To answer this question, let's examine each statement individually:

Statement 1: The penetration of suspended matter is deep in the slow sand filter.

In a slow sand filter, suspended matter is removed through a combination of physical, biological, and chemical processes. The filter bed consists of several layers, including a top layer of fine sand or gravel, a middle layer of coarser sand, and a bottom layer of larger gravel or stones.

As water passes through the slow sand filter, suspended matter such as particles, bacteria, and organic material are removed. The top layer of fine sand acts as a physical barrier, trapping larger particles and preventing them from penetrating deeper into the filter bed. Smaller particles, bacteria, and organic material may penetrate deeper into the filter bed, where they are subjected to biological processes such as predation by microorganisms.

Therefore, statement 1 is correct as the penetration of suspended matter is indeed deep in the slow sand filter.

Statement 2: The penetration of suspended matter is superficial in the rapid sand filter.

In a rapid sand filter, the filtration process is primarily based on physical processes, such as straining and adsorption. The filter bed consists of a single layer of sand or other granular media.

Unlike the slow sand filter, the rapid sand filter does not have multiple layers to trap and remove suspended matter. Instead, water flows through the single layer of sand, and suspended matter is trapped on the surface or within the top few millimeters of the filter media. This means that the penetration of suspended matter is indeed superficial in the rapid sand filter.

Therefore, statement 2 is correct as the penetration of suspended matter is indeed superficial in the rapid sand filter.

Statement 3: Coagulation is not required in the slow sand filter.

Coagulation is a chemical process used to destabilize and aggregate suspended matter in water, making it easier to remove through filtration. In the slow sand filter, the physical, biological, and chemical processes that occur naturally in the filter bed are usually sufficient to remove suspended matter without the need for additional coagulation.

Therefore, statement 3 is correct as coagulation is typically not required in the slow sand filter.

In conclusion, all three statements are correct. The penetration of suspended matter is deep in the slow sand filter, superficial in the rapid sand filter, and coagulation is not required in the slow sand filter.