Inhibition of the respiration of activated sludge
Toxicity of chemicals and paper additives
- Evaluate the toxicity of chemicals on the treatment of paper mill effluents
- Limit the impacts of additives and papermaking adjuvants on the wastewater Treatment Plant (WWTP)
- Simulate the losses and transfer of chemicals between the paper machine and the wastewaster treatment plant
General informations
The effluent laboratory is equipped with an aeration bench and a respirometer to measure the oxygen consumption (respiration) of activated sludge from wastewater treatment plants.
The method is applicable for measurements of oxygen consumption in aerated lagoons, treatments with fixed cultures and all types of aerobic treatments.
The method allows to quantify the inhibition of sludge respiration.
The following parameters are determined:
- Inhibitory concentration (IC50) of a product (additive / adjuvant).
- Assessment of microbial activity in industrial effluent and in aerobic biological treatments.
Technical Data and Achievements
Activated sludge respiration test
The activated sludge respiration measurement is carried out using the Strathtox Kelvin instrument respirometer.
The device is used to perform inhibition tests of oxygen consumption by activated sludge according to standard NF EN ISO 8192 (2007) - Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation. This method allows to assess the inhibitory effect of a chemical or paper additive on oxygen consumption by purifying microorganisms. This inhibitory effect may include effects on respiration and nitrification.
The test is carried out on industrial effluents, products and activated sludge sampled on site. The chemical or additive to be tested is diluted, at different concentrations, in the effluent during a time corresponding to the hydraulic retention time, then mixed with the activated sludge under aeration.
The kinetics of oxygen consumption (Standard Oxygen Uptake Rate - SOUR) is determined after a short exposure time with activated sludge.
The inhibitory or stimulatory effects are determined by comparing the oxygen consumption of the control without additive.
The test makes it possible to determine the IC50 which corresponds to the concentration of additive inhibiting 50% of respiration. The residual and cumulative effects of additives on activated sludge can be assessed by injecting the additive several times.
The device contains six oxygen sensors to perform several tests simultaneously and evaluate different test conditions (concentration, contact time, etc.).
Sample management during the test
The samples are aerated at controlled flow rate and kept at constant temperature by water baths.
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| StratOx Respirometer: Probes and wells for measuring oxygen consumption | Standard Oxygen Uptake Rate (SOUR) for different biocides - Example of EC50 inhibitory determination of |