Waste water treatment for chemical engineering notes

About water treatment and types

1. UNIT – I Introduction to Wastewater Treatment Wastewater Sources and Flow rates- Constituents in waste water – Impact of Regulations -Health and Environment Concerns in wastewater- Wastewater treatment methods- Wastewater Reclamation and reuse 1

2. Need for Wastewater Treatment Enable waste water to be disposed off safely Without being a disturbance to public health Without polluting water courses or Other nuisance Recover energy, nutrients and water from other resources 2

3. Compositions of wastewater

4. To protect public health and the environment, it is necessary to have knowledge of: Constituents of concern in waste water Impacts of these constituents Transformation and long term fate of these constituents Treatment methods to modify/ remove Methods for beneficial use or disposal of solids 5 CH6007 Wastewater Treatment

5. Common terms: Characteristics Composition Constituents Impurities Recycling Sludge Solids Biosolids 6 CH6007 Wastewater Treatment

6. Regulations India: Water (Prevention and Control of Pollution), 1974 Interstate River Water Disputes Act (1956) National Water Policy (2012) USA: The Clean Water Act (1972) Water Quality Act (1987) 10 CH6007 Wastewater Treatment

7. National Water Policy The major provisions under the policy are: Envisages to establish a standardized national information system with a network of data banks and data bases Resource planning and recycling for providing maximum availability To give importance to the impact of projects on human settlements and environment. Guidelines for the safety of storage dams and other water-related structures Regulate exploitation of groundwater Setting water allocation priorities in the following order: Drinking water, Irrigation, Hydropower, Navigation, Industrial and other uses. The water rates for surface water and ground water should be rationalized with due regard to the interests of small and marginal farmers. 14 CH6007 Wastewater Treatment

8. Health and Environmental Concerns Humans "catch" diseases from wastewater in a variety of ways. Pathogens in wastewater may be transmitted by direct contact with sewage, by eating food or drinking water contaminated with sewage, or through contact with human, animal, or insect carriers. For e.g., swimming or bathing in contaminated water 15 CH6007 Wastewater Treatment

9. Diseases Caused by Bacteria Typhoid, Cholera Diseases Caused By Virus Hepatitis A, polio, and viral gastroenteritis Parasites in Wastewater protozoans and helminths (parasitic worms) Metals, such as cadmium, copper, lead, nickel, and zinc Minamata disease 18 CH6007 Wastewater Treatment

10. Historic events 1817  A major epidemic of cholera hit Calcutta, India, after a national festival. There is no record of exactly how many people were affected, but there were 10,000 fatalities among British troops there alone. The epidemic then spread to other countries and to the U.S. and Canada in 1832. The governor of New York quarantined the Canadian border in a vain attempt to stop the epidemic. When cholera reached New York City, people were so frightened they either fled or stayed inside, leaving city streets deserted. 1854  A London physician, Dr. John Snow, demonstrated that cholera deaths in an area of the city could all be traced to a common public drinking water pump that was contaminated with sewage from a nearby house. Although he couldn't identify the exact cause, he did convince authorities to close the pump. 19 CH6007 Wastewater Treatment

11. 1859  The British Parliament was suspended during the summer because of the stench coming from the Thames. As was the case in many cities at this time, storm sewers carried a combination of sewage, street debris and other wastes, and storm water to the nearest body of water. According to one account, the river began to ‘seethe and ferment under a burning sun.’ 1892  The comma-shaped bacteria that causes cholera was identified by German scientist Robert Koch during an epidemic in Hamburg. His discovery proved the relationship between contaminated water and the disease. 20 CH6007 Wastewater Treatment

12. 1939  Sixty people died in an outbreak of typhoid fever at Manteno State Hospital in Illinois. The cause was traced to a sewer line passing too close to the hospital's water supply. 1940  A valve accidentally opened caused polluted water from the Genessee River to be pumped into the Rochester, New York, public water supply system. Approximately 35,000 cases of gastroenteritis and six cases of typhoid fever were reported. 1955  Water containing a large amount of sewage was blamed for overwhelming a water treatment plant and causing an epidemic of hepatitis in Delhi, India. An estimated 1 million people were infected. 21 CH6007 Wastewater Treatment

13. 1961  A worldwide epidemic of cholera began in Indonesia and spread to eastern Asia and India by 1964; Russia, Iran, and Iraq by 1966; Africa by 1970; and Latin America by 1991. 1968  A four-year epidemic of dysentery began in Central America resulting in more than 500,000 cases and at least 20,000 deaths. Epidemic dysentery is currently a problem in many African nations. 1993  An outbreak of cryptosporidiosis in Milwaukee, Wisconsin, claimed 104 lives and infected more than 400,000 people, making it the largest recorded outbreak of waterborne disease in the U.S. 22 CH6007 Wastewater Treatment

14. What is Wastewater? Dairy and industrial waste slaughterhouse waste, dairy waste, tannery wastewater, etc. Domestic waste: human and animal excreta and waters used for washing, bathing, and cooking. 100-500 g wet weight of feces and 1-1.3 L of urine/capita/day 15-20 g BOD/day is contributed by each person 23 CH6007 Wastewater Treatment

15. Wastewater Contaminants Suspended solids Priority pollutants: metalloids (As, Se) and metals (Cd, Hg), benzene compounds, and chlorinated compounds Microorganisms: pathogenic and nonpathogenic Organics: refractory and biodegradable Nutrients: Phosphorus Nitrogen (ammonia, nitrites, nitrates) 24 CH6007 Wastewater Treatment

16. Wastewater treatment Primary treatment Sedimentation and screening of large debris Secondary treatment Biological and chemical treatment Tertiary treatment Further chemical treatment 25 CH6007 Wastewater Treatment

17. Treatment Objectives Identify contaminants of concern. Effectively remove identified contaminants. Return effluent to the natural water bodies or the land. Dispose of Contaminants. Do so in a manner that protects the environment and human health. Do so in a sustainable manner. 26 CH6007 Wastewater Treatment

18. Objectives To understand various terms used in wastewater treatment To understand basics of wastewater treatment To acquaint with different steps involved in primary treatment of wastewater.

19. Suspended Solids : When unremoved, lead to sludge deposits and anaerobic conditions in the aquatic environment. Biodegradable Organics : If discharged untreated, leads to depletion of natural oxygen in the receiving waters. Pathogens: Diseases can be transmitted via pathogens in wastewater. Nutrients : Nitrogen and phosphorus can lead to growth of undesirable aquatic life. Heavy Metals : Usually added in industrial or commercial processes. Priority Pollutants : Other contaminants selected for removal based on known carcinogenicity or toxicity Contaminants of Concern 28 CH6007 Wastewater Treatment

20. Wastewater Characteristics Improved analytical techniques Measuring the concentration of constituents Importance of characterization RNA and DNA typing for active mass identification Implementing process modeling tools 29 CH6007 Wastewater Treatment

21. Treatment methods Application of physical forces predominate are known as unit operations Removal of contaminants by chemical or biological reactions are known as unit processes Preliminary, primary, advanced primary, secondary and tertiary treatment 30 CH6007 Wastewater Treatment

22. Treatment Level Description Preliminary Removal of rags, sticks, floatables, grit Primary Removal of a portion of suspended solids and organic matter Advanced primary Enhanced removal of suspended solids and organic matter Secondary Removal of biodegradable organic matter and suspended solids Secondary with nutrient removal Removal of biodegradable organics, suspended solids and nutrients Tertiary Removal of residual suspended solids by microscreens Advanced Removal of dissolved and suspended materials remaining after normal biological treatment 31 CH6007 Wastewater Treatment

23. Primary treatment (physical) Metal grating - Large debris Short retention time - Settling out of sand and gravel Primary settling tank - Approximately half suspended solids sediment. The sediment material is called primary sludge 34 CH6007 Wastewater Treatment

24. Secondary Treatment Biological treatment activated sludge trickling filter oxidation ponds A disinfection step is usually included at the end of the biological treatment chlorination Objective is to reduce BOD, odors and pathogens 35 CH6007 Wastewater Treatment

25. Activated sludge process – most common Primary wastewater mixed with bacteria-rich (activated) sludge and air or oxygen is pumped into the mixture Promotes bacterial growth and decomposition of organic matter Last step is a settling tank where sludge settles out and then the treated wastewater moves on for tertiary treatment Some settled sludge is used to inoculate incoming primary effluent BOD removal is approximately 85% Microbial removal by activated sludge 80-99% removal of bacteria (sunlight, temperature, antagonistic microorganisms, predation by ciliated protozoans, competition from other bacteria, adsorption to sludge solids) 36 CH6007 Wastewater Treatment

26. Trickling filters are beds of stones or corrugated plastic. The primary wastewater is sprayed over the filter and microbes decompose organic material aerobically. Low pathogen removal - Bacteria, 20-90% - Viruses, 50-90% - Giardia cysts, 70-90% Secondary treatment – Trickling filters 37 CH6007 Wastewater Treatment

27. Stabilization or oxidation ponds Oxidation ponds are a few meters deep, and up to a hectare in size. They are low cost with retention times of 1 to 4 weeks. Types: Aerobic, Aerated, Anaerobic Odor and mosquitoes can be a problem Pathogen removal: - Bacteria, 90-99% - Virus, 90-99% - Protozoa, 67-99% Mechanisms include the long detention time (natural die-off), high pH (10-10.5) generated by photosynthesis, predation, sunlight, temperature Stabilization ponds are the preferred wastewater treatment process in developing countries due to low cost, low maintenance. This is balanced by larger land requirement. 38 CH6007 Wastewater Treatment

28. Tertiary treatment Tertiary treatment involves a series of additional steps to further reduce organics, turbidity, N, P, metals and pathogens. This is for wastewater that may impact recreational areas, will be used for irrigation, or will be used for drinking water. Physicochemical process Coagulation Filtration Activated carbon adsorption of organics Disinfection 39 CH6007 Wastewater Treatment

29. Coagulation Flocculation and Sedimentation Synthetic organic polymers Alum (aluminum sulfate) Iron salts (ferric sulfate, ferric chloride) Slow mixing Reduces microorganisms (transfer to sludge) Bacteria 90 % Virus 60 % Protozoa 90 % 40 CH6007 Wastewater Treatment

30. Removal of flocculated matter Organic matter Microorganisms Mineral colloids Filtration 41 CH6007 Wastewater Treatment

31. Sludge Treatment Processes Thickening (water removal) Digestion (pathogen inactivation and odor control) Conditioning (improved dewatering with alum and high temp, 175-230 o C) Dewatering (pathogen inactivation and odor control) Incineration (volume and weight reduction) Final disposal 42 CH6007 Wastewater Treatment

32. Discharge of Wastewater and Sludge Sludge land farming landfill incineration ocean Wastewater Bodies of water: oceans, lakes, etc. Land application Constructed wetlands 43 CH6007 Wastewater Treatment

33. Wastewater Treatment Alternatives Septic tanks raw domestic wastewater Constructed wetland systems wastewater effluent Composting Municipal solid waste Sludge 44 CH6007 Wastewater Treatment

34. Septic Tanks Underground tanks where solids are separated from incoming wastewater. Some biological digestion of the waste organic matter occurs under anaerobic conditions. Also involves a leachfield. Rural areas – septic tanks serve approx. 25% of U.S. pop. Constructed Wetlands Used for further treatment of wastewater effluent, mine drainage, pulp mill effluent, etc. Three types aquatic ponds surface flow subsurface flow Composting Organic component of solid waste is biologically decomposed under controlled aerobic conditions End product: humus-like product useful as fertilizer This is one common method of sludge treatment 45 CH6007 Wastewater Treatment

35. New Directions and Concerns Aging infrastructure New methods of process analysis and control Treatment plant performance and reliability Wastewater disinfection Combined sewer overflows Impacts of stormwater and sanitary outflows and nonpoint sources of pollution Separate treatment of return flows Odour control Retrofitting and upgrading wastewater treatment plans 46 CH6007 Wastewater Treatment

36. Sampling and analytical procedures Sampling is done for various reasons: Routine operating data on overall plant performance Data that can be used to document the performance of a given treatment or operation process Data that can be used to implement proposed new programs Data needed for reporting regulatory compliance 47 CH6007 Wastewater Treatment

37. Sampling data collected must be, Representative Data must represent the water being sampled Reproducible Others following the same data and procedure must be able to reproduce Defensible Documentation to validate Useful Meet the objectives of the monitoring plan CH6007 Wastewater Treatment 48

38. Sampling Protocol Sampling protocol along with quality assurance project plan (QAPP) Sampling plan Sample types and sizes Sample labelling and chain of custody Sampling methods Sampling storage and preservation Sample constituents Analytical methods CH6007 Wastewater Treatment 49

39. Methods of Analysis Vary from quantitative methods to qualitative methods – gravimetric, volumetric, physicochemical Physicochemical: instrumental methods of analysis like turbidimetry, colorimetry, potentiometry, polarography, adsorption spectrometry, spectroscopy, fluorometry, and nuclear radiation CH6007 Wastewater Treatment 50

40. Detection level Instrumental detection level (IDL) Lower level of detection (LLD) Method detection level (MDL) Level of quantification (LOQ) CH6007 Wastewater Treatment 51

41. Units of Measurement Mole fraction Milligrams per litre Grams per cubic centimetre Parts per million CH6007 Wastewater Treatment 52

42. Solid Constituents TS – Total solids TVS – Total volatile solids TFS – Total fixed solids TSS – Total suspended solids TDS – Total dissolved solids CH6007 Wastewater Treatment 53

43. Chemical Parameters Hardness – expressed in mg of calcium carbonate per litre of water Determined by Versenate Method the water is titrated against EDTA salt solution using Eriochrome Black T as indicator solution color changes from wine red to blue Underground water is generally harder than the surface water, as they have more opportunity to come in contact with minerals CH6007 Wastewater Treatment 54

44. Chlorides - Sodium chloride is the main substance in chloride water natural water near the mines and sea has dissolved sodium chloride the presence of chlorides may be due to the mixing of saline water and sewage in the water Chloride content is determined by titrating the wastewater with silver nitrate and potassium chromate CH6007 Wastewater Treatment 55

45. Chlorine - Dissolved free chlorine is never found in natural waters It is present in the treated water resulting from disinfection with chlorine The chlorine remains as residual in treated water for the sake of safety against pathogenic bacteria Residual chlorine is determined by the starch-iodide test In starch-iodide test, potassium iodide and starch solutions are added to the sample of water due to which blue color is formed This blue color is then removed by titrating with sodium thiosuplhate solution CH6007 Wastewater Treatment 56

46. On the addition of ortho-iodine solution if yellow color is formed, it indicates the presence of residual chlorine in the water. The intensity of this yellow color is compared with standard colors to determine the quantity of residual chlorine. The residual chlorine should remain between 0.5 to 0.2 mg/L in the water so that it remains safe against pathogenic bacteria. CH6007 Wastewater Treatment 57

47. Iron and Manganese - These are generally found in ground water The presence of iron and manganese in water makes it brownish red in color Presence of these elements leads to the growth of micro-organism and corrodes the water pipes Iron and manganese also causes taste and odor in the water The quantity of iron and manganese is determined by colorimetric methods CH6007 Wastewater Treatment 58

48. pH - pH value is the logarithm of reciprocal of hydrogen ion activity in moles per liter Depending upon the nature of dissolved salts and minerals, water may be acidic or alkaline When acids or alkalis are dissolved in water, they dissociate into electrically charged hydrogen and hydroxyl radicals, respectively Dissolved gases such as carbon dioxide, hydrogen sulphide and ammonia also affect the pH of water CH6007 Wastewater Treatment 59

49. Lead and Arsenic - These are not usually found in natural waters But sometimes lead is mixed up in water from lead pipes or from tanks lined with lead paint when water moves through them These are poisonous and dangerous to the health of public The presence of lead and arsenic is detected by means of chemical tests CH6007 Wastewater Treatment 60

50. Dissolved gases - Oxygen and carbon dioxide gases are found in the natural waters of all types water may contain some amount of hydrogen sulphide and ammonia depending upon the pH and anaerobic/aerobic condition of water Surface water absorbs oxygen from the atmosphere. Algae and other tiny plant life of water also give oxygen to the water CH6007 Wastewater Treatment 61

51. Nitrogen - Nitrogen may be present in the water in the form of nitrites, nitrates, free ammonia, and albuminoidal nitrogen The presence of nitrogen in the water indicates the presence of organic maters in the water The presence of the nitrites in the water, due to partly oxidized organic matters, is very dangerous The nitrites are rapidly and easily converted to nitrates by the full oxidation of the organic matters nitrates > 45 mg/L can cause “mathemoglobinemia” disease to the children CH6007 Wastewater Treatment 62

52. Metals and other chemical substances - Arsenic, selenium are poisonous, therefore they must be removed totally Human lungs are affected by the presence of high quantity of copper in the water Fewer cavities in the teeth will be formed due to excessive presence of fluoride in water CH6007 Wastewater Treatment 63

53. Biological Constituents Microorganisms present in surface water and ground water. Living cell microorganisms Prokaryotes and Eukaryotes Bacteria – salmonella, clostridium, etc Pathogenic protozoan Helminths Virus CH6007 Wastewater Treatment 64

54. Indicator Organisms Microorganisms which are many in number are used as surrogate to identify the pathogenic organisms that are few and difficult to isolate Bacterial indicators Other indicators CH6007 Wastewater Treatment 65

55. Characteristics of Indicator Organisms Must be present when faecal contamination is present No. of indicator organisms should be equal to or greater than the target organisms Must exhibit the same survival characteristics as the target Must not produce outside the host Isolation and quantification must be faster than target Should be a member of the intestinal micro flora of warm-blooded animals CH6007 Wastewater Treatment 66

56. Toxicity Assess the suitability of environmental conditions for aquatic life Establish acceptable receiving water concentrations Study the effects of water quality parameters Assess the toxicity of waste water Establish the relative sensitivity of a group of standard aquatic organisms CH6007 Wastewater Treatment 67

57. Assess the degree of wastewater treatment needed Determine the effectiveness of wastewater treatment methods Establish permissible effluent rates Determine compliance with central and state water regulations CH6007 Wastewater Treatment 68

58. Wastewater Reclamation and Reuse ‘ Wastewater reclamation’ is the treatment or processing of wastewater to make it reusable, while ‘wastewater reuse’ is using wastewater in a variety of beneficial ways. In addition, ‘reclamation’ or ‘reuse’ of water frequently implies the existence of a pipe or other water conveyance facilities for delivering the reclaimed water. The development of wastewater reclamation and reuse in many countries is related to looming water scarcity, water pollution control measures and protection of the aquatic environment. There is also the need to obtain alternative water resources for a growing population. In cities and regions of developed countries, where wastewater collection and treatment have been the common practice, wastewater reuse is practiced with proper attention to sanitation, public health and environmental protection. CH6007 Wastewater Treatment 69

59. A bout 99 percent of most wastewater is water, and only 1 percent is solid waste. Therefore, natural shortage of water can be overcome by reuse of wastewater. Wastewater is a preferable unconventional water source, since the supply is increasing because of population growth, Wastewater needs to be treated before disposal in order to safeguard the environment. Reuse of wastewater will help to maintain environmental quality, and, simultaneously, to relieve the unrelenting pressure on conventional, natural freshwater sources. Therefore, much of the waste water generated after first use can be used again in the same location (usually referred to as recycling), or collected from one or more utilities that generate wastewater for use elsewhere (referred to as reuse). Managing water demand through recycle, reuse and reclamation, therefore, requires a thorough understanding of the sources, types, and effects of water pollution, as well as the water and wastewater treatment practices needed to achieve the water quality requirements of recycle and reuse, and the technological and socio- economic considerations that affect these water demand management practices.

60. Wastewater Reuse and reclamation:   Water reuse:  Water reuse involves taking what was once wastewater, treating and disinfecting it, then using the resulting high-quality reclaimed water for a beneficial use, such as irrigation for golf courses, parks, highway medians, playgrounds and residential properties. The degree of treatment depends on what purpose the water will serve. Irrigation is the most common type of reuse. Water reclamation:  Reclaimed water is wastewater that has been thoroughly treated to remove harmful organisms and substances, such as bacteria, viruses and heavy metals, so it can be reused. By using reclaimed water, communities can conserve traditional freshwater supplies and provide an environmentally responsible alternative to disposal of wastewater. Reclaimed water can be safely used for a wide variety of purposes, including landscape irrigation for golf courses, parks, highway medians, playgrounds and residential properties. Reclaimed water also is used for agricultural irrigation; decorative ponds and fountains; groundwater recharge; industrial uses such as cooling; fire protection; and wetlands creation, restoration and enhancement. Water recycling : Recycling generally means reuse of wastewater back in the same cycle where it is generated.

61. What is benefit of water reuse?  Important element of integrated water resources utilization and management Treated effluent is used as a water resource for many possible beneficial purposes For cities, wastewater would not be discharged to the water bodies thus reducing pollution to the water environment and not creating public health issues

62. Successful water reuse programme:   Providing reliable treatment to meet water quality requirements and environmental regulations for the intended reuse. Protection of public health and the Environment. Gaining public acceptance. Economic viability

63. IS RECLAIMED WATER SAFE TO DRINK   The water is clear, odorless and safe, but usable for only nondrinking or nonpotable water purposes in Florida.  Reclaimed water is permitted for many nonpotable uses, including landscape and commercial agricultural irrigation, groundwater recharge; industrial uses such as cooling, process or wash waters; fire protection; wetlands creation; restoration and enhancement.  Reclaimed water is used in commercial agricultural operations including irrigation of edible food crops such as citrus, corn and soybeans. The use of reclaimed water for raising edible crops by the general public is not permitted. It is necessary to provide public education on appropriate uses of reclaimed water. Water users must understand that reclaimed water cannot be connected to potable water plumbing systems and should not be consumed. Reclaimed water service providers also need to monitor their systems to ensure that there is no cross connection with their potable water systems.  

64. Power Point Link: https://www.slideshare.net/pulkitshukl/recycle-and-reuse-of-wastewater https://www.slideshare.net/Tulasiram42/water-reclamation-and-reuse