PATENT ABSTRACTS 115

methanogenesis, of organic products, by- products or waste from human, animal and/or plant origin, involving feeding said products to be degraded into a closed fermentation vessel, forcing said products to flow in a direction of cir- culation within said vessel and recovering the gas produced called biogas evolved above said body of degraded products, with the feeding and/or discharge of the products performed pneu- matically, preferably through pneumatic thrust and, according to a preferred embodiment, by injection of gas, preferably biogas. A further im- provement comprises using the biogas produced for homogenizing said body of products con- tained within said vessel, the pressure of injection being in relation to the actual density of the products, in the injection related section.

A method and apparatus for determining the ox- ygen uptake rate of bacteria in a body of liquid incorporates withdrawing a sample of the liquid into a chamber where a dissolved oxygen probe is located, the probe outputting a signal which is a function of the amount of dissolved oxygen in the sample. The sample is aerated, and a compu- ter is used to sample the signal at regular inter- vals to produce a series of time-separated values corresponding to the sampled signals, the values representing the dissolved oxygen in the sample at the timed intervals. Repeated samples can be taken, so that the O.U.R. can be monitored on a continuing basis. The O.U.R. information can be used to control the rate of aeration in a tank, or to control the rate of recycling of activated sludge from the downstream to the upstream end of the tank.

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D E T E R M I N A T I O N O F O X Y G E N U P T A K E R A T E IN W A S T E W A T E R

T R E A T M E N T P L A N T S

Daniel W Smith, Edmonton, Canada assigned to The Governors of the University of Alberta