Complexing agents in waste waters of finnish electrolytic and chemical surface treatment plants |
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Authors: | Kari Pirkanniemi Anna-Maria Vuorio Sari Vilhunen Sirpa Metsärinne Mika Sillanpää |
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Institution: | (1) Department of Environmental Sciences, Laboratory of Applied Environmental Chemistry, University of Kuopio, P.O. Box 181, FI-50101 Mikkeli, Finland |
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Abstract: | Goal, Scope and Background Complexing agents are one of the major environmental concerns in electrolytic and chemical surface treatment (ECST) industry;
e.g. the EU reference document on the best available technology (BREF) pays special attention to the usage of EDTA. However,
no comprehensive studies are available on usage of EDTA or other complexing agents or their load to the receiving waters from
ECST industry. In this study, the concentrations of complexing agents were analyzed to get an overview of their usage and
load and also to recognize their relevance in the environmental permitting and compliance monitoring of such facilities.
Methods Complexing agent concentrations of treated waste water samples of 23 ECST plants with vat volume exceeding 30 m3 was studied. HPLC and GC-MS were used to analyze and identify complexing agent concentrations, ICP-AES to analyze metals,
and TOC to analyse the organic load. The number of the plants in this study equals around 50% of such installations in Finland
subject to environmental permit as the IPPC directive provides.
Results EDTA, DTPA, and NTA were found in 11 samples out of 23 mainly in rather small concentrations. Their annual load to the receiving
waters may be estimated to be 0.3 tons and the total load from Finnish ECST industry can be extrapolated to be up to 1 ton.
Compared to the estimated use of 5–10 tons in the industry this finding is rather low, even though in Finland cast-off treatment
baths are typically delivered to the hazardous waste treatment plants.
Discussion Since the load of complexing agents is rather low, the chemical waste water treatment seems to be either capable of reducing
complexing agent concentrations to some extent or their usage is lower than expected. On the other hand, it is possible that
not all complexing agents were identified from the samples. The metal concentrations and TOC were well hand in hand with concentrations
found in the Finnish environmental database, which proves that the samples were of average quality of the waste water from
the facilities.
Conclusions According to the results, complexing agents cannot be considered as an environmental risk in the ECST industry in Finland;
EDTA concentrations are clearly below PNECaqua (2.2 mg/l) and the total discharge is very marginal compared to the discharge from the pulp and paper industry. However,
DPTA seems to be as commonly used as EDTA, but also biodegradable NTA was found.
Recommendations and Perspectives Since EDTA has gained plenty of attention in the BREF, DTPA and other, poorly biodegradable complexing agents should also
be taken into account when the BREF is updated within a few years. Also an EU risk assessment report especially for DTPA should
be supplied, since its use is obviously increasing. |
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Keywords: | Complexing agents NTA EDTA DTPA IPPC electroplating electrolytic and chemical surface treatment heavy metals |
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