Abstract: A method and apparatus for backflushing downflow filters is disclosed which comprises providing a closed container having contiguous, vertically adjacent filter layers. A layer of gravel is provided below the filter layers and is separated from the bottom filter layer by a foraminous gravel retention member. Fluid under pressure is introduced through a plurality of fluid nozzles into the gravel layer to backflush the filter layers. Backflush fluid in introduced at a sufficient flow rate to fluidize all of the filter layers to segregate them in accordance with their specific densities and particle size. Introducing the backflush fluid into a gravel layer through a plurality of nozzles helps prevent development of localized areas of high fluid velocity that can cause intermingling of the filter layers during backflush.

Abstract: An ultrasonic streaming current detector for developing, on a continuous basis, an electric signal which is a function of the charge condition existing in a stream containing charged particles. The present invention has a cross shaped housing having a cross member and a longitudinal member containing a pump chamber having a reciprocating piston on a pair of signal generating electrodes. A fluid injection connection is provided to the base of the longtudinal member. The piston pumps a sample stream within the pump chamber, creating a reciprocating shear force against the sample stream, generating an electric signal across the electrodes. The generated signal is representative of the average electric charge of the suspended particles in the sample stream. To prevent buildup of sample particles in the pump chamber, which would bias the signal, a periodic wash backflow of a fluid is injected into the pump chamber, preferably at a point opposite the point of sample fluid injection.

Abstract: An ultrasonic streaming current detector for developing on a continuous basis, electrical signal which is a function of the charge condition existing in the stream containing charged particles therein, for thereby facilitating the determination of the dosage of floculate to be added to a charge implacing species field stream, for thereby ultimately controlling floculation of such streams. The present invention employs a cross-shaped housing having cross-member and a longitudinal member, a piston receiving member, a reciprocating piston, a pair of electrodes, a meter recorder and a electrical mortar. The piston pumps, the simple stream within its interior and by means of this reciprocating shear force against the simple stream generating an electrical signal across electrodes dispositioned at either end of the pump stroke of the piston to thereby generate an electrical signal through lead wires connected to a meter recorder box.