water quality. Clean water is essential
for all life - plants, animals and of course ourselves. It is up to us
all all to do what we can to preserve the Shannon for future
generations.
The main threat to the Shannon comes from an increase in
the amount of nutrients, including phosphates being released into the
water. An excess of nutients in the water leads to increased algal
growth, which often results in algal blooms in summertime. The algae in
turn uses up oxygen in the water reducing its capacity to support fish
life. These nutrients come from a number of sources including
agricultural, industrial and domestic.
According to the Lough Derg and Ree Catchment Monitoring
and Management System, a population of about 157,000 in the catchment ar
not connected to a public sewerage system. The vast majority of these
rely on septic tanks to treat their wastewater.
Conventional septic tank systems (septic tanks and
percolation area), properly installed and maintained, are satisfactory
where suitable subsoil conditions exist.
However, the Environmental Protection Agency(EPA) has
stated that a significant number of septic tank systems do not function
properly. This is mainly because they have been poorly constructed,
installed, operated, maintained or located in areas with unsuitable sub
soils, or the percolation area is inadequate.
There are a number of alternatives to relaying solely on
a conventional septic tank system, these include:
Constructed Wetlands
Wetlands are areas with high water tables, which
promote aquatic vegetation or water tolerant plants such as reeds.
Primary treatment by a septic tank is used prior to discharge to a
constructed wetland.
Compost Toilets
These toilets require no water and turn the waste into
compost, which can be re-used in the garden. Of course they only treat
toilet waste and must be used in conjunction with some alternative
treatment for other wastewater.
Filter Systems
Where the subsoil is unsuitable for treating the
wastewater from a septic tank, filter systems may be used. These include
intermittent soil filters, sand filters, peat filters and otherfilters
using materials such as plastic foam filters and geo-synthetic strips
Mechanical Aeration Systems
There are several different types of mechanical aeration
systems available. These can be used on a site which is unsuitable for a
septic tank. Systems available include: biofilm aerated (BAF), rotating
biological contactor (RBC), SEQUENCING BATCH REACTORS (SBR)
SEPTIC TANKS - DO'S AND DONT'S
DO consult the EPA Manual, Treatment Systems for Single
Houses before constructing a septic tank
DO construct a tank and percolation area in accordance
with regulations
DO desludge when necessary
DON'T site a septic tank or percolation area within 10
metres of a watercourse or stream, or 50 meters from a lake.
DON'T allow pesticides, paints, thinners, solvents,
disinfectants, or household hazardous substances to discharge into the
tank
DON'T allow rainwater to enter the tank.
For further information see
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Wastewater Treatment Manuals - Treatment Systems for
Single houses - EPA 2000
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Groundwater Protection Responses for On-Site Systems for
Single Houses - Geographical Survey of Ireland, Dublin
Websites
NB: You can request this brochure by contacting our Limerick
Office - see below or the Angling Section Email
info@shannon-fishery-board.ie
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