L1- INTRODUCTION TO WASTE WATER ENGINEERING.pptx

Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environment or is reused for various purposes (called water reclamation).

1. WASTE WATER ENGINEERING MODULE I – INTRODUCTION definition sources quantity Objectives effects Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 1

2. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 2

3. Historical Background Many ancient cities had drainage systems, but they were primarily intended to carry rainwater away from roofs and pavements. Privy vaults and cesspools were used, but most wastes were simply dumped into gutters to be flushed through the drains by floods. Toilets (water closets) were installed in houses in the early 19th century, but they were usually connected to  cesspools , not to  sewers . Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 3

4. Historical Background In densely populated areas, local conditions soon became intolerable because the cesspools were seldom emptied and frequently overflowed.  In England in the middle of the 19th century, outbreaks of cholera were traced directly to well-water supplies contaminated with human waste from privy vaults and cesspools. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 4

5. Historical Background It soon became necessary for all water closets in the larger towns to be connected directly to the storm sewers. This transferred sewage from the ground near houses to nearby bodies of water. Thus, a new problem emerged: surface water pollution . Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 5

6. Background Urbanization - rise to a number of environmental problems : water supply with desirable quality and quantity In urban areas for domestic and industrial uses the source of water is generally reservoir, river, lake, and wells . Out of this total water supplied, generally 60 to 80% contributes as a wastewater. In most of the cities, wastewater is let out partially treated or untreated and it either percolates into the ground and in turn contaminates the ground water or it is discharged into the natural drainage system causing pollution in downstream water bodies. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 6

7. DEFINITIONS Sewage: It indicates the liquid waste originating from the domestic uses of water. It includes Sullage Discharge from toilets Urinals Commercial establishments Institutions Industrial establishments Groundwater and stormwater Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 7

8. DEFINITIONS Sullage(Grey Water) : This refers to the wastewater generated from bathroom sink, kitchens, washing place and wash basins, etc. Composition of this waste does not involve higher concentration of organic matter and it is less polluted water as compared to sewage. Wastewater: The term wastewater includes both organic and inorganic constituents, in soluble or suspended form, and mineral content of liquid waste carried through liquid media. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 8

9. DEFINITIONS Sanitary sewage(Black Water): Sewage originated from the residential buildings comes under this category. This is very foul in nature. It is the wastewater generated from the lavatory basins, urinals and water closets of residential buildings, office building, theatre and other institutions. It is also referred as domestic wastewater. Industrial wastewater: It is the wastewater generated from the industrial and commercial areas . This wastewater contains objectionable organic and inorganic compounds that may not be amenable to conventional treatment processes. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 9

10. DEFINITIONS Sewer: It is an underground conduit or drain through which sewage is carried to a point of discharge or disposal. There are three types of sewer systems that are commonly used Separate sewers are those which carry the house hold and industrial wastes Storm water drains are those which carry rain water from the roofs and street surfaces. Combine sewers are those which carry both sewage and storm water together in the same conduit. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 10

11. DEFINITIONS Sewerage: The term sewerage refers the infrastructure which includes device, equipment and appurtenances for the collection, transportation and pumping of sewage , but excluding works for the treatment of sewage. Sewage Treatment Plant is a facility designed to receive the waste from domestic, commercial and industrial sources and to remove materials that damage water quality and compromise public health and safety when discharged into water receiving systems or land. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 11

12. SOURCES OF SEWAGE Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 12

13. Quantity of discharge Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 13

14. Quantity of discharge (i) RATE OF WATER SUPPLY: The rate of sewage may be 60 to 70 percent of water supply due to various reasons such as consumption, evaporation, use in industries etc. This may be changes daily, seasonal and also standard of living of people. (ii) POPULATION: As the population increases the quantity of sewage also increases because the consumption of water is more. (iii) TYPE OF AREA SERVED: The quantity of sewage depends upon the type of area as residential, industrial or commercial. The quantity is depends on population if it is residential, type of industry if it is industrial Commercial and public places can be determined by studying the developing of other such places. (iv) GROUND WATER INFILTRATION: When sewers laid below the water table in the ground, the ground water may percolate in the sewer from the faulty joints and cracks in the pipelines. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 14

15. Quantity of discharge . Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 15

16. SEWAGE DISCHARGE Practically the average sewage never flows in the sewer, it continuously varies from hour to hour of the day and season to season. The consumption of water in summer is more than in winter or rainy season and this change in consumption of water directly affects the quantity of sewage. The quality of sewage and its characteristics show a marked range of hourly variation Peak Average Minimum In the absence of any data an average quantity of 150 LPCD may be adopted for design. Maximum discharge = 2.0 to 3.5 Average discharge . (unless specified) Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 16

17. OBJECTIVES OF SEWAGE COLLECTION AND DISPOSAL Thus, efficient sewerage scheme can achieve the following: To provide a good sanitary environmental condition of city protecting public health. To dispose the human excreta to a safe place by a safe and protective means. To dispose of all liquid waste generated from community to a proper place to prevent a favorable condition for mosquito breeding, fly developing or bacteria growing. To treat the sewage, as per needs , so as not to endanger the body of water or groundwater or land to get polluted where it is finally disposed off. Thus, it protects the receiving environment from degradation or contamination. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 17

18. EFFECT OF UNTREATED WASTEWATER DISPOSAL Unhygienic conditions The organic matter present in the wastewater will undergo decomposition with production of large quantities of malodorous gases. If the wastewater is discharged without treatment in the water body, this will result in the depletion of Dissolved Oxygen (DO) from the water bodies. Due to depletion of DO, the survival of aquatic life will become difficult, finally leading to anaerobic conditions in the receiving waters. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 18

19. EFFECT OF UNTREATED WASTEWATER DISPOSAL The nutrients present in the wastewater can stimulate the growth of aquatic plants, leading to problems like eutrophication. The untreated domestic wastewater contains numerous pathogenic or disease causing microorganisms, that dwell in the human intestinal tract or it may be present in certain industrial wastewaters. The wastewater contains inorganic gritty materials . The continuous deposition of this inorganic material may reduce the capacity of water body considerably over a period. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 19

20. Questions Describe advantages and disadvantages offered by the water carriage system. What are the possible adverse effects when untreated or partially treated sewage is discharged to the environment? Why it is necessary to treat wastewater before disposal? What is the objective of the sewerage works? Define sewage, sullage, sewer, and sewerage. Asst. Prof. Prachi Dessai, Dept of Civil Eng. DBCE 20