Materials and methods – Biodegradability – STABILGREEN® K

Test Substance

Specification

The following information of the test substance was provided by the sponsor.

Name : STABILGREEN®K (Polyglyceryl-4 Oleyl Ether, Dioleyl Phosphate)
Batch no. : not stated
Expiry date: not stated
Storage: not stated

Pre-Treatment

The carbon content of 72.3 % was determined by elemental analysis. The test item was used directly, in amounts according to its carbon content.

Positive Control

Aniline (Phenylamine, C6H5NH2, CAS-No. 62-53-3) was used as readily bio-degradable positive control. A stock solution containing 2127.8 mg/L in deionized water was prepared and its organic carbon content was measured with 1729.9 ppm, corresponding to an organic carbon content of the positive control of 81.3 %.

Test System

Specification

Activated sludge from a biologic sewage treatment plant was used. The chosen plant is treating mostly domestic sewage.

Source

The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf.
Date of collection: 09 February 2020, batch no: 20150320.

Pre-Treatment

The sludge was filtrated, washed with tap water twice, then washed with and re-suspended in test medium. It was then aerated for > 12 hours. The dry matter was determined with 4880 mg suspended solids/litre.

Chemicals

All chemicals used in the test were “analytical grade” or otherwise proved suitable.

Stock solutions

Solution a 

   Potassium dihydrogenephosphate (KH2PO4) 8.5 g 
   Di-potassium hydrogenephosphate (K2HPO4)  21.75 g 
   Di-sodiumhydrogenephosphate dihydrate
   (Na2HPO4*2H2O) 		 33.4 g 
   Ammonia chloride (NH4Cl) 0.5 g 
   H2O demin. ad  1000 mL 

The pH was adjusted to 7.4 ± 0.1.

Solution b

   Calcium chloride dihydrate (CaCl2*2H2O)  36.4 g 
   H2O demin. ad  1000 mL 

Solution c

   Magnesium sulfate heptahydrate (MgSO4*7H2O) H2O
   demin. ad 		 22.5 g 
   H2O demin. ad  1000 mL

Solution d 

   Iron(III) chloride hexahydrate (FeCl3*6H2O)  0.25 g
   Di-sodium-ethylendiamintetraacetate dihydrate
   (Na2EDTA*2H2O) 		  0.4 g 
   H2O demin. ad  1000 mL

Test Medium

The medium was freshly prepared.
Composition:

   Solution a 10 mL 
   Solution b 1 mL 
   Solution c 1 mL 
   Solution d 1 mL 
   H2O demin. Ad  1000 mL