问题 问答题 简答题

污泥回流的方式有哪几种?它们各自的优缺点是什么?

答案

参考答案:

污泥回流的方式主要有依靠污泥泵、空气提升器和螺旋泵提升回流。

污泥泵的运行效率较高,可用于大规模的污水处理工程。采用污泥泵时,将二沉池流出的回流污泥集中到污泥井,再抽到曝气池;

空气提升器利用升液管内外液体的密度差而使污泥提升的。它的结构简单,管理方便,而且有利于提高活性污泥中的溶解氧和保持活性污泥的活性,多为中、小型污水处理厂所采用;

近几十年,回流污泥系统中,比较广泛应用螺旋泵。螺旋泵效率高,而且稳定;能够直接安装在曝气池与二沉池之间,不必另设污泥井和其他附属设备;转速较慢,不会打碎活性污泥絮凝体颗粒;不因污泥而堵塞,节能,维护方便;相比较其费用较高的。

阅读理解

阅读理解。

       Michelle Kwan is a famous American figure skater  ( 花样滑冰运动员 ).  Many young people like

her a lot.  She is half-Chinese and was born on July 7,  1980.  Her hometown is in Guangdong, China.  

Her mother is an American.  Michelle is the youngest of their three children.  She has a brother and a

sister.  They also like figure skating.

      Michelle has won seven National Championships of America and has won eight medals at the World Championships.  She has also won two Olympic medals.  She got the third place in 1998, and the second

in 2002.  When she talks about her success, she says, "My parents taught mc to work hard. If you do,

your dreams may come true."

      She also says,  "What you give is what you get back. " In the future,  the popular skate: wants to be

the Michael Jordan of her sport.

1.There are______people in Kwan's family.

A. 3

B. 4

C. 5

D. 6

2. She's a half-Chinese because______.

A.her mum is Chinese and her dad is American

B.her dad is Chinese and her mum is American

C.both of her parents are Chinese except her

D.she has a brother and a sister

3. In the 2002 Olympic Games Michelle Kwan got______in the 1998 Olympic Games.

A.a worse medal than

B.a better medal than

C.a medal as good as

D.We don't know.

4. The secret of Kwan's success is______.

A.to work hard

B.to give less

C. to get more

D. to smile to others

5. The last sentence in the passage means Kwan wants to______.

A.play basketball instead of skating

B.learn basketball from Jordan

C. be the best figure skater

D.practice basketball and skating

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