In order to comply with the Wastewater Ordinance (AbwV) and to determine the monitoring values required for the release permit, wastewater must be examined for any environmental hazards. In concrete terms, this means, in addition to the chemical and physical tests, ecotoxicological and microbiological analyses are also required. These are used to test the effect wastewater has on a representative number of test organisms, such as bacteria, algae, microcrustaceans and fish eggs.
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Our service portfolio for microbiological analysis:
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.
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.
Using this method, we can make statements about the inhibitory effect wastewater constituents have on the respiration of Pseudomonas putida after an exposure time of 30 minutes. The results give an indication of the bacterial toxicity of the wastewater, which could disrupt the biological degradation process in wastewater treatment plants.
The oxygen content of various sample dilutions (diluted with a microorganism-containing mineral medium) is determined after 0 and 5, or 0 and 7 days. This BOD5 or BOD7 value measures the sum of all biodegradable organic substances in an aqueous sample and is given as an mg O2/L sample. The BOD provides information about the oxygen depletion caused by wastewater in a body of water or wastewater treatment plant.
The umu-test is used to determine the mutagenic potential of the constituents of water and wastewater. By comparing the spontaneous activation of the umuC gene with the rate induced by the effects of the test material, it is possible to measure the genotoxicity or the mutagenic potential of the wastewater being analyzed after several hours of exposure.
This is a method for estimating the short-term inhibitory effect of wastewater on nitrifying bacteria in activated sludge. The term “nitrification” refers to the oxidation of ammonium compounds by bacteria, which usually produces nitrite as both an intermediate and end product. After a test period of 3 to 24 hours, the percentage of nitrification inhibition caused by the test material is determined by measuring the difference between the concentrations of the nitrogen compounds formed (nitrite and nitrate).