## Core Concept
Tertiary wastewater treatment processes are advanced methods used to further purify wastewater after primary and secondary treatments. These processes are designed to remove specific contaminants, improve water quality, and make the water safer for discharge or reuse. Tertiary treatments can include physical, chemical, or biological processes.

## Why the Correct Answer is Right
The correct answer, **C. Ozonization**, is a type of tertiary wastewater treatment process. Ozonization involves the use of ozone (O3) as a disinfectant and oxidizing agent to remove organic matter, color, and odors from wastewater. Ozone reacts with pollutants, breaking them down into simpler, less harmful substances. This process can achieve high levels of purification and is often used for water reclamation and reuse.

## Why Each Wrong Option is Incorrect
- **Option A:** is incorrect because it does not specify a known tertiary treatment process directly related to wastewater treatment.
- **Option B:** is incorrect because, although filtration can be part of tertiary treatment, the term is too general and does not specifically denote a tertiary process like ozonization does.
- **Option D:** is incorrect because, while chemical coagulation can be used in tertiary treatment to remove suspended solids and some dissolved substances, it is not as specifically indicative of a tertiary process as ozonization.

## Clinical Pearl / High-Yield Fact
A key point to remember is that tertiary wastewater treatment processes like ozonization are critical for ensuring water quality meets safety standards for discharge into sensitive ecosystems or for reuse in applications like irrigation or drinking water. These processes can remove a wide range of contaminants, including bacteria, viruses, and chemical pollutants.

## Correct Answer Line
**Correct Answer: C. Ozonization.**