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AERATION: Principles and Practice ( VOLUME 11 ) - Chapter 4

Sâu bể sục khí với cân nhắc Blower và nén Độ sâu tiêu biểu của các bể sục khí khuếch tán khác nhau trên phạm vi từ 3,50 đến 6,00 m. Phạm vi này được minh họa bằng một đánh giá của 98 bài kiểm tra được công bố ở Đức (Pöpel và Wagner, 1989) cho thấy sự phân bố xe tăng độ sâu sau: • bể độ sâu lớn hơn 6,00 m: 10% • độ sâu bể 4,00 đến 6,00 m: | 4 Deep Tank Aeration with Blower and Compressor Considerations 4.1 INTRODUCTION Typical depths of diffused aeration tanks vary over a range from 3.50 to 6.00 m. This range is illustrated by an evaluation of 98 published performance tests in Germany Popel and Wagner 1989 showing the following tank depth distribution tank depths greater than 6.00 m 10 percent tank depths 4.00 to 6.00 m 50 percent tank depths less than 4.00 m 40 percent Greater tank depths 20 to 30 m equipped with special ejector systems for oxygenation have been used for treating industrial effluents only by applying the so-called tower-biology Bayer company Diesterweg et al. 1978 and bio-high-reactor Hoechst company Leistner et al. 1979 . These systems produce very small bubbles micrometer range which remain stable at the high salinity some 20 g l of the wastewater. However at municipal wastewater conditions these bubbles would coalesce and lead to poor oxygen transfer performance. There is however a strong tendency towards greater tank depths probably due to the following reasons when upgrading wastewater treatment plants for biological nutrient removal especially for biological nitrogen removal the required increase of tank volume leads to much less area usage at greater depth due to the higher oxygen transfer efficiency at greater tank depth less air is required producing less off-gas and odor problems and leading to less extensive gas cleaning equipment in addition to the rise of the oxygen transfer efficiency also an increase of the aeration efficiency is expected which would lead to energy savings. Consequently a number of activated sludge plants in Europe have been upgraded for nutrient removal using significantly greater tank depths than stated above. Table 4.1. Wagner 1998 gives more detailed information on this development. In this context deep diffused aeration tanks can be defined by having a depth of significantly greater than 6.00 m. 2002 by CRC Press LLC TABLE 4.1 Examples of Deep .