Abstract: Process for the production of citric acid, characterized in that E. Coli KG 93, F.sup.- is cultivated in a first step for 15-24 hours at a temperature of 20.degree.-37.degree. C. and a pH of 5.0-7.5 on a substrate consisting of whey permeate to which has been added phosphates in a content of 0.8-1.6 g/l and nitrates in a content of 0.8-1.2 g/l or a corresponding quantity of urea, that H. Wickerhamii CBS 4308 in a second step is cultivated for 20-26 hours at a temperature of 15.degree.-35.degree. C. and a pH of 4.5-6.5 on the cultivating solution from the first step, whereupon citric acid is obtained from the cultivating solution in a way known per se.

Abstract: A sterilizing apparatus for liquid, preferably water, in which the liquid passes through a sterilizing chamber only when the apparatus has sufficient sterilizing capability. The apparatus is provided within ultraviolet-light source, a heat sensing means, and a light intensity sensing means, the latter two means being connected to a valve controlling the flow of liquid through the apparatus. A filter is also provided through which the liquid passes before it reaches the light source.

Abstract: An improved process for biological purification of liquid wastes is provided. The improvement is obtained by utilizing anaerobic bacteria in the presence of extra-cellular enzymes produced by Gram-positive bacteria and separated from said Gram-positive bacteria and the intra-cellular enzymes contained therein. As compared to the current technique the anaerobic process according to the invention may produce only 0.2% of sludge, while the retention time may be only 25% of the time currently used.