flota in Carthagin. translacio

Toxicity tests consist in exposing test organisms to an environment (here an original or diluted waste water sample) to determine the effects on physiological properties, survival, growth or reproduction. Different organisms representing distinct trophic levels are used including algae, bacteria, plants, invertebrates, fish and fish eggs. Toxicity tests are carried out in laboratories (also called laboratory bioassays) where test organisms (mainly from standardised cultures) are exposed to waste water that has been transferred to the laboratory.

Table 3.5 presents examples of available standard methods that can be used to conduct toxicity tests.

Table 3.5: Example of standard methods that can be used to conduct toxicity tests

Test organisms Standards

Algae

EN ISO 8692:2012; Water quality – Freshwater algal growth inhibition test with unicellular green algae

EN ISO 10253:2006; Water quality – Marine algal growth inhibition test with Skeletonema costatum and Phaeodactylum tricornutum

EN ISO 10710:2013; Water quality – Growth inhibition test with the marine and brackish water macroalga Ceramium tenuicorne

Bacteria

EN ISO 11348–1 to –3:2008; Water quality – Determination of the inhibitory effect of water samples on the light emission of Vibrio fischeri (Luminescent bacteria test) – Part 1: Method using freshly prepared bacteria, Part 2: Method using liquid-dried bacteria, Part 3: Method using freeze-dried bacteria

EN ISO 10712:1995; Water quality – Pseudomonas putida growth inhibition test (Pseudomonas cell multiplication inhibition test)

ISO 11350:2012; Water quality – Determination of the genotoxicity of water and waste water – Salmonella/microsome fluctuation test (Ames fluctuation test) ISO 15522:1999; Water quality – Determination of the inhibitory effect of water constituents on the growth of activated sludge microorganisms

ISO 13829:2000; Water quality – Determination of the genotoxicity of water and waste water using the umu-test

Plants EN ISO 20079:2006; Water quality – Determination of the toxic effect of water constituents and waste water on duckweed (Lemna minor) – Duckweed growth inhibition test

Rotifers ISO 20666:2008; Water quality – Determination of the chronic toxicity to Brachionus calyciflorus in 48 hours

Crustaceans

EN ISO 6341:2012; Water quality – Determination of the inhibition of the mobility of Daphnia magna Straus (Cladocera, Crustacea) – Acute toxicity test ISO 10706:2000; Water quality – Determination of long term toxicity of substances to Daphnia magna Straus (Cladocera, Crustacea)

ISO 20665:2008; Water quality – Determination of the chronic toxicity to Ceriodaphnia dubia

ISO 14669:1999; Water quality – Determination of acute lethal toxicity to marine copepods (Copepoda, Crustacea)

Fish and fish eggs

EN ISO 7346–1:1997; Water quality – Determination of the acute lethal toxicity of substances to a freshwater fish Brachydanio rerio Hamilton-Buchanan (Teleostei, Cyprinidae) – Part 1: Static method, Part 2: Semi-static method, Part 3: Flow-through method

EN ISO 15088:2008; Water quality – Determination of the acute toxicity of waste water to zebrafish eggs (Danio rerio)

In stream bioassays, living organisms (e.g. fish) are placed into the water stream to be studied (e.g. in cages upstream and downstream of effluent discharges). Stream bioassays are at an experimental stage.

The use of toxicity tests is less comprehensive than whole effluent assessment (WEA, see Section 3.2.2.3) which also includes persistence and bioaccumulation.

Achieved environmental benefits

Toxicity tests allow for an integrated assessment of the properties of a waste water sample (including synergistic/antagonistic effects) that cannot be achieved by analysing single substances or other chemical sum parameters. They provide the basis for measures to control pollution and to minimise the ecotoxic impact of waste water effluents.

Operational data

There is a lot of experience with toxicity measurements and two different procedures are usually applied for the evaluation of toxicity data:

 Response concentration. The ECX/LCX (effect/lethal concentration) approach using statistical data analysis where at least five data pairs of concentration/response between 0 % and 100 % response are needed. Typical results are EC50, EC20 or EC10, the concentration that has a particular effect on 50 %, 20 % or 10 % of the population. The ECX/LCX methodology is usually applied to single substances. However, dilution values for a water sample representing a given response level can in principle also be obtained from the LID approach (see below) as described in ISO TS 20281 [ 100, ISO 2006 ].

 Threshold concentration. The concentration having no statistically significant adverse effect is the no observed adverse effect concentration (NOAEC). In the case of waste water, the concentration of the substance(s) is generally not known. The LID (Lowest Ineffective Dilution) approach therefore uses dilutions of the original waste water with defined ratios of sample and dilution water until no effects are observed. A statistical evaluation of the concentration/response relationship is not necessary, because a yes/no-type decision is made with regard to the defined effect level described in the respective standard (usually 10 % or 20 % effect in comparison to test control). This makes the test design concerning the test concentrations easier. Statistical requirements for the calculation of EC values are often not met for moderately toxic samples. LID values are used for monitoring the total waste water effluents of many German chemical sites [ 105, COM 2006 ].

Toxicity data may also be expressed as toxic units (TU), an acute toxic unit TUa being 100/EC50, and a chronic toxic unit TUc being 100/NOAEC or 100/EC10.

Chronic toxicity tests are less widespread than acute toxicity tests and short-term chronic tests are to be preferred in order to avoid any possible change in the characteristics of the effluent during the test [ 146, TOTAL 2009 ].

Toxicity tests are generally used in at least five EU Member States for setting emission limit values (ELVs) [ 139, COHIBA 2010 ]:

 Germany: Five different toxicity tests are used in combination for all chemical sites (fish egg, daphnia, algae, luminescent bacteria, genotoxicity). These tests have been in use since 1999. Toxicity tests with fish were already used since the late 1980s [ 65, OSPAR 2000 ] [ 105, COM 2006 ] [ 135, LANUV NRW 2009 ].

 Ireland has mandatory ELVs in terms of toxicity units for direct discharges from IED plants. Toxicity tests may also be required for indirect discharges.

 Austria has mandatory ELVs for toxicity for several subsectors of the chemical industry.

Up to four toxicity tests are used in combination (fish, daphnia, algae, and luminescent bacteria).

 Lithuania requires effluents entering surface waters to pass acute daphnia tests.

 Italy has obligatory acute toxicity tests (e.g. with daphnia, algae or luminescent bacteria).

The legal consequences of exceeding an emission limit value are, however, less stringent than for other parameters.

Furthermore, other EU Member States sometimes use toxicity tests in permits: Flanders (Belgium), Denmark, Finland and Sweden.

In the course of the last twenty years, biomonitoring in Germany resulted in thousands of biotest data from the chemical industry. Recent results can be found in [ 135, LANUV NRW 2009 ].

Earlier statistics can be found in the LVOC BREF [ 104, COM 2003 ].

Experience of some years shows that [ 105, COM 2006 ]:

 generally, the data derived from using different test species (algae, daphnia, bacteria, fish eggs) complement each other;

 even at a larger complex production site, it is usually technically possible to identify the cause of residual acute toxicity and to minimise the effects;

 the sampling frequency should correspond to the frequency of changes in the production spectrum (in the given example [ 105, COM 2006 ], 20 samples were tested per year).

Applicability

Toxicity tests are especially applicable where other parameters indicate variations in the performance of the biological WWTP or where toxicity is already identified as a major concern due to the production spectrum (e.g. biologically active ingredients).

This technique is generally applicable to identify situations where a production site has an inherent toxicity problem which is not easily identified by the observation of other parameters.

The monitoring frequency for toxicity tests may be based on a risk assessment, after an initial characterisation.

Toxicity tests are rarely carried out online. The time needed to obtain the results, typically between 24 hours and 96 hours, does not allow the waste water treatment to be directly controlled.

Economics

Economic factors include:

 costs for sampling and measurements;

 high value of the obtained information.

Driving force for implementation

Reducing the residual acute toxicity in effluents is the driving force for implementing the technique.

Example plants

Toxicity tests of waste water effluents are used at chemical sites in a number of EU Member States.

Reference literature

[ 65, OSPAR 2000 ] [ 100, ISO 2006 ] [ 104, COM 2003 ] [ 105, COM 2006 ] [ 135, LANUV NRW 2009 ] [ 139, COHIBA 2010 ] [ 146, TOTAL 2009 ]

3.2.2.3 Whole effluent assessment (WEA)