Groundwater vulnerability and protection in County Tipperary (South Riding), Ireland

The aim of the project was to determine the extent and quality of the groundwater in Tipperary South Riding with a view to developing a groundwater protection plan which would allow the Local Authority to manage, protect and develop the groundwater as efficiently as possible. The geology of the area varies with topography. The low-lying areas of the county comprise mainly Carboniferous limestones while the elevated regions consist of sandstones and shales of Upper Carboniferous, Devonian and Silurian ages. Deformation of these rocks decreases in magnitude moving northwards over the area; the Southern Synclines having suffered the effects of the Hercynian orogeny and the northern region exhibiting Caledonian orogenic trends. Quaternary (subsoil) deposits are found throughout the area and are of variable thickness and permeability. Till is the most widespread deposit with discontinuous pockets of sand and gravel in various proportions, and some marl, alluvium and peat in places. The principal aquifers of the area are the Kiltorcan sandstone formation and various limestone units within the Carboniferous succession. 50 % of south Tipperary constitutes either regionally or locally important aquifers. Secondary permeabilities created by structural deformation, dolomitisation, karstification and weathering processes create high transmissivities and often have large well yields. Specific baseflow analysis highlighted the complexity of the aquifers and proved that the lower part of the Suir river system is a major groundwater resource region. The hydrochemistry and water quality of the local authority groundwater sources was examined briefly. The majority of south Tipperary is underlain by limestone or Quaternary deposits derived from limestone and, consequently, calcium/magnesium bicarbonate waters predominate. The quality of the groundwater in south Tipperary demonstrates that the main concern originates from the presence of E.coli, and Total coliforms. The primary sources of contamination are from farmyard wastes and septic tanks. The vulnerability of groundwater to diffuse and point sources of pollution has been found to be dependent on the overlying soil, subsoil and the thickness of the unsaturated zone. A conceptual rather than quantitative approach is used and it is found that approximately 60% of south Tipperary is designated as being extremely or highly vulnerable. The groundwater protection plan was devised subsequent to an understanding of the aquifer systems, an assessment of the vulnerability, and a review of the Irish planning system and environmental law. It is recommended that the plan be integrated into the county development plan for legislative purposes. A series of acceptability matrices were devised to restrict potentially polluting activities in vulnerable areas while maintaining a balance between protection of the groundwater resource and the need to site essential developments.

Development of a rehabilitation system for the red mud waste generated at the Aughinish Alumina Bayer Plant

Aughinish Alumina Limited (AAL) have an obligation by terms of their Integrated Pollution Control Licence (IPCL) and Planning Permission to establish vegetation on the red mud stack at their plant at Aughinish, Co. Limerick. High pH and high exchangeable sodium percentage are the main known factors limiting the establishment of vegetation on red mud. Gypsum addition has been known to assist in alleviating these problems in other countries. However, there is no experience or published information on red mud rehabilitation under Irish conditions. Red mud with organic and inorganic waste-derived ameliorants as well as selected grassland species were examined under laboratory controlled environment conditions as well as in field plot trials. Also, in order that it would be economically achievable, the research utilised locally available waste products as the organic amendments. Screening trials found that physical constraints severely limit plant germination and growth in red mud. Gypsum addition effectively lowers pH, exchangeable sodium percentage and the availability of A1 and Fe in the mud. A strong relationship between pH, ESP and A1 levels was also found. Gypsum addition increased germination percentages and plant growth for all species investigated. Greenhouse trials demonstrated that organic wastes alone did not greatly improve conditions for plant growth but when used in conjunction with gypsum plant performances for all species investigated was significantly increased. There was a high mortality rate for grasses in non-gypsum treatments. An emerging trend of preferential iron uptake and calcium deficiency in non-gypsum treatments was found at pot screening stage. Species also displayed manganese and magnesium deficiencies.

The production of vermicompost from dairy sludge and its value as a plant growth medium

Dairy sludge generated at Glanbia Ingredients Ltd., Kilkenny has up until now been landspread. This study investigated the feasibility of using earthworms to vermicompost the sludge as an alternative method of treatment. It was found that high levels of ammonia in the sludge led to earthworm fatality but that by manually aerating the sludge the ammonia could be volatilised or by adding zeolite the ammonia could be absorbed, thus solving the problem. In a medium scale trial, the earthworm species Dendrobaena veneta and Eisenia fetida dominated the polyculture. Earthworms grew and generated cocoons during vermicomposting. During vermicomposting no leachate was generated. Nutrient changes took place during vermicomposting. There were high levels of nitrate, increased calcium and sulphate in the vermicomposted dairy sludge. The amount of magnesium, potassium and chloride did not change, while phosphate was undetectable after vermicomposting. The levels of nitrate and phosphate were good indicators of the extent of vermicomposting. The vermicomposted dairy sludge provided improved growth and yields of radishes and barley compared to the dairy sludge and control. Compared to the vermicompost, the dairy sludge provided heavier ryegrass yields and more marigolds with larger flower diameters. Generally, it is the amount of phosphate in dairy sludge that dictates how much can be applied as a fertiliser on land. Vermicomposting reduced the amount of phosphate to an undetectable level but on the other hand created a problem of high nitrate levels. In a pot trial with grass grown in vermicompost the nitrate leached from the vermicompost. In field conditions the leaching of nitrate might occur and could cause an increased risk of contamination of groundwater and watercourses.