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waste Management q3
Modules 8 and 9
| Question | Answer |
|---|---|
| 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
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