The proportion of solids in sewage is about
0.1% or less
Understanding the Composition of Sewage
Sewage, also known as wastewater, is the liquid waste discharged from homes, businesses, and industries. It is primarily composed of water with a small amount of dissolved and suspended solids.
When we talk about the composition of sewage, it's important to understand that water makes up the vast majority of its content. The other components, which include organic matter, inorganic materials, nutrients, and microorganisms, constitute a very small fraction.
Proportion of Solids in Sewage
The term "solids" in sewage refers to all matter other than pure water. These solids can be either dissolved in the water or suspended as small particles. The concentration of these solids is typically measured in milligrams per liter (mg/L) or as a percentage of the total weight.
Typical municipal sewage is about 99.9% water. This means that the remaining 0.1% constitutes the solids. The concentration of total solids in typical domestic sewage is generally in the range of 500 to 1200 mg/L, which is equivalent to about 0.05% to 0.12% by weight.
Therefore, the proportion of solids in sewage is very low.
Analyzing the Given Options
Let's examine the options provided based on our understanding of typical sewage composition:
- 2.5% or more: This percentage is significantly higher than the typical solid content in sewage.
- 1% or more: This is also much higher than the usual proportion of solids found in municipal sewage.
- 0.1% or less: This range aligns well with the typical concentration of solids in sewage, which is around 0.1% (or 1000 mg/L) or even less in weaker sewage.
- zero: Sewage contains waste materials and dissolved substances, so the solid content is never zero.
Conclusion on Sewage Solid Proportion
Based on standard wastewater characteristics, the proportion of solids in sewage is very low, typically around 0.1% or less. The majority of sewage is water.
| Component | Approximate Proportion |
|---|---|
| Water | ~99.9% |
| Solids (Dissolved & Suspended) | ~0.1% |
Revision Table: Key Sewage Composition Facts
| Characteristic | Typical Value/Range | Notes |
|---|---|---|
| Water Content | ~99.9% | Primary component |
| Total Solids | 0.05% - 0.12% | Includes suspended and dissolved solids |
| Equiv. Solids (mg/L) | 500 - 1200 mg/L | Equivalent concentration |
Additional Information: Types of Solids in Sewage
Solids in sewage can be categorized in several ways:
- Total Solids (TS): All solid matter remaining after evaporation of water.
- Total Suspended Solids (TSS): Solids that are retained by a filter. These are the non-dissolved particles.
- Total Dissolved Solids (TDS): Solids that pass through a filter. These are the substances dissolved in water.
- Volatile Solids: The portion of solids that can be volatilized (burned off) at high temperatures, primarily organic matter.
- Fixed Solids: The portion of solids remaining after volatilization, primarily inorganic matter.
The measurement of these different types of solids is crucial for designing and operating wastewater treatment plants.
Important Questions from Quality and Characteristics of Sewage
Identify the correct relation from the following:
Where BOD, COD, and TOD are Biochemical, Chemical, and Theoretical oxygen demand, respectively.
What is the correct range of \(\frac{{BO{D_u}}}{{COD}}\) for a waste water to be considered as fully biodegradable?
(where BODu = ultimate Bio-chemical oxygen demand and COD = chemical oxygen demand)
Determine ultimate BOD for sewage having 5-day BOD at 20°C as 180 ppm. Assume the de-oxygenation constant as 0.8 per day.
What does Chemical Oxygen Demand (COD) indicate?
The rate of BOD exerted at any time is:
