Abstract: A process for decontaminating a solid material contaminated with an organic pollutant wherein the solid material contains grains with a particle size of up to 60 microns, which includes the steps of:(a) extracting the organic pollutant from the solid material containing grains with the particle size up to 60 microns by using a microemulsion which includes a thermodynamically stable, macroscopically homogeneous and optically transparent mixture of water, an apolar hydrophobic solvent, and a surfactant to form a cleaned solid material and a pollutant-containing microemulsion;(b) separating the cleaned solid material from the pollutant-containing microemulsion; and(c) splitting the pollutant-containing microemulsion into a surfactant-rich phase and a pollutant-containing phase.

Abstract: The coalescence and release of bubbles from packing that supports the growth of microorganisms is promoted by mechanical action on the packed bed arrangement, in particular by continuous or intermittent vibrations, rotations, or by rocking motions. With particular advantage, a reactor vessel which is typically tubular is filled with packing upon which microbial growth is sustained, preferably leaving a free space of 10% to 35%, in particular 15% to 20%. The reactor vessel has an axis that is substantially horizontal but preferably inclined by at least about 3.degree., and is set continuously or intermittently, for example, by an axle drive or by means of friction wheel drive, into rotational or rocking motions about that axis. The gas can be discharged, for example, via valves and a cam mechanism. Alternatively, a vent pipe, taken through the hollow shaft on the discharge side and upwards, can be provided behind a screen plate.

Abstract: Aerobic purification of waste water with intermittent batchwise supply of waste water to the activated sludge tank from which the treated waste water drains continuously is disclosed, in which the nitrate content in the waste water is simultaneously reduced by throttling the aeration of the activated sludge tank, starting with the admission of the waste water to the tank, to values equivalent to less than or equal to 0.5 mg/l dissolved oxygen. In particular, aeration may be off until such time as the nitrate content in the tank has dropped below 5 mg/l, in particular below 1 mg/l. In the case of urban waste waters a cycle time of about 1 hour is expediently employed under these circumstances and the aeration is shut off for about 5 minutes, starting from the rapid admission of the waste water charge. Preferably, inlet charges are less than or equal to 30%, in particular between about 5% and 20%, of the tank capacity.

Abstract: A method is provided for optimally supplying autotrophic organisms with CO.sub.2 nutrient, the requirement for the nutrient fluctuating in dependence on growth and thus on the incident light, temperature and the density of the organisms. The pH in a culture channel containing the organisms is continuously measured and the introduction of CO.sub.2 into the culture channel is regulated in response to the measured pH. An arrangement is provided for practicing the method and comprises a channel in which a suspension of the organisms can be moved in one direction, at least one discharge means in the channel for introducing the CO.sub.2 gas into suspension, at least one control member connected to the discharge means for controlling the operation of the discharge means, at least one pH measuring means in the channel for immersion into the suspension, and a circuit connecting the pH measuring means and the control member to actuate the control member for introducing the CO.sub.