(F) 20 - Waste Management Flashcards
The main waste streams:
municipal waste, agriculture/forestry, industry, energy production, construction, mining, water purification and distribution
- A lot of variation btw countries
- Per capita waste increases based on wealth
Concept and structure of a waste pyramid:
The waste hierarchy
Prevention
Reuse
Recycling
Energy recovery
Disposal
Definition of municipal waste and municipal wastewater
Municipal Waste: waste produced by consumers, public facilities, and small businesses
Municipal Wastewater: water that has been used by ppl in some way, including sewage, water from showers, sinks, washing machines, etc.
Waste disposal methods and relative problems: landfills, incinerators, exportation (e.g., e-waste)
LANDFILLS
- Most of the garbage we collect for disposal ends up in landfills, some is incinerated (Canada)
- Sanitary landfills: engineered to collect waste but prevent it from contaminating soil, groundwater, and environment; using layers of impermeable material
- Ex. Freshkills Park Project (NYC)
- Problem: You’re stuck with a literal pile of trash; ppl do not want this near them so…
EXPORTATION
- Wealthy communities often export their garbage to landfills in less-wealthy areas
- Basel Convention (1992): Treaty on control of transboundary movements of hazardous wastes and their disposal
- E-waste is the most problematic bc there are a lot of toxic elements involved; workers are exposed
INCINERATORS
- The combustion of waste at very high temperatures, reducing it’s volume by as much as 90% (and wt by as much as 75%)
- Metals (which can be recycled) are removed before incineration
- Problems: produce air pollution and secondary pollutants, SO2 can be scrubbed out of emissions, along with some PM to reduce pollution, special consideration for heavy metals and PCBs
Example: Edmonton Waste Management Centre (its four waste streams - in general)
- Recycling
- material collected from: blue bag program, blue bin program, recycling depots
- also manage an e-waste recycling facility - Compost
- divert approx. 50% of residential waste from landfill to either composting or recycling facilities
- sold as ‘Second Nature’ compost and topsoil around the city
- new facility: Anaerobic Digestion Facility (ADF); goal is to divert 90% of waste from landfill; collect biogenic natural gas emissions to use as a fuel source and reduce GHG emissions - Biofuel production
- feedstock preparation: sorting, shredding, drying, and feeding
- gasification: conversion of carbon-rich residues into synthetic gas
- cleaning and conditioning process: primary syngas purification
- catalytic synthesis and product purification: conversion of chemical-grade syngas into final renewable products - Landfill
- Clover Bar Landfill
- landfill gas recovery collects CH4 and CO2 and uses it to power generators
Definition of Planned Obsolescence
Designing a product with an artificially limited useful life, to force consumers to purchase new products in shorter intervals (shortened replacement cycle).
- usually achieved by making products difficult to repair (tech), excessively trendy (clothing), or programming them so they automatically shut off at a prescribed point
Municipal wastewater treatments (in general what each treatment is for)
PRETREATMENT
1. Aerated grit tank
- remove large, heavy materials (rocks, etc.)
2. Bar screens
- remove large, light materials (plastics, wood, etc.)
PRIMARY TREATMENT
1. Settling tanks
- allows heavier solids (sludge) to settle at bottom of tank
- can remove up to 60% of suspended solids
2. Fate of sludge
- fermented
- digested (biogas)
- used (sometimes) as fertilizer
SECONDARY TREATMENT
1. Aeration
- encourages growth of microbes which degrade organic pollutants
- removes biological nutrients, such as phosphorus and nitrogen
- sometimes called “bioreactors”
TERTIARY TREATMENT
1. Clarification
- second set of settling tanks, allows microbes to floc
2. UV disinfection
- treat effluent with UV light to kill any remaining microbes
3. Membrane filtration
- similar effect as UV disinfection
- use micropore filters to remove microbes
QUATERNARY TREATMENTS
- Removal of pharmaceutical pollutants, and other persistent compounds
Problems:
- we don’t know how to do it efficiently (yet)
- regardless, it will be very expensive
- testing methods involved activated carbon, and ozone
What happens when wastewaters are untreated or improperly treated (pathogens, eutrophication, fatbergs, etc.)
What can go wrong:
1. Equipment malfxn
2. Overburdened system
3. Too expensive to do properly
4. Non-compliance or lack of regulations
Disruptions to Biological Treatment
- occurs when hazardous waste, toxins, get into wastewater (flushed)
- can disrupt or kill the microbes involved in secondary treatment
- municipal systems not design to treat this waste
Pathogens
- in effluent
- in solid waste used as fertilizer
Excess nutrients
- phosphorus —> eutrophication
- nitrogen —> disrupt O2 transport in humans
Fatbergs
- conglomerates of products that can’t degrade in sewage systems
- a “fun” mix of fats, oils, diapers, condoms, wet wipes, menstrual products, etc…
Municipal Wastewater Reduction
- Treating wastewater takes energy, resources, and time
- Also, some sludge is disposed of in landfills
- Some systems produce energy (biogas) but are rarely energy neutral
- Globally, wastewater treatment isn’t always as stringent as in Canada
