Aerobic Biodegradability in water

General informations

Effluent laboratory is equipped with an aeration bench as well as equipment for COD analysis in effluents. This allow us to realize organic matter elimination testing in aerobic activated sludge. This test aim at determining the following parameters:

• Adsorption capacity of organic substances by activated sludges
• Determination of aerobic biodegradability of organic compounds or effluent
• Determination of refractory COD (non biodegradable)
• Testing nitrogen and phosphorus elimination
• Assessment of aerobic activity of microbes in industrial effluents and/or sludges

Thanks to this apparatus, the Team Water Energy Environment helps industrials to improve effluent treatment and purification plant.

Technical Data and Achievements

Measurement of biodegradation kinetics
The effluent to be tested is mixed in an erlenmeyer with activated sludges from the industrial site. Parallel controls are realized in sludge mixed with reference samples from treatment plant outlet. The mixed samples are placed in controlled aeration an temperature in water-bath.
COD is periodically analysed (t = 5 min, 1h, 3h, 6h et 24h) with kit micro-method, to observe biodegradation kinetics. Refractory COD is defined as a ratio between residual COD after 24h and initial COD from effluent.
Biodegradability of paper manufacturing or process chemical additives can be determined as well. Is this case the additive is added in an effluent with various concentrations during a period corresponding to the hydraulic retention time preliminary determined. The effluent is then mixed with activated sludge and the biodegradation kinetics as well as residual COD are determined following the method previously described. The method adapted from OECD « Guidelines for testing ready biodegradability of chemicals » makes possible to realize biodegradability testing with reduced delay.

Measurement of COD additives adsorption in effluent
This specific testing has been developed to determine COD reduction by adsorption.
The test is similar to ISO 18749 : 2004 (Water quality - Adsorption of substances in activated sludge). Activated sludge are placed under nitrogen bubbling to remove dissolved oxygen and inhibit aerobic COD degradation. COD is analysed initially and after 5 minutes of contacting between the additive and activated sludge and compared with blank control. COD variations represent the additive fraction adsorbed in activated sludge flocs.

COD measurement with micro-method
Measurement is made according to ISO 15705 : 2002 standard. This measurement is realized in closed test tubes, with major advantage related with simplicity and sort delay.