Which of the following statements about sanitary landfilling is INCORRECT?
- AAnother name of sanitary landfilling is controlled tipping.
- BRefuse is dumped into a low-lying area.
- CIn the sanitary landfilling, filling of refuse is actually carried out by dividing the entire landfill area into smaller portions called cells.
- DWaste is stabilised by the aerobic process alone.Correct
Solution
Concept
In a sanitary landfill, waste breaks down first by aerobic action and then mainly by anaerobic action.
Step-by-step solution
1. Check A: Sanitary landfilling is also called controlled tipping. This is correct. 2. Check B: Refuse is usually dumped in low-lying areas or depressions and then covered with soil. This is correct. 3. Check C: The landfill area is divided into small units called cells. Each day's waste is compacted and covered. This is correct. 4. Check D: Oxygen is used up soon after covering, so most stabilisation is anaerobic, producing CH4 and CO2. Saying 'aerobic process alone' is wrong. 5. So the INCORRECT statement is D.
Explanation
In sanitary landfilling, waste is spread, compacted and covered with soil in cells. Aerobic decomposition happens only for a short time, until the trapped oxygen is used up. After that, anaerobic decomposition dominates and produces landfill gas (methane and CO2) and leachate.
Why the other options are wrong
A: Correct statement, since controlled tipping is another name for sanitary landfill. B: Correct statement, since low-lying areas are commonly used for filling. C: Correct statement, since filling is done in cells.
Shortcut
Landfill produces methane gas, so anaerobic action must be involved. 'Aerobic alone' is false.
Common mistake
Thinking the landfill stays aerobic because it is near the surface. Daily soil cover and compaction cut off the oxygen.
Correct answer: D) Waste is stabilised by the aerobic process alone.