engineering recuitment TNPSC AE Civil 2024 Test series Environmental Engineering Water Treatment Filtration
Consider the following types of filters
1. Contact beds
2. Intermittent sand filter
3. Rapid sand filter
4. Trickling filter
Which of the following filters are used for secondary treatment of sewage?1
1 and 4 only
2
2 and 4 only
3
1, 2 and 4
4
1, 2, 3 and 4