Solid Waste Exam 1 Lecture 4 Flashcards
What are Sanitary Landfill issues?
Landfill gas, Leachate, ground settling,
Noise, vector, odor , nuisance
Aesthetics
Constituents of Oxygen Demand
Total COD (Chemical oxygen demand, typically always larger than BOD, how much organic material can be oxidized through a chemical reaction)
Biodegradable COD (Biochemical Oxygen Demand (BOD), only the biodegradable fraction of COD)
Non biodegradable COD (what decomposers cannot process, not organic content that will be metabolized)
Constituents of Oxygen Demand
TKN (don’t know what this means)*
Organic Nitrogen
Ammonia
What kind of process is nitrification ?
It is an aerobic process because it requires oxygen
What is Carbon Fate?
It is when the landfill process is aerobic, then over time all of the oxygen content is used up and the process switches to anaerobic . Microbes use up all of the available oxygen and then the process become anaerobic (because a limited supply of oxygen) . Organisms are active in aerobic state for 4 to 60 days.
The effluent (what is remaining) is carbon that is left over
What is a benefit of the Carbon Fate anaerobic process?
Generation of bio gas : methane and a lot less sludge made.
Methane is used to produce electricity
When there is a high oxygen demand there is a . . .
High availability of carbon
What is sludge also known as?
Biomass
-Sludge helps microorganisms grow in aerobic state
What are the five complex interactions among different microorganisms
- Fermentative bacteria –turn it into fatty acids
- H2 producing acidogenic bacteria : generate acids
- H2 consuming acetogenic bacteria : generates acetates
- CO2 reducing methanogens –> CO2 and hydrogen to make methane
- Aceticlastic methanogens
Concerns of gas generation
Methane gas is explosive
Anaerobic decomposition
CO2 dissolve in water can acidified to to carbonic acid (corrosive)
Nitrate, traces of oxygen, VOCs
Health threats, destroys vegetation, and contaminates groundwater
Major concern of Leachate “garbage juice”
Formed as water migrates through solid waste, picking up a variety of biological and chemical contaminates
Greatest threat is contamination of groundwater
Usually collected and taken to a wastewater treatment plant for processing
Leachate Properties
Concentrated soluble organic materials
Increase concentration of inorganic
Depletes dissolved oxygen
Bacteria and viruses
Leachate basics
Follows the path of least resistance for migration
To control leachate : inspect, have a lining system, and control what goes into the trash (biodegradable)
For disposal and treatment : discharged to a lake, settling pond depending on what it is .
- discharged to a sewer
- land farming : soil amendment
- recycled back into land fill
Migration of gas and leachate
High soil permeability and low moisture content = moderate migration rate
Low soil perm and high moisture content = moderate migration
High soil perm and high moisture content = high migration rate
Low soil perm and low moisture content = low migration rate
Landfill siting and design process
Planning - identify need, site design strategy , asses alternatives, set criteria
Site selection - surrounding community, facility design to be approved by regulatory agencies and county , must be 6 statue mile between airports and new landfills
Facility design
Implementation / operation - daily log book or files, inspection records, gas monitoring results, records of weights / volumes/ excavations, no more than 1.25% methane within any portion of any on site structures and no more than 5% of methane gas migrating from the disposal site
Landfill Cell
Individual building block
1 days worth of trash
8-30 ft in depth, dimensions determined by type of waste
Portion of compacted solid wastes in a landfill that is enclosed by a natural soil or cover material during a designated period
Landfill toe
End of a cell
2 cells meet at lowest point
Point of possible leakage, leachate collection area
Daily cover
6 inches of material
Top and between a cell
End of each operating day in order to control vectors, fire, odors, blowing litter and scavenging
Soils / earthen materials or alternative materials used in covering compacted solid wastes in disposal site
Landfill Intermediate cover
Cover between tiers
12 inches of compacted soil
Cover material placed on all fill surfaces where additional cells are not to be constructed for 180 days or more to control vectors, fires, odors, blowing litter, scavenging and drainage
Landfill final cover
Additional 12 inches of soil on top of clay to grow grass or vegetation
12-24 inches of clay
Landfill alternate daily cover material (ADCM)
Replace daily cover (soil)
Foam can be use but may be fracture after it hardens
Geo-synthetic panels to cover the trash
Indigenous materials : green waste, leaves, grass
Landfill geomembrane
Impermeable membrane , man made structure, or system designed to limit the movement of liquid or gas in the system
Synthetic liner and flexible membrane liner
Landfill site closure factors to consider
Settlement : types of waste, wood, : settle is minimal
Control of gas and leachate, monitor liner, continuous monitoring
Landfill closure requirements
Minimum of 30 years of maintenance
Reuse for parks and golf course
Landfill site closure vegetation cover
Root system can penetrate cap
Vegetation to reduce erosion
What is a landfill gas recovery (LFG)?
Methane produced in landfill, approx 6 months to five years
Landfills are designed with perforate gas collection pipes to prevent gas migration
Header pipe is connected to the LFG recovery system
Methane properties
Colorless, odorless
Nearly insoluble in water
Methane in prescience of air is combustible at concentrations between 5 and 15%
Methane recovery production
Acidic conditions inhibit methane production
Alkaline conditions promote methane production
Conditions that need to be considered : amount and type of waste, and moisture and temp
