D10: Impact of Contaminants - Hydromod

Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas
EUROLAKES
D10: Impact of Contaminants
FP5_Contract No.: EVK1-CT1999-00004
Version: 4.0
Date: 25/07/01
File: D10-vers.4.0.doc
Page 105 of 136
other with low sludge age). The results clearly demonstrate that there is a relation between
reduction of NPnEOs and the process parameters like sludge age, sludge load,
nitrification and reduction of organic wastewater contents as outlined above.
Transformation of NPnEOs in anaerobic sludge stabilisation
The further degradation of NPnEOs (NP2EO and NP1EO) which are adsorbed to the
excess biological sludge, takes place during anaerobic stabilisation in the sludge digester,
by elimination of the Ethoxy groups down to NP. Tschui et al (18) could verify
this reduction in a batch test. After a retention time of 20 days some 60% of the NP2EO
and NP1EO were decomposed and the amount of NP was doubled.
They could even notice a surplus of NP which did not result from the degradation of
NP2EO and NP1EO.
This could be explained by the fact that probably remaining NP3EO – NP10 EO chains
and CAPEs as well as CAPECs (which were not measured) are reduced to NP under
anaerobic conditions.
11.2 SUMMARY AND OUTLOOK
Obviously endocrine substances can be reduced in wastewater treatment plants but not
fully. With the Council Directive 91/271/EEC on urban waste water treatment, May 21 th ,
1991, most European WWTPs are obliged to apply aerobic biological treatment processes
with high sludge age what favours the growth of bacteria capably of metabolising
substance which are contained in low concentrations in the wastewater.
Further advantageous are aerobic conditions for the deposed excess sludge as provided
in agricultural use or composting of the sludge. According to studies regarding
future trends in the European Union it may be expected that an increase of the sludge
used for agriculture will take place.
However, still the information required to prepare strategies in design and operation of
WWTPs is insufficient, and most probably it will not be able to completely eliminate the
substances in the course of the treatment.
Theoretically the effluent could be further treated by membrane processes or activated
carbon processes which can completely eliminate nearly all substances targeted. In
other words “technically everything is possible”, but these processes are extremely
costly and it is not considered a sound approach to invest in end of pipe technology.
Avoiding of these substances by production restrictions and strict regulations would be
a much more economic and reasonable approach for reducing the emission of endocrine
modulators into the environment.
11.3 PROCESSES TO ELIMINATE CONTAMINANTS FROM SOURCES FOR
DRINKING WATER SUPPLY
General considerations