Liquid waste management

1. Waste water management and treatment JIJEESH V

2. Wastewater Wastewater is a mixture of sewage; water from household use; water used in commercial and industrial applications etc… Wastewater contains a variety of biological and chemical pollutants which make it unsafe for humans and the environment.

3. Wastewater treatment The objective of wastewater treatment is to remove or modify these pollutants, so that it can be safely discharged into the environment. Wastewater treatment uses microbes to decompose organic matter in sewage.  If too much untreated sewage or other organic matter is added to a lake or stream, dissolved oxygen levels will drop too low to support sensitive species of fish and other aquatic life.

4. Wastewater treatment systems are designed to digest much of the organic matter before the wastewater is released so that this will not occur. Treatment of wastewater typically involves primary, secondary, and sometimes tertiary steps. Secondary treatment is entirely dependent upon the activity of microbes such as  Acidovorax .

5. Wastewater treatment Processes Wastewater treatment methods Chemical Sedimentation Gas Transfer Filtration Flocculation Flotation Mixing Screening Biological Physical Aerobic Anaerobic Precipitation Adsorption Disinfection

6. 1. Primary treatment Physically removes large solids using grates, screens, and settling tanks. Large pieces of debris are removed by screening, and suspended particles are removed from the water through settling processes. 2. Secondary treatment Elimination of organic and inorganic contaminants, through the effect of microbiological activity upon wastewater material.

7. The most widely used and effective methods of secondary treatment involve activated sludge treatment. 3. Tertiary treatment Removal of further nutrients and pathogens, using methods such as filtration, passage through wetlands, or disinfection by treatment with chlorine, ozone or ultraviolet light. Tertiary treatment is not always included in wastewater treatment systems.

8. Preliminary treatment It 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 that are commonly removed during pretreatment include trash, tree limbs, leaves, branches, and other large objects. 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 .

9. This is most commonly done with an automated mechanically raked bar screen in modern plants serving large populations, while in smaller or less modern plants, a manually cleaned screen may be used. The raking action of a mechanical bar screen is typically paced according to the accumulation on the bar screens and/or flow rate. The solids are collected and later disposed in a landfill, or incinerated.

10. Bar screens or mesh screens of varying sizes may be used to optimize solids removal. If gross solids are not removed, they become entrained in pipes and moving parts of the treatment plant, and can cause substantial damage and inefficiency in the process

11. 1. Primary treatment( physical or mechanical) Typical materials that are removed during primary treatment include fats, oils, and greases sand, gravels and rocks larger settleable solids including human waste floating materials Screening : to remove large objects, that could plug lines or block tank inlets Grit chambers : slows down the flow to allow grit to fall out. (horizontal, aerated and vortex).

12. Sedimentation tank ( settling tank or clarifiers) : Settleable solids settle out & are pumped away, while oils float to the top & are skimmed off. Settleable solids are then passed for aeration in aeration tanks .

13. Bar screen & sedimentation tank

14. Sewage is held in sedimentation tanks for 2-10 hours. Greasy material , fats, oils etc..rise to the surface, forming scum which is skimmed off. The organic matter which settle down is called primary sludge . 30-40% BOD removal- treatment efficiency. Sedimentation is enhanced by the addition of alum at the treatment plant which produces a sticky flocculant precipitate . Settleable solids are then passed for aeration in aeration tanks

15. Aeration tanks The effluents from primary treatment are then carried to aeration tanks. Continuously aerated for the growth of aerobic m.os . Flocculation occurs. These m.os degrade the organic matter present in the effluents.

16. 2. Secondary treatment ( biological treatment) Typically uses biological treatment processes , in which microorganisms convert non- settleable solids to settleable solids. Sedimentation process follows, allowing the settleable solids to settle out. 4 methods include :- Activated sludge Trickling filters Oxidation ponds or lagoons Biological contractor system/ Rotating disc

17. Activated sludge system . Aerobic sewage treatment in which flocculated biological growth is circulated & in contact with organic waste in oxygen presence is called activated sludge process

18. The activated sludge process is usually employed following primary sedimentation.   The wastewater contains some suspended and colloidal solids and when agitated in the presence of air, the suspended solids form nuclei on which biological life develop and gradually build up to larger solids or gelatinous masses which are known as activated sludge. 

19. Activated sludge is a brownish floc -like substance consisting of organic matter obtained from the wastewater and inhabited by myriads of bacteria and other forms of biological life.  Activated sludge with its living organisms has the property of absorbing or adsorbing colloidal and dissolved organic matter . The biological organisms utilize the absorbed material as food and convert it to inert insoluble solids and new bacterial cells.

20.   Much of this conversion is a step-by-step process.   Some bacteria attack the original complex substances to produce simpler compounds as their waste products.  Other bacteria use the waste products to produce still simpler compounds and the process continues until the final waste products can no longer be used as food for bacteria

21. The generation of activated sludge or floc in wastewater is a slow process and the amount so formed from any volume of wastewater during its period of treatment is small and inadequate for the rapid and effective treatment of the wastewater which requires large concentrations of activated sludge.  Such concentrations are built up by collecting the sludge produced from each volume of wastewater treated and re-using it in the treatment of subsequent wastewater flows

22. The sludge so re-used is known as returned sludge .  This is a cumulative process so that eventually more sludge has been produced and is available to maintain a viable biological population of organisms to treat the incoming wastes.  The surplus, or excess activated sludge, is then permanently removed from the treatment process and conditioned for ultimate disposal. 

23. Activated sludge organism Particles of the flock inactivated sludge consist of mixed species of bacteria. They embed themselves in a mass of polysaccharide gum called zooglea . Zooglea ramigera Z. ramigera & related organisms need complex nutrient requirement . Oxidize sewage rapidly ; active in floc formation Other m.os in zooglea are Escherichia, sps of Pseudomonas, Alkaligens , Bacillus, Sphaerotilus , several protozoans etc.

24. Different flora act in antagonism & synergism. Bacterial population increases Free swimming ciliates & flagellates increases Protozoans increases Rotifiers & nematodes increases End result is mineralization of C,N & P Complete mixing, rigorous aeration – efficient oxidation & reduction Fluid part passed- final settling tank Part of activated sludge retained – seed to reinoculate new sewage BOD reduction – 80-95% Most of settled sludge moved-aeration stopped-settling stops- bulging process- to anaerobic sludge digestor .

25. Anaerobic sludge digestors These can be used to further treat aerobically treated sewage or for very highly concentrated sewage. Vats have heating, venting, mixing, sludge seeding, draw - off. Protozoa a nd fungi are insignificant. 3 step process: faculatively or o bligately anaerobic. organic acid and CO 2 . H2, CO2, Acetate Methanogens- Get methane. Products a re methane and CO 2 . Opt temp 35-37C and pH 6-8. Get a better reduction in volume o f sludge.

26. 2. Trickling filters Sewage is sprayed or drained over a rock bed or molten plastic. Rocks large- air penetrates Small- increased surface area for microbial activity No filtration action Slimy gelatinuous film of aerobes (zoogleal slime, a biofilm) grow on bed Envelop- Exopolysacc.-gum

27. M.os oxidizes organic matters trickling over the surfaces to CO2 & water. As the biofilm layer thickens, it eventually sloughs off into the treated effluent and subsequently forms part of the secondary sludge . Typically, a trickling filter is followed by a clarifier or sedimentation tank for the separation and removal of the sloughing 80-85 % BOD removal.  The underdrain system in trickling filters serves two purposes:  (a)  to carry the wastewater passing through the filter and the sloughed solids from the filter to the final clarification process, and (b)  to provide for ventilation of the filter to maintain aerobic conditions.

28. 3. Biological contractor system/ Rotating disc A biofilm – based design. Series of disc of several diameters are mounted on a shaft. Disc rotates slowly ; their lower part(40%) submerged in waste water. Aeration provided. Rotation causes accumulated biofilm to slough off when thick Equivalent to floc accumulation.

29. 4. Oxidation ponds or lagoons Sewage pond is deep- entirely anaerobic. 2 stages : Sludge settles out Effluent pumped to an adjoining pond or system of shallow ponds enough to aerated by wave action Algal growth is encouraged ; since difficult to manage aerobic condition.

30. Bacterial action – decomposing organic matter & generate CO2 Algae use CO2- photosynthesis- produce O2-inturn encourage aerobial activity in the sewage. Considerable amount of organic matter in the algal form accumulates ; not a problem ; since pond is nutrient-rich.

31. Microbial processes in wastewater treatment Many microbial activities are observed. Microorganisms associated, do not persist long (fragile). Secondary treatment is entirely dependent upon the activity of microbes. Eg : Biofilters (Trickling filters) , Activated sludge etc..

32. Microbes frequently present in activated sludge : Achromobacter , Flavobacterium , Nitrosomonas , Beggiatoa , Thiothrix , Nocardia , Mycobacterium, Geotrichum , Nitrobacter . Biofilters hosts : Nematodes, insect larvae, microfungi , algae, small worms and freshwater leech.

33. Microorganisms Microorganisms are present in sewage water treatment vats well throughout the entire process. Microorganisms encompassing : bacteria , protozoa, and viruses , in the treatment vats, exist and grow in the sewage water and are transferred throughout the vats with the movement of sewage water. Some microorganisms are used during the secondary treatment to remove pollutants. However, most microorganisms will be removed from the wastewater during the disinfection stage of the treatment.

34. There are some microorganisms that continue on to the tertiary treatment to utilize removal of other pollutants like nitrogen, but will later be disinfected and killed.  BACTERIA Wastewater treatment vats are inhabited by varied and broad strains of bacteria like Escherichia coli ,  Vibrio cholerae , Helicobacter pylori etc ..

35. Beneficial bacteria Biofilm forming bacteria Are present in the trickling filter phase of the secondary treatment process, considered to be beneficial in the removal of organic materials.   Pseudomonas , Zooglea , Chromobacter , and , namely a few of whom are aerobic heterotrophic organisms. Flavobacterium Such bacteria are exposed to oxygen during the treatment to break down the organic molecules.

36. 2.Nitrogen removing bacteria Nitrogen removing bacteria ( nitrifiers and denitrifiers ) - Nitrifiers include strains  Nitrosomonas europaea  as well as  Nitrobacter hamburgensis . Denitrifiers include strains Thiobacillus denitrificans .

37. Bdellovibrio bacteriovorus Traces of Gram-negative bacteria can also be found in the wastewater treatment vats, such as  Bdellovibrio bacteriovorus , which penetrate and lyses other gram-negative bacteria within sewage water. obligate aerobic, parasitic bacterium  able to replicate on the aerobic filter film but is unable to live in anaerobic sludge. main function of this bacterium is to purify waste water by reducing gram-negative bacteria with the ability to survive within sewage. penetrate a host, replicate, and finally lyses the host’s cell.

38. Brocadia anammoxidans anaerobic chemolithoautotrophic   bacteria and is one of several oxidizers of ammonia. Take in ammonia from the sewage water, by the release hydrazine (rocket fuel) via an enzyme called hydroxylamine oxidoreductase. clarifying wastewater of forms of ammonia.

39. Nitrogen removal from wastewater is carried out through the: oxidation of ammonia to nitrite , the oxidation of nitrite to nitrate , and finally, the conversion of nitrate to nitrogen gas . There are several other bacteria, in addition to Brocadia anammoxidans , used during nitrification and denitrification processes. 

40. Nitrosomonas europaea ( Nitrifier )   a Gram-negative chemolithoautotroph   ammonia-oxidizing bacterium catalyzes the foremost phase in the oxidation of toxic ammonia to nitrite . optimum temp 20-30 C and pH 6.0- 9.0 derives energy from burning ammonia together with oxygen

41. Nitrobacter hamburgensis ( Nitrifier ) Nitrobacter hamburgensis  is a gram negative, obligate chemolithotroph which exhibit an aerobic lifestyle, dependent on oxygen.  a nitrifying organism and is vital during the process of sewage water treatment due to the fact that it is capable of catalyzing the oxidation of nitrite to nitrate , the second phase of nitrification. 

42. Thiobacillus denitrificans Are implicated for the duration of the third phase of the nitrogen removal cycle. This organism denitrifies nitrate to nitrogen gas, which is then released into the atmosphere . T. denitrificans use inorganic sulfur compounds as an energy source. Their optimal conditions vary between 30C and pH 7.5 - 8.0.

43. sulfate reducing bacteria Lastly, sulfate reducing bacteria which such as Desulfotomaculum and Desulfovibrio , whom reduce sulfate to hydrogen sulfide (H 2 S). These sulfate reducing microbes prefer environments with an approximate pH 7 and are inhibited below pH value of 5.5 and above 9. Optimum temperature ranges between 28 - 32C.

44. Phosphorus removal Phosphorus is a nutrient which makes the growth of algae possible. Chemicals including: ferric chloride, alum, or lime are added to the wastewater, which allow the smaller particles including phosphorus to group into larger masses. Then are removed through the sedimentation tanks.

45. Protozoa Amoebae, ciliates, and flagellates are found present for sewage treatment . Importance of protozoa in wastewater treatment is to maintain a slime layer within trickling filter systems. Play a predatory role in removing bacteria, other protozoa, and several small particles. have multiple feeding mechanisms: filter and raptorial feeding . Filter feeders consume during the trickling filter phase when water is passed through the filter.  Raptorial feeders , such as flagellates and amoebae, feed on different types of bacteria. Larger forms of amoebae eat ciliates and flagellates as well as smaller amoebae feed primarily on bacteria.

46. Virus Enterovirus  and  rotavirus , amongst a handful of viruses are excellent indicators of human fecal contamination in wastewater . These viruses must be maintained at temperatures below 10 C and a pH 3.5- 4. Two enteroviruses present in sewage water treatment involve Hepatitis A and Polio myelitis . Viruses are removed from water through ozonation , a process of disinfection .

47. 3. Tertiary treatment (chemical treatment) Removes disease-causing organisms from wastewater . 3 different disinfection process are : Chlorination UV light radiation (a physical treatment ) Ozonation

48. chlorination Chlorine is used in 2 forms – Cl2 gas form or hypochlorite tablets Cl react with water to form HOCl , which rapidly dissociate to form hypochlorite ion. Cl is effective against enteric bacteria. Most common Advantages : low cost & effective Disadvantages : chlorine residue could be harmful to environment. Dechlorination done.

49. ozonation Disinfection achieved by formation of free radicals as oxidizing agents. More effective against viruses & bacteria than chlorination. Advantages : safer than chlorination fewer disinfection by-product Disadvantage : high cost low solubility of ozone in water

50. Uv radiation Damage the genetic structure of bacteria, viruses and other pathogens. Advantages : no chemicals are used More rapid water taste more natural No by-products formed Disadvantages : high maintenance of the UV-lamp

51. Membrane filtration Membrane technologies disinfect treated wastewater by physically filtering out m.os . Does not require addition of reactive chemicals No toxic by-products are produced. Membrane technologies include: reverse osmosis, ultrafiltration , microfiltration, nanofiltration .

52. Thank you……….