Managing Waste Pollution: Solid, Hazardous, and Sewage Systems (APES Unit 8)

Solid waste

Discarded materials that are not liquids or gases (e.g., food scraps, packaging, electronics, construction debris) that can pollute air, soil, and water if mismanaged.

Municipal solid waste (MSW)

Everyday trash from homes, schools, offices, and some businesses (e.g., paper, plastics, food waste).

Hazardous waste

Waste that poses significant danger to people or ecosystems because it is toxic, reactive, corrosive, ignitable, infectious, or otherwise harmful.

Sanitary landfill

An engineered waste burial site designed to isolate waste from the environment using containment systems (liners, leachate collection, gas controls, caps, and monitoring).

Leachate

Contaminated liquid produced when water percolates through waste and dissolves/carries chemicals out of the landfill.

Landfill gas

Gas produced by microbial decomposition of organic waste under low-oxygen conditions; typically rich in methane (CH4) and carbon dioxide (CO2), and often collected for flaring or energy use.

Incineration

Controlled burning of waste to reduce waste volume; can generate air pollutants and produces ash that must be managed/disposed.

Waste-to-energy facility

An incineration system that uses heat from burning waste to generate steam and electricity (energy recovery from waste).

Incinerator ash

Solid residue left after incineration; may contain concentrated heavy metals/contaminants and sometimes requires special (hazardous) disposal.

Deep-well injection

Disposal method where liquid hazardous waste is injected into deep, confined rock formations; intended to isolate waste but carries long-term leakage/uncertainty risks.

Waste management hierarchy

Preferred order of waste strategies: source reduction (reduce) → reuse → recycling/composting → energy recovery → disposal (last resort).

Source reduction

Designing, buying, and using products in ways that create less waste and less toxicity (e.g., lightweighting, durability/repairability, safer substitutes).

Extended producer responsibility (EPR)

Policy approach that shifts some end-of-life management responsibility (and cost) from consumers/taxpayers to manufacturers to encourage less waste and better recyclability.

Reuse

Using a product again without reprocessing it into raw material (e.g., refill, repair, refurbish), preserving embedded energy and materials.

Recycling

Converting used materials into new products via collection, sorting, processing, and manufacturing; depends on low contamination and stable markets/demand.

Composting

Controlled aerobic decomposition of organic waste into a soil-like amendment; reduces landfill methane potential and returns nutrients to soils.

Sewage (wastewater)

Used water from toilets, sinks, showers, and industry containing organic matter, nutrients, pathogens, and chemicals; untreated discharge can pollute waterways.

Biochemical oxygen demand (BOD)

Measure of how much dissolved oxygen microbes will consume while decomposing organic matter in water; high BOD can rapidly deplete oxygen and harm aquatic life.

Eutrophication

Nutrient-driven process where excess nitrogen/phosphorus causes algal blooms and subsequent oxygen depletion when algae die and decompose.

Septic system

On-site wastewater treatment where solids settle in a septic tank and effluent percolates through a drain (leach) field; failure can contaminate groundwater with nutrients/pathogens.

Primary treatment

First stage of municipal wastewater treatment using physical separation (screening, grit removal, settling) to remove large solids and suspended particles.

Secondary treatment

Wastewater treatment stage using microbes to biologically break down dissolved and remaining organic matter, significantly reducing BOD (e.g., activated sludge, trickling filters).

Tertiary treatment

Advanced wastewater treatment processes used to remove nutrients (N and P), remaining solids, specific chemicals, and/or pathogens to prevent eutrophication and improve water quality.

Disinfection (wastewater)

Process to reduce pathogens before discharge (e.g., chlorination, UV light, ozonation); helps prevent disease spread but does not address overflows that bypass treatment.

Combined sewer overflow (CSO)

Release of mixed stormwater and raw sewage from combined sewer systems during heavy rain/snowmelt when flow exceeds treatment capacity, causing sudden pathogen/BOD/nutrient pollution.