Whole effluent assessment (WEA) DescriptionDescription

Chemicals which are persistent, liable to bioaccumulation and/or toxic (PBT) are of specific concern to the aquatic environment. WEA aims at estimating the persistency, bioaccumulation potential and toxicity of waste water as a whole. In contrast to this, the substance-orientated approach focuses on measuring hazardous substances that have been selected and prioritised using the PBT criteria.

The aim of WEA is to assess the possibly hazardous character of effluents, which would be insufficiently controlled when relying only on the physical and chemical indications provided

The advantages of using WEA are as follows:

 All waste water compounds are considered regardless of their origin. The compounds do not necessarily need to be identified. Side products and metabolites are assessed as well.

 Toxic effects on aquatic organisms are directly displayed; combined/synergistic effects of several compounds are also considered.

 The sources of hazardous effluents (production steps or hot spots) inside industrial areas can often be identified (backtracking).

Generally, WEA can be used as a tool within an EMS (see Section 3.1.2). WEA can be one of the measures used in an effluent stream inventory/register as described in Section 3.1.5.2.3.

Achieved environmental benefits

WEA allows for a way to monitor complex and variable waste water effluents including the possible synergistic effects of chemicals.

Cross-media effects

Some equipment, chemicals and energy are required for carrying out WEA. Some toxicity tests affect animal welfare (e.g. toxicity tests using fish).

Operational data

Test methods and test sequences

The methodology of WEA is aimed at determining possible adverse effects of effluents and addresses basically the same effect measurements (PBT) that are used in a substance-orientated approach.

Persistence is typically studied in 28-day biological degradability tests, and gives information on whether the biotreatment already given is adequate or whether such treatment should be considered for untreated waste water. It is often quantified by measurements of dissolved organic carbon (DOC), but CO2 evolution is an alternative and there are others (see ISO/TR 15462:1997 Water quality – Selection of tests for biodegradability). Furthermore, if followed by toxicity tests, an indication of the potential for the reduction of toxicity is given.

Liability to bioaccumulate is often measured (both before and after biodegradation) by chemical analysis showing a partition of an extract of the sample between water and a less polar phase (liquid/liquid extraction (LLE)), alternatively directly extracting the sample with a solid phase polymer (solid-phase microextraction (SPME)). Quantification is done by gas or liquid chromatography.

Toxicity tests are described in Section 3.2.2.2. The advantage of using toxicity tests over chemical analyses of single substances is that the hazardous properties of the water samples are determined in an integrated manner and interactive/synergistic effects which may occur in the presence of several pollutants are directly accounted for. In some cases, toxicity tests could be quicker and cheaper than extensive chemical characterisation associated with ecotoxicological characteristics and thereby simplify regulation.

The application of WEA presents challenges for the scientific community. They include the following:

 A dominating focus on the toxicity component of PBT in combination with a lack of agreement on standardised tests for bioaccumulation and persistence.

 The protection of sediments is taken into account in WEA thanks to the PB substances that are likely to adsorb on sediments; the food chain exposure is taken into account in the bioaccumulation tests. Some methods are under standardisation in ISO to assess adverse effects on soil (e.g. determination of fresh water sediment chronic toxicity to

on growth, fertility and reproduction of Caenorhabditis elegans; determination of the toxic effect of sediment and soil on the growth behaviour of Myriophyllum aquaticum).

 Finding laboratories that are competent to routinely run WEA tests. The availability of the laboratory is an issue because the effluent samples refrigerated for 24 hours must be tested as soon as they arrive at the laboratory; the effect of freezing on effluent bioaccumulation, persistence and on acute and chronic toxicity cannot be disregarded [ 146, TOTAL 2009 ]. Good planning and coordination between the operator of the installation and the laboratory is key to the successful application of WEA tests.

It is therefore important to communicate the results of WEA testing with an adequate account of the effluent sampling, applied test methods, and the statistical analyses applied to the data.

Further agreement on such issues has been reached in the last decade, however work is still required in particular concerning bioaccumulation and degradability methods.

Applicability

Below, the reader will find the potential applications of WEA divided into sections with a brief description of each.

Regulations or guidance on effluent ecotoxicity

Some jurisdictions set numerical ecotoxicity criteria in discharge permits, while others use ecotoxicity data as a planning and assessment tool (see Section 3.2.2.2). Establishing ecotoxicity criteria ensures consistent evaluation of effluents: enforcement or management action is usually taken only when the effluent repeatedly fails the ecotoxicity criteria. Alternatively, less formal approaches to using ecotoxicity data can reduce uncertainties about the risks of effluent discharge by complementing conventional chemical effluent data. In addition to ecotoxicity data, evaluations of persistence and bioaccumulation can be used in the same way [ 35, De Maagd 2000 ].

Ranking the environmental risk of discharges to an aquatic system

WEA can be used to evaluate relative risks posed by multiple discharges with the objective of prioritising attention where it is needed.

Toxicity identification/reduction evaluations (TIE/TRE)

TIE/TRE are used to determine why an effluent is toxic and what can be done to reduce that toxicity to an acceptable level. TRE can be defined as site-specific studies conducted in a step-wise procedure designed to [ 27, US EPA 1991 ]:

 identify the substance causing effluent toxicity;

 isolate the source of toxicity;

 evaluate the effectiveness of toxicity control options; and

 confirm the reduction in effluent toxicity.

TIE are defined as a set of procedures that identify the specific substance responsible for effluent toxicity (they might be a subset of tools used in TRE). Reduction of toxicity to an acceptable level may be accomplished through the identification and control of the source of the toxicity or identification and implementation of a treatment strategy that reduces toxicity to an acceptable degree. TIE/TRE can range from very simple to highly complex means and they provide a logical process for operators to address a significant toxicity issue. TRE can guide the efforts of treatment engineers to focus on the minimisation of costs for effluent improvements.

By convention, TIE/TREs evaluate 'toxicity', but elements of both persistence and bioaccumulation could be an addition to the process (e.g. PIE/PRE or BIE/BRE).

Prioritisation of waste water treatment measures

Identification/reduction evaluations (as described above) can be used to predict the effectiveness

This kind of information helps decision-makers to get the most value for their investment in waste water treatment.

Judging effectiveness of treatment improvements

Once a facility has upgraded its waste water treatment system, toxicity and other testing of the effluent over a period of operation can be used to evaluate the improvements to the treatment over time.

Backtracking of effects observed in receiving environments

If environmental conditions in the receiving environment show negative impacts, WEA (often at a range of concentrations to match dilution in the receiving environment) can be used to try to establish cause and effect. For example, the hypothesis that poor benthic community quality is caused by an effluent discharge could be tested using carefully designed WEA. In addition, methods for effluent assessment can be used to evaluate the receiving environment quality, allowing a direct comparison between the effluent and the recipient water. This is recommended procedure in some countries.

Site-specific hazard/risk assessment

As demonstrated in the examples above, WEA might be used to support decisions on BAT in a number of practical ways. Each jurisdiction can decide which combination of applications will suit its effluent control policies and practices. Whether strictly emission-based or combined with a water quality-based approach, WEA supports most approaches to effluent discharge management.

WEA is used both within and outside the EU. One of the main differences between the approaches used by each country is the combination and types of tests that are used (toxicity/genotoxicity, persistence and/or bioaccumulation). In the EU, WEA implementation in a regulatory context is still developing and is mostly focused on toxicity tests (see Section 3.2.2.2).

In Sweden, effluent characterisation (including WEA) is used to assess whether the effluent treatment for a particular operation is adequate. This is usually done as a check on new production units (in-process and end-of-pipe installations) that have been online for some time as part of the permitting process. This approach, however, can be used at any time to assess the need for further installations.

On a broader European scale, OSPAR (Oslo and Paris Convention for the Protection of the Marine Environment of the North East Atlantic) took up the issue of the ecotoxicological evaluation of waste water as a means of assessing effluent quality through the Point and Diffuse Sources Group (PDS) in 1994. In November 1999, the German Federal Environment Agency drafted a background document on the use of WEA in waste water evaluation [ 65, OSPAR 2000 ]. Subsequently, an intersessional expert group (IEG) worked for several years developing WEA within the context of OSPAR's Hazardous Substances Strategy [ 129, OSPAR 2007 ].

Availability of laboratories to conduct tests in WEA may be a limitation to the use of the technique.

Economics

For a complex effluent, WEA is expected to be less expensive than comprehensive chemical and ecotoxicological analyses on the substances present in the effluent.

Substance by substance analysis will often be preferred for processes with few substances, or where there is no chemical reaction involved (typically blending, such as paint manufacture), whereas WEA is normally the first choice for chemical processes. It may well be augmented by analysis of specific known substances, especially hazardous ones. Indications on how to use

Driving force for implementation

WEA provides an additional and more direct means of assessing the potential impact of effluents on the aquatic environment and is playing an increasing role in the regulation of discharges, supplementing or sometimes replacing the common measurements of effluent quality in environmental monitoring and risk assessment. In Germany, toxicity tests are routinely used (i.e. LID approach, see above as well Section 3.2.2.2) for monitoring total water effluents [ 135, LANUV NRW 2009 ] [ 105, COM 2006 ].

With WEA test methods, an indication of the environmental significance of a complex effluent can be determined. This is usually quicker and cheaper than extensive chemical characterisation and thereby simplifies regulation.

Example plants

 Chemical manufacturing site of pharmaceutical ingredients, Germany [ 132,CEFIC 2009]

and several other chemical installations (e.g. OFC plants) in Germany [ 135, LANUV NRW 2009 ] [ 105, COM 2006 ].

 Chemical installation producing intermediates for the pharmaceutical industry in the Netherlands [ 133, ECETOC 2004 ].

 Conglomerate of many petrochemical and raw material-producing plants in the Netherlands [ 133, ECETOC 2004 ].

Reference literature

[ 27, US EPA 1991 ] [ 35, De Maagd 2000 ] [ 65, OSPAR 2000 ] [ 105, COM 2006 ] [ 128, Unden 2009 ] [ 129, OSPAR 2007 ] [ 130, OSPAR 2007 ] [ 132, CEFIC 2009 ] [ 133, ECETOC 2004 ] [ 135, LANUV NRW 2009 ] [ 146, TOTAL 2009 ]

3.2.3 Monitoring of emissions to air