1. Environmental Pollution: Water Pollution
Mr. Rohan Dashupta, Asst. Professor
Department: B.E. Civil Engineering
Subject: Environmental Studies
Semester: I
Teaching Aids Service by KRRC Information Section

2. SEWAGE TREATMENT

3. SEWAGE TREATMENT Pre-treatment:
Pre-treatment removes all materials that can be easily collected from the raw sewage before they damage or clog the pumps and sewage lines of primary treatment clarifiers. Objects commonly removed during pretreatment include trash, tree limbs, leaves, branches, and other large objects.
Bar Screen –
The influent in sewage water passes through a bar screen to remove all large objects like cans, rags, sticks, plastic packets etc. carried in the sewage stream. This is most commonly done with an automated mechanically raked bar screen in modern plants serving large populations. The solids are collected and later disposed in a landfill, or incinerated.

4. SEWAGE TREATMENT Pretreatment:
Grit Removal - Pretreatment may include a sand or grit channel or chamber, where the velocity of the incoming sewage is adjusted to allow the settlement of sand, grit, stones, and broken glass. These particles are removed because they may damage pumps and other equipment. For small sanitary sewer systems, the grit chambers may not be necessary, but grit removal is desirable at larger plants. Grit chambers come in 3 types: horizontal grit chambers, aerated grit chambers and vortex grit chambers.
Fat and Grease Removal - Fat and grease are removed by passing the sewage through a small tank where skimmers collect the fat floating on the surface. Air blowers in the base of the tank may also be used to help recover the fat as a froth.

5. SEWAGE TREATMENT Pretreatment:
Flow Equalization - Clarifiers and mechanized secondary treatment are more efficient under uniform flow conditions. Equalization basins may be used for temporary storage of diurnal or wet-weather flow peaks. Basins provide a place to temporarily hold incoming sewage during plant maintenance and a means of diluting and distributing batch discharges of toxic or high-strength waste which might otherwise inhibit biological secondary treatment (including portable toilet waste, vehicle holding tanks, and septic tank pumpers). Flow equalization basins require variable discharge control, typically include provisions for bypass and cleaning, and may also include aerators. Cleaning may be easier if the basin is downstream of screening and grit removal.

6. SEWAGE TREATMENT Primary Treatment:
In the primary sedimentation stage, sewage flows through large tanks, commonly called "pre-settling basins", "primary sedimentation tanks" or "primary clarifiers". The tanks are used to settle sludge while grease and oils rise to the surface and are skimmed off. Primary settling tanks are usually equipped with mechanically driven scrapers that continually drive the collected sludge towards a hopper in the base of the tank where it is pumped to sludge treatment facilities. Grease and oil from the floating material can sometimes be recovered for saponification.

7. SEWAGE TREATMENT Secondary Treatment:
Secondary treatment is designed to substantially degrade the biological content of the sewage which are derived from human waste, food waste, soaps and detergent. The majority of municipal plants treat the settled sewage liquor using aerobic biological processes. To be effective, the biota require both oxygen and food to live. The bacteria and protozoa consume biodegradable soluble organic contaminants (e.g. sugars, fats, organic short-chain carbon molecules, etc.) and bind much of the less soluble fractions into floc.
List of process types: Activated sludge, Aerated lagoon, Aerobic granulation, Constructed wetland, Membrane bioreactor, Rotating biological contactor, Sequencing batch reactor and Trickling filter

8. SEWAGE TREATMENT Tertiary Treatment:
The purpose of tertiary treatment is to provide a final treatment stage to further improve the effluent quality before it is discharged to the receiving environment (sea, river, lake, wet lands, ground, etc.). More than one tertiary treatment process may be used at any treatment plant. If disinfection is practised, it is always the final process. It is also called "effluent polishing.“
Biological Nutrient Removal
Nitrogen Removal
Phosphorus Removal
Disinfection
Environmental Persistent Permanent Pollutant (EPPP) Removal
Odour Control

9. CASE STUDY: POLLUTION OF THE GANGES
The Ganga is the largest river in India with an extraordinary religious importance for Hindus.
Situated along its banks are some of the world's oldest inhabited cities like Varanasi and Patna.
It provides water to about 40% of India's population across 11 states, serving an estimated population of 500 million people or more, which is larger than any other river in the world.

10. CASE STUDY: POLLUTION OF THE GANGES
Fecal coliform counts up to 100,000,000 MPN (most probable number) per 100 ml.
BOD (biological oxygen demand) levels averaging over 40 mg/l in the most polluted part of the river in Varanasi.
The overall rate of water-borne diseases was estimated to be about 66%.
A systematic classification done by UEPPCB on river waters into the categories A: safe for drinking, B: safe for bathing, C: safe for agriculture, and D: excessive pollution, put the Ganga in D. 
Coliform bacteria levels in the Ganga have also been tested to be at 5,500, a level too high to be safe for agricultural use let alone drinking and bathing.
Chromium levels are more then 70 times the maximum recommended value.
NCRP suggested that "those living along its banks in Uttar Pradesh, Bihar and Bengal are more prone to cancer than anywhere else in the country".

11. CASE STUDY: POLLUTION OF THE GANGES

12. CASE STUDY: POLLUTION OF THE GANGES
Causes
1. Human waste:
An area of 1,800,000 km2 (400,000 square miles), the river flows through 29 cities with population over 100,000; 23 cities with population between 50,000 and 100,000, and about 48 towns. A large proportion of the sewage water with higher organic load in the Ganges is from this population through domestic water usage.

13. CASE STUDY: POLLUTION OF THE GANGES
2. Industrial waste:
Because of the establishment of a large number of industrial cities on the bank of river Ganga like Kanpur, Allahabad, Varanasi and Patna, countless tanneries, chemical plants, textile mills, distilleries, slaughterhouses, and hospitals prosper and grow along this and contribute to the pollution of the Ganga by dumping untreated waste into it. Industrial effluents are about 12% of the total volume of effluent reaching the Ganga. Although a relatively low proportion, they are a cause for major concern because they are often toxic and non-biodegradable.
3. Religious events:
During festival seasons, over 70 million people bathe in the Ganga over a few weeks to clean themselves from their past sins. Some materials like food, waste or leaves are left in the Ganga for ritualistic reasons.

14. CASE STUDY: POLLUTION OF THE GANGES
Effects
Marine Life:
The results of mercury analysis in various specimens collected along the basin indicated that some fish muscles tended to accumulate high levels of mercury. Of it, approximately 50–84% was organic mercury. A strong positive correlation between mercury levels in muscle with food habit and fish length was found.
The Ganges River dolphin is one of few species of fresh water dolphins in the world. Listed as an endangered species, their population is believed to be less than Hydroelectric and irrigation dams along the Ganga that prevents the dolphins from travelling up and down river is the main reason for their reducing population.

15. CASE STUDY: POLLUTION OF THE GANGES
2. Wildlife:
Some of the dams being constructed along the Ganga basin will submerge substantial areas of nearby forest. For example, the Kotli-Bhel dam at Devprayag will submerge 1200 hectares of forest, wiping out the river otters and the mahaseer fish that are found there. Wildlife biologists in India have been warning that the wild animals will find it difficult to cope with the changed situation.
3. Human beings:
Water in the Ganga has been correlated to contracting dysentery, cholera, hepatitis, as well as severe diarrhea which continues to be one of the leading causes of death of children in India.

16. CASE STUDY: POLLUTION OF THE GANGES
Cleaning Efforts
The Ganga Action Plan was launched by Shri Rajeev Gandhi, the then Prime Minister of India on 14 Jan, 1986 with the main objective of pollution abatement, to improve the water quality by interception, diversion and treatment of domestic sewage and present toxic and industrial chemical wastes from identified grossly polluting units entering in to the river.
India's current Prime minister Narendra Modi affirmed to work for cleaning the river and controlling Pollution. Subsequently, Namami Ganga project was announced by the Government in July 2014 budget. An estimated Rs 2,958 crores have been spent till July 2016 in various efforts for clean up of the river.

17. Thank you!