0725_Contribution of combined sewer overflows to trace contaminant loads urban streams...



ESEL Paper Review_20110725
By Hong Guo

1,Title and Author

Title: Contribution of combined sewer overflows to trace contaminant loads urban streams


Philip Weyraucha, Andreas Matzingera,*, Erika Pawlowsky-Reusingb, Stephan Plumea, Dorthe von Seggernc, Bernd Heinzmannd, Kai Schroedera, Pascale Rouaulta
a  Kompetenzzentrum Wasser Berlin, Cicerostrasse 24, 10709 Berlin, Germany
b Berliner Wasserbetriebe, Netz-und Anlagenbau, Neue Judenstrasse 1, 10864 Berlin, Germany
c Berlin Senate Department of Health, Environment and Consumer Protection, Bruckenstrasse 6 10179 Berlin, Germany
d  Berliner Wasserbetriebe, Research and Development, Cicerostrasse 24, 10709 Berlin, Germany 

2. Summary of Paper
This paper shows the contribution of CSO (combined sewer overflows) to loads and concentrations of trace contaminates in receiving surface water.
 The author show that annual loads are dominated by CSO for substances with removal in WWTP above 95%, moreover, it showed that substances with high removal in WWTP can lead to concentration peaks in the river during CSO events, despite dilution with rain water. We can see this behavior from the NTA(nitrilotriacetic acid), which was detected at up to 10-fold background concentrations during CSO. On the other hand, the substances such as EDTA(ethylenediaminetetraacetic acid) decrease in CSO-influenced samples due to dilution effects. And the from the eq(5)(in the paper), we also know that CSO can lead to concentration peaks during storm events, depending on substance removal fraction.

Identification of samples during CSO
As we know that the most important for the CSO is to identify the CSO samples, in this paper, 2-4 samples with CSO influence was expected for 43-103 available monthly samples. And from Riechel(2009) , we can know drops in conductivity and DO after storm events are reliable sign for CSO influence. But direct identification is impossible due to the natural environment. Author told the method that grab the samples only considered impacted by the CSO
1 if they were taken within a 10-day period after a criticalrain event with a total height > 4.7 mm,
2 if continuous DO and conductivity measurements showed a sharp decrease following the critical rain event,
3 if DO and conductivity of grab samples verify that the sample was taken during the observed CSO signal in continuous measurements and
4 if at least one of the two parameters NH4-N or BOD5 in grab sample showed a higher value than grab samples taken in the months before and after the sample (or similarly high, if these samples were also identi?ed as CSO-in?uenced)

3. Contribution:
I only get the some of key idea just like what substances are affected by the CSO events. And I learn how to grab the CSO samples and how recognize among the whole samples, this work also need to be proved by the experiment data that I do now(key point: for identifying the extent of the problem of the CSO, we need to do the frequent sampling). I hope this paper can give the idea for the lab mates to learn the CSO event and non-point sourcing project.

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