MICROBIAL ECOLOGY_2023_24_LAAO-home slides4.pdf

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana BIOL 252: MICROBIAL ECOLOGY 2023/2024 Name: Prof. (Mrs.)Linda Aurelia Ofori (PhD) Email: [email protected] /[email protected] Phone Number...

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana BIOL 252: MICROBIAL ECOLOGY 2023/2024 Name: Prof. (Mrs.)Linda Aurelia Ofori (PhD) Email: [email protected] /[email protected] Phone Number: 0244220064  Course Outline Natural Microbial Environments---done Microorganisms of Extreme environments-- done Strategies for survival---done Some important diseases ---- done Water and excreta-related diseases--- done Biofilms ------done Water Treatment----- done Wastewater/Sewage Treatment www.knust.edu.gh 7/23/24 2023/24 2  Recommended texts for further reading Introduction to Microbiology – Ingraham and Ingraham MICROBIOLOGY - Prescott, Harley and Klein Fundamentals of Microbiology – Frobisher Essential Microbiology – S. Hogg Any good Microbiology book Authentic Microbiology journals www.knust.edu.gh 7/23/24 2023/24 3  Assessment Requirements ü Punctuality, Attendance ü Presentations (Group) Continuous ü Assignments (Individual and Group) Assessment ü Short Quizzes – Un/announced 30% ü Mid Semester Examination** ü Practical Assignments – Weekly ü End of Semester Examination 70% www.knust.edu.gh 7/23/24 2023/24 4  WASTEWATER/SEWAGE TREATMENT www.knust.edu.gh 7/23/24 2023/24 5  Where does it all go! Where does the When you flush the water from the toilet where does the washer go? contents go? By gravity flow, the waste is on its way to your local wastewater treatment plant! www.knust.edu.gh 7/23/24 2023/24 6 NORWEGIAN UNIVERSITY OF LIFE SCIENCES (Corcoran et al. 2010) 7 More than 80% of the worlds wastewater does not receive any treatment www.knust.edu.gh 7/23/24 2023/24 7  WASTEWATER/SEWAGE TREATMENT Applies knowledge and technology to improve or upgrade the quality of wastewater. To reduce organic matter content of wastewater (i.e. reduction of BOD) Removal/reduction of nutrients (N, P) to reduce pollution of receiving surface waters or groundwater if the effluents are applied onto land Removal or inactivation of pathogenic microbes and parasites www.knust.edu.gh 7/23/24 2023/24 8  Why treat wastewater? Causes a demand for dissolved oxygen (lower DO levels of streams) Increases nutrients in the streams (nitrate and phosphate) to cause excessive growth Increases suspended solids or sediments in streams (turbidity increase) www.knust.edu.gh 7/23/24 2023/24 9  Wastewater Treatment Tertiary www.knust.edu.gh 7/23/24 2023/24 10  Wastewater Treatment Screening Primary Sludge settlement digestion Secondary treatment activated sludge trickle Sludge disposal to sea, land burial, incineration, composting Tertiary treatment; Effluent disposal; chlorination, UV, river, sea, ozone irrigation www.knust.edu.gh 7/23/24 2023/24 11  Wastewater Treatment Conventional Wastewater/Sewage Treatment – Processes 1. Primary Treatment – Mechanical process » Screening » Grinding » Grit Chamber (heavy particles - “grit”) » Sedimentation Tank/ settling tank (suspended solids - “sludge”) www.knust.edu.gh 7/23/24 2023/24 12  Primary treatment: 1. Separation of liquids and solids 2. Does not purify sewage www.knust.edu.gh 7/23/24 2023/24 13  Conventional Wastewater/Sewage Treatment – Processes 2. Secondary Treatment –Biological process »Uses bacteria to remove Oxygen demanding wastes (ODW) and lower BOD –Types »Trickling Filter »Activated Sludge www.knust.edu.gh 7/23/24 2023/24 14  Conventional Wastewater/Sewage Treatment – Processes Secondary Treatment With Trickling Filters – Effluent leaves the sedimentation tank and flows through the trickling filters. » Bed of stones 3-10’ deep through which sewage passes » Bacteria gather on stones and multiply, consuming ODW » Cleaner water trickles through pipes at the bottom of the filter for additional treatment www.knust.edu.gh 7/23/24 2023/24 15  Trickling filter It is a bed of crushed rocks or moulded plastics about 2m thick The bed must be large to allow air to penetrate the bottom and with a large surface area Wastewater (effluent) is sprayed onto it The effluent slowly passes through the bed www.knust.edu.gh 7/23/24 2023/24 16  Biofilms in the effluent attach to the rocks and plastics Bacteria in the biofilms extract and digest organic compounds (BOD) up to 80-85% Protozoa and Rotifers are mainly responsible for the removal of suspended solids www.knust.edu.gh 7/23/24 2023/24 17  Activated sludge system In the aeration tank, air or pure oxygen is passed through the effluent Here, some sludge from the OLD batch is added to the NEW incoming sewage This inoculum is called activated sludge as it contains large numbers of sewage-metabolizing microbes (Zoogloea bacteria) These microbes oxidize the organic matter in the effluent into carbon dioxide and water www.knust.edu.gh 7/23/24 2023/24 18 Conventional Wastewater/Sewage Treatment – Processes Secondary Treatment With Activated Sludge –Effluent leaves the sedimentation tank and is pumped into an aeration tank –Effluent is mixed with air and sludge loaded with bacteria (“activated sludge”) –Sludge contacts with raw sewage and bacteria in the sludge then decompose the raw sewage, lowering BOD www.knust.edu.gh 7/23/24 2023/24 19 Conventional Wastewater/Sewage Treatment – Processes Secondary Treatment With Activated Sludge – Activated sludge-sewage mixture is called mixed liquor – Mixed liquor leaves the aeration tank and flows to another sedimentation tank, where suspended solids settle out for reuse as activated sludge www.knust.edu.gh 7/23/24 2023/24 20  Activated Sludge System This produces bacteria containing masses called Floc or sludge granules After 4 to 8 hrs, the whole content is transferred to a settling tank where the floc settles out, removing much of the organic matter The solids are then treated in a sludge digester The effluent is then discharged www.knust.edu.gh 7/23/24 2023/24 21  Secondary process To tertiary process From primary process air Aeration Settling diffuser and rapid collects sludge mixing on bottom www.knust.edu.gh 7/23/24 2023/24 22  Rotating Biological Contactor Series of disks several feet in diameter mounted on a shaft The disks rotate slowly with their lower 40% submerged in wastewater Rotation provides aeration and contact between the biofilm on the disks and the wastewater The rotation causes the accumulated biofilm to slough off when it becomes too thick www.knust.edu.gh 7/23/24 2023/24 23  Sludge digestion Generated sludge is pumped into anaerobic sludge digesters Carried out in large tanks without oxygen, thus encouraging the growth of anaerobic bacteria, especially the methane- producing bacteria The bacteria degrades organic matter to soluble substances and gases, mostly methane (60-70%) and carbon dioxide (20- 30%) Methane is harvested and used as fuel for running the digester, cassava grating, corn milling, lighting and singeing of animals www.knust.edu.gh 7/23/24 2023/24 24  www.knust.edu.gh 7/23/24 2023/24 25  www.knust.edu.gh 7/23/24 2023/24 26  Septic Tank A SEPTIC TANK serves areas of our country not connected to municipal sewerage systems Septic systems are a type of On-Site Sewage Facility In affluent areas in Ghana, approximately 80% of the population relies on septic tanks In Europe, septic tanks are limited to rural areas. "septic" refers to the anaerobic bacterial environment that develops in the tank. www.knust.edu.gh 7/23/24 2023/24 27  Considerations Aerobic Anaerobic Biochemical/Biological Oxygen Demand Effluent Scum Sludge Sewage Depends on two kinds of bacteria: 1. Aerobic 2. Anaerobic www.knust.edu.gh 7/23/24 2023/24 28  In a Septic tank…..... Here, sewage enters a holding tank, and suspended solids settle out Sludge is pumped out occasionally and disposed of – e.g Lavender Hill, Accra. It is mostly three-chambered Effluent flows through the perforations into the leaching field and is decomposed by microbes www.knust.edu.gh 7/23/24 2023/24 29  Treat sewage so that it is made harmless www.knust.edu.gh 7/23/24 2023/24 30  Septic Tanks chamber Sedimentation Digestion tank Storage of digested sludge www.knust.edu.gh 7/23/24 2023/24 31  www.knust.edu.gh 7/23/24 2023/24 32  Oxidation Ponds/Lagoons/Stabilization Ponds Inexpensive but requires large land It often comes in TWO stages The first stage, like the primary treatment – sludge settles out in the first stage The second stage, like secondary treatment – it is shallow enough to allow aeration by wave action and encourage aerobic conditions for bacterial growth. www.knust.edu.gh 7/23/24 2023/24 33 Oxidation ponds/lagoons/stabilization ponds Encouraged decomposition of organic matter Algae grow on top of the oxidation ponds, Algae use carbon dioxide in photosynthesis to produce oxygen, which promote aerobic microbial activity. www.knust.edu.gh 7/23/24 2023/24 34  Most often, treated sewage is disinfected by chlorination before discharge into receiving waters (Tertiary treatment) Sometimes it can be treated to a level of purity that allows its use as drinking water Here a combination of UV light and other disinfectants are employed www.knust.edu.gh 7/23/24 2023/24 35 Conventional Wastewater/Sewage Treatment – Processes 3. Tertiary Treatment – Effluent is chlorinated (kills bacteria) and released into lakes, ocean or river – Activated sludge in the sedimentation tank is reused. www.knust.edu.gh 7/23/24 2023/24 36  Levels of Treatment Primary – removal by physical separation of grit and large objects (material to landfill for disposal) Mostly dead microbes Secondary – aerobic microbiological process (sludge) organic matter + O2 à CO2 + NH3 + H2O NH3 à NO3- aquatic nutrient - lowers suspended solids content (into sludge) Tertiary Chlorination www.knust.edu.gh 7/23/24 2023/24 37  When the treatment is done… Effluent discharged back to stream after – a final carbon filtration and – chlorination/dechlorination Sludge – very nutrient-rich – applied directly to land as fertilizer – incinerated (good fuel after drying) – composted www.knust.edu.gh 7/23/24 2023/24 38  Removal Efficiency (%) Parameter Primary Secondary Tertiary Treatment Treatment Treatment SS 50-80 80-90 >90 BOD 20-40 70-90 >90 P 90 N