Challenge Technology applications

The CHALLENGE AER-200 Respirometer System consists of one or more biological reaction vessels, gas flow measuring cells, and a computer. The gas measuring base contains eight flow ceHs and associated interconnecting circuitry. As gas flows through each cell under the influence of a slight pressure caused by gas production in the reaction vessel, bubbles of a fixed volume are formed in the lower section of the cell. These bubbles in turn pass through a detection section where a counter is activated. Finally, the number of bubbles is registered by the computer to produce a measure of flow volume and rate. This data is stored by the computer for later data processing.

The methane production activity of anaerobic sludges is related to the history of the sludge, the biomass yield from the wastewater the sludge has been treating, the fraction of methanogens, and the presence of toxic substances.

OUR measurements were made for two waste streams from a chemical production plant. The fingerprint for Waste 1 indicated the presence of three major groups of organic constituents. The first group of readily biodegradable organic constituents is oxidized at maximum kinetic rate through about one hour of contact. Oxidation of a second group of constituents causes the OUR to increase through about 3.5 hours of incubation. This increase in OUR is caused by growth of microorganisms during the oxidation reaction. Oxidation of a third group of constituents - in this case thought to be nitrification - extends beyond six hours of contact. The test was terminated before the reaction was complete. The OUR fingerprint for Waste 2 shows a sharp biodegradation peak for readily biodegradable organics followed by a small plateau between one and 1,5 hours. The fact that the OUR for Waste 2 returned to endogenous within five hours indicates that the biodegradation reaction was essentially complete.

Test Setup: 40 and 60 mL of wastewater were added to individual respirometer flasks each containing nutrient/mineral/buffer medium to form two different dilutions. TCMP was added to inhibit nitrification. 25 mL of seed from a laboratory scale reactor was added to each test reactor. Oxygen uptake was monitored using a CHALLENGE AER-200 respirometer for five days. A second dose of 40 and 60 mL of leachate sample was then added to each reactor and oxygen uptake was measured for another 5 days.

Sample Type: Mixed liquor solids from an activated sludge process MVLSS = 1320 mg/L.

Waste Type: Activated sludge process effluent.

Measurement of oxygen uptake of the pesticides: carbaryl, carbofuran and aldicarb in samples seeded with microorganisms extracted from compost.

A pharmaceutical company was interested in knowing whether a specific component, MCB, inhibited the biodegradation of other wastewater constituents. A series of respirometer tests was set up using identical mixtures of wastewater and return activated sludge (RAS) plus varying amounts of MCB. The OUR fingerprint of this wastewater includes a first peak of about 500 mg/L-hr within the first hour of contact that represents the oxidation of highly-biodegradable organic constituents. A second group of readily biodegradable constituents caused a second high OUR peak between one and two hours.

A pulp mill was interested in evaluating the impact of increasing organic loading rates on the performance of their activated sludge systems.

METHOD: A seed culture from a full-scale anaerobic digester was placed in a number of 200 mL respirometer vessels. A synthetic wastewater having a 20,000 mg COD/L in a nutrient/ mineral/buffer solution was fed daily to each reaction vessel — along with various amounts of the cleaning agent The reactors were operated for a four day test period with measurement of gas production using a CHALLENGE ANR-200 anaerobic respirometer.