Registration Dossier

Administrative data

Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
August 1982
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline method, good quality GLP study with good reporting detail; considered acceptable for assessment

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1983
Report Date:
1983
Reference Type:
secondary source
Title:
Unnamed
Year:
2000

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
other: Department of the Environment, UK (1977). Amenability of sewage sludge to anaerobic digestion. HMSO, London
Deviations:
yes
Remarks:
A modified approach, the general principles of which have been described by Owen WF et al. (1979). Bioassay for monitoring biochemical methane potential and anaerobic toxicity. Water Research 13, 485-492
Principles of method if other than guideline:
Toxicity of Chlorowax 500C to the anaerobic sewage sludge digestion process assessed for up to 10 days
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Chlorowax 500C
- Substance type: technical product
- Physical state: slightly viscous, clear liquid
- Analytical purity: "100% chlorinated paraffin"
- Impurities (identity and concentrations): free HCl, 7.0 ppm, without stabilisers
- Composition of test material, percentage of components: C10-12 chlorinated paraffin; 58% chlorination
- Lot/batch No.: R201-198
- Expiration date of the lot/batch: dependent on routine analysis
- Stability under test conditions: "unstable"
- Storage condition of test material: -20 degrees C
- Other: specific gravity 1.360 at 25oC; viscosity 21.0 stokes or 28.9 poise at 25oC
- Water solubility (under test conditions): not water soluble to any significant extent
- Stability in water: humidity, urine or water in diet will hydrolyse
- Stability in light: degrades on prolonged exposure

Sampling and analysis

Analytical monitoring:
not specified
Details on sampling:
No data

Test solutions

Vehicle:
yes
Details on test solutions:
An emulsion was made by ultrasonic dispersion of the chlorinated paraffin in distilled water and the concentration in the stock emulsion determined by extraction into carbon tetrachloride followed by infra-red analysis and found to be 9500 mg/l.

Test organisms

Test organisms (species):
other: raw feed sludge and sludge from an active digester from Countess Weir Sewage Treatment Works, Exeter, Devon, UK
Details on inoculum:
Samples were sieved (4 mm mesh size) and sub-samples withdrawn for determination of mixed liquor solids and volatile solids. Digested sludge was incubated overnight at 35 +/- 1 degree C and feed sludge was stored at ambient temperature. Digested sludge was found to be pH 7.3 while feed sludge was pH 5.4 and was adjusted with 2.5N NaOH to pH 7.2. The two were then mixed in the ratio 6 parts digested to 4 parts feed sludge and the volatile solids of the mixture calculated. 4.525 L of the mixture were diluted to 5 L with tap water to produce a volatile solid of 2% (w/w), maintained at 35 +/- 1 degree C and used in the test within 2 h of preparation.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
10 d
Post exposure observation period:
None

Test conditions

Hardness:
Not specified
Test temperature:
Incubation temperature range 35.5-35.8oC, mean 35.7oC
pH:
Prior to starting the test, digested sludge was pH 7.3 and feed sludge was adjusted to pH 7.2
Dissolved oxygen:
Not specified
Salinity:
Not specified
Nominal and measured concentrations:
0.56, 1.0, 1.8, 3.2, 5.6 and 10% w/w chlorinated paraffin with respect to digester volatile suspended solids content corresponding to 33.3, 59.9, 108.3, 190, 332.5 and 598.5 mg chlorinated paraffin respectively. According to the final RAR (EU, 2000), these concentrations equate to 5,600, 10,000, 18,000, 32,000, 56,000 and 100,000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: bottle
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: glass bottle, 500 mL nominal capacity
- Aeration: no
- No. of organisms per vessel: 300 ml of feed/digested sludge mixture; sludge concentration 1.5% (w/v) volatile solids
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: distiled water
- Intervals of water quality measurement: water bath temperature recorded daily

OTHER TEST CONDITIONS
- Adjustment of pH: feed sludge pH adjusted to 7.2 with 2.5N NaOH

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): inhibition of gas production measured on a daily basis
Reference substance (positive control):
no

Results and discussion

Effect concentrations
Duration:
24 h
Dose descriptor:
LOEC
Effect conc.:
32 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: inhibition of gas production
Details on results:
Addition of chlorinated paraffin to anaerobic sludge digesters at concentrations of 32,000 mg/L or more caused inhibition of gas production within 24 h, the top concentration causing a 29% inhibition. After 4-5 days incubation, gas production at these higher concentrations was inhibited by less than 10% when compared with the controls. No significant effects were seen at 18,000 mg/L or below at any of the time intervals (see Table 1 under any other information on results). Derivation of the concentrations producing 10, 20 and 30% inhibition at various time intervals showed that very high concentrations of chlorinated paraffin would be required to produce long-term inhibitory effects (see Table 2 under any other information on results).

Any other information on results incl. tables

Table 1: Effect of chlorinated paraffin on anaerobic digester gas production

Concentration of chlorinated paraffin % (w/w) on volatile solids

% Inhibition of gas production (daily values)

1

2

3

4

5

6

7

8

9

10

10 (10, 000 mg/L)

29

24

21

16

9

7

5

5

4

4

5.6 (56,000 mg/L)

20

17

15

11

8

7

7

7

7

7

3.2 (32,000 mg/L)

12

11

11

9

7

7

7

7

7

7

1.8 (18,000 mg/L)

5

5

4

3

2

2

2

3

3

3

1.0 (10, 000 mg/L)

3

3

3

2

1

1

1

1

1

1

0.56 (5,600 mg/L)

2

2

1

1

0

0

0

0

0

0

 

Table 2: Concentration of chlorinated paraffin causing inhibition at various time intervals

Time (days)

% Chlorinated paraffin (w/w) on volatile solids

1

3

5

10

IC10

2.65

3.25

16.0

-

IC20

5.6

9.2

-

-

IC30

11.5

26.0

-

-

 

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
Conclusions:
In a well conducted study, toxic effects of Chlroowax 500C (a C10-12 chlorinated paraffin; 58% chlorination) on an anaerobic sewage sludge digestion process, assessed by measurement of the degree of inhibition of gas production at various time intervals, were found at concentrations of 3.2% (w/w) on volatile solids (corresponding to 32,000 mg/L) during the first 3-4 days of the study. Recovery was evident after this period.
Executive summary:

In a well conducted GLP study, the toxicity of Chlorowax 500C (a C10-12 chlorinated paraffin; 58% chlorination) to the anaerobic sewage sludge digestion process was investigated. Toxic effects, after treatment of a mixture of feed and digested sludges with concentrations of 0.56, 1.0, 1.8, 3.2, 5.6 and 10% chlorinated paraffin w/w with respect to digester volatile suspended solids content, were assessed by the measurement of the degree of inhibition of gas production at various time intervals of up to 10 days. According to the EU RAR, the test concentrations equate to 5600, 10,000, 18,000, 32,000, 56,000 and 100,000 mg/L respectively.

Significant inhibition of gas production occurred at concentrations of 32,000 mg/L and above during the first 3-4 days of treatment. Recovery was seen after this time, which continued up to day 10. No significant effects were noted at 18,000 mg/L and below. This study showed that short term exposure to Chlorowax 500C concentrations of 32, 000 mg/L and above may cause transient partial inhibition of gas production. However, recovery of affected digesters is likely to be rapid with no long-term effects.