Both susceptibility to chemical oxidation and biodegradability of nitrobenzene are determined. Nitrobenzene is found to be resistant to chemical oxidation with potassium permanganate and is partially oxidized with potassium dichromate. Biodegradability is studied in a batch and in a flow-through system both with municipal and with artificially prepared wastewaters. Nitrobenzene present in municipal wastewater a t 300 g/m3 concentrations is found t o be biodegradable after adaptation of the biomass. In a flow-through system nitrobenzene is degradable a t 400 g/m3 concentration. Concentrations exceeding 10 g/m3 inhibit the nitrification process.

Whenever possible, neutralization of alkaline wastewater should involve low-cost acid. It is conventional to make use of carbonic acid produced via the reaction of carbon dioxide (contained in flue gases) with water according to the following equation: Carbon dioxide content in the flue gas stream varies from 10% to 15%. The flue gas stream may either be passed to the wastewater contained in the recarbonizers, or. enter the scrubbers (which are continually sprayed with wastewater) from the bottom in oountercurrent. The reactors, in which recarbonation occurs, have the ability to expand the contact surface between gaseous and liquid phase. This can be achieved by gas phase dispersion in the liquid phase (bubbling), by liquid phase dispersion in the gas phase (spraying), or by bubbling and spraying, and mixing. These concurrent operations are carried out during motion of the disk aerator (which is a patent claim). The authors describe the functioning of the disk aerator, the composition of the wastewater produced during wet gasification of carbide, the chemistry of recarbonation and decarbonation, and the concept of applying the disk aerator so as to make the wastewater fit for reuse (after suitable neutralization) as feeding water in acetylene generators.

Presented is an analytical method which enables a quick determination of the total cation content in water. I n this method, total alkalinity is determined before passage, and mineral acidity after passage through the ion exchange bed. The sum of the two parameter values gives the total cation content in the water. Verification was carried out with model solution and natural water samples. The method makes it possible t o verify the ion balance of the electrolytes, as well as t o determine the salinity level (i.e. the concentration of dissolved substimces) in the sample.

Su7rci)rnry:The successful purification of waste waters from the leather and textile industries is possiblo by flocculation with aluminium sulphate and alkaline-earth chlorides. BaCI, proved very successful among the applied alkaline-earth chlorides. The removal of oily emulsions and tensides was very effective when the waste waters were treated by a two-stage flocculation process. By an excessive application of BaClz also a reduction of sulphate was obtained. Wastewaters treated in the neutral range showed a purification effect of 98 O/", so that the effluents were clear and colourless. The time of sedimentation amounted to 1 h only. Segregated oil was successfully removed m ith the aid of a very absorptive polyurethane foam. cn