Key Properties and Uses of Sewage in Daily Life
Prior to the late 1800s, the majority of the population practised open defecation and the outdoor toilet was the primary method of disposing of human waste. After Louis Pasteur and other researchers demonstrated that sewage-borne germs were to blame for a number of infectious diseases, sewage treatment plants were put in place in urban areas. Initial efforts to cure sewage water in the 1900s typically involved buying huge farms and dispersing the waste across the field, where it decomposed due to the action of microorganisms. It was quickly discovered that the earth had grown sick.
Subsequent efforts involved sewage disposal straight into aquatic areas, but this significantly worsened the quality of the water in those bodies. As cities grew, there was a restricted quantity of land accessible for sewage treatment and disposal, primarily through irrigation and sporadic filtration. Additionally, as populations increased, the quantity of sewage produced increased quickly, and the declining grade of this enormous volume of sewage outpaced the waterways' and rivers' degree of self-purification capacity. As a result, different forms of sewage treatment were created in relatively tiny treatment centres to speed up the natural forces beneath regulated circumstances.
What is Sewage?
Wastewater generated by a group of individuals is referred to as sewage. Generally, a sewer system is used to carry it. Sewage is wastewater that is released from homes as well as from nearby businesses, industrial, and public institutions. Numerous dangerous compounds are present in the wastewater that drains from highways and rooftops. Waste that is liquid is sewage. Impurities are both dispersed and decomposed in sewage. Contaminants are another name for these pollutants.
Sewage Treatment Plant
The initial sewage treatment plans were created in response to the unfavourable effects of sewage disposal on the ecosystem and the awareness of public hygiene. There are numerous hazardous organic compounds in sewage. In sewage treatment plants, microorganisms are frequently utilised to remove this hazardous organic waste. Two phases make up a sewage treatment plant like primary and biological treatment phases which are explained below in detail.
Primary Treatment
It entails the scientific techniques utilised to remove massive or tiny elements from sewage.
Biological Treatment
Aerobic bacteria are injected further into sewage treatment plants as part of the biological treatment process. These microorganisms utilise the organic sewage elements and lessen the toxins. BOD (Biological oxygen demand) can be utilised to gauge this.
The sewage is transported from the treatment centre into a big tank after the biological treatment. Anaerobic bacteria in this sizable tank aid in the decompasition of waste. Biogas is created via decomposition and is utilised as a power source. Therefore, sewage regulation and the framework of the sewage treatment plant diagram are vital for preserving human wellbeing.
Domestic Sewage Treatment
Both large companies and small-scale residential buildings can use a sewage water treatment system. A domestic sewage water treatment plant is a facility located at residential housing that serves a smaller population. These plants are put in place in locations or on-premise where there is already a water shortage to avoid one. Domestic sewage primarily consists of waste products including paper, food, bathroom and kitchen sink effluent, human waste, and similar items. Prior to releasing the wastewater into the atmosphere, it is required to eliminate all of these wastes. Since the cleansed water is fit for reuse, it won't be wasted.
This will support the creation of a stable and environmentally favourable habitat and contribute to water conservation for a better future. Regardless of whether they are solid or extremely small, sewage water treatment plants can eliminate all significant contaminants from water. The household plant uses a technique to obtain high-quality purified water for this purpose.
Health Effects of Sewage
Wastewater and sewage both comprise bacteria, fungi, worms, and viruses which can attack the lungs, the digestive system, and other organs. Bacteria can result in vomiting, headaches, weakness, cramps, diarrhoea, fever, and occasionally even loss of appetite.
Waste is a favourable environment for fungi to develop. These can worsen asthma or trigger lung infections, as well as cause allergic reactions (like a runny nose). Viral infection damages the liver. The signs and symptoms include fatigue, stomach pain, nausea, jaundice (yellow skin), diarrhoea, and a lack of appetite.
Interesting Facts
The best environment for the growth of algae is sewage. It offers each and every nutrient required for algae development.
The Aquaflow Bionomic Corp. of New Zealand is now the 1st company in the world to create biofuel utilising algae that grows in sewage ponds.
One major plus of the human-sewage technique is that a sewage-derived alga seems to contain a significant amount of oil.
For organic decomposition to take place, aerobic bacteria required a lot of dissolved oxygen.
Key Features to Remember
Sewage is effectively the society's sewer system when it has been contaminated by a wide range of activities.
Sewage is the general term used to describe the wastewater released from domestic facilities such as homes, institutions, and commercial entities.
It is organic since it contains carbon compounds like human waste, paper, vegetable matter, etc. It is composed of 99.9% water and 0.1% solids.
To lessen the toxicity of sewage, preserve a clean and secure environment, and advance human well-being, sewage treatment is essential.
FAQs on What is Sewage in Chemistry?
1. What is sewage from a chemical perspective?
From a chemical perspective, sewage is a complex aqueous mixture, comprising over 99% water that acts as a solvent for various substances. Its chemical identity is defined by its components, which include organic matter (like proteins, carbohydrates, and fats), inorganic matter (grit, salts, and metals), essential nutrients such as nitrogen and phosphorus compounds (e.g., ammonia, nitrates, phosphates), and a large population of diverse microorganisms.
2. What are the main chemical components found in typical domestic sewage?
The main chemical components of typical domestic sewage include:
Organic Compounds: Primarily from human waste, food scraps, soaps, and detergents, contributing to high levels of carbon, nitrogen, and phosphorus. Urea is a significant component.
Inorganic Salts: These include chlorides, sulphates, phosphates, and bicarbonates, originating from cleaning products and human excreta.
Gases: Dissolved gases like hydrogen sulfide (H₂S), methane (CH₄), and ammonia (NH₃) are commonly produced during anaerobic decomposition, causing foul odours.
Trace Metals: Small but potentially harmful quantities of metals such as zinc, copper, lead, and nickel can be present.
3. What are the different types of sewage?
Sewage is generally classified based on its origin:
Domestic Sewage: This is wastewater from residential sources like kitchens, bathrooms, and laundry. It is characterized by high organic content and pathogens.
Industrial Sewage: Wastewater from commercial and manufacturing processes. Its chemical makeup is highly variable and can contain specific toxins like heavy metals, acids, or synthetic organic compounds.
Storm Sewage: This refers to surface runoff from rain or snowmelt, which collects pollutants like oils, pesticides, and debris from roads and other surfaces.
4. What is the importance of treating sewage before its disposal?
Treating sewage is crucial for protecting both public health and the environment. Untreated sewage carries dangerous pathogens (bacteria, viruses, and protozoa) that can contaminate water sources and cause severe waterborne diseases like cholera, dysentery, and typhoid. Additionally, the high concentration of organic matter and nutrients like nitrogen and phosphorus leads to eutrophication in water bodies, a process that depletes dissolved oxygen and results in the death of fish and other aquatic life.
5. What is sewage treatment and what are its main stages?
Sewage treatment is a multi-step process to purify wastewater before it is safely returned to the environment. The primary stages are:
Primary Treatment: This is a physical stage where large objects are screened out, and grit and solid organic matter are allowed to settle in sedimentation tanks.
Secondary Treatment: A biological stage where aerobic microorganisms are used to consume the dissolved organic pollutants, drastically reducing the pollution level.
Tertiary Treatment: An advanced stage involving chemical and physical processes to remove residual nutrients and disinfect the water, often using agents like chlorine or UV radiation.
6. How is BOD (Biochemical Oxygen Demand) used to measure the pollution level of sewage?
BOD, or Biochemical Oxygen Demand, is a critical parameter in environmental chemistry to quantify water pollution. It measures the amount of dissolved oxygen that aerobic bacteria require to decompose the organic matter in a sample of water. A high BOD value directly corresponds to a high concentration of organic pollutants, indicating that the sewage is highly polluted and will heavily deplete oxygen levels if discharged untreated into a river or lake.
7. What is the chemical difference between sewage and sludge?
The main chemical difference is in their physical state and concentration of pollutants. Sewage refers to the liquid wastewater entering a treatment plant, which is over 99% water with dissolved and suspended solids. In contrast, sludge is the semi-solid residual material that is separated from sewage during treatment. Sludge is a highly concentrated mixture of the organic solids, microorganisms, and inorganic compounds that have been removed from the water.
8. Why are microorganisms essential for secondary sewage treatment and not just chemical filters?
While physical or chemical filters can remove suspended particles, they are largely ineffective against dissolved organic matter, which is a major source of pollution (BOD). Microorganisms, particularly aerobic bacteria, are essential because they perform a biological function: they metabolise and consume these dissolved organic compounds. They convert harmful pollutants into harmless substances like carbon dioxide, water, and more microbial cells, which can then be settled out as sludge. This biological process is the most efficient method for removing the bulk of dissolved organic waste.
9. What are some advanced, or tertiary, chemical treatments applied to sewage effluent?
Tertiary treatment employs advanced chemical methods to polish the effluent after secondary treatment. Key examples include:
Nutrient Removal: Using chemical precipitation with salts like alum or ferric chloride to remove excess phosphorus, which helps prevent eutrophication.
Disinfection: Applying strong oxidising agents like chlorine, ozone (O₃), or non-chemical methods like ultraviolet (UV) light to eliminate any remaining pathogenic microbes.
Activated Carbon Adsorption: Filtering the water through activated carbon to adsorb and remove trace organic chemicals, unwanted colours, and odours.
10. Can the gases produced during sewage treatment, like methane, have a practical application?
Yes, absolutely. The anaerobic digestion of sludge, a key part of the treatment process, produces biogas. This gas is a valuable resource, as it is composed mainly of methane (CH₄), a combustible fuel. Modern sewage treatment facilities often capture this biogas and use it in generators to produce electricity or heat for the plant's own operations. This practice, known as cogeneration, makes the treatment process more energy-efficient and sustainable.
