As representative examples of bacteria, the inhibitory effect of wastewater on the light emission of luminescent bacteria is determined by combining specified volumes of the test sample with the luminescent bacteria suspension. The test criterion is the decrease in luminescence measured after an exposure time of 15 and 30 minutes in comparison to a control solution.
As representative examples of plants as primary producers, we analyze green algae. Green algae are cultivated over several generations in a specified culture medium in various concentrations (dilution levels) of wastewater and under defined conditions. There are certain substances that can inhibit the algae’s biomass production throughout this process depending on their concentration. This inhibitory effect is used to measure the toxicity of the test material in relation to the test organism.
Daphnia toxicity (DIN 38 412, Part 30: 1989):
As representative examples of primary consumers in aquatic systems, we analyze microcrustaceans (Daphnia magna), which can be damaged by wastewater constituents. These analyses measure the toxic effect wastewater has on the microcrustaceans over a series of dilutions within a 24-hour period. Damage to the microcrustaceans manifests as a loss of ability to swim.
The development of fertilized fish eggs can be impaired by wastewater constituents. Once the test organisms have been exposed to the wastewater contents for 48 hours, it is possible to determine the acute toxic effect these contents have on the development of the fish embryos.
To determine whether wastewater constituents are biodegradable, tests are conducted with aerobic microorganisms that track the elimination of these contents over a period of up to 28 days using COD or DOC measurement methods. The ratio of the eliminated COD or DOC is expressed as a percentage of the initial COD or DOC value (0 h). Additional analyses are carried out depending on the order placed, e.g. TOC, AOX, individual substance analyses, luminescent bacteria tests.