Abstract: There is disclosed a method for sampling and examining a fluid from a tank or flow line to determine density or turbidity, including a sampling chamber attached to the tank or line with a piston in a chamber. The piston is provided with a sealing ring which circumscribes one end of the piston and which provides a fluid-tight seal within the chamber so that moving the piston away from the tank or line pulls a sample into the chamber. The sealing ring comprises a main body portion which circumscribes the piston and is in contact therewith but which is not in sealing engagement with the chamber. Extending outwardly from the main body portion of the sealing ring and integral therewith is a frusto-conical skirt. The outermost edge of the frusto-conical skirt is in sealing contact with the cylinder. A light source is provided to transmit light into the sample and a photodetector is provided to detect light from the interior of the chamber.

Abstract: Activated sludge sewage treatment process comprising aerating a mixed liquor comprising phosphate-containing influent sewage material to cause the microorganisms present to take up phosphate, separating phosphate-enriched sludge from the mixed liquor, and settling the separated sludge in a phosphate stripping zone to form supernatant liquor and settled sludge. At least part of the settled sludge is maintained under anaerobic conditions to cause release of soluble phosphate and the resulting sludge containing released phosphate is contacted with a lower soluble phosphate content medium to effect phosphate enrichment of the supernatant liquor in the stripping zone, with at least a portion of the anaerobic sludge being recirculated to the aeration zone.

Abstract: There is disclosed a process and apparatus for measuring the amount of a dissolved gas in a liquid wherein the device used to measure the gas is not immersed in the liquid and wherein there is no requirement that a sample of the liquid be removed from the main body of the liquid to be tested. A vertical zone is provided in the body of liquid which is to be measured for the amount of gas contained in the liquid, such as in the aeration tank in a sewage treatment system. The zone is at least partially open at the lower end so that it is in communication with the body of liquid and is closed to contact with the body of liquid on the sides. A gas is passed into the lower portion of the zone and a gas-lift effect is created in the zone. Gas is recovered at the upper portion of the zone and is returned to the lower portion of the zone, thereby creating a closed recirculating gas system -- i.e., the system is closed to the atmosphere and to the liquid outside of the zone.