Tag: personal and public cleanliness

A.Primary treatment – Removal of large and small particles from sewage through sequential filtration and sedimentation is called primary treatment.

B.Secondary treatment – It involves biological process of microbial degradation of organic matter contained in sewage effluent. In this activated sludge acts an inoculum.

C.Tertiary treatment – There is no occurrence of tertiary sewage treatment.

So, the correct option is ‘Secondary treatment’.    

Sewage is wastewater that contains various contaminants, including human waste or faeces. While it may contain paper or nutrients, faeces is the primary defining component of domestic sewage.

Filtration is a key physical process in wastewater treatment used to remove suspended solids and impurities. While other processes like sedimentation or chlorination are also used, filtration is a fundamental step in cleaning water.

Temperature is a critical parameter in sewage treatment because it significantly affects the rate of biological decomposition and the solubility of oxygen. While chemicals and decomposition are important, temperature regulates these biological and chemical processes.

Domestic sewage is composed primarily of water, typically accounting for about 99.9 percent of the total volume. The remaining small fraction consists of dissolved and suspended solids, organic matter, and other contaminants.

In the context of wastewater treatment, constructed wetlands or specific plant-based treatment systems are considered artificial ecosystems. They are engineered by humans to perform specific ecological functions like purification.

Primary treatment is a physical process that involves sedimentation to remove suspended solids. Standard engineering references typically cite that primary treatment removes approximately 40 to 60 percent of suspended solids.

Biomagnification refers to increase in concentration of the toxicant at successive trophic levels. This happens because a toxic substance accumulated by an organism cannot be metabolised or excreted, and is thus passed on to the next higher trophic level. This phenomenon is well known for mercury and DDT. 

Chlorination is a common final treatment process used to disinfect wastewater by killing pathogens and bacteria before the water is discharged or reused. While BOD and sedimentation are part of the treatment, they occur in earlier stages.

Wastewater contains a diverse microbial community, including bacteria, fungi, algae, and protozoa like rotifers. Rotifers are microscopic multicellular organisms commonly found in wastewater treatment systems.