SEWAGE
Sewage is a liquid waste and refers to a mixture of domestic, industrial, and sometimes stormwater runoff that contains water, human waste, soaps, detergents, and other debris. It is generated primarily from residential, commercial, and industrial activities and is typically carried away from homes and buildings through a system of pipes. The collection and treatment of sewage are crucial for public health and environmental protection.
Here are the key components of sewage:
Domestic Wastewater: This includes water used for washing, bathing, toilet flushing, and other household activities. It contains human waste, soap, detergents, and other household chemicals.
Industrial Wastewater: Some industries discharge wastewater containing various pollutants, depending on the nature of their operations. Industrial sewage can contain chemicals, heavy metals, and other contaminants.
Stormwater Runoff: During rainfall, water runs off surfaces such as roads, pavements, and roofs, picking up pollutants along the way. In some sewage systems, stormwater runoff may be combined with domestic and industrial wastewater.
Sewage is caused due to
Organic impurities –Human faeces, animal waste, oil, urea (urine), pesticides, herbicides, fruit and vegetable waste, etc.
Inorganic impurities – Nitrates, Phosphates, metals.
Nutrients – Phosphorus and Nitrogen.
Bacteria – Such as vibrio cholera which causes cholera and salmonella paratyphi which
causes typhoid.
Other microbes – Such as protozones which cause dysentery
SEWAGE COLLECTION AND TREATEMENT
The management of sewage involves a two-step process: collection and treatment.
Collection: Sewage is collected through a network of underground pipes that transport it from homes, businesses, and industries to a centralized treatment facility. These network of big and small pipes, called sewers, forming the sewerage. Manholes are a small covered opening in a paved area allowing access beneath, especially one leading to a sewer and are located at every 50 m to 60 m within the sewerage.
Treatment: At treatment plants, sewage undergoes a series of physical, chemical, and biological processes to remove contaminants and pathogens. Treatment aims to produce treated water, also known as effluent, that can be safely discharged into the environment or reused for non-potable purposes. The remaining solid residues, known as sludge, are also treated to reduce their environmental impact.
Proper sewage treatment is essential for protecting public health, preventing water pollution, and maintaining the health of ecosystems. Inadequate or untreated sewage can introduce harmful pathogens and pollutants into water bodies, leading to the spread of diseases and environmental degradation. As such, effective sewage management is a critical component of modern sanitation and environmental protection efforts.
TREATEMENT OF SEWAGE WATER
Wastewater Treatment Plant
It is a facility where physical, chemical and biological processes are used to treat the wastewater. The treatment of polluted water typically involves a series of processes to remove impurities and contaminants, resulting in cleaner and safer water for various uses. Here's an overview of the key stages in the treatment of polluted water, including "Before treatment," "After aeration," "Filteration," and "Chlorination":
Before treatment
In the wastewater treatment plant, firstly wastewater is passed through bar screens which removes large objects like rags, sticks, cans, plastics etc. Water then goes to a grit and sand removal tank. The process of removing grit and sand is known as screening.
After aeration:
The water is then allowed to settle in the large tank which is sloped towards the centre to separate sludge. (Sludge is the solid waste settled at the bottom of the sewage water). Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared
is called clarified water.
After this the sludge is transferred to an aeration tank where it is decomposed by the anaerobic bacteria and air is pumped to assist aerobic bacteria to grow. Bacteria consume unwanted matter still remaining in water.
Filteration
The activated sludge contains 97% water this water is removed by sand drying beds or machines.
Chlorination
It is necessary to disinfect water chemically with chlorine and ozone to kill unwanted bacteria and microbes.