Unit 8.9 (Solid Waste Disposal)

Solid Waste Types and Source

• MSW (Municipal Solid Waste)

  • Solid waste from cities (households, businesses, schools, etc.)

  • Waste “steam” refers to flow of solid waste to recycling centers, landfills, or trash incineration (burning) facilities

• E-Waste

  • Old computers, TVs, phones, tablets

  • Only ~2% of MSW; considered hazardous waste due to metals like cadmium, lead, mercury, and PBDEs (fireproof chemicals)

• Can leach endocrine disrupting chemicals out of landfills if thrown away with regular MSW (should be disposed of at specials facilities that recycle parts)

  • AKA - trash, litter, garbage, refuse

Sanitary Landfills

• APES lingo for “landfills” or where developed nations dispose of trash; different than “dumps” which are just areas where trash is dumped, without the features below

  • Clay/plastic bottom liner: layer of clay/plastic on the bottom of a hole in the ground; prevents* pollutants from leaking out into soil/groundwater

  • Leachate Collection System: System of tubes/pipes/ at bottom to collect leachate (water draining through waste & carrying pollutants) for treatment & disposal 

  • Methane Recovery System: System of tubes/pipes to collect that methane produced by anaerobic decomposition in the landfill 

    • Methane can be used to generate electricity or heat buildings

  • Clay Cap: Clay-soil mixture used to cover the landfill once it’s full; keeps out animals, keeps in smell, and allows vegetation to regrow

Landfills Contents & Decomposition

• Landfills generally have very low rates of decomposition due to low O2, moisture, and organic material combination

  • Since these 3 factors are rarely present together in landfills, little decomp. occurs landfills typically remain about the same size as when they were filled

• Things that should NOT be landfilled

  • Hazardous waste (antifreeze, motor oil, cleaners, electronics, car batteries) 

  • Metals like copper & aluminum (should be recycled)

  • Old tires; often left in large piles that hold standing water ideal for mosquito breeding

• Things that SHOULD be landfilled: 

  • Cardboard/food wrappers that have too much food residue & can’t be recycled 

  • Rubber, plastic films/wraps 

  • Styrofoam

    • Food, yard waste, and paper can and do go in landfills, but should be recycled or composted

Landfill Issues

• Landfills have environmental impacts like groundwater contamination and release of GHGs

  • Groundwater can be contaminated with heavy metals (lead, mercury), acids, medications, and bacteria if leachate leaks through lining into soil/groundwater beneath 

  • Greenhouse gases (CO₂ and CH₄ - methane) are released from landfills due to decomposition, both contribute to global warming & climate change

• NIMBY (Not in my Back Yard): idea that communities don’t want landfills near them for a number of reasons

  • Smell & sight

  • Landfills can attract animals (rats, crows)

  • Groundwater contamination concerns

    • Landfills should be located far from river & streams and neighborhoods to avoid H₂O cont.

• Landfills are often placed near low-income or minority communities that don’t have the resources or political power to fight against these decisions

Waste Incineration & Ocean Dumping 

• Waste can be incinerated (burned) to reduce the volume that needs to be landfilled; since most waste (paper, plastic, food) = hydrogen, carbon, and oxygen, it easily combusts at high temperatures

  • Can reduce volume by 90%, but also releases CO₂ and air pollutants (PM, SO_x, NO_x)

    • Bottom ash may contain toxic metals (lead, mercury, cadmium) & is stored in ash ponds, then taken to special landfills

    • Toxic metals can leach out of storage ponds or be released into atmosphere

• Can be burned to generate electricity

• Illegal ocean dumping occurs in some countries with few environmental regulations or lack of enforcement

  • Plastic especially collects into large floating garbage patches in the ocean

  • Can suffocate animals if they ingest it or entangle them so they can’t fly or swim and may starve

Unit 8.10 (Waste Reduction Methods)

Reduce, Reuse, Recycle

• The Three Rs

  • Reducing consumption is the most sustainable because it decreases harvesting and the energy inputs to creating, packaging, and shipping

    • Ex: Metal/reusable water bottle to reduce plastic use. Riding bike or walking to reduce gasoline use

• Reusing = the next most sustainable because it doesn’t require additional energy to create a product

  • Ex: Buying second hand clothes

• Recycling = Processing and converting solid waste into new products

  • Ex: Glass being turned into glass again (closed loop)

  • Least sustainable of the three Rs due to the amount of energy it requires to process and convert waste materials

Recycling Pros/Cons

• Pros

  • Reduces demand for new materials, especially metals and wood which cause habitat destruction & soil erosion when harvested

    • Reduce energy required to ship raw materials and produce new products (fewer  FF comb, less CC)

    • Reduces landfill volume, conserving landfill space & reducing need for more landfills

• Cons

  • Recycling is costly and still requires significant energy

    • Cities that offer recycling services need to process, sort, and sell collected materials: prices change rapidly, leading to “recycled” materials often being thrown away

    • When citizens recycle items that shouldn’t be recycled (wrappers with food, styrofoam)

Composting

• Org. matter (food scraps, paper, yard waste) being decomposed under controlled conditions

  • Reduces landfill volume and produces rich organic matter that can enhance water holding capacity, nutrient levels of agricultural or garden soil

    • Produces valuable product to sell (compost)

  • Reduces the amount of methane released by anaerobic decomposition of organic matter in landfills

  • Should be done w/proper mix of “browns” (Carbon) to “greens” (N) ~ 30:1

    • Should also be aerated and mixed to optimize decomp.

• Potential drawbacks include the foul smell that can be produced

E-Waste

• Waste from electronics that often contain heavy metals (lead, merc, cadmium)

  • Can leach these toxic metals into soil & groundwater if disposed in landfills or open dump

  • Can be recycled and reused to create new electronics, but often sent to developing nations for recycling due to health hazards, more strict env. & worker protection laws in developing nations

    • Can be dismantled and sold to countries that extract valuable metals (gold, silver, platinum) from motherboards

    • OFten burned or dumped due to less strict. env. Regulations or lack of enforcement in developing nations

Waste To Energy

• Waste can be incinerated to reduce the volume & also generate electricity; most waste (paper, plastic, food) = hydrogen, carbon, and oxygen so it easily combusts at high temp.

  • Same process as burning coal, NG, biomass

  • Heat → water → steam → turbine → generator → electricity

  • Produce electricity without fracking or mining for FFs

Unit 8.11 (Sewage Treatment)

Water Treatment Process

1. Primary Treatment 

   1. Physical removal of large debris (TP, leaves, plastic, sediment) with a screen or grate

   2. Screens or grates filter out large solids (paper, plastic) 

   3. Grit chamber allows sediment to settle out & be removed

2. Secondary Treatment

   1. Biological breakdown of organic matter (feces) by bacteria; aerobic process that requires O₂

   2. O₂ is bubbled into aeration tank filled with bacteria that break down organic matter into CO₂ and nutrients like N & P

   3. Secondary treatment removes 70% of P and 50% of N

      1. DOESN’T remove POPs such as medications or pesticides

3. Tertiary Treatment 

   1. Chemical filters to remove more of the nitrates & phosphates from secondary treatment discharge

   2. Critical step because effluent that is discharged into surface waters with elevated N & P levels leads to eutrophication

   3. Expensive and not always used

4. Disinfectant

   1. UV light, ozone, or chlorine is used to kill bacteria or other pathogens, such as e.coli

• Sludge: inorganic, solid waste that collects at the bottom of tanks in primary and secondary treatment

  • Water is spun/pumped off to concentrate it further

  • Dry, remaining physical waste is collected to be put in landfill, burned, or turned into fertilizer pellets

• After primary & secondary treatment, some plants go directly to disinfectant (UV, ozone, chlorine) & discharge into surface water, while some will use tertiary treatment to remove more nutrients before discharge

Sewage Treatment Issues

• Combined sewage and stormwater runoff normally, but causes overflow during heavy rains

  • Beneficial b/c it treats stormwater runoff normally, but causes overflow during heavy rains

  • Raw sewage release contaminates surface waters with:

    • E coli

    • Ammonia

    • Nitrates

    • Phsophates 

    • Endocrine disruptors (medications)

• Even treated wastewater effluent released into surface water often has elevated N/P levels and endocrine disruptors (medications passed through the body

Unit 8.12 and 8.13 (LD50 and Dose-Response Curves)

Dose Response Studies & LD₅₀

• Studies that expose an organism to different doses of concentration of a chemical to measure the response of the organism

• Independent variable: concentration of the chemical (added to food, water, or air)

• Dependent variable: response measured in organism (usually death or impariment)

• LD₅₀ refers to the dose or concentration of the chemical that kills 50% of the population being studied (ex: arsenic LD₅₀ in mice = 13 mg/kg)

  • LD₅₀ data are usually expressed as:

    • Mass (g. mg)/body unit (kg)

    • Ppm - parts per milliion (in air)

    • mass/volume (in water of blood)

Dose Response Curve

• The data from a dose response study. Graphed with a percent mortality or other effect on the y-axis and dose concentration of chemical on x-axis 

  • Lowest dose where an effect (death, paralysis, cancer) starts to occur is called the threshold or toxicity threshold

  • Dose-response curves are usually “S-shaped” - low mortality of low doses, rapid increase in mortality as dose increases, level off near 100% mortality of high dosage

    • LD₅₀ dose (50% mortality) 100 mg/kg

ED₅₀ & Other Dose Responses

• ED₅₀ refers to the dose concentration of a toxin or chemical that causes a non-lethal effect (infertility, paralysis, cancer, etc.) in 50% of the population 

  • Ex: the concentration of atrazine in water that causes 50% of frogs to become infertile

  • Same general “s-shape” as LD₅₀ dose-response curve, but at lower dose concentrations

Dose-Response Data & Human Health

• Dose-response studies for toxic chemicals are not done on humans; data from other mammals (mice, rats) are used to stimulate human toxicity 

  • To determine maximum allowable levels for humans, we generally divide LD₅₀ or ED₅₀ dose concentration by 1000 for extreme caution 

  • Acute vs. Chronic studies: Most dose-response studies are considered acute, since they usually only measure effects over a short period of time, they’re also isolated to a lab, so they don’t measure ecological effects of organisms dying (trophic cascades)

    • Chronic studies are longer-term and follow developmental impacts

      • Ex: study of fish from hatchlings to adults to study sexual maturation

Unit 8.14 (Pollution and Human Health) 

Routes of Exposure & Synergism

• It’s difficult to establish exactly how toxic different pollutants are to humans because we have so manny routes of exposrue to so many different pollutants, that studying the effects of just one pollutant is difficult

• Routes of Exposure

  • Ways that a pollutant enters the human body

    • Lead → water pipes & paint chips

    • Mercury → Seafood (tuna)

    • CO → indoor biomass combustion

    • PM → Pollen, dust, etc. 

    • Arsenic → rice, groundwater

• Synergism

  • The interaction of two or more substances to cause an effect greater than each of them individually

    • Ex: Asthma caused by PM from coal PPs and COVID-19 damaging lungs

    • Carcinogenic effects of asbestos combined with lung damage from smoking

  • Synergisms make it especially hard to pinpoint the exact effects of one specific pollutant on humans

Dysentery 

• Bacterial infection caused by food or water being contaminated with feces (often from sewage release into rivers & streams used for drinking water)

• Causes intestinal swelling and can result in blood in feces

  • Results in severe dehydration due to diarrhea (fluid loss)

  • Kills 1.1 million people annually, mostly in developing countries with poor sanitation and limited access to water filtration 

• Can be treated with antibiotics that kill the bacteria causing the infection and access to treated/filtered water that can rehydrate

Mesothelioma (asbestos)

• A type of cancerous tumor caused by exposure to asbestos, primarily affected the lining (epithelium) of the respiratory tract, heart, or abdominal cavity 

  • Asbestos exposure comes primarily from old insulation materials used in attics, ceilings and flooring boards; when the insulation becomes physically disturbed, asbestos particles are released into the air & inhaled

  • Removal of asbestos-containing insulation materials should be done by professionals with proper training and equipment that protects them from inhaling asbestos

    • The area where asbestos is removed from should be sealed off from other areas in the building and well-ventilated during the removal process

    • Insulation without asbestos should be used to replace it

Tropospheric Ozone (O₃)

• Worsens respiratory conditions like asthma, emphysema, bronchitis, COPD

  • Limits overall lung function

    • Irritates muscles or resp. Tract causing constriction of airways & shortness of breath

    • Irritates eyes

  • Sources: photochemical breakdown of NO₂ (car exhaust, coal, & NG combustion)

• ONLY HARMFUL IN TROPOSPHERE (beneficial in stratosphere)

Unit 8.15

Pathogens & Vectors

• Pathogen

  • A living organism (virus, bacteria, fungus, protist, worm) that causes an infectious disease Infectious diseases are capable of being spread or transmitted (HIV, ebola, COVID-19); noninfectious diseases are not transmissible (heart disease, asthma, cancer, diabetes)

  • Pathogens adapt and evolve to take advantage of humans as hosts for their reproduction a spread (COVID-19 is a SARS-associated coronavirus that evolved to become especially effective at surviving and reproducing in humans)

• Vectors

  • A living organism (rat, mosquito) that carry and transmit infectious pathogens to other organisms

    • Climate change is shifting equatorial climate zones north and south away from the equator; this brings warmer temperatures to subtropical and temperate regions

  • Warmer temperatures allow pathogens and their vectors (mosquitos) to spread north & south to parts of the world previously too cold

    • Many pathogenic bacteria and viruses survive and replicate better in warmer

Infectious Disease & Development 

• Less developed, poorer countries typically have higher rates of infectious disease

• Less sanitary waste disposal; pathogens can reproduce in open waste areas where children may play or animals may scavenge & pass to humans

• Less access to healthcare facilities and antibiotic medications to treat infectious diseases cause by bacteria & other pathogens

• Lack of treatment/filtration for drinking water & sewage treatment exposes people to bacterial and viral pathogens in water, often from human waste

• Tropical climates & more open-air living can expose people to vectors like mosquitoes; less money for vector eradication (spraying mosquito breeding grounds)

Plague

• Bacterial (pathogen) infection transmitted by fleas (vector) that attach to mice & rats (vectors as well)

  • Transmitted by flea bite, rodent contact or contaminated human fluids 

  • Aka "bubonic" or "black" plague; modern antibiotics are highly effective against it, but some isolated instances still occur

Tuberculosis (TB)

• Bacterial (pathogen) infection that targets the lungs

  • Transmitted by breathing bacteria from body fluids (resp. droplets) of an infected person, which can linger in air for hours

• Causes night sweats, fever, coughing blood; treatable in developed nations with access to powerful antibiotics

• Leading cause of death by disease in the developing world ~ 9 million cases per year and 2 million deaths (for comparison ~ 2.8 million global deaths from Covid-19)

Malaria

• Parasitic protist (pathogen) infection caused by bite from infected mosquitoes (vector)

  • Most common in sub-Saharan Africa (& other tropical regions of Middle East, Asia, South & Central America; recurring flu-like symptoms; kills mostly children under 5

West Nile

• Virus (pathogen) infection caused by bite from infected mosquitoes (vector)

  • Birds are the main host, but the virus can be transmitted to humans by mosquitoes that bite infected birds and then bite humans

  • Causes brain inflammation, which can be fatal

Zika Virus

• Virus (pathogen) infection caused by bite from infected mosquitoes (vector) & sexual contact

  • Causes babies to be born with abnormally small heads and damaged brains; can be passed from mother to infant

  • No known treatment currently, so prevention is focused on eliminating mosquito populations

SARS (Severe Acute Respiratory Syndrome)

• Coronavirus (pathogen) infection caused by respiratory droplets from infected people

  • Primarily transmitted by touching or inhaling fluids from an infected person 

  • Causes a form of pneumonia

  • Initial outbreak was in Southeast Asia

  • SARS-CoV-2 is the virus that causes the disease COVID-19

MERS (Middle East Respiratory Syndrome)

• Virus (pathogen) respiratory infection transmitted from animals to humans

  • Originated on the Arabian peninsula

Cholera

• Bacterial (pathogen) infection caused by drinking infected water

  • Vomiting, muscle cramps and diarrhea; can cause severe dehydration

  • Can be introduced by water contaminated with human feces or undercooked seafood