tailieunhanh - AERATION: Principles and Practice ( VOLUME 11 ) - Chapter 5

Bề mặt và sục khí Cơ khí Thông khí cơ học được xác định trong văn bản này là việc chuyển giao oxy nước bằng thiết bị cơ khí để gây ra entrainment oxy không khí vào chất lỏng số lượng lớn bằng cách kích động bề mặt và pha trộn. Ngoài ra, thiết bị là nguyên nhân gây phân tán hoặc nguyện vọng của khí nén, oxy tinh khiết cao, hoặc không khí trong khí quyển bằng cách cắt và bơm của cánh quạt tua-bin quay hoặc cũng sẽ được bao gồm. Người ta có thể phân loại các thiết. | 5 Surface and Mechanical Aeration INTRODUCTION Mechanical aeration is defined in this text as the transfer of oxygen to water by mechanical devices so as to cause entrainment of atmospheric oxygen into the bulk liquid by surface agitation and mixing. In addition equipment that causes dispersion or aspiration of compressed air high purity oxygen or atmospheric air by the shearing and pumping of a rotating turbine or propeller will also be included. One may classify mechanical aeration devices based on the physical configuration of the equipment and its operation. Classifications that will be used in this text include low speed surface aerators motor speed high speed axial surface aerators horizontal rotors submerged sparged turbine aerators and aspirating aerators. Detailed descriptions applications and performance ranges for these devices will be provided below. It appears that mechanical aeration in wastewater was introduced to overcome problems with diffuser clogging in activated sludge systems. The concept was introduced in Europe in the late 1910s predominantly in the UK and spread to the . slowly. By 1929 mechanical aeration plants outnumbered diffused aeration plants in the UK by two to one. In the . a survey by Roe 1938 indicated that about 100 activated sludge plants employed mechanical aeration 200 were using diffused aeration and approximately 20 had combined aeration systems. Porous tile diffuser clogging in Sheffield England spurred the development of an Archimedian screw-type aerator in 1916. In 1920 Sheffield built a full-scale facility using submerged horizontal paddle wheels in narrow channels to m 4 to 6 ft that were about m 4 ft deep called the Haworth System. Located midway between the channel ends that interconnected each aeration tank the shaft rotated at 15 to 16 rpm producing a longitudinal velocity of m s ft sec. The movement of wastewater along the channel created a wave action that allowed transport of .

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