Ammonium dihydrogen citrate

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Data waiving:

other justification

Justification for data waiving:

other:

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

activated sludge nitrification inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline followed

Principles of method if other than guideline:

Ammonia oxidizers were enumerated in 34 activated sludges, including sludges which were from sewage treatment plants (S-sludge), nightsoil treatment plants (N-sludge) and activated sludges cultivated with organic (O-sludge) or inorganic (I-sludge) artificial wastewaters in the laboratory. Two media were used for enumeration, one containing 0.76 mM (AL medium) and the other 37.9 mM (AH medium) of (NH4)2SO4. The MPN estimated with AL medium were higher than those with AH medium in S-sludges, N-sludges and O-sludges, while both media gave almost the same MPN for I-sludges. Ten ammonia oxidizers, all identified as Nitrosomonas spp, were isolated from sludge samples. Isolates obtained as predominants in S- and O-sludges were sensitive to (NH4)2SO4; they grew in medium containing 0.71 mM of (NH4)2 SO4 but not in medium containing 35.7 mM of (NH 4)2504- On the other hand, those obtained as predominants in an I-sludge, as well as ATCC strains grew in both media.

Activated sludge was adjusted to an MLSS concentration of about 5000 mg/L prior to serial dilution. A 20-mL activated sludge suspension was sonicated for 2 min at 40 W. Serial 10-fold dilutions of the inoculum sources were prepared in sterile distilled water and 1 mL portions were transferred to MPN tubes containing AL or AH media. Ten replicate tubes per dilution were used for enumeration. S-sludges were inoculated within 6 h after sampling. Inoculated MPN tubes were incubated for 42 days at 25°C unless otherwise stated.

Ammonia-oxidizing bacteria were isolated by the serial dilution process from four sludges with C basal medium containing 0.71 or 35.7 mM (NH4)2SO4. After heterotroph-free cultures were obtained, strains GH22 and GH23 were purified on silica gel plates containing 35.7 mM (NH4)2SO4 three times (Suwa, 1989). The remaining strains were purified by three successive dilution procedures in C basal medium containing 0.71 or 35.7 mM (NH4)2SO4.

GLP compliance:

not specified

Test organisms (species):

Nitrobacter sp.

Details on inoculum:

The sewage treatment study (Suwa et al., 1994) investigated 14 strains of Nitrobacter spp. (ammonium oxidising bacteria) isolated from 25 different sludges including three sludges from primary sewage treatment plants and two sludges from nightsoil treatment plants.

Water media type:

freshwater

Duration:

42 d

Dose descriptor:

NOEC

Effect conc.:

>= 94 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of nitrification rate

Details on results:

Nitrite production kinetic studies showed that insensitive strains (those which grew well at 4700 mg/L ammonium sulfate) showed Monod growth, while sensitive strains (those which grew at 94 mg/L but not at 4700 mg/L) followed Haldane kinetics. The results suggested that ammonium sulfate sensitive strains had a growth advantage in lower ammonium sulfate concentrations, while insensitive strains had a growth advantage at higher ammonium sulfate concentrations. Both sensitive and insensitive strains were found in the primary and nightsoil sludges, with the sensitive strains predominating. This explained the operational observations in several sewage treatment plants concerning the efficacy of nitrifying bacteria.

Validity criteria fulfilled:

not specified

Conclusions:

Nitrification during sewage treatment plant operation involves both sensitive (no growth at 4700 but growth at 94 mg/L ammonium sulfate) and insensitive (growth at 4700 mg/L ammonium sulfate) strains of Nitrobacter spp (Suwa et al., 1994). This indicates that a NOEC for specific nitrifying bacteria will be greater than 94 mg/L.

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline available

Principles of method if other than guideline:

The SIDS report did not state the methods used.

GLP compliance:

not specified

Test organisms (species):

other: several microorganisms were reported in the SIDS

Duration:

16 h

Dose descriptor:

EC0

Effect conc.:

> 10 000 mg/L

Remarks on result:

other: Pseudomonas putida (freshwater)

Remarks:

method not stated

Duration:

8 d

Dose descriptor:

EC0

Effect conc.:

80 mg/L

Remarks on result:

other: Microcystis (freshwater cyanobacteria)

Remarks:

method not stated

Duration:

72 h

Dose descriptor:

EC0

Effect conc.:

485 mg/L

Remarks on result:

other: Entosiphon sulcatum (freshwater protozoa)

Remarks:

method not stated

Details on results:

Other results:
Protozoa:
Tetramitus rostratus (freshwater): 35-h TLC ≤ 108 mg/L toxic limit concentration, exposure period ambiguous, method not stated
Uronema parduczi (freshwater): TLC = 622 mg/L toxic limit concentration, exposure period and method not stated
Tetraselmis tetrathele (saltwater): 7-day TLC = 1–300 mg/L toxic limit concentration, method not stated

Bacteria (all freshwater):
Nitrosomonas sp.: EC0 = 100 mg/L no inhibition of nitrification,exposure period and method not stated
“37 Strains of bacteria”: all strains positive growth; 30-day EC0 = 500 mg/L; microbes isolated from acidic mine water, pH = 3, citric acid as sole carbon source, method not stated
Arthrobacter globiformis,10 strains: good to excellent degradation; microbes isolated from soil, citric acid as sole C sour ce, mineral salts added, exposure period and method not stated

Validity criteria fulfilled:

not specified

Conclusions:

The lowest reported EC0 in cyanobacteria was 80 mg/L.
Different strains of bacteria showed positive growth respectively good to excellent degradation with citric acid as the sole carbon source and the same holds for sewage sludge micro-organisms that thrive on citric acid.