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Lecture: Applied Microbiology & Bioremediation
Lecturer: David Simonds
Required Videos: None
Recommended Readings: None
Learning Objectives
After attending the lecture and completing any assigned videos/readings, students will:
Define terms from terminology list
Understand the concept of bioremediation and the factors that influence it
In home septic systems, understand the roles of microbes in the tank and leach field
Understand the roles of microbes in primary and secondary treatment of sewage
Describe how renewable natural gas is generated
Describe what is happening in each step of water treatment
Understand why coliform testing is performed on potable water
Describe the role of microbes in oil spills
Provide examples of how microbes are helping to generate new, usable products
Concepts and Definitions
Biodegradation vs. Bioremediation
Biodegradation: A natural process that leads to the breakdown of organic substances into simpler compounds. This process relies on microorganisms such as bacteria and fungi.
Bioremediation: Refers to the process of using microorganisms, plants, or fungi to remove or neutralize contaminants from a polluted area. It typically involves human intervention and is considered faster than biodegradation alone.
Bioremediation Process
Definition of Bioremediation
“Bioremediation is a natural process which relies on bacteria, fungi, and plants to alter contaminants as these organisms carry out their normal life functions. The metabolic processes of these organisms are capable of using chemical contaminants as an energy source, rendering the contaminants harmless or less toxic products in most cases.”
Primary Ingredients for Bioremediation
Contaminants: Presence of a specific contaminant that needs to be degraded.
Microorganisms: Presence of microorganisms capable of degrading the specific contaminant.
Environmental Factors:
Nutrient availability
Moisture content
pH levels
Temperature of the soil matrix
Inorganic nutrients such as nitrogen and phosphorus
Understanding Septic Systems
History and Function
Toilets: Historically a luxury in the late 19th century.
Septic System: Patented in London in 1900.
Waste is directed from households into a holding tank where:
Water seeps into the leach field and surrounding soil.
Solid waste (sludge) remains in the tank and is partially digested by several microorganisms, including:
Aerobic & anaerobic bacteria
Fungi
Protozoans
Nematodes (roundworms)
Rotifers (freshwater zooplankton)
Step 1: Septic Tank
Organic matter is primarily digested by anaerobic bacteria.
This process yields sludge and gases.
Accelerator Products: Dried endospores and enzymes to assist in solid waste digestion.
Sludge must be pumped out periodically, which is either sent to treatment plants or exposed to oxygen for further aerobic digestion.
Step 2: Leach Field
Wastewater from the septic tank continues to be digested by bacteria.
A balance of oxygen is crucial; insufficient oxygen levels can lead to anaerobic digestion predominating, resulting in biomass accumulation and the formation of a biomat.
Eventually, this can cause black effluent to seep to the surface.
Step 3: Bioremediation Process in Sewage
Sewage Composition: 99.9% water and 0.1% solids or dissolved wastes.
Primary Treatment: Separation of solids from effluent, which is then sent to an anaerobic tank.
Secondary Treatment: Involves treating the effluent with O₂ and aerobic microbes (e.g., Zoogloea ramigera) to form activated sludge.
Part of the activated sludge is reprocessed while the rest goes to the anaerobic tank.
Trickling filters or MBBR (moving bed bioreactor) can also be employed, relying on biofilm formation.
Tertiary Treatment: At this stage, secondary effluent is filtered and treated to remove harmful chemicals, using chlorine, UV light, or ozone for disinfection.
Disinfected water can be utilized or released back into the environment.
Anaerobic sludge digestion converts 40-60% of solids into biogas, primarily methane and CO₂, with the potential for methane being used as an energy source, and the remaining sludge being disinfected for fertilizer applications.
Renewable Natural Gas (RNG) - Biomethane
Overview
The Newtown Creek Digester Eggs in Brooklyn, NY can process 1.5 million gallons of sludge daily, producing enough biogas to heat 2,500 homes.
The Persigo Wastewater Treatment Plant in Grand Junction, CO turns 8 million gallons of human waste into RNG, generating 460 gasoline gallon equivalents daily, powering 40 garbage trucks, street sweepers, and buses.
RNG represents a sustainable fuel source with near net-zero emissions and is interchangeable with conventional natural gas.
Global Market Trends
Driven by climate policy and market demands, the global biomethane market is projected to reach 100 billion cubic meters (bcm) by 2030.
In 2020, there was a 20% increase in RNG production, totaling 5 bcm, doubling since 2015, with Europe currently leading but the US becoming the world’s top producer since 2019.
Methane (Biogas) & Hydrogen Fuel
Microbial Community Shift
The microbial communities shift during the anaerobic digestion process, leading to organic waste hydrolysis, followed by acetogenesis and methanogenesis to produce methane.
Key groups of bacteria involved include Clostridium, Azotobacter, and Syntrophomonas.
Applications also explore the utilization of the produced hydrogen (H₂) for various industrial and energy purposes.
Urine-Tricity: Electricity from Urine
The UWE Bristol has developed microbial fuel cells that utilize bacteria from activated sludge to metabolize urine and generate electricity.
The processed fluid can yield nitrogen and phosphorus (fertilizers) and can charge cell phones with a single deposit, demonstrating potential for use in refugee camps.
Water Treatment Process
Steps Involved
Sedimentation: Addition of flocculating agents such as alum, causing particulates to aggregate into floc for precipitation.
Filtration: Physically removing microbes using methods like slow and fast sand filters, membrane filtration, and activated charcoal.
Chlorination: Application of chlorine gas (0.2-1 ppm) to kill bacteria within a 30-minute timeframe; alternatives include UV light or ozone.
Additional Steps: May include softening and fluoridation of the water.
Testing for Water Quality
The EPA and Safe Drinking Water Act mandate regular testing of municipal and public water supplies for bacteria, inorganic chemicals, and radioactivity.
Private wells should see yearly testing for coliform bacteria, and every five years for contaminants like arsenic and lead.
Biodegradation and Oil Spills
BP Deepwater Horizon Incident
On April 20, 2010, an explosion led to the release of approximately 210 million gallons of oil, affecting 1,000 miles of the Gulf coastline.
A large-scale bioremediation effort involved using chemically dispersants and exposing oil to naturally occurring bacteria that had adapted to degrade oil.
Exxon Valdez Oil Spill
In 1989, 11 million gallons of heavy crude oil contaminated around 1,300 miles of shoreline.
The response involved injecting nitrogen fertilizers to promote indigenous oil-eating bacteria, marking the first large-scale biostimulation effort.
Declining degradation rates have been observed, indicating ongoing challenges with oil persisting in the marine environment.
Biodegradation of Plastics
Overview and Problems
Humans have produced over 8.3 billion tons of plastics, with 79% leading to landfill or environmental entry, causing major ecological issues.
Almost all conventional plastics are derived from fossil fuels.
Microbial Solutions
Recent studies identified microbes capable of metabolizing various plastics.
The goal is to identify and produce large amounts of microbial enzymes for rapid degradation of plastics, which could provide promising biotechnological approaches for recycling post-consumer plastic waste.
Bioleaching
Concept
A process utilizing microbes to extract metals from ores or electronic waste through natural mechanisms.
Approximately 20% of the world's mined copper is extracted via bioleaching, yielding an 80-90% copper removal rate from ores.
Applications
Bioleaching is employed for various metals, including copper, zinc, lead, and gold, utilizing diverse bacteria known for their ability to oxidize ferrous iron and sulfur.