The sewage of the last problem is 6600 m³ in a day…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The sewage of the last problem is m³ in a day. Each litre holds mg of solids. In the primary settling tank, of the solids settle.
- What mass of solids is in the sewage each day?
- What mass of primary sludge forms each day?
- What is the concentration of solids that is left in the effluent, in mg per litre?
Need a reminder? The key ideaShow
Sewage is the waste water of a town. Primary treatment is physical: filtration removes floating debris, sedimentation removes grit, and the settled solids are the primary sludge. The liquid above is the effluent. One m³ is L, and mg per litre is g per m³. The mass of a solid in a flow is the flow times its concentration.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Flow: m³ in a day. Solids: mg per litre, which is g per m³. Settling: .
Plan. Find the mass of solids, take the share that settles, and keep the rest.
Step 1. Solids. g, which is kg each day.
Step 2. Sludge. kg each day.
Step 3. The effluent. of the solids stay in the liquid, so the concentration is mg per litre.
Answer: kg; kg; mg per litre.
Check. kg. The kg left in m³ of effluent is g in each m³.
Watch out. The sludge is a wet mass. The masses here are those of the dry solids.
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