Diffuser (sewage)

About: Diffuser (sewage) is a research topic. Over the lifetime, 6487 publications have been published within this topic receiving 40404 citations.

Maintaining optimum settling rate of activated sludge

Abstract: A completely mixed system for controlling the return rate of activated sludge to the aeration tank in activated sludge sewage treatment system plants is disclosed wherein the return rate of activated sludge is controlled to maintain the density of the activated sludge in the aeration tank at an optimum value, which value will result in the optimum settling rate of the activated sludge in the secondary clarifier. The control system is continuous and requires the use of a computer, which continuously receives various measured quantities necessary to compute the control signal for the returned activated sludge pump. The carbon dioxide respired by the cells in the aeration tank is collected along with the aeration air and a non-dispersive infrared ray analyzer determines the percent of carbon dioxide in the collected gases. This determination is one of the factors entering into the computation of the rate of substrate consumption by the activated sludge. Other measured quantities entering the computer are the rate of air flow entering the diffuser, the density of the activated sludge in the aeration tank, the rate of flow of effluent from the aeration tank and the density of returned activated sludge collected in an activated sludge storage tank. Various physical and biological constants are manually set into the computer, the principal output of which is a signal for controlling the rate of return of activated sludge in the sludge storage tank to the aeration tank. The density of the stored activated sludge is also determined and enters the computer. The computer also compares this density with the actual measured density of the activated sludge in the aeration tank and if the stored sludge density does not exceed the measured density, a warning is given indicating that it is futile to return the stored activated sludge to the aeration tank.

Assessment of microbial aerosol emissions in an urban wastewater treatment plant operated with activated sludge process

Abstract: Wastewater that enters wastewater treatment plants contains lots of pathogenic and nonpathogenic microorganisms which can become bioaerosols during treatment processes and pose health hazard to workers and nearby residents The emission of the bioaerosols from an urban wastewater treatment plant in spring and summer in different locations and downwind of the plant adopting an extended mechanical aeration system was investigated Samples of bacteria and fungi were collected within 6 months at 10 selected points by an Anderson one-stage impactor The highest concentration of bacteria (mean 1373 CFU/m3, 741–2817 CFU/m3) and fungi (mean 1384 CFU/m3, 212–1610 CFU/m3) was found in downwind of the aeration basins Statistical analysis showed a significant relationship between concentration of bacterial bioaerosols at downwind side of the aeration basins and wind speed (p value <005) and temperature (p value <005) Also, in the spring and summer, between the number of bacteria and fungi inside the plant and outside the plant (downwind) a significant correlation was observed (p value ≤005) The concentrations of bacteria at a distance of 500 m downwind were much higher than those at the background (upwind) point in spring and summer The processes of wastewater treatment especially using mechanical equipment to create turbulence can be considered as a major source of spreading airborne microorganisms to ambient air of wastewater treatment plants, and the bioaerosols can be dispersed to downwind distances affecting the nearby neighboring Therefore, in order to decrease the bioaerosols emission, doing some course of actions such as covering the surface of aeration basins, changing the aeration methods and aeration equipment (e g using diffuser aerator) may be effective

Variable geometry device for turbine compressor outlet

Abstract: A variable geometry device is provided for use with the compressor outlet of a turbine engine. The turbine engine includes a support housing, a compressor contained within the support housing and having a compressed air outlet and in which a pair of spaced walls define an annular and radially extending diffuser passageway. The inner end of the diffuser passageway is open to the compressed outlet while the outer end of the diffuser passageway is open to the combustion chamber for the turbine engine. A plurality of circumferentially spaced diffuser vanes are mounted to one of the diffuser walls and protrude across the diffuser passageway. An annular recessed channel is formed around the opposite diffuser wall and an annular ring is mounted within the channel. A motor is operatively connected to this ring and, upon actuation, displaces the ring transversely across the diffuser passageway to variably restrict the diffuser passageway. In addition, the ring includes a plurality of slots which register with the diffuser vanes so that the vane geometry remains the same despite axial displacement of the ring.