Aquatic Toxicity Testing in Ireland – A review of 2011

How do we know a substance is hazardous to the aquatic environment?
According to EC Regulation 1272/2008 on the classification, labelling and packaging of substances and mixtures, and EC Regulation 1907/2006 on the Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH), a substance is hazardous if it is Persistent, Bio-accumulates and is Toxic (PBT).

Assessment of whether a substance is toxic is based on aquatic toxicity testing using a variety of fish, crustaceans and algae.

The Shannon Aquatic Toxicity Laboratory (SATL) has extensive experience in toxicity testing, and provides a nation-wide service to industry, local authorities and state agencies.

Aquatic toxicity tests can be used for the following purposes:

  • Determining compliance with IPPC/WWDA/Local authority licenses
  • Classification, Labelling and Packaging Regulations
  • ADR Regulations
  • Hazardous Waste Classification
  • Determination of the toxicity of individual waste streams within a process (Toxicity Identification Evaluation – TIE)
  • Determination of the most appropriate waste treatment options (Toxicity Reduction Evaluation – TRE)

The EPA has been using aquatic toxicity tests to assess compliance of effluent discharges since 1992 in conjunction with the more conventional substance-by-substance approach. The tests are applied to complex discharges to measure the effect of the whole effluent. The EPA has, so far, issued approximately 800 IPPC licences and some 25% of these have a toxicity limit.

Effluents tested in the laboratory in 2011 came from a variety of industrial categories:

  • 44% – Chemical Industry,
  • 18% – Local Authority wastewater treatment plants.
  • 6% – Local Authorities/Consultants,
  • 6% – Food and Drink Industry.
  • The remaining samples were from enterprises producing energy, metals, mineral fibres and glass, wood, paper, textiles and leather, fossil fuels and cement.

These effluents are discharged to freshwater (35%), estuarine (3%), marine (24%) systems and, increasingly, to waste water treatment plants (30%).

All toxicity limits contained in Irish discharge licenses (IPPC/WWDA/Local authority licenses) are expressed in Toxic units (TU), where
TU = 100/EC50
(EC50 is the Effective Concentration that causes an effect to 50% of the test organisms)

In the majority of IPPC licences, the toxicity limit is 10 Toxic units.

In 2011, 10% of effluent samples failed at least one test where the result was >10 Toxic units.

Generally, it is found that fish are the least sensitive test species and marine algae are most sensitive.

The toxicity results for all the effluents tested in 2010 are shown in Table 1.

The table shows that the marine alga Skeletonema costatum was the most sensitive species followed by the marine copepod Tisbe battagliai. Using the other species, more than 90% of samples complied with the 10 Toxic unit limit.

In cases where the effluent sample fails the emission limit value further tests can be carried out to identify the substance(s) causing the toxicity (TIE) or to determine the most appropriate effluent treatment (TRE).

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