waste water engineering report 2

• Microbes play an extremely important role in sewage treatment. It is largely through biological digestion that sewage is converted from a highly contaminated, infectious liquid into a relatively stable, inert sludge and a harmless effluent needing only chlorination before it may be discharged into a receiving stream, leaching bed, or other disposal area.
• Microorganisms are significant in water and wastewater because of their roles in disease transmission.
• Domestic wastewater contains enormous quantities of microorganisms.
• Depending on sewage age and the quantity of dilution of water, bacterial counts in raw sewage may be expected to range from 500,000 to 5,000,000 per mL.
• Bacteria


  Single-celled plants which metabolize soluble food and reproduce by binary fission
• Bacterial Growth Pattern

  1. Lag Phase

  2. Log growth Phase

  3. Declining growth Phase

  4. Stationary Phase

  5. Endogeneous Phase
• Anaerobic bacteria


  • Oxidize organic matter utilizing elecron acceptors other than oxygen
  • Produce CO2, H2O, H2S, CH4, NH3, N2, reduced organics and more bacteria
  • A large part of the available energy appears in the form of end products, hence cell production is low
  • End products of anaerobic fermentation are likely to be odorous
  • Production of a stable effluent is unlikely, since wastes do not contain sufficient electron acceptors to permit oxidation
• Aerobic bacteria


  • Utilize free oxygen as an electron acceptor
  • End products: CO2, H2O, SO4,-2, NO3,- ,NH3, and more bacteria
  • Bulk of availble energy is converted into either cell mass or heat, yielding a stable effluent which will not undergo decomposition
  • The oxygen required may be furnished naturally from the atmosphere or mechanically by bubble aeration
• Facultative bacteria


  • Can function in both aerobic and anaerobic environment
  • They are the major contributor to stabilization of wastewater
  • Example reactions: reduction of CO2 to CH4 and oxidation of NH3 to NO3-
• Significant Bacteria

  • Pseudomonas denitrifying bacteria
  • Zooglea
  • Sphaerotilus natans
  • Acinetobacter
  • Bdellovibrio
  • Nitrosomonas
  • Nitrobacter
• Algae


  • Photosynthetic microorganisms which can produce oxygen and organic cell mass from inorganic chemicals
  • Not important in most waste treatment process but play a role in oxidation ponds
• Protozoa


  • Single celled protists which reproduce by binary fission
  • Can be aerobic, anaerobic, or facultative
  • Their major food source is the bacteria
  • Protozoa of importance to sanitary engrs include amoebas, flagellates, and free-swimming stalked ciliates
• Fungi


  • Multicellular non-photosynthetic plants
  • Most fungi are aerobic, but anaerobic species are known
  • Tend to predominate over bacteria in wastes which are deficient in nitrogen or low in pH
  • Their large filamentous shape makes them to settle poorly and are thus difficult to remove by sedimentation
• Rotifers


  • Simplest multicellular animal
  • Feed on bacteria and small protozoa, thus further stabilizing the waste
  • Require a high level of DO, their presence is a good indication of the relative stability of a treated waste
• Crustaceans


  • Microscopic organisms characterized by a rigid shell structure
  • Strict aerobes, and as primary producers they feed on bacteria and algae
  • Have been used to clarify algae-laden effluents from oxidations ponds
• Bacteria convert the food to energy and use the energy to make new cells. Some bacteria can use inorganics (e.g., minerals such as iron) as an energy source and can multiply even when organics (pollution) are not available.
• Protozoa are responsible for improving the quality of the effluent, maintaining the density of dispersed bacterial populations by predation.
• Algae and cyanobacteria typically grow in the aerobic zone and provide bacteria in the pond with plenty of oxygen during the daytime. However, algal photorespiration may consume oxygen during night-time when it is dark.
• Algae can be used in wastewater treatment for a range of purposes, some of which are used for the removal of coliform bacteria, reduction of both chemical and biochemical oxygen demand, removal of N and/or P, and also for the removal of heavy metals.
• Fungi are indicated for their superior aptitudes to produce a large variety of extracellular proteins, organic acids, and other metabolites, and for their capacities to adapt to environmental constraints.
• Viruses are a major hazard to public health. Some viruses can live if 41 days in water and wastewater at 20 °C. The cause of lots dangerous diseases.
• More attention must be paid to viruses, however, when surface water supplies have been used for sewage disposal. Viruses are difficult to destroy by normal disinfection practices, as they require increased disinfectant concentration and contact time for effective destruction.
• Microorganisms


  • Ability to produce a large variety of extracellular proteins, organic acids, and other metabolites
  • Capacity to adapt to environmental constraints
• Virus


  The smallest form of microorganisms (others classify it as particle and not as microorganism) capable of causing disease
• Viruses are a major hazard to public health
• Some viruses can live if 41 days in water and wastewater at 20 °C
• Viruses are the cause of lots dangerous diseases
• More attention must be paid to viruses, however, when surface water supplies have been used for sewage disposal
• Viruses are difficult to destroy by normal disinfection practices, as they require increased disinfectant concentration and contact time for effective destruction
• Rotifers


  A well-defined group of the smallest, simplest multicellular microorganisms found in nearly all aquatic habitats
• Rotifers


  • They are a higher life form associated with cleaner waters
  • They can be used to indicate the performance of certain types of treatment processes
• Microorganisms' preferences


  • Enough room to move around
  • Just sufficient food
  • Enough nutrients
  • Enough oxygen to breath
• Coliform Organisms


  Rod shaped bacteria thriving inside the intestinal tract of man
• Each person discharges from 100 to 400 billion coliform organisms per day
• Coliform organisms are harmless to man and are, in fact, useful in destroying organic matter in biological waste treatment processes
• The presence of coliform organisms is taken as an indication that pathogenic organisms may also be present, and the absence of coliform organisms is taken as an indication that the water is free from disease producing organisms
• Types of Coliform Organisms


  • Total Coliform (all aerobic, facultative and anaerobic gram-negative, non-spore forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hours)
  • Escherichia
  • Aerobacter
  • Citrobacter
  • Hafnia
  • Klebsiella
• There is difficulty in determining E.coli to the exclusion of the soil coliforms; as a result, the entire coliform group is used as an indicator of fecal pollution
• E.coli is the preferred pathogen indicator. Note: this is not the pathogenic E.coli O157:H7 strain
• Properties of E.coli


  • Found in much higher concentrations than most pathogens in fecal matter
  • Non pathogenic
  • Easy detect, relatively fast and inexpensive analysis
  • Its absence indicates absence of enteric pathogens