Why should the starting liquid level of the pumping station be set at the bottom of the water inlet pipe?

Chapter 1 Overview

1. 1 Main contents of graduation project (thesis) (including main technical parameters)

1. 1. 1 design theme

Process design of 300,000 tons/day municipal sewage secondary treatment plant

1. 1.2 design scale and water quality

1, design scale:

The service scope of this sewage treatment plant is domestic sewage and industrial wastewater in urban areas. The amount of sewage is 30× 104m3/d, in which the ratio of domestic sewage to industrial wastewater is about 6:4.

2. Design inlet water quality:

According to the feasibility study report of the sewage treatment plant project and referring to similar projects, the water quality indicators of the sewage treatment plant are determined as follows:

COD:480mg/L； bo D5:230mg/L； SS:250mg/L；

Ammonia nitrogen: 35 mg/L; TN:45m g/L； TP:4mg/L；

Water temperature: ≥12oc; pH:6 ~ 9； Total alkalinity: 280mg/L (calculated by CaCO3)

3, sewage treatment plant effluent quality:

The effluent quality meets the Grade I B standard in the Discharge Standard of Pollutants for Urban Sewage Treatment Plants (GB 189 18-2002). Specific main water quality indicators are as follows:

COD:≤60mg/L； bo D5:≤20mg/L； SS:≤20mg/L；

NH3-N:≤8mg/L； TN:≤20mg/L； Total phosphorus: ≤ 1 mg/L.

1. 1.3 basic data

1, meteorological conditions:

Annual average temperature:11℃;

Extreme maximum temperature: 42.4℃;

Extreme minimum temperature:-18.8℃;

Annual average precipitation: 637.9 mm; ;

Average sunshine hours: 2 147.3 hours; Maximum wind speed:17.0m/s; The dominant wind direction is northeast wind, and the second dominant wind direction is southwest wind.

2. Hydrogeology

Diving: it is mainly distributed in the pores of loess, silt, silt and gravel layers, and the average buried depth of water level is 4 ~ 5m.

Confined water: 30m underground.

Geology: Surface sediments are composed of Quaternary Holocene plain fill, impact aeolian loess, impact silty clay, silt, spun yarn and gravel layer, with a thickness of 5~20m.

3. Topography

The proposed sewage treatment plant is flat and suitable for engineering construction, with an average elevation of 420m m.

4. Elevation of water inlet pipe:

The water inlet pipe is located on the west side of the proposed sewage treatment plant, and the elevation of the inner bottom of the water inlet pipe is 415m; ;

5. Receiving water body

The receiving water body is located 300 meters to the east of the plant, and the river water quality meets the Class III standard in the Environmental Quality Standard for Surface Water. The highest water level of the river once every 30 years is 4 17m.

1.2 Work to be completed for graduation project (thesis) (including the number of drawings)

A graduation internship report;

An English translation;

A written report on the results of the stage;

Six graduation design drawings (A 1 Drawings), mainly including general plan, process flow chart, elevation layout and plan and section of main single buildings. At least one hand-drawn drawing (drawing A 1) is required.

A graduation design calculation instruction, including: (1) cover; (2) Graduation design (thesis) task book; (3) An overview or abstract of the design; (4) English design summary or English abstract; (5) catalogue; (6) text; (7) references; (8) Appendix; Thank you.

1.3 degree of treatment

The degree of sewage treatment is determined by the discharge standards of the object and area.

1.3. 1 inlet and outlet water quality BOD5

Chemical oxygen demand (mg/L)

(mg/L) Suspended solids

(mg/L) Ammonia nitrogen

(mg/L) Total nitrogen

Total phosphorus (mg/L)

(mg/L)

water penetration

Effluent removal rate ≤ 20 ≤ 60 ≤ 20 ≤ 8 ≤ 20 ≤11.3.2

E=× 100%