Question

During wastewater treatment, a trickling filter is used for
(a)Primary treatment
(b)Secondary aerobic treatment
(c)Secondary anaerobic treatment
(d)Tertiary treatment

Answer 1

Hint: Trickling filter is a sewage treatment system that utilizes micro-organisms attached to a medium to remove organic matter from waste-water. Trickling filters are used in wastewater treatment in which the organic contaminants are converted to carbon dioxide, water, and additional microorganisms in presence of oxygen.

Complete answer:
Trickling filters are used to remove organic matter from waste-water. Trickling filters use aerobic processes for treatment while anaerobic filters operate under strictly anaerobic conditions. TFs enable organic material in the wastewater to be absorbed by a population of microorganisms attached to the medium as a slime layer. As the wastewater flows over the medium the microorganisms present in the water gradually attach themselves to a rock, slag, or plastic surface and form a film. The organic material is degraded by the aerobic microorganisms. As the layer thickens due to microbial growth, oxygen cannot penetrate the face and anaerobic microorganisms develop. TFs are simple, reliable, biological processes. It is suitable for where large tracts of land are not available for the land-intensive treatment system.

Additional Information: -TFs are effective in treating high concentrations of organic depending on the type of medium used. Appropriate for small to medium-sized communities.
-They rapidly reduce soluble BODs in applied wastewater. They are efficient nitrification units. They have durable process elements and they require low power.
-Moderate level of skill and technical expertise needed to manage and operate the system.
So, the correct answer is ‘Secondary aerobic treatment’.

Note: - Possibly of excess biomass that cannot retain an aerobic condition and can impair TF performance.
-This type of system is common to a number of technologies such as rotating biological contactors and packed bed reactors.
-Wastewater treatment generally involves three stages of treatment; primary, secondary, and tertiary.