**Core Concept**
Slow sand filters are a type of water filtration system that uses a combination of physical, biological, and chemical processes to remove contaminants and improve water quality. The filtration process involves the passage of water through a layer of sand, which is supported by a layer of gravel and a layer of sand or other materials.

**Why the Correct Answer is Right**
The correct answer is related to the unique feature of slow sand filters, which is the development of a biological layer on the surface of the sand called the "schmutzdecke." This layer is composed of microorganisms, such as bacteria and protozoa, that break down organic matter and other contaminants in the water. The schmutzdecke acts as a natural barrier, trapping particulate matter and improving the overall efficiency of the filtration process. The slow flow rate of the water through the filter also allows for the removal of smaller particles and contaminants, resulting in high-quality water.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because slow sand filters do not rely on chemical disinfection to remove contaminants.
**Option B:** Incorrect because slow sand filters do not use a single layer of activated carbon to remove impurities.
**Option C:** Incorrect because slow sand filters do not require a high flow rate to be effective.

**Clinical Pearl / High-Yield Fact**
One key aspect of slow sand filters is that they can remove up to 99.9% of bacteria and viruses from contaminated water, making them an effective method for providing safe drinking water in areas with limited resources.

**Correct Answer: C. Slow sand filters do not require a high flow rate to be effective.