Measurement of Biodegradable Material in Wastewater

Standards for testing wastewater for bacteria, toxicity, and biodegradable material specify test and screening methods. Detailing the scenarios in which a particular test is applicable, as well as the sampling and scale elements of a test, these standards address the detection and enumeration of multiple types of bacteria, as well as both the effects of wastewater on bacteria and the effects of the bacteria on larger forms of life.

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ISO 11733:2004

Water quality - Determination of the elimination and biodegradability of organic compounds in an aqueous medium - Activated sludge simulation test

ISO 11733:2004 specifies a method for the determination of the elimination and the biodegradability of organic compounds by aerobic micro-organisms. The conditions described simulate a wastewater treatment plant. Two test systems can be used: activated sludge plants or porous pots. The tests can optionally be performed under conditions of nitrification and denitrification and coupling of the units. The method applies to organic compounds which, under the conditions of the test, are soluble in tap water at the test concentration and not expected to be transformed to insoluble metabolites if biodegradation, in addition to elimination, is determined; poorly water-soluble, but which are satisfactorily dispersible in water and allow detection with suitable analytical means (e.g. organic carbon measurements); non-volatile, or which have a negligible vapour pressure under the test conditions; not inhibitory to the test micro-organisms at the concentration chosen for the test. Compounds inhibitory at concentrations used in this test may be tested at concentrations less than their EC 20 value, followed by higher practical concentrations after a period of acclimatization. The method can also be used to measure the biodegradation and elimination of dissolved organic compounds in waste water (also called test compound in the method).

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ISO 9888:1999

Water quality -- Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium -- Static test (Zahn-Wellens method)

This International Standard specifies a method for the evaluation in aqueous medium of the ultimate biodegradability and, as additional information, the primary biodegradability and the total elimination from water, of organic compounds at a given concentration by aerobic microorganisms. The conditions described in this International Standard normally correspond to optimal conditions for allowing the maximum value of biodegradation to occur with the chosen inoculum in the test time. These conditions may even be more favourable than in full-scale wastewater treatment plants, especially if their hydraulic retention time, sludge age or the adaptation of the activated sludge is not optimal. The method applies to organic compounds which are water-soluble at the concentration used under the test conditions and not expected to be transformed to insoluble metabolites if biodegradation and not elimination only shall be determined; nonvolatile, or which have a negligible vapour pressure under the test conditions; not lost by foaming from the test solution; not inhibitory to the test microorganisms at the concentration chosen for the test. Inhibitory effects can be determined using a suitable test method (e.g. see ISO 8192). If the test compound is toxic, the test concentration must be lowered, or a pre-exposed inoculum can be used. This International Standard is also applicable to the measurement of biodegradation and elimination of dissolved organic compounds in wastewater (also called "test compound" in the method).

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