Registration Dossier

Administrative data

Endpoint:
monitoring data
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Meets generally accepted scientific standards, well documented and acceptable for assessment.

Data source

Reference
Reference Type:
publication
Title:
Behaviour of NTA and EDTA in Biological Wastewater Treatment
Author:
Alder, A.C.; Siegrist, H.; Gujer, W.; Giger, W.
Year:
1990
Bibliographic source:
Wat. res. Vol. 24, No. 6, pp. 733-742

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The behaviour and diurnal load variation of NTA, COD, nitrification and oxygen demand were investigated in the sewage treatment plant (STP) Glatt of the city of Zürich (wastewater discharge: Q = 55 - 60000 m³/d, 100000 inhabitants) during 48 h in winter and 36 h in summer on two consecutive days. The STP has four parallel lanes of the secondary treatment. One lane was chosen for measurements (volume of aeration tanks = 1812 m³, Q = 147000 m³/d), which consists of three reactors in series, each with 603 m³ volume with high laying medium bubble aeration (air flow: 14 m³/(m³ * reactor volume * h). The sludge age of the plant was about 3.6 d in winter and 4.8 d in summer.
NTA, COD, TSS and nitrogen components were measured; activated sludge was analysed twice a day for TSS, COD, total nitrogen, and volatile suspended solids (VSS).
Tracer experiments with sodium bromide were performed to determine hydraulic residence time of the activated sludge reactors and the secondary clarifiers.
Additional lab scale experiments were conducted with a pilot plant with a volume of 4.4 L in the steady state, with sludge ages 2.1 and 12 d and mean temperatures of 10.5 and 20 °C, respectively.
GLP compliance:
no
Type of measurement:
other: measurements at STP Glatt
Media:
other: sludge

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
No details reported

Study design

Details on sampling:
- Geographic coordinates: STP Glatt of the city of Zürich (wastewater discharge: Q = 55 - 60000 m³/d, 100000 inhabitants)
- Known emission sources near sampling site:
- Period of sampling: during 48 h in winter and 36 h in summer on two consecutive days
- Sampling: 2 h composite samples during 48 h and 36 h, respectively, of the primary and secondary effluents, as well as samples of the effluents of each of the three reactors every 2h
- Sample storage before analysis: 24 h (maximum)

Results and discussion

Concentrationopen allclose all
Country:
Switzerland
Location:
STP Glatt near Zürich
Substance or metabolite:
substance
Conc.:
>= 300 - <= 1 500 µg/L
Remarks on result:
other: NTA influent concentrations (diurnal variation)
Country:
Switzerland
Location:
STP Glatt near Zürich
Substance or metabolite:
substance
Conc.:
>= 9 - <= 45 µg/L
Remarks on result:
other: NTA effluent concentrations (97 % degradation of influent concentrations)
Details on results:
Tracer experiments:
- One reactor has the same hydraulic retention time as 8 mixed reactors in series.
- 15 % of the secondary clarifier was flowed through by recycling sludge and 85 % by the secondary effluent, with both parts having about the same hydraulic residence time distribution as two mixed reactors in series.

NTA effluent concentrations:
- Primary effluent concentrations increased 4 times from the winter of 1984 (40.380 µg/l) to the winter of 1987 (330-1490 µg/l) due to phosphate ban in laundry detergents in Switzerland.
- However, secondary effluent concentrations only increased 1.5 times

NTA degradation:
- To achieve 80-90 % degradation in winter (t = 10 °C) a minimum sludge age of at least 4 d is necessary for a completely mixed reactor. Up to 97 % degradation are achieved with a plug-flow reactor with the same sludge age.

Applicant's summary and conclusion

Conclusions:
In the Swiss Glatt municipal plant near Zürich, NTA influent concentrations of 300 – 1,500 µg/l (diurnal variation) were detected. In both seasons, NTA was degraded to 97%. The average sludge age was 3.6 days in winter and 4.8 days in summer. The influent concentrations increased by a factor of 4 between 1984 and 1987, whereas the effluent concentrations rose only by a factor of 1.5.
Executive summary:

The behaviour and diurnal load variations of nitrilotriacetate (NTA) was investigated in winter and in summer in the Glatt sewage treatment plant near Zürich. The plant had a sludge age of 3.6 d in winter and 4.8 d in summer and was in winter only partly nitrifying.

The average daily loads of NTA in the primary effluent in the investigated lane was during the two investigated periods 13 +/- 7 kg NTA per day (0.5 +/- 0.3 g NTA/(person * day)).

The influent concentration ranged between 300 and 1500 µg NTA/l. In both seasons NTA was biologically degraded up to 97%.

The influent concentrations increased by a factor of 4 between 1984 and 1987, whereas the effluent concentrations rose only by a factor of 1.5.