People use water everyday, your liquid waste would go to WasteWater Treatment Plant through underground pipeline. The liquid waste is going to primary treatment plant where wood, stone, sands and other solids are removed, after that, waste goes to secondary treatment where the most of organic, bacteria and solid sludge are filtered. After all the procedures, the water would be discharged to river. What is the cost every time you flush? I looked at my toilet, it costs 6 litres of water per flush, from the utility billing of Vancouver, one unit water is $2.385 (one unit is 2,831.6 litres), one unit of sewer water is $1.906, thus, through calculation we can get that one flush cost about $0.01. That is so cheap that could be negligible for every one. However, what I calculated is the basic cost that would appear on your billing, there could be more social cost and negative externalities that is unpredictable if people flush food, cooking grease, medication and oil. Cost of flushing these waste:
- Less oxygen in ocean because food need oxygen to decompose which is harmful to the fishes and our fishery industry.
- Blockage happens in the pipeline because cooking oil become solid and this may lead sewer overflow.
- The medication is hard to clean out so your drinking water could contain limited level of pharmaceutical.
- One drop of motor oil can pollute 50 litres of water, and cost more to consume the organic from the wastewater.
On the other hand, if people recycle the waste in proper ways, there is no such cost to us and there could be more benefit. For example, cooking grease can be recycled and converted into biofuel which is in application currently. If food go to landfill and composted properly, it would produce “compost (like soil) and biofuel” that can run vehicles.
Bottom Line: When you know how our wastewater treatment plants work and the cost of flushing food and chemicals, we should not flush everything. Recycle the waste as much as you can.
* These guest posts are from students in my resource economics class at Simon Fraser University. Please leave feedback on their logic, ideas and style and suggestions of how to improve.