Sludge management and disposal have been a challenge to waste engineers because they spend more money and time removing the waste than treating and disposing of it. This has led to poor disposal that has caused trouble in the properly designed and operated waste treatment plants.
When people dispose of sludge wrongly, its solid build up in the flow-through waste treatment units. As a result, the overall removal efficiencies start to decrease.
Therefore, proper disposal of sludge waste starts with appropriate handling and treatment. Sludge treatment is essential because its solids are potential environmental contaminants. Failure to do this shifts all the pollutants in the waste stream to disposal sites where they’ll end up contaminating the wider environment.
Waste engineers dispose of sludge using five broad methods:
- Filling on land
- Disposal in water
- Anaerobic digestion
The sludge is exposed to the atmosphere without creating odour nuisances. To dispose of the sludge this way, make sure to properly digest it without mixing it with raw or undigested sludge.
You can use either wet or partially dewatered sludge to fill low areas. For instance, sludge obtained from vacuum filters or drying beds is great for making lagoons in low areas.
If you want to prevent the creation of odour nuisances, it would be advisable to use a burial method when disposing of raw sludge. Run the sludge into trenches with a 2-3 ft width and a depth of 2 ft. Then cover the raw sludge with at least 12 inches of earth.
In areas where large pieces of land are available, burying raw sludge is the cheapest way of disposing of sludge as it eliminates the sludge treatment costs.
3. Disposal in water
While this is a cheap way of discarding sludge, it isn’t common because its suitability is based on the availability of water bodies. At seacoast cities, sludge is pumped in deep-sea waters, whether it’s raw or digested. The deep waters dilute the sludge and prevent its effects along the shore.
4. Anaerobic digestion
Sewage sludge contains essential elements like nitrogen, potassium, and phosphorus, beneficial for plant growth. The sludge humus also benefits the soil by boosting the water retention capacity and improving soil tilth. This makes it possible to make good seedbeds on heavy soils. Therefore, it’s advantageous to anaerobically digest sewage sludge to make plant fertilizers and soil conditioners instead of pumping it to the sea or burying it in the earth where it won’t have any benefits.
Municipal sludge can also be disposed of in landfills. Landfill operators put the waste in a deep trench and cover it with earth. However, most countries are increasingly adopting sludge composting due to the limited landfill spaces and the benefits of anaerobic digestion of sludge waste.
Sludge disposal has been a challenge, especially in the developing countries. However, developed countries are increasingly adopting safer ways of disposing of the waste. Filling, burying and landfilling are some of the safe ways of disposing of sludge in areas without large water bodies. In cities neighbouring oceans and seas, sludge removal companies dispose of the waste in deep waters.