The topics covered in this chapter can be summarized as follows:
|14.1 The Waste Stream
|Solid waste from domestic sources—which amounts to hundreds of kg per person per year—is dominated by organic matter, paper and plastic. Although recycling programs exist in most developed countries, we all need to get better at diverting GHG-producing organic matter (including paper) from landfills.
|14.2 Dumps and Landfills
|While a dump is a hole in the ground where waste is deposited without any controls, a landfill is an engineered structure with barriers to prevent the waste or its liquid and gaseous products from escaping to the environment (land surface, atmosphere, groundwater). Contaminated water from within a landfill can be treated, and gases can be recovered to produce energy.
|14.3 Leachate and Landfill Gas
|Leachate is the water that is in equilibrium with the waste in a landfill. It typically has a high chemical and biological oxygen demand, and elevated levels of ammonia, chloride and metals. Landfill gas is generated by the breakdown of organic waste. It can have elevated levels of hydrogen, but tends to be dominated by carbon dioxide and methane.
|14.4 Waste to Energy
|Methane produced by a landfill can be burned to produce heat or electricity (or both). Domestic, commercial and some industrial wastes are generally flammable and can be burned directly to produce heat and electricity.
|14.5 Liquid Waste
|Liquid waste (sewage) has a high chemical and biological oxygen demand because it is rich in suspended organic matter. It also contains pathogens, so it needs to be dealt with carefully. Secondary, and especially tertiary, sewage treatment processes can significantly reduce the COD and BOD and destroy the pathogens so that the effluent water is safe to release into the environment.
Answers for the review questions can be found in Appendix 1
- What do we need to get better at keeping out of our landfills to reduce their contribution to climate change?
- Why is it important to provide daily cover over the working surface of a landfill?
- Provide two reasons why an inactive section of a landfill should be covered with an impermeable membrane.
- You are in charge of designing a water monitoring program at a landfill. List a few of the important constituents you would analyze in samples collected from monitoring wells and surface water locations in order to detect dispersal of contaminated water from the site.
- What are the two main constituents of the gas produced in a mature landfill?
- If landfill gas isn’t used to produce energy, it should be flared. Why is this important?
- Based on Figure 14.1.3, list some of the materials in the waste stream that are not burnable.
- What constituents of wastewater are most likely to affect human health? What about ecosystem health?
- Why is important that the natural material underlying a septic drainage field is permeable, but not too permeable?