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waste Management q3

Modules 8 and 9

QuestionAnswer
What is a landfill? A facility for disposal/long term storage of solid wastes
What is a sanitary landfill? Specifically engineered to decrease environmental and public health risks
What is a secure landfill? Used for hazardous solid wastes
Three processes involved in landfilling. Monitoring, waste placement/compaction, and environmental controls
What is a cell? Volume of waste in a specific operating period
What is the daily cover? 15 cm of native soil
What is final cover? Multiple layers of synthetic/natural materials plus native soil.
What is the purpose of the final cover? Prevents infiltration, collects surface runoff, and supports vegetative growth
What is a lift? A complete layer of cells
What is a terrace? Think of aztec pyramids. Maintains the slope and includes collection spillways
What is leachate? Liquid collected along the bottom of the landfill due to precipitation, surface runoff, residual liquids, reaction products and groundwater seepage
Main components of landfill gas Methane and carbon dioxide
Purpose of the landfill liner Prevents liquid/gas from going in or out of landfill
Post-closure activities Environmental monitoring, leachate collection, gas management, cap repairs, and vegetation maintenance
The landfill design not allowed in Alberta Canyon
The three landfill designs Area, Trench, Canyon
Classes of landfill I- hazardous II- sanitary III- inert c/d
Do landfills that receive less than 10 000 tonnes of nonhazardous waste need an approval? No but they do need a code of practice
Landfills cannot be near airports, T or F T
What is the hydraulic conductivity requirement of liners? 1 x 10^-7
Site selection criteria for landfills. 40/52 rule Enough area Not near airports/waterbodies Accessible Good soil Climate considerations
From bottom to top, what are the layers in a class I landfill? Dewatering pump Recompacted clay (30cm) Secondary liner (x2 welded HDPE) Geonet Leak detection Geotextile Sand (30cm) Gets repeated with primary liner and leachate collection 60 cm gravel
How do you inspect for leaks in the double welded liner? Vacuum box
Why are cells useful? Keeps landfill organized and provides a means of record keeping
Typical cell depth after compaction? 70 cm to 1m
Benefits of landfill compaction? Decrease landfill volume and increase landfill life
Disadvantage of landfill compaction? Slows down biodegragation
Benefits of daily cover. Decreases odor, prevents pests, marks each cell
Daily cover ratio 1 cover: 5 waste
Why is the landfill sloped? Aids in leachate collection
How many gas collection areas are there in a landfill? One per lift
Why recover landfill gas? Methane has a high fuel value. Prevent fires and explosions Methane has a high GWP
Gas collection installation types Mini flares and steam turbines
Gas evolution phases I - Aerobic decomposition- N2 and O2 II- Transition phase- Anaerobic starts- CO2 starts rising III- Acid phase- CO2 peaks and OA rises IV- Methane fermentation- methanogenic processes V- Maturation phase- N2 and O2
Gas evolution timelines I- 1 week II- 6 mo III- 3-5 yr IV- 40 yr V- Forever
What do you do with leachate once it is collected? Recycle it, thicken it, treat it
Leachate characteristics High TDS, BOD, COD, nutrients, heavy metals
Aerobic leachate treatment 1 kg of O2 per kg COD Shallow ponds, sludge, biofilters, RBC
Anaerobic leachate treatment Deep lagoons, biofilters, bioreactors
The good and bad of biological treatment Aerobic- low/medium conc., sensitive to DO and metals Anaerobic - high conc., sensitive to acid and temperature
Physical leachate treatment Equalization, settling, reverse osmosis
Chemical leachate treatments Neutralization Flocculation Redox Steam stripping Carbon adsorption
Describe steam stripping Steam in at bottom, leachate in at top. Steam removes organics
Piezometers Nested piezometers measure landfill gas in the vadose/unsaturated zone
Lysimeters Detect leachate in the unsaturated vadose zone. Vacuum aids.
Where does groundwater monitoring occur Upstream and downstream
Created by: swilson67