Chromium total (total-Cr)

The corrosion of pipes and equipment is an important source of chromium in the influent of WWTPs. At some sites, the manufacture of organic chromium compounds (e.g. dyes) is a source of chromium in waste waters.

Overview of WWTP performance on total-Cr

Out of a total of 95 directly discharging WWTPs, total-Cr concentration values in the effluent were reported for 53 WWTPs (or 55 %), and for 12 (or 23 %) of the latter, total-Cr values in the influent were also reported. Some 16 effluent values were given as below a certain concentration or below the limit of detection (Figure 2.20).

54 11 111 14 108 102 40 53 100 62 74 36

Effluent values not shown in the graph:

< LOD: #52 (Bio), #94 (PC)

Bio = biological treatment; LOD = limit of detection; PC = physico-chemical treatment only.

Source: [ 246, EIPPCB 2014 ] based on data from [ 222, CWW TWG 2013 ]

Figure 2.20: Average total-Cr concentrations (mostly yearly averages) in the influents and effluents of directly discharging WWTPs

Average total-Cr levels in the effluents are generally ≤ 25 µg/l. Effluent concentrations

> 25 µg/l were reported for the WWTPs #06, #28, #83, #109, and #116. Installation #06 produces chromium-organic dyes. The WWTPs #28, #83, and #116 also showed high emission levels of other metals, while the effluents of the WWTPs #28 and #83 also showed high emission levels of TSS (i.e. > 35 mg/l).

Total-Cr can often be effectively abated by biological treatment; this is shown by WWTPs #02,

#11, and #22 (abatement efficiency > 90 %). However, in the case of WWTP #06, the abatement efficiency is < 50 % due to the presence of chromium-organic compounds.

Techniques reported to reduce total-Cr emissions

The following pretreatment and treatment operations (carried out at the installation(s) from which the waste waters originate or the final WWTP) were reported in the questionnaires:

 precipitation and filtration (with other metals),

 ion exchange (with other metals),

 activated sludge systems.

Fluctuations of emissions around the average (in concentration)

Maximum total-Cr values reported for 24 WWTPs vary around the average by a factor of 1.0–

76, but more generally by a factor of 1.4–20 (10th to 90th percentile).

Limits of detection (LOD) and quantification (LOQ)

In Flanders (Belgium), total-Cr is considered not quantifiable below 10 µg/l. In France, the LOQ is 5 µg/l for chromium and chromium compounds. In Germany, the LOQ for total-Cr is 0.5 µg/l based on EN ISO 17294–1. Analytical methods to measure total-Cr include ICP-OES with an approximate LOQ of 2 µg/l (EN ISO 11885) and ICP-MS with a lower limit of

2.4.3.4 Chromium VI (Cr VI)

Chromium VI is not expected at the outlet of the WWTPs.

Overview of WWTP performance on Cr VI

Data on Cr VI were only gathered during the first survey, but not during the second. Out of the 52 directly discharging WWTPs participating in the first survey, 6 reported Cr VI values in the effluent. Of these values, one is of spot-type while the others are given as range-type values (i.e.

< X or < LOD). Cr VI concentrations in the influent were only reported in one questionnaire as

< LOD. Therefore, no analysis on abatement efficiencies was performed.

Techniques reported to reduce Cr VI emissions

Reduction of Cr VI to Cr III, followed by abatement of total-Cr, was reported in the questionnaires.

Limits of detection (LOD) and quantification (LOQ)

In Flanders (Belgium), Cr VI is considered not quantifiable below 10 µg/l. Analytical methods to measure Cr VI include spectrometry with 1,5-diphenylcarbazide in a concentration range of 50–3000 µg/l (ISO 11083) and flow analysis (FIA/CFA) in a concentration range of 2–

2000 µg/l (EN ISO 23913).

2.4.3.5 Copper (Cu)

The corrosion of pipes and equipment is an important source of copper in waste waters. At some sites, the manufacture of copper-based catalysts, the manufacture of organic copper compounds (e.g. dyes), or the use of catalysts (e.g. ethylene dichloride production via oxychlorination [ 104, COM 2003 ]) are a source of copper in waste waters.

Overview of WWTP performance on Cu

Out of a total of 95 directly discharging WWTPs, Cu concentration values in the effluent were reported for 60 WWTPs (or 63 %), and for 20 (or 33 %) of the latter, Cu values in the influent were also reported. Some 14 effluent values were given as below a certain concentration or below the limit of detection (Figure 2.21).

Cu (µg/l)

Effluent values not shown in the graph:

< LOD: #52 (Bio)

Bio = biological treatment; LOD = limit of detection; PC = physico-chemical treatment only.

Source: [ 246, EIPPCB 2014 ] based on data from [ 222, CWW TWG 2013 ]

Average Cu levels in the effluents are generally ≤ 50 µg/l. Effluent concentrations > 50 µg/l were reported for the WWTPs #05, #06, #27, #28, #51, #80, #83, #105, #116, and #117.

Installation #05 produces copper-containing catalysts, installation #06 produces copper-organic dyes, and installations #27 and #80 produce ethylene dichloride. The WWTPs #27, #28, #83,

#116, and #117 also showed high emission levels of other metals, while the effluents of the WWTPs #28, #51, #80, and #83 also showed high emission levels of TSS (i.e. > 35 mg/l).

In many cases, biological treatment can be used effectively to abate copper emissions; this is shown by WWTPs #02, #11, and #22 (abatement efficiency > 90 %). However, in the case of WWTP #06, the abatement efficiency is around 50 % due to the presence of copper-organic compounds.

Techniques reported to reduce Cu emissions

The following pretreatment and treatment operations (carried out at the installation(s) from which the waste waters originate or the final WWTP) were reported in the questionnaires:

 precipitation and filtration (with other metals),

 ion exchange (with other metals),

 activated sludge systems.

Fluctuations of emissions around the average (in concentration)

Maximum Cu values reported for 33 WWTPs vary around the average by a factor of 1.0–26, but more generally by a factor of 1.1–8.2 (10th to 90th percentile). The ratio between maximum concentrations and average concentrations tends to be higher for installations with lower average concentrations.

Limits of detection (LOD) and quantification (LOQ)

In Flanders (Belgium), Cu is considered not quantifiable below 25 µg/l. In France, the LOQ is 5 µg/l for copper and copper compounds. In Germany, the LOQ for Cu is 0.1 µg/l based on EN ISO 17294–1. Analytical methods to measure Cu include ICP-OES with an approximate LOQ of 2 µg/l (EN ISO 11885) and ICP-MS with a lower limit of application of approximately 1 µg/l (EN ISO 17294–1).

2.4.3.6 Mercury (Hg)

The production of chlorine using the mercury cell technique as well as contaminated sites can be important sources of mercury for final WWTPs. Mercury can adsorb relatively easily onto sludge which has to be controlled if the sludge is incinerated.

Mercury is included in the list of priority hazardous substances in Annex X to the Water Framework Directive [ 28, Directive 2000/60/EC 2000 ]. Substances of this annex are included in the indicative list of polluting substances in Annex II to the IED (2010/75/EU) to be taken into account for setting emission limit values [ 5, Directive 2010/75/EU 2010 ].

Overview of WWTP performance on Hg

Out of a total of 95 directly discharging WWTPs, Hg concentration values in the effluent were reported for 49 WWTPs (or 52 %), and for 13 (or 27 %) of the latter, Hg values in the influent were also reported. Some 17 effluent values were given as below a certain concentration or below the limit of detection (Figure 2.22).

100 25 11 111 108 12 14 36 74 40 15 102

Effluent values not shown in the graph:

< LOD: #52 (Bio), #73 (PC), #92 (Bio), #94 (PC)

Bio = biological treatment; LOD = limit of detection; PC = physico-chemical treatment only.

Source: [ 246, EIPPCB 2014 ] based on data from [ 222, CWW TWG 2013 ]

Figure 2.22: Average Hg concentrations (mostly yearly averages) in the influents and effluents of directly discharging WWTPs

Average Hg levels in the effluents are generally ≤ 1 µg/l. Effluent concentrations > 1 µg/l were reported for the WWTPs #53, #79, #80, #81, #93, and #117. The mercury cell technique is used at installation #80. The WWTPs #81 and #117 also showed high emission levels of other metals, while WWTP #80 also showed high emission levels of TSS (i.e. > 35 mg/l).

Techniques reported to reduce Hg emissions

The following pretreatment and treatment operations (carried out at the installation(s) from which the waste waters originate or the final WWTP) were reported in the questionnaires:

 precipitation and filtration,

 ion exchange,

 reduction with hydrazine,

 activated carbon,

 activated sludge systems combined with sludge incineration/waste gas treatment.

Fluctuations of emissions around the average (in concentration)

Maximum Hg values reported for 18 WWTPs vary around the average by a factor of 1.0–57, but more generally by a factor of 1.4–6.6 (10th to 90th percentile).

Limits of detection (LOD) and quantification (LOQ)

In Flanders (Belgium), Hg is considered not quantifiable below 0.25 µg/l. In France, the LOQ is 0.5 µg/l for mercury and mercury compounds. In Germany, the LOQ for Hg is 0.01 µg/l based on EN ISO 17852 and 0.1 µg/l based on EN 1483. Analytical methods to measure Hg include atomic fluorescence spectrometry in a concentration range of 0.01–10 µg/l (EN ISO 17852) and cold vapour atomic absorption spectrometry in a concentration range of 0.1–10 µg/l (EN 1483).

2.4.3.7 Nickel (Ni)

The corrosion of pipes and equipment is an important source of nickel together with the use of nickel-based catalysts. Process gas scrubber/input from heavy fuel oil or catalyst manufacture is also a source of nickel emissions at some sites. Nickel in soluble form is more difficult to remove.

Nickel is included in the list of priority substances in Annex X to the Water Framework Directive [ 28, Directive 2000/60/EC 2000 ]. Substances of this annex are included in the indicative list of polluting substances in Annex II to the IED (2010/75/EU) to be taken into account for setting emission limit values [ 5, Directive 2010/75/EU 2010 ].

Overview of WWTP performance on Ni

Out of a total of 95 directly discharging WWTPs, Ni concentration values in the effluent were reported for 49 WWTPs (or 52 %), and for 13 (or 27 %) of the latter, Ni values in the influent were also reported. Nine effluent values were given as below a certain concentration or below the limit of detection (Figure 2.23).

8382 53 25 40 62 11

Effluent values not shown in the graph:

< LOD: #042 (PC), #52 (Bio)

Bio = biological treatment; LOD = limit of detection; PC = physico-chemical treatment only.

Source: [ 246, EIPPCB 2014 ] based on data from [ 222, CWW TWG 2013 ]

Figure 2.23: Average Ni concentrations (mostly yearly averages) in the influents and effluents of directly discharging WWTPs

Average Ni levels in the effluents are generally ≤ 50 µg/l. Effluent concentrations > 50 µg/l were reported for the WWTPs #28, #41, and #116. The WWTPs #28 and #116 also showed high emission levels of other metals, while the effluent of WWTP #28 also showed high emission levels of TSS (i.e. > 35 mg/l).

Nickel is to some extent abated by biological treatment, albeit less than copper or chromium.

This is shown by WWTPs #02, #07, and #11 (abatement efficiency approximately 50–80 %).

Techniques reported to reduce Ni emissions

The following pretreatment and treatment operations (carried out at the installation(s) from which the waste waters originate or the final WWTP) were reported in the questionnaires:

 precipitation and filtration (with other metals),

 ion exchange (with other metals),

 filtration (Raney-Ni),

 activated sludge systems.

Fluctuations of emissions around the average (in concentration)

Maximum Ni values reported for 28 WWTPs vary around the average by a factor of 1.0–10, but more generally by a factor of 1.3–5.1 (10th to 90th percentile).

Limits of detection (LOD) and quantification (LOQ)

In Flanders (Belgium) as well as in France, Ni is considered not quantifiable below 10 µg/l. In Germany, the LOQ for Ni is 1 µg/l based on EN ISO 17294–1. Analytical methods to measure Ni include ICP-OES with an approximate LOQ of 2 µg/l (EN ISO 11885) and ICP-MS with a lower limit of application of approximately 1 µg/l (EN ISO 17294–1).

2.4.3.8 Lead (Pb)

Lead is included in the list of priority substances in Annex X to the Water Framework Directive [ 28, Directive 2000/60/EC 2000 ]. Substances of this annex are included in the indicative list of polluting substances in Annex II to the IED (2010/75/EU) to be taken into account for setting emission limit values [ 5, Directive 2010/75/EU 2010 ].

Overview of WWTP performance on Pb

Out of a total of 95 directly discharging WWTPs, Pb concentration values in the effluent were reported for 43 WWTPs (or 45 %), and for 9 (or 21 %) of the latter, Pb values in the influent were also reported. Some 19 effluent values were given as below a certain concentration or below the limit of detection (Figure 2.24).

108 100 102 62 111 11 40 36

Effluent values not shown in the graph:

< LOD: #042 (PC), #52 (Bio), #94 (PC)

Bio = biological treatment; LOD = limit of detection; PC = physico-chemical treatment only.

Source: [ 246, EIPPCB 2014 ] based on data from [ 222, CWW TWG 2013 ]

Average Pb levels in the effluents are generally ≤ 10 µg/l. Effluent concentrations > 10 µg/l were reported for the WWTPs #27, #32, #93, #98, #115, and #116. Installation #32 produces Pb-based PVC stabilisers and installation #115 blends Ca-, Pb-, and Zn-organic stabilisers. The WWTPs #27 and #116 also showed high emission levels of other metals.

Techniques reported to reduce Pb emissions

The following pretreatment and treatment operations (carried out at the installation(s) from which the waste waters originate or the final WWTP) were reported in the questionnaires:

 precipitation with sodium carbonate,

 activated sludge systems.

Fluctuations of emissions around the average (in concentration)

Maximum Pb values reported for 15 WWTPs vary around the average by a factor of 1.0–7.1, but more generally by a factor of 1.2–5.9 (10th to 90th percentile).

Limits of detection (LOD) and quantification (LOQ)

In Flanders (Belgium), Pb is considered not quantifiable below 25 µg/l. In France, the LOQ is 5 µg/l for lead and lead compounds. In Germany, the LOQ for Pb is 0.1 µg/l based on EN ISO 17294–1. Analytical methods to measure Pb include ICP-OES with an approximate LOQ of 5 µg/l (EN ISO 11885) and ICP-MS with a lower limit of application of approximately 0.1 µg/l (EN ISO 17294–1).

2.4.3.9 Zinc (Zn)

The corrosion of pipes and equipment (tank insulation, building roofs) is an important source of zinc. Raw materials are also a source of zinc that can ultimately be released into water. Zinc emissions may also originate from the production of viscose [ 106, COM 2007 ] or from its use as a corrosion inhibitor in cooling systems [ 114, COM 2001 ].

Overview of WWTP performance on Zn

Out of a total of 95 directly discharging WWTPs, Zn concentration values in the effluent were reported for 57 WWTPs (or 60 %), and for 19 (or 33 %) of the latter, Zn values in the influent were also reported. Four effluent values were given as below a certain concentration (Figure 2.25).

6211 74

Effluent values not shown in the graph:

< 10 µg/l: #01 (Bio)

< 20 µg/l: #16 (Bio), #51 (Bio), #84 (PC)

NB: Data labels indicate the plant code (see Table 7.1 in Section 7.2, Annex II) and the type of treatment.

Bio = biological treatment; PC = physico-chemical treatment only.

Source: [ 246, EIPPCB 2014 ] based on data from [ 222, CWW TWG 2013 ]

Figure 2.25: Average Zn concentrations (mostly yearly averages) in the influents and effluents of directly discharging WWTPs

Average Zn levels in the effluents are generally ≤ 300 µg/l. Effluent concentrations > 300 µg/l were reported for the WWTPs #28, #35, #57, #60, #81, #108, and #116. At installation #35, the majority of the Zn emissions originate from contaminated groundwater. The WWTPs #28, #81, and #116 also showed high emission levels of other metals.

Zinc is to some extent abated by biological treatment, albeit less than copper or chromium. This is shown by WWTPs #02, #07, #11, #21, #22, and #49 (abatement efficiency approximately 50–

90 %).

Techniques reported to reduce Zn emissions

The following pretreatment and treatment operations (carried out at the installation(s) from which the waste waters originate or the final WWTP) were reported in the questionnaires:

 precipitation and filtration (with other metals),

 ion exchange (with other metals),

 activated sludge systems.

Fluctuations of emissions around the average (in concentration)

Maximum Zn values reported for 39 WWTPs vary around the average by a factor of 1.2–27, but more generally by a factor of 1.4–8.6 (10th to 90th percentile).

Limits of detection (LOD) and quantification (LOQ)

In Flanders (Belgium), Zn is considered not quantifiable below 25 µg/l. In France, the LOQ is 10 µg/l for zinc and zinc compounds. In Germany, the LOQ for Zn is 1 µg/l based on EN ISO 11885. Analytical methods to measure Zn include ICP-OES with an approximate LOQ of 1 µg/l (EN ISO 11885) and ICP-MS with a lower limit of application of approximately 1 µg/l (EN ISO 17294–1). The operator of WWTP #57 indicated a limit of quantification for zinc of

2.4.4 Nitrogen compounds

In document Best Available Techniques (BAT) Reference Document for Common Waste Water and Waste Gas Treatment/Management Systems in the Chemical Sector. Industrial Emissions Directive 2010/75/EU (Integrated Pollution Prevention and Control) (Page 93-102)