1. Microbial Biotechnology
Lecture:8
Microbial Biotechnology

2. Wastewater / Sewage treatment
Generally, the wastewater discharged from domestic premises like residences, institutions, and commercial establishments is termed Sewage / Community wastewater.
It is made up of 99.9% water and 0.1% solids which are organic because it consists of carbon compounds like human waste and other organic matter.
Many industrial wastes are also organic in composition and can be treated physico-chemically and/or by micro-organisms in the same way as sewage (biological treatment).
Wastewater treatment involves breakdown of complex organic compounds in the wastewater into simpler compounds that are stable and nuisance-free.

3. WHY SHOULD SEWAGE BE TREATED BEFORE DISPOSAL?
The decomposition of the organic materials contained in wastewater can lead to the production of large quantities of malodorous gases.
Untreated wastewater (sewage) contains a large amount of organic matter; if it is discharged into a river or stream, it will consume the dissolved oxygen for satisfying the Biochemical Oxygen Demand (BOD) of wastewater and thus deplete the dissolved oxygen of the stream; this will cause fish killing and other undesirable effects.

4. Biological Oxygen Demand (BOD) is a measure of the oxygen used by microorganisms to decompose waste.
If there is a large quantity of organic waste in the water supply there will also be a lot of bacteria present working to decompose this waste. In this case, the demand for oxygen will be high (due to all the bacteria) so the BOD level will be high. As the waste is consumed or dispersed through the water, BOD levels will begin to decline.
Wastewater may also contain nutrients, which can stimulate the growth of aquatic plants and algal blooms, thus leading to eutrophication of the lakes and streams.

5. Eutrophication
In eutrophication the environment becomes enriched with nutrients.
It is the process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates.
These typically promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish.
Eutrophication is a natural, slow-aging process for a water body, but human activity greatly speeds up the process.

6. Untreated wastewater usually contains numerous pathogenic, or disease causing microorganisms and toxic compounds; these may contaminate the land or the water body,
When fertilisers run-off into nearby water, they cause an increase in nutrient levels.
This causes phytoplankton to grow and reproduce more rapidly, resulting in algal blooms.
This bloom of algae disrupts normal ecosystem functioning and causes many problems.

7. The algae may use up all the oxygen in the water, leaving none for other marine life. This results in the death of many aquatic organisms such as fish.
The bloom of algae may also block sunlight from photosynthetic marine plants under the water surface.
Some algae even produce toxins that are harmful to higher forms of life. This can cause problems along the food chain and affect any animal that feeds on them.

8. Nitrification and de-nitrification
Nitrification is the biological oxidation of ammonia into nitrite followed by the oxidation of the nitrite into nitrate.
Nitrate can be assimilated by plants through their roots and converted to organic form such as amino acids and proteins.
Ammonia (from decayed animals and plants) in the soil is used by bacteria such as nitrosomonas and nitrococcus as an energy source.  They oxidize ammonia to nitrite.
Nitrite is oxidized by other bacteria, nitrobacter, to nitrate.
Nitrifying organisms are chemoautotrophs, and use carbon dioxide as their carbon source for growth.
NH3 + CO O2 + Nitrosomonas → NO2- + H2O + H+
NO2- + CO O2 + Nitrobacter → NO3-

9. Types of treatment sewage treatments
Mechanical treatment
Biological treatment
Chemical treatment

10. Biological treatment
Biological treatment is used primarily to remove the biodegradable organic substances in wastewater.
Basically, these substances are converted into gases that can escape to the atmosphere and into biological cell tissue.

11. 3 stages of waste water treatment
Primary
solids are separated
Secondary
dissolved biological matter is converted into a solid mass by using water-borne bacteria
95% of the suspended molecules should be removed
Tertiary
biological solids are neutralized then disposed, and treated water may be disinfected chemically or physically. There are 3 different disinfection process.
Chlorination
UV light radiation
Ozonation

12. Wastewater Treatment

13. Chlorination
Most common
Advantages: low cost & effective
Disadvantages: chlorine residue could be harmful to environment.

14. UV light radiation
Damage the genetic structure of bacteria, viruses and other pathogens.
Advantages: no chemicals are used
water taste more natural
Disadvantages: high maintenance of the UV-lamp

15. Ozonation
Oxidized most pathogenic microorganisms
Advantages: safer than chlorination
fewer disinfection by-product
Disadvantage: high cost

16. 3 different sludge treatments
Aerobic digestion
Anaerobic digestion
Composting

17. Aerobic digestion
Bacterial process
Need oxygen
Consume organic matter
Convert into carbon dioxide (CO2)
Anaerobic digestion
Bacterial process
Do not require oxygen
Consume organic matter
Produce biogas, which can be used in generators for electricity
Composting
aerobic process
requires the correct mix of carbon, nitrogen, oxygen and water with sludge
Generate large amount of heat

18. Sludge disposal
Superheat sludge and convert into small granules that are rich in nitrogen
Sell it to local farmer as fertilizer
Spread sludge cake on the field
Save landfill space

19. The wastewater treatment plant lab conducts a number of measurements and tests on the water.
suspended solids
B.O.D. pH
Temperature
Nitrogen
phosphorus
In addition to test performed at the wastewater lab, an off-site contract lab performs additional tests.
heavy metals
priority pollutants
W.E.T (Whole Effluent Toxicity) tests