Wastewater Management

Improper Management Of Sewage

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Improper Management Of Sewage

One of the most common sources of water pollution is the discharge of untreated or partly treated sewage into water bodies; sometimes due to improper sewage handling processes of municipal bodies. This is very common in major cities. Many of our major rivers such as Ganges and Yamuna receive tones of untreated sewage daily, thereby making the water unfit for drinking and other domestic uses. These rivers are regarded as open sewers as large quantities of waste are dumped in them every day. This contamination is responsible for major water-borne epidemics such as jaundice, cholera, and hepatitis.

Another problem which can occur is leakages in several places in the main water supply line, where the water gets mixed with sewage. Due to faulty sewer lines, the dirt often flows into the open, enters the water pipelines, and contaminates the water supply. People consuming contaminated water may suffer from diseases like gastroenteritis, dysentery, and typhoid.

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Improper Management of Sewage

Sanitation in Public Places
Proper sanitation should be maintained at public places such as bus depots, railway stations, airports, malls, fairs, etc. As a large number of people gather at these places, the waste generated is subsequently large, too. This must be disposed off properly. Public conveniences and dustbins have been built by the government that help in maintaining sanitation in public places.

As a responsible citizen, we should maintain cleanliness even outside our homes. Plastic bags, metal cans, and other wastes should be thrown in the bins meant for them. This becomes necessary because these wastes can, otherwise, find their way to the underground drainage system and clog them up. This would result in blockage of sewage pipes and the sewage would flow back onto the streets and colonies. During the monsoon season, it will lead to flooding of streets and traffic jams.

How Can You Control Sewage Generation

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Controlling Sewage Generation

A few measures that can be adopted to control the generation of sewage are given below.

  • Use flushes with low capacity.
  • Never pour household products such as cleansers, beauty products, medicine, automobile oil, and paint down the drain. These contain chemicals which the wastewater treatment plants may not be able to remove. These should be properly disposed.
  • Excess cooking oil, butter, meat fats, and plastic should be disposed off in the garbage can. These materials can clog pipes, and could cause sewage to overflow in your home or in public areas.
  • Fix leakages in sewer pipes. These leaks can contaminate drinking water, and seep into the water table. It can also stagnate in certain areas on the ground and become the breeding place of disease-causing insects like flies, cockroaches, and mosquitoes

Alternative Methods Of Sewage Disposal

Some alternative methods of sewage disposal are septic tanks, biogas plants, and vermi- composting tanks.

Septic Tanks
In semi urban areas, low-cost septic tanks, also known as onsite disposal system, are encouraged to manage the waste. In this method, household wastewater is allowed to flow into an underground septic tank. Inside the tank, the sludge settles down at the bottom and the lighter waste float on the surface.
Bacteria present in the sewage help in partially decomposing the solid waste.
The liquid waste is then allowed to flow out of the tank through pipes and into the ground where it mixes with the soil below.
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Biogas Plants
Another method of waste disposal, which is prevalent especially in village and small towns in India, is setting up of biogas plants. In this method, human and animal excreta flow through covered drains into biogas plants. Microorganisms break down the materials present in the waste and produce biogas. This biogas is then used to produce electricity.

Vermi-composting Toilets
Recently vermi-composting toilets have been developed in India as an alternative method for proper disposal of waste. It is based on an innovative design in which earthworms are used to convert human excreta into compost. There is minimal use of water, and it is a safe and hygienic way of processing human waste.

What Are The Methods Of Sludge Disposal

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Methods Of Sludge Disposal

What happens to the sludge that is produced after the wastewater passes through the sewage treatment plant? Sludge consists of human faeces and other organic matter. It also has large amounts of water and needs to be thickened so that it can be transported easily and used as compost in farmlands. There are three methods to do so.
Sludge may be incinerated, i.e., burnt into ashes.The ash is used as soil conditioner or as a construction material.

What Are The Methods Of Sludge Disposal 1
Incinerating

Sludge may be dewatered and then combined with other wastes to make fertilizers.

What Are The Methods Of Sludge Disposal 2
Dewatering

Sludge may be composted or processed to produce gases that can be used as fuel.

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Solid composting

How Does A Wastewater Treatment Plant Work

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Wastewater Treatment Plant

A facility that treats wastewater from domestic as well as industrial sources is called a wastewater treatment plant. There are basically three stages involved in treating wastewater: primary, secondary, and tertiary.

Primary Treatment
This is a mechanical process which involves screening and settling of large particles. First, the sewage is passed through screens of vertical bars to remove larger impurities such as metal cans, plastic bags, cloth pieces, etc. The wastewater is then passed through a grit and sand removal tank called the grit chamber.
The speed of the incoming wastewater is reduced so that sand, grit, pebbles, etc., settle down. The water is then passed through huge sedimentation tanks. Here solid wastes such as faeces is allowed to settle down and the light floatable waste such as soaps, oils, plastics, and grease rise. Solid waste that settles at the bottom in the primary treatment of wastewater is called the sludge. Light waste that rises to the top and floats, during wastewater treatment, is called the scum. The water that comes out of the sedimentation tanks is called clarified water.

How Does A Wastewater Treatment Plant Work 1
Vertical bars
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Grit chamber

Secondary Treatment
This is a biological process in which the organic matter in the sludge is broken down with the help of bacteria. This process is called digestion and as a result of it, biogas is produced. The biogas can be used either as a fuel or to produce electricity. The treatment at this stage can be speeded up by allowing water to flow into large aeration tanks, where air is blown onto the sewage.

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Aeration tank

Tertiary Treatment
This is basically a chemical process in which chemicals are used to remove phosphorus and nitrogen from the water. Addition of chlorine and exposure to ultraviolet light kills any remaining bacteria and disinfects the water. The water is then discharged into water bodies.

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Schematic diagram of wastewater treatment plant

Where Does All The Wastewater Come From

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Sources Of Wastewater

Water that has been used and has become dirty is called wastewater. It is generated as a result of numerous human activities.

  • Agriculture: Wastewater generated from farms contains harmful pesticides, biocides, animal waste, etc.
  • Construction of buildings: Large amount of wastewater is generated from construction of buildings.
  • Industries: Wastewater generated from paint and dye industries contains harmful chemicals such as lead, chromium, etc. The discharge of liquid wastes into a river or the sea is called effluent.
  • Hospitals, hotels, offices: Wastewater from hospitals contains disease-causing germs.
  • Domestic activities: The wastewater generated from our houses contains detergents, food wastes, human faeces, plastics, paper, metal objects, etc.
  • Mining: Wastewater is also generated as a result of mining operations.
    Where Does All The Wastewater Come From 1

All the wastewater that is released from various sources contains suspended impurities. This wastewater, containing suspended impurities, is called sewage. These impurities are called contaminants.

Where Does Domestic Wastewater Go?
Each time we wash something or flush our toilets, water containing paper, cloth, soap, detergent, oil, grease, food scrap, faeces, etc., goes down the drain. This water accumulates and forms sewage. In large cities, this is known as municipal wastewater.

The Sewer System
A channel system of pipelines used to carry sewage is called the sewer system. The sewage leaves houses through drain pipes and flows to the sewer mains of the city. The sewer mains flow into progressively larger pipes until they reach the wastewater treatment plant.
Waste flows easily through sewers due to a slight slope given to the drainage system. Most sewer pipes are underground. So, what does one do if there is a leak or blockage in any of these pipes? For this purpose, there are manholes (a hole, usually with a cover) through which a person may enter a sewer or drain to fix the faulty pipes.