Focus falls on country’s wetlands

Arecent column on alternative means of treating waste has attracted a deal of reaction, which is not surprising given the ongoing outcry about charges for septic tanks.

In that column, the focus was on integrated constructed wetland systems (ICW) which are working successfully in different parts of country and are dealing with waste from private houses, farms, and commercial enterprises. The systems involve the free flow of water through a number of ponds, with plants aiding the treatment process.

Undoubtedly, the debate will continue as the issue has such an important bearing on water quality and, indeed, the water we drink each day.

A Cork-based company, VESI Environmental Ltd, has more than 10 years’ experience in the design and construction of such systems, which are being flagged as an alternative to traditional septic tanks and other forms of waste treatment.

According to the company’s Aila Carty, the treatment levels can be better than 95% removal of organic matter, a figure we mentioned. The removal efficiency of an ICW can be greater than 99%, as shown in Glaslough, Co Monaghan, where a system has been built to cater for a population of 1,750 people, she points out.

Ms Carty says low temperatures do not unduly affect the process: “When discussing the disadvantages of ICWs, temperature, and specifically cooler conditions from our experience is not generally associated with lower efficiency.

“Freezing conditions can have some effect on performance. However, in this country, luckily, we don’t generally have to deal with any significant prolonged -00C conditions.It is true that discharges to surface water (stream, river etc) does require monitoring, however not all ICWs actually discharge to surface water and some can discharge to ground where conditions are suitable.”

Ms Carty says ICWs can be designed as “zero discharge” systems and where discharge to ground does not require a discharge licence.

VESI, based in Little Island, is in the construction phase of an ICW in Kilkenny that has been designed as a “zero discharge” system. The company is in the planning process for another in Co Monaghan.

“ICWs, like all on-site wastewater treatment systems, require maintenance. Studies have shown, in particular with larger wastewater treatment systems, that ICW have considerably lower costs to operate and maintain (up to 90% less) than conventional treatment systems,” Ms Carty says.

In terms of the large land area that must be used for a single dwelling, for example, the area required is approximately 100-150 sq m, Ms Carty says. An area less than that would reduce efficiency of the ICW to treat effluent, which is approximately the size of two traditional percolation areas, side by side.

Ms Carty says this is based on a house with four occupants and would not be regarded as excessive. The ICW can be incorporated into the garden and regarded as a landscape feature, which would not be the case with a traditional percolation area.

In relation to the Glaslough facility, she says the population equivalent is understood to be 1,400, instead of 700 as stated. The ICW there was designed to allow for future expansion. Glaslough also increased biodiversity in the area and has low maintenance and energy costs.

The success of systems in the Anne Valley, Co Waterford, has also been lauded and, she says, not only has there been a return of trout to the Annestown stream, but salmon parr have also been spotted in the watercourse.

Regarding the ICW at Kilmeaden, it was very successful when in operation treating 1300 sq m a day of wash waters from the facility and, at times, raw milk and whey. However, this ICW has since been decommissioned due to the closure of the factory in 2005 and the relocation of the Kilmeaden cheese processing to Glanbia in Co Kilkenny.

Separately, an An Taisce report has highlighted the potential of what could be described as natural wetlands, including those in flood plains and coastal areas, to relieve flooding. The heritage trust points out that flooding may become more frequent due to changing weather patterns.

The report, authored by Lauren Williams and Dr Simon Harrison, of UCC, states flood plains and coastal wetlands have the greatest potential to mitigate to deal with large-scale flood events.

There is also a need for a national policy on the use of wetlands, they stress. The main findings of the report are that wetlands can alleviate frequent low- to medium-scale floods by taking in excess water, as well as delaying run-off time.

They say that, at present, not enough attention is being paid to the value of wetlands when land use decisions are made — an issue which often gives rise to controversy, especially when roads and other developments are planned for wetland areas.