Abstract: The invention relates to a process for the purification of a polluted aqueous effluent to obtain an overall reduction in its chemical oxygen demand. The aqueous effluent is introduced into a reactor. Added to the reactor is a reagent comprising an agent supplying active alumina and lime. The reaction forms mineral sludge and an effluent. The mineral sludge and supernatant effluent are then extracted by decantation or filtration.

Abstract: The invention relates to a process for the purification of aqueous solutions polluted by nitrate ions. This process is characterised in that it consists in precipitating hydrated double or mixed calcium nitroaluminates, such as, in particular, hydrated calcium mononitroaluminate, by adding at least one agent supplying the element aluminium and at least one agent supplying the element calcium to the solutions to be treated, the overall mole ratio of the element aluminium to nitrate, Al/NO3, being superior to 1 and the overall mole ratio of calcium to nitrate, Ca/NO3, being superior to 2, and in that the precipitation reaction is performed with stirring and at a basic pH, preferably above 10.5.The process according to the invention is intende, in particular, to the treatment of polluted waters such as municipal waste water and factory effluents and to the treatment of liquid manure.

Abstract: The device improves the decoding of the replies in S mode deformed by multiple-path phenomena or by imbrication with replies in standard A or C mode. To do this, the device carries out the following in the reception video signal Log .SIGMA. of the secondary radar: determines a pulse level reference value of the data block of the reply by a study of the histogram of the presumed pulse levels of data and compares the level of the reception signal Log .SIGMA. taken at the middle of each time interval that may be occupied by a data pulse with the level reference value, a data pulse being detected or not detected according to the result of the comparison. Should there be a negative result in a baud period, it may recommence similar operations on the angle measurement video signal .SIGMA./.DELTA. if the secondary radar is a monopulse radar.