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civil engineering

Water Pollution – Effects and Causes

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Water pollution has become a pressing problem all over the globe. In the previous blog, we had a look at the major water pollutants. In this blog, let me walk you through the effects and causes of water pollution.

Water pollution is a critical issue impacting ecosystems and human health worldwide. It refers to the contamination of water bodies such as rivers, lakes, and oceans, resulting from harmful substances. The causes of water pollution are diverse, including industrial discharge, agricultural runoff, and improper waste disposal. These water pollution causes contribute to a range of environmental and health problems. The effects of water pollution are profound. It leads to the degradation of aquatic habitats. It causes disruption of food chains. It also increases health risks for humans. Addressing water pollution requires understanding both the causes and effects to implement effective solutions. Tackling these issues is essential for safeguarding our water resources and ensuring a healthy environment for future generations.

All water bodies have an innate ability to cleanse themselves. They can easily handle small volumes of pollutants. They degrade these pollutants with the help of dissolved oxygen and the microbial population residing there. However, every day, 2 million tons of sewage, industrial, and agricultural waste reaches water bodies all over the world.

Together these wastes exert a huge Biochemical Oxygen Demand. The dissolved oxygen in water becomes insufficient to meet the BOD requirements. In such a situation, when oxygen demand exceeds oxygen availability the water body becomes polluted. Let us dive deep into the details of the effects and causes of water pollution.

  1. Causes of water pollution
  2. Effects of Water pollution
    1. Eutrophication
    2. Disruption of the food chain
    3. Loss of Species
  3. Economic Effects of Water Pollution
  4. Loss of Aesthetic Value
  5. Biomagnification
  6. Water Pollution Effects on Human Health
    1. Bacterial diseases
    2. Viral Diseases
    3. Parasitic Diseases
    4. Key Takeaways
  7. Conclusion

Causes of water pollution

Water being the Universal Solvent dissolves a wide range of substances easily. Therefore any unwanted substance that reaches a water body easily mixes with the water and pollutes it. The causes of water pollution can be natural and anthropogenic. The natural causes of water pollution include oil spills from sedimentary rocks in the seabed, storms, natural eutrophication etc. However, these contribute only to a very small percentage of the pollution load.

The causes of water pollution are varied and impact water bodies in numerous ways. Industrial discharge, agricultural runoff, and improper waste disposal are significant water pollution causes. These activities introduce harmful substances like chemicals, heavy metals, and nutrients into water sources. The effects of water pollution include the contamination of drinking water, harm to aquatic life, and disruption of ecosystems. Understanding the primary causes of water pollution is crucial for developing strategies to mitigate its effects. Addressing these water pollution causes is essential for improving water quality and protecting environmental and public health.

The major cause of water pollution is the release of sewage and industrial effluents into water bodies without treating them. These effluents introduce a variety of water pollutants. These include inorganic chemicals, plant nutrients, detergents, oil, and pathogens to the water bodies. Please visit our blog, What are Water Pollutants for complete information about all the water pollutants.

Now, let’s look at the effects of water pollution.

Effects of Water pollution

Water pollution affects humans and the organisms thriving in and around the water body. This includes the benthic, aquatic and semi-aquatic organisms and also their predators.

The effects of water pollution are far-reaching and severe, impacting both the environment and human health. Water pollution can lead to the contamination of drinking water supplies. This poses significant health risks such as gastrointestinal diseases. It can also cause long-term conditions like cancer. Additionally, the effects of water pollution include the destruction of aquatic habitats, which disrupts food chains and endangers wildlife. The primary causes of water pollution are industrial discharge and agricultural runoff. They contribute to these detrimental effects by introducing harmful substances into water bodies. Addressing water pollution causes is crucial for mitigating its effects and ensuring clean, safe water for all. Effective management and reduction of these causes are key to improving water quality and overall environmental health.

Let’s look at the effects of water pollution on the environment in the first section.

  • Eutrophication
  • Disruption of the food chain
  • Loss of Species
  • Economic effects of water pollution
  • Loss of Aesthetic Value
  • Bio-magnification
  • Water pollution effects on human health

Eutrophication


Eutrophication is the excessive enrichment of water bodies with nutrients, leading to harmful algal blooms and oxygen depletion.

  • The enrichment of a water body by plant nutrients like phosphorous and nitrogen is eutrophication.
  • The surface runoff from agricultural lands and untreated industrial effluents transport large volumes of these plant nutrients. They end up in rivers and lakes.
  • This accelerates the growth of algae.
  • The algal bloom eventually dies and settles to the lake’s bottom.
  • Bacterial populations begin to break down the remnants, consuming oxygen in the process.
  • Further, the lake turns into a dead zone supporting no life.

For more details : Eutrophication – Definition, Causes, effects and Control

Disruption of the food chain

One of the unseen effects of water pollution is the disruption of food chain. Organisms in a particular trophic level accumulate toxins due to water pollutants. Their predators in the next trophic level get poisoned. The predators may die. The number of predators comes down drastically. This in turn has consequences on organisms in both the succeeding and preceding trophic levels.

Let me make it clear with an example. During eutrophication, the aquatic plants die off since they can’t do photosynthesis. As a result, small fishes which feed on these plants experience a food shortage. Slowly, their population also starts to decline.

The same process repeats in higher trophic levels too. The consequences are so far-reaching that it affects not only aquatic organisms but also piscivorous birds. Thus the accumulation of pollutants in a water body can disrupt the entire food chain in and around it.

Also read : Secondary Treatment for Wastewater – Methods and Process

Loss of Species

The 2010 spill on the Gulf of Mexico harmed over 82,000 birds. This information is from the Centre for Biological Diversity on the effects of the Deep Horizon spill. It also harmed 25,900 marine animals, 6165 sea turtles, and an unknown number of fish and invertebrates.

Along with eutrophication, oil spills are a major cause of the massive death of organisms. Vast expanses of oil spills trap the seabirds and prevent them from flying away. Thus, they die either due to drowning or by their predators like sharks. Even if the birds manage to escape from the oil spill, oil destroys the water repellence of its feathers.

Birds and mammals die from hypothermia when they lose the ability to repel water and insulate from the cold water. Also, marine organisms and birds may die due to oil poisoning as they tend to ingest oil while cleaning themselves.

Water Pollution – Death of Marine Species

Economic Effects of Water Pollution

It is costly to manage and restore polluted water bodies. For example, following the Fukushima tragedy, Japan announced in 2019 that it is running out of space. There is not enough space to retain the polluted water. Over a million tonnes of contaminated water are currently kept in tanks. According to estimates, cleaning up the disaster’s aftermath will cost at least $660 billion.

Purifying drinking water costs more under normal circumstances. This does not include the health costs of treating diseases caused by contaminated water. Eutrophication in US freshwater costs approximately $2.2 billion per year.

Loss of Aesthetic Value

Winds and currents carry the oil spills into the shore. Oil forms a thick layer over the beaches and rocks. Thus it reduces the aesthetic value of beaches and is a big threat to tourism and recreation on beaches. Moreover, polluted water bodies develop foul odours. They also develop unpleasant colors. Both of these factors destroy their aesthetic beauty and reduce human interaction.

Water Pollution – Oil Spills

Also read : Wastewater Treatment- Stages and Process full details

Biomagnification

  • Biomagnification refers to the progressive increase in the concentration of toxins from organisms of one trophic level to the next.
  • As a result, organisms in the higher trophic level which may not have direct exposure to water pollutants are also harmed.
  • For instance, predatory birds like vultures and eagles accumulate dieldrin, DDT in their bodies by consuming fish poisoned with pesticides.
  • When these pesticides reach their body, the concentrations are high enough to impact them severely. Dieldrin affects the calcium metabolism in predatory birds and leads to thinning of their eggshells.

The worst-hit are always the ones in the highest trophic level, which in most cases are human beings. Diseases like itai-itai and Minamata disease remain painful reminders of the effects of biomagnification and water pollution. In the next section, let’s have a closer look at the effects of water pollution on human health.

Water Pollution Effects on Human Health

Water acts as a carrier of many harmful pathogens which causes water-borne diseases in human beings. Since contaminated water is the primary mode of transmission for these diseases, they are known as water-borne diseases.

The majority of intestinal (enteric) disorders are contagious and spread by faeces. Pathogens are disease-causing agents found in the faeces of infected people. They include viruses, bacteria, protozoa, and parasitic worms. These infections spread through water sources and directly infect people who handle food and water. Let me show you a few of those diseases:

Bacterial diseases

Vibrio Cholerae is responsible for diarrhoea, the most common water-borne disease. This bacterium releases toxins in the digestive tract and leads to watery bowel movements, dehydration and renal failure. According to WHO, diarrhoea kills around 525000 children below 5 years, every year.

Shigella bacteria cause Shigellosis that affects the digestive tract of humans and damages the intestinal lining. Salmonella bacteria are found in contaminated water. It causes fatal salmonellosis that results in inflammation of the intestine and death.

Bacterial diseases
Bacterial diseases
Bacterial Diseases

Viral Diseases

Firstly, drinking contaminated water causes Hepatitis, a viral disease that infects the liver. Secondly, contaminated water also becomes a breeding ground for mosquitoes that spread Encephalitis. Poliomyelitis virus is responsible for poliomyelitis and spreads through contaminated water.

Parasitic Diseases

Parasitic diseases transmitted via contaminated water includes Cryptosporidiosis by cryptosporidium parvum. Galloping amoeba is caused by the Entamoeba histolytica. Giardiasis is caused by Giardia lamblia.

Now, let me show you the health effects of some particular water pollutants.

  • Pesticides – carbonates and organophosphates present in them damage the nervous system and cause cancer. Chlorides can cause reproductive and endocrinal damage.
  • Nitrates – especially affect babies that drink formula milk. It reduces the amount of oxygen in the blood and causes the “blue baby” syndrome.
  • Arsenic – causes liver damage, skin cancer and vascular diseases
  • Fluorides – in excessive amounts makes the teeth yellow and causes spinal cord damage.

Also read : Activated Sludge Process – Stages and Process Control

Key Takeaways

  • Addressing Pollution: Effective solutions require reducing water pollution causes and mitigating their effects.
  • Global Issue: Water pollution is a widespread problem impacting ecosystems and human health.
  • Major Causes: Key causes of water pollution include industrial discharge, agricultural runoff, and improper waste disposal.
  • Eutrophication: Excess nutrients lead to harmful algal blooms and oxygen depletion.
  • Food Chain Disruption: Water pollution disrupts food chains, affecting both aquatic and terrestrial predators.
  • Economic Impact: Managing and restoring polluted water bodies incurs high costs.
  • Aesthetic Loss: Polluted waters diminish natural beauty, affecting tourism and recreation.
  • Health Risks: Contaminated water poses significant health risks, including bacterial, viral, and parasitic diseases.

Conclusion

Water is a natural resource that all living things require for survival. Any reckless behavior on the part of humanity has an impact on all other organisms. As a result, water bodies must be protected from pollution.

In summary, water pollution presents severe challenges that affect both natural ecosystems and human well-being. Understanding the causes of water pollution and their effects is essential for developing effective solutions. We can achieve cleaner water bodies by targeting the primary water pollution causes. Addressing their impacts leads to healthier environments. It is imperative to implement comprehensive strategies to reduce pollutants. Managing their effects effectively ensures sustainable water resources for future generations.

Environmental engineering, Land pollution

Constructed Wetlands for Wastewater Treatment

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Constructed wetlands are wastewater treatment systems that utilise natural processes such as plants, soil, and organisms to treat wastewater, greywater, or stormwater runoff from municipal or industrial sources. In this blog, let’s go for a trip exploring the different types of constructed wetlands and their mechanism.

Let’s get started by understanding the basics of a constructed wetland.

  1. What are constructed wetlands?
  2. Constructed Wetlands Components
  3. Pollutants Removal In Constructed Wetlands
    1. Nitrogen Removal
    2. Phosphorus Removal
  4. Constructed Wetlands Types
    1. Subsurface Flow Wetlands
      1. Horizontal Flow Constructed Wetlands
      2. Vertical Flow Constructed Wetlands
    2. Surface Flow Wetlands
  5. Floating treatment wetlands
  6. Conclusion

What are constructed wetlands?

Constructed wetlands are manmade wetlands that find applications in land reclamation after mining and compensating for natural areas lost to development. They operate as a biofilter and remove a variety of pollutants from the water such as organic substances, fertilisers, pathogens, and heavy metals. It can also eradicate pathogens (bacteria, viruses, protozoa, and helminths) to a certain extent.

Constructed Wetlands Components

There are three main components in constructed wetlands:

  • An impermeable layer of Clay
  • A Substrate layer of gravel
  • Ground Vegetation Zone

The impermeable layer, which is often comprised of clay, inhibits pollutants from filtering into the lower aquifers. It is the bottom-most layer.

Above the impermeable layer lies the substrate layer. that nourishes and protects the root zone. The water passes through this layer and into the root zone. Bioremediation and denitrification take place in this layer with the help of bacteria present in the roots. The ground vegetative layer rests above the substrate layer.

Constructed wet lands
Constructed wet lands

In a wetland, vegetation offers a substrate (roots, stems, and leaves) for microbes to proliferate as they decompose organic matter. This microbial colony or the periphyton accomplishes around 90% of pollution removal and waste decomposition. When the plants degrade, they provide a carbon source for the microorganisms and eliminate roughly 7% to 10% of contaminants.

Also read : Secondary Treatment for Wastewater – Methods and Process

Pollutants Removal In Constructed Wetlands

  • As wastewater flows through the wetland medium and the plant rhizomes, it undergoes treatment through various physical, chemical and biological processes.
  • The oxygen which comes out of the rhizomes, roots, and rootlets, forms a thin layer surrounding each root hair.
  • This creates aerobic conditions for the aerobes to act. Along with the aerobic bacteria, anaerobic bacteria also acts on the wastewater.
  • Microbial nitrification and subsequent denitrification releases nitrogen gas. In the root-bed media, phosphorus coprecipitates with iron, aluminium, and calcium compounds.
  • Filtration and adsorption by biofilms on the gravel or sand media reduces the harmful bacteria and viruses.

Nitrogen Removal

Ammonia present in the wastewater converts to ammonium ions. The aerobic bacterium Nitrosomonas sp. oxidizes these ammonium ions to nitrite. Nitrite converts to nitrate by the action of the the bacterium Nitrobacter sp. Finally, nitrate reduces to relatively harmless nitrogen gas under anaerobic conditions. It then enters the atmosphere.

Phosphorus Removal

Phosphorus removal and storage occurs within the constructed wetland itself since the phosphorus cycle is closed and there is no release of it into the atmosphere. A wetland system sequesters phosphorus by:

  1. Incorporating phosphorus into living biomass and thereby becoming a part of the organic matter present in living beings.
  2. Precipitation of phosphorus as insoluble phosphates with ferric iron, calcium, and aluminium compounds found in wetland soil.

Constructed Wetlands Types

The following are the three primary types of built wetlands:

  • Subsurface flow constructed wetland
  • Surface flow constructed wetland
  • Floating treatment wetland

Let’s have a closer look at each one of them.

Subsurface Flow Wetlands

There is no water surfacing in subsurface flow constructed wetlands because wastewater flows through the roots of the plants which lies below the gravel. As a result, these types of constructed wetlands offer the following advantages:

  • The system is more efficient
  • Attract fewer mosquitoes and flies.
  • Emit less stink.
  • Less susceptible to cold temperatures.
  • Water purification takes up lesser space.

There are two types of subsurface flow constructed wetlands: Horizontal flow and vertical flow constructed wetlands

Horizontal Flow Constructed Wetlands

The effluent in the horizontal flow built wetland moves horizontally and parallel to the surface. Absence of surface water, preventing mosquito breeding. Subsurface flow wetlands can treat a variety of different wastewaters, such as household wastewater, agricultural, paper mill wastewater, mining runoff, tannery or meat processing wastes, stormwater.

Vertical Flow Constructed Wetlands

A vertical flow constructed wetland is a planted filter bed with a bottom drain. A mechanical dosing system pours or doses wastewater onto the surface from above. Water runs down vertically through the substrate layer to the basin’s bottom, where it is collected in a drainage pipe. In comparison to horizontal flow constructed wetlands, vertical flow constructed wetlands are more efficient and use less space.

Also read : Activated Sludge Process – Stages and Process Control

Surface Flow Wetlands

Surface flow wetlands resemble wastewater treatment ponds in appearance such as “waste stabilisation ponds”. They find applications in tertiary treatment, wastewater treatment plant effluent polishing and stormwater runoff treatment

Along with natural decay, predation by higher species, pathogens die by UV radiation due to the exposure of water to direct sunlight, . The soil layer beneath the water is anaerobic, but the roots of the plants produce oxygen, allowing complex biological and chemical interactions to take place.

A wide range of soil types, including bay mud and various silty clays, can support surface flow wetlands.Plants like Water Hyacinth (Eichhornia crassipes) and Pontederia spp. are employed.

Constructed Wetlands
Constructed Wetlands
  • Surface flow constructed wetlands, on the other hand, may increase mosquito breeding.
  • They also produce a lot of algae, which degrades the effluent quality.
  • In comparison to subsurface flow built wetlands, they require a larger area to cleanse water.
  • They have a stronger odour and lesser performance in the winter.

Floating treatment wetlands

The floating treatment wetlands (FTWs) are artificial wetlands that replicate natural ones. Floating rafts support hydroponically grown plants in FTWs. The rafts float on the surface of a wet pond and they improve water quality by filtering, consuming, or breaking down contaminants (such as nutrients, silt, and metals) in the water.

Shall we wrap up?

Conclusion

Due to the self-sustaining nature of the constructed wetlands they have a significantly lower lifetime costs compared to the conventional treatment systems. Hence they provide an economical and nature-friendly option for wastewater treatment.

So, how was the trip? Let us know in the comments.

Environmental engineering, Water pollution

Chemical Oxygen Demand and Total Organic Carbon Analysis

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Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) are widely used analysis methods in water treatment plants, petrochemicals and drinking water treatment. In this blog, let me walk you through the analysis of Chemical Oxygen Demand, Total Organic Carbon and its applications.

Let’s get started with Chemical Oxygen Demand.

  1. What is Chemical Oxygen Demand?
  2. Why COD and TOC are important
  3. Significance of COD/TOC Ratio
  4. Chemical Oxygen Demand Determination
    1. Procedure for Chemical Oxygen Demand
    2. Chemical Oxygen Demand Testing Advantages
    3. Chemical Oxygen Demand Testing Limitations
  5. Total Organic Carbon (TOC)
  6. What does TOC Analyse?
    1. Oxidation Methods
    2. TOC Applications

What is Chemical Oxygen Demand?

Chemical Oxygen Demand is the amount of oxygen required to oxidise all the biodegradable and non-biodegradable organic matter. It evaluates all chemically oxidizable components present in a given wastewater sample. It can be directly linked to the effluent’s actual oxygen requirement on releasing into the environment. Total Organic Carbon testing, in addition to Chemical Oxygen Demand, provides us with a better understanding of a waste stream’s true organic load.

Why COD and TOC are important

COD (Chemical Oxygen Demand) and TOC (Total Organic Carbon) analysis play a vital role in keeping our waterways safe and healthy. By measuring the levels of organic pollution in water and wastewater, these tests help us monitor water quality, evaluate the efficiency of treatment processes, and ensure that we’re meeting environmental regulations. Ultimately, they safeguard our well-being and the delicate balance of aquatic ecosystems.

Significance of COD/TOC Ratio

  • The COD/TOC ratio is a useful tool for assessing the biotreatability of wastewater treatment.
  • At a given point in the wastewater treatment process, the ratio of COD to TOC provides insight into the nature of organic wastewater constituents present.
  • A high COD/TOC ratio indicates easily oxidisable organic molecules like alcohols.
  • Ratios in the range of 0.8 or higher indicate wastes with a high biochemical treatment potential.
  • Lower ratios indicate that the wastes are not amenable to biochemical treatment.
  • The amount of oxygen required as measured by the COD value may change during wastewater treatment, but the carbon concentration as measured by the TOC value does not.
  • As the COD/TOC ratio of wastewater decreases during treatment, it means that the organic compounds are undergoing oxidation and the treatment plant is functioning smoothly.

Also read : Wastewater Treatment- Stages and Process full details

Chemical Oxygen Demand Determination

The COD determination is similar to the BOD determination in the fact that both methods use titration. The basic principle of the COD test is that a strong oxidizing agent can fully oxidize almost all organic compounds to carbon dioxide under acidic conditions.

The best choice would be potassium dichromate which is a strong oxidizing agent under acidic conditions. The addition of sulfuric acid creates acidic conditions for titration. Usually, we use a 0.25 N solution of potassium dichromate for COD determination. However, for samples of COD below 50 mg/L, we use a lower concentration of potassium dichromate.

During the oxidation of the organic substances found in the water sample, potassium dichromate undergoes reduction and forms Cr3+. After the completion of the oxidation reaction, the amount of Cr3+ gives an indirect measure of the organic contents in the water sample.

Procedure for Chemical Oxygen Demand

  • Pipette out 50 ml of the wastewater sample into a flat bottom Erlenmeyer flask.
  • Gently add HgSO4 and 5 mL of sulfuric acid. Swirl the flask continuously until all the mercuric sulfate has dissolved.
  • Now, add 25.0 mL of 0.25N potassium dichromate.
  • Carefully add 70 mL of previously prepared sulfuric acid-silver sulfate solution and gently swirl until the solution is thoroughly mixed.
  • Add glass beads to the refluxing mixture to prevent bumping.
  • Heat the mixture under total reflux conditions for 2 hours.
  • Cool down the mixture to room temperature and titrate it with standard ferrous ammonium sulfate along with 10 drops of ferroin indicator.
  • The end-point of titration is a sharp colour change from blue-green to reddish-brown.
  • Run a blank, with 50 mL of distilled water in place of the sample along with all reagents and subsequent treatment.

COD in mg/l = [(A-B)*M*8000]/sample volume in ml

A = Volume (ml) of Ferrous Ammonium Sulphate used for blank.

B = Volume (ml) of Ferrous Ammonium Sulphate used for sample

M = Molarity of Ferrous Ammponium Sulphate

8000 = milliequivalent weight of oxygen * 1000 ml/L

The COD test doesn’t differentiate between biodegradable and non-biodegradable organic materials. It gives a measure of total oxidisable organic materials in the sample. Therefore, we get higher values of COD than BOD for the same sample. Dichromate oxidises the chlorides and nitrites present in the sample. They create an inorganic COD and generates error in the COD determination.

Chemical Oxygen Demand Analysis
Chemical Oxygen Demand Analysis

Chemical Oxygen Demand Testing Advantages

  • COD is ideal for checking treatment plant performance and water quality regularly.
  • In comparison to the 5-day BOD test, COD testing is more accurate and has a shorter analysis period (2-hour digesting time).
  • Toxic elements in the sample do not affect the COD oxidant.
  • Changes in COD between influent and effluent may be correlated with BOD content and can be used to augment BOD data.

Chemical Oxygen Demand Testing Limitations

  • The COD technique does not completely oxidise some organic molecules.
  • Chloride ions might cause interference in COD measurements.

Now you got a clear idea about COD determination. Let’s move on to Total Organic Carbon Analysis.

Total Organic Carbon (TOC)

Total Organic Carbon refers to the total amount of organic carbon (including elemental carbon) bound to dissolved or suspended organic substances in water. It is a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment.

What does TOC Analyse?

The basic principle behind the Total Organic Carbon test is the oxidation of the carbon in the organic matter to carbon dioxide. After that, a non-dispersive infrared analyzer measures the amount of CO2. The amount of CO2 evolved gives a measure of the carbon content in the sample. Further stoichiometric calculations based on the method employed gives the amount of TOC.

TOC analysis measures the following:

  • Total carbon (TC)
  • Inorganic carbon (IC)
  • Total organic carbon (TOC)
  • Purgeable organic carbon (POC)
  • Nonpurgeable organic carbon (NPOC)

TOC analysis measures Total Carbon and Inorganic Carbon. Then we subtract the Inorganic Carbon (IC) from Total Carbon (TC) to find the Total Organic Carbon. This is the TC-IC method.

TOC Analysis
TOC Analysis

According to the TC-TIC method, TOC = TC -T IC

TIC-NPOC method employs acidification of the sample to evolve carbon dioxide. It gives the measure of inorganic carbon (IC) and then oxidation of sample and measurement of the remaining non-purgeable organic carbon (NPOC).

Oxidation Methods

We have a variety of oxidation and detection methods to find out the TOC. Let me show a few of them:

  • High-temperature combustion at 1,200 °C in an oxygen-rich atmosphere. The CO2 passes through scrubber tubes to remove interferences. After that, non-dispersive infrared absorption (NDIR) gives the amount of CO2.
  • High-temperature catalytic oxidation at 680 °C in an oxygen-rich environment inside tubes filled with a platinum catalyst and then NDIR.
  • Thermochemical oxidation in the presence of heat and a chemical oxidizer, usually a persulphate.
  • Photochemical oxidation in the presence of UV and a chemical oxidizer like persulphate.
  • Photo-oxidation by ultra-violet (UV) light alone or with a catalyst. In a UV-irradiated chamber, combine sample with persulfate to convert organics to carbon dioxide. The UV oxidation method offers the most reliable, low maintenance method of determining TOC in ultra-pure waters.

Accurate detection and quantification are very crucial to get accurate results in TOC analysis. The most commonly used methods include conductivity and non-dispersive infrared (NDIR).

TOC Applications

  • In oil exploration, the initial chemical study on a prospective petroleum source rock is TOC.
  • TOC helps in detecting pollutants in drinking water, cooling water, semiconductor production water, and pharmaceutical-grade water.
  • It finds applications in controlling the release of organic chemicals into the environment at a production facility.
  • Furthermore, a low TOC can demonstrate the absence of potentially dangerous organic compounds in pharmaceutical manufacturing water.
  • Because of the byproducts, TOC is also of importance in the field of drinking water treatment.

That’s it about the analysis of Chemical Oxygen Demand and Total Organic Carbon. Hope you found it informative. Let us know your queries in the comments section.

Fiber reinforced concrete

Fiber Reinforced Concrete (FRC) – Types and Advantages

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Fiber-reinforced concrete (FRC), an advanced form of Reinforced Cement Concrete is finding wide applications these days. Fiber-reinforced concrete (FRC) is a versatile and durable composite material consisting of a cementitious matrix with uniformly dispersed fibers. The addition of discontinuous, discrete fibers to cement, mortar or concrete mixes can enhance the concrete properties. Ever thought why do we add different kinds of fibres to the Reinforced Cement Concrete and what are the different types of fibres that we add? Stay with me till the end of this blog and we will find answers to all these questions.

Before proceeding further, make sure you check out our blog, Reinforced Cement Concrete (RCC)|Definition|Advantages to have your concepts clear.

First, let’s have a look at the basics of fiber-reinforced concrete and its applications.

What is Fiber-reinforced concrete?

Fiber-reinforced concrete (FRC) is a versatile and durable composite material consisting of a cementitious matrix with uniformly dispersed fibers. The addition of discontinuous, discrete fibers to cement, mortar or concrete mixes can enhance the concrete properties. These fibers act as reinforcement throughout the concrete matrix, and control cracking due to plastic shrinkage and drying shrinkage. Fiber-reinforced concrete reduces the permeability of concrete and reduces water bleeding.

Fiber reinforced concrete finds extensive applications in various infrastructure works, industrial flooring works and other construction works that demand enhanced durability and crack control. FRC improves the flexural and impact resistance and hence we prefer it for structures subjected to dynamic or heavy loads.

Now, let’s discuss the reason behind the addition of fibres to the reinforced concrete.

Principle of Fiber-reinforced concrete

Fibre-reinforced concrete uses discrete fibres to improve its mechanical properties, making it stronger, more durable, and resistant to cracking. Fiber is a small piece of circular or flat reinforcing material possessing certain characteristics and properties. These fibers are of steel, glass, synthetic polymer fibers and natural fibers like jute or hemp.

Fibers are available in various sizes ranges from a few millimeters to a few centimetres. They are uniformly distributed throughout the concrete matrix. The features of Fiber reinforced concrete depends on the character and percentage, diameter and length of fibers and water-cement ratios. Typically fiber reinforced concrete is used in shotcrete but can also be used in normal concrete.

The addition of fibres to concrete controls the shrinkage cracking, lower permeability, and reduce water bleeding. Some fibers enhance impact, abrasion, and shatter resistance. However, they do not increase flexural strength or replace structural steel reinforcement.

We measure the amount of fiber as a percentage of total volume (Vf) and typically ranges from 0.1 to 3%. Aspect ratio (l/d) affects strength and toughness, but long fibers can hinder workability. Recent research shows limited impact resistance improvement, with microfibers performing better than longer fibers.

Types of Fiber-reinforced concrete

The type of fiber-reinforced concrete depends on the nature of the structure and applications. Let us have a look at the most common types of fibre reinforced concretes commonly used in construction.

  • Steel Fiber Reinforced Concrete
  • Polypropylene Fiber Reinforced (PFR) Concrete
  • GFRC Glass Fiber Reinforced Concrete
  • Asbestos Fibers
  • Polyester fiber
  • Carbon Fibers
  • Macro synthetic fibers
  • Organic Fibers
  • Cellulose fibers
  • Micro-synthetic fibers
  • Synthetic Fiber Reinforced Concrete (SFRC)Natural Fiber Reinforced Concrete (NFRC)Carbon Fiber Reinforced Concrete (CFRC)Basalt Fiber Reinforced Concrete (BFRC)Nylon Fiber Reinforced Concrete (NyFRC)Polyvinyl Alcohol Fiber Reinforced Concrete (PVAFRC)High-Performance Fiber Reinforced Concrete (HPFRC)

Steel fiber-reinforced concrete

SFRC is a composite material that includes a certain amount of steel fibers in the concrete mix. These fibres can change the properties of concrete and thereby enhance the performance of concrete. The typical diameter lies in the range of 0.25 to 0.75mm. Steel fibers having a rectangular c/s are produced by silting the sheets about 0.25mm thick.

Steel fibre reinforced Concrete

SFRC offers numerous advantages, including improved tensile strength, crack resistance, impact resistance, and durability. The steel fibers act as reinforcement, effectively bridging cracks and enhancing the concrete’s structural integrity. The steel fiber types are as per ASTM A.820 Type I: cold-drawn wire, Type II; cut sheet, Type III: melt-extracted, Type IV: mill cut and Type V: modified cold-drawn wire.

SFRC finds applications in industrial floors, pavements, tunnels, and precast elements, where increased toughness and load-bearing capacity are required. It is also widely used in applications prone to dynamic loading, such as blast-resistant structures and earthquake-resistant buildings.

Glass fiber-reinforced concrete

Glass Fiber Reinforced Concrete (GFRC) is a composite material incorporating fine glass fibers into the concrete mix. These fibers, typically around 3-12 mm in length, enhance the concrete’s strength, durability, and flexibility. GFRC is commonly used in architectural applications, such as cladding, facades, and decorative elements, due to its lightweight nature and ability to create intricate designs.

Glass fiber reinforced concrete

You can get the full details about glass fiber-reinforced concrete here. Glass Fiber Reinforced Concrete – GFRC Ingredients and Uses

Polypropylene Fiber Reinforced Concrete (PFRC)

Polypropylene Fiber Reinforced Concrete (PFRC) is a composite material that combines polypropylene fibers with concrete. One of the cheapest & abundantly available synthetic fiber/ polymer is polypropylene. They are resistant to most chemicals and only the cementitious matrix will deteriorate first. These discrete fibers, typically ranging from 6 to 30 mm in length uniformly dispersed in concrete will control cracking due to plastic and drying shrinkage.

We usually use these fibers in concrete to control cracking due to plastic shrinkage and drying shrinkage. The fibers act as reinforcement and reduce the permeability of concrete and thus reducing the bleeding of water and improving crack resistance, impact resistance, and durability. Polypropylene fibers being hydrophobic can be easily mixed as they do not need lengthy contact during mixing and only need to be evenly distressed in the mix.

Polyester fiber reinforced concrete

Polyester fiber-reinforced concrete is a composite material that incorporates polyester fibers into the concrete mix. These fibers, typically short and discrete, improve the concrete’s toughness, crack resistance, and impact resistance. Polyester fibers due to the high tensile strength and resistance to alkalis make them suitable for various construction applications that demand enhanced durability.

Carbon fibers

Carbon fiber reinforced concrete (CFRC) is a composite material that combines concrete with carbon fibers about 5-10 microns in diameter having carbon atoms. The carbon fibers, known for their exceptional tensile strength and stiffness, low weight, high chemical resistance, high-temperature tolerance and low thermal expansion impart their qualities to the concrete.

We manufacture carbon fibers by baking plastic resins. They have high strength-to-weight ratio. Carbon fibers form the most recent and probably the most spectacular addition to the range of fiber available for commercial use. Since they are more vulnerable to damage than even glass fiber, we generally treat them with resin coating.

Macro synthetic fibers

Macro synthetic fibers are synthetic fibers used as reinforcement in concrete. These fibers, typically longer and thicker than traditional fibers, are manufactured from a blend of polymers. These fibers are developed for shot create or sprayed concrete. But they find extensive applications in floor slabs for enhancing the concrete’s toughness, crack resistance, and impact resistance.

They offer improved durability and control of plastic shrinkage cracking. This makes them suitable for various construction applications in marine and coastal structures which require enhanced performance and reduced maintenance.

Advantages of fibre-reinforced concrete

  1. Enhanced Durability: FRC increases the impact, fatigue, and abrasion resistance of concrete structures while minimising cracking. It increases the tensile strength and durability of the concrete.
  2. Crack prevention: The use of fibres reduces the spread and enlargement of cracks by controlling plastic and drying shrinkage cracking.
  3. Permeability Reduction: Fibres make concrete less permeable, which reduces water bleeding and improves resistance to moisture infiltration.It reduces the air voids and water voids and the inherent porosity of gel.
  4. Improved Impact Resistance: Certain types of fibres enhance the impact resistance of concrete, making it more resilient against sudden loads and external forces.
  5. Increased Toughness: The bridging action of the fibres, which absorbs energy and prevents abrupt failure, gives FRC an improved level of toughness.
  6. Design Flexibility: Using fibres in concrete allows for design flexibility, enabling the creation of complicated shapes and architectural freedom.
  7. Simplicity: Using fibre reinforcement instead of or less frequently than standard steel reinforcement simplifies construction operations.
  8. Better Workability: Fibres can make concrete mixes more workable and cohesive, making placement and compaction easier.
  9. Corrosion Resistance: In some circumstances, fibre reinforcement can reduce the likelihood that concrete buildings will corrode.
  10. Sustainable: Fibre-reinforced concrete is a sustainable solution since it can increase the longevity of structures and lessen the reliance on non-renewable resources.
  11. Creep Resistance: Fibres such as graphite and glass have excellent resistance to creep, while the same is not true for most resins. Therefore, the orientation and volume of fibres have a significant influence on the creep performance of rebars/tendons.

Shall we wrap up?

Conclusion

In this blog, we saw the properties, uses, types and advantages of fiber-reinforced concrete. If you have any queries please feel free to ask in the comments.

Azeotropes, chemical engineering

Azeotropes – Definition, Types, Properties and Methods of Separation

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Azeotropes or azeotropic mixtures have always been a topic of interest due to their unique properties and the inability to separate them completely using conventional distillation. A classic example of azeotropes occurs in winemaking wherein an Ethanol-water mixture forms an azeotropic mixture at 96% Ethanol by volume which prohibits its further purification by distillation. In this blog, let’s look at how this happens and how we can separate such azeotropic mixtures.

Before diving into azeotropes and azeotropic distillation, let’s have a quick look at the distillation process.

  1. What are azeotropes or azeotropic mixtures?
    1. Maximum boiling azeotropes
    2. Minimum boiling azeotropes
    3. Azeotropic Distillation
    4. Extractive Entrainers
    5. Azeotropic Entrainers
  2. Molecular Sieves
  3. Conclusion

What are azeotropes or azeotropic mixtures?

Azeotropes are constant boiling point mixtures. Azeotropes are mixtures of two or more liquids whose composition cannot be altered or changed by simple distillation. This occurs because the vapour’s constituent ratios are identical to those of the unboiled mixture when an azeotrope is boiled. Azeotropes are also known as constant boiling point mixtures since distillation leaves their composition unaltered.

There is a distinctive boiling point for each azeotrope. An azeotrope’s boiling point is either lower or higher than the boiling points of any of its constituents. Depending on the boiling point deviation, we have two types of azeotropes as follows:

Azeotropes

Maximum boiling azeotropes

Maximum boiling azeotropes are those mixtures that have a boiling point higher than any of their constituents. These azeotropes show a large negative deviation from Raoult’s Law. So we can call them negative azeotropes or pressure minimum azeotropes.

Hydrochloric acid at a concentration of 20.2% and 79.8% water (by mass) is an example of a negative azeotrope. Water and hydrogen chloride both boil at 100 °C and 84 °C, respectively, but the azeotrope boils at 110 °C, exceeding the boiling points of both of its ingredients. Any hydrochloric acid solution can boil at a maximum temperature of 110 °C. Other negative azeotropes include:

  1. Nitric acid (68%)/water, which boils at 120.2 °C at 1 atm
  2. Hydrofluoric acid (35.6%)/water, which boils at 111.35 °C
  3. Water with perchloric acid (71.6%), 203 °C boiling point
  4. Water and sulfuric acid (98.3%), boiling at 338 °C

Minimum boiling azeotropes

Minimum boiling azeotropes are those mixtures that have a boiling point higher than any of their constituents. These azeotropes show a large positive deviation from Raoult’s Law. So we can call them positive azeotropes or pressure maximum azeotropes.

The mixture of 95.63% ethanol and 4.37% water (by mass), which boils at 78.2 °C, is a well-known example of a positive azeotrope. The azeotrope boils at 78.2 °C, which is lower than any of its components as ethanol boils at 78.4 °C and water boils at 100 °C.

Azeotropic Distillation

Since the vapours of azeotropes produced after boiling have the same composition as that of its liquid mixture, conventional distillation techniques can’t separate azeotropes. Hence we should add an additional component ie the entrainer, which can first break the existing azeotrope and make one of the components of the azeotrope more volatile than the other. In other words, azeotropic distillation is the process of converting a binary azeotrope into a ternary azeotrope by the addition of an entrainer.

An entrainer is a substance that we introduce to an azeotropic mixture to break it by changing the molecular interactions and creating a new azeotrope with a different composition and boiling point. The characteristics of the azeotropic mixture that undergoes separation determine the appropriate entrainer. The entrainer should be easily separable from the other components of the azeotropic mixture and form a new azeotrope with one of them.

The entrainer can change the activity coefficient of different compounds in different ways when added to the liquid phase, changing the relative volatility of a mixture. Greater deviations from Raoult’s law make it simpler to add another component and create considerable changes in relative volatility. In azeotropic distillation, the additional component has the same volatility as the mixture and one or more of the components combine to generate a new azeotrope due to polarity differences.

The most common types of entrainers in azeotropic distillation include:

  • Extractive entrainers
  • Azeotropic entrainers

Extractive Entrainers

Extractive entrainers are substances having a higher boiling point than the initial mixture and combining with one of the components in the azeotropic mixture to generate a new azeotrope. The mixture is heated after the addition of the extractive entrainer.

The extractive entrainer combines one of the original mixture’s components to create a new azeotrope as the mixture’s temperature rises. We can distill out the new azeotrope from the original mixture since it has a higher boiling point than the latter. A further distillation separates the entrainer from the isolated component.

Azeotropic Entrainers

Azeotropic entrainers are substances having a lower boiling point than the initial mixture and produces a new low boiling azeotrope. The most well-known example is the water – ethanol azeotrope when benzene or cyclohexane is added. The ternary azeotrope, which is 7% water, 17% ethanol, and 76% cyclohexane, boils at 62.1 °C with cyclohexane acting as the entrainer. The water/ethanol azeotrope is given just enough cyclohexane to engage all of the water in the ternary azeotrope. The azeotrope ( Benzene – water ) vaporises when the combination is then heated, leaving a residue that is almost entirely made up of ethanol.

Molecular Sieves

A common approach involves the use of molecular sieves. Treatment of 96% ethanol with molecular sieves gives anhydrous alcohol, the sieves having adsorbed water from the mixture. The sieves can be subsequently regenerated by dehydration using a vacuum oven.

Shall we wrap up?

Conclusion

In this blog, we had a short discussion on azeotropes, their formation, properties and the methods of separating them. Azeotropic distillation, pressure swing distillation and molecular sieves are some of the existing methods available. In case of any doubts, please feel free to ask in the comments section. Happy Learning!

chemical engineering, Steam distillation

Steam Distillation – Process, Principle and Diagram – Full Details

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Steam distillation is a separation process in which we separate a mixture of immiscible components by introducing steam and subsequently condensing the vapours. In this blog, I will walk you through steam distillation and its principles. First, let us understand the instances in which we opt for Steam distillation over other separation processes.

  1. What is Steam Distillation?
  2. Steam Distillation Principle
  3. Steam Distillation Process
  4. Steam Distillation Advantages
  5. Conclusion

What is Steam Distillation?

In the typical distillation process, we usually have a mixture of components that are miscible with one another. The vapour pressure that the combination exerts on heating depends on the components that make up the mixture.

steam distillation diagram

To start boiling, the vapour pressure of the mixture should become equal to the atmospheric pressure or the pressure to which it is subjected to. Hence we must heat the system of the liquid mixture to a temperature where the system can create enough vapour to equalise the operating pressure or the atmospheric pressure.

The temperature that must be attained depends on the operating pressure; if it is less than one atmospheric pressure, the temperature that is to be attained is relatively lower; if it is greater than one atmospheric pressure, the temperature to be attained is relatively higher.

In some circumstances, it might not be possible to perform this. Some of those instances are as follows:

  • When separating materials with very high boiling points, we have to supply more heat to raise the temperature of the mixture. As a result, the procedure uses more energy and is more expensive.
  • If the mixture contains any thermally unstable components, raising the temperature too high could cause the components to decompose and have an impact on their qualities.
  • The process becomes energy-intensive if we have a binary combination in which one component boils at a high temperature while the other is non-volatile in nature.
  • We can easily handle these situations using the method of steam distillation.

Steam Distillation Principle

In the previous blog, we saw Raoult’s law which states that the partial pressure of each component in a miscible ideal mixture is equal to the product of its vapour pressure and mole fraction.

Pa = Xa * Pv

Steam distillation process

Hence it is clear that the liquid components can’t exert their actual vapour pressure but a corrected vapour pressure (or what we call the partial pressure) which is always less than its pure component vapour pressure ( since mole fraction is always less than 1 )

But, in the case of liquid mixtures in which the components are non-miscible, they can exert their entire vapour pressure as its partial pressure. That is, the total pressure becomes equal to the sum of the individual vapour pressures for immiscible liquid mixtures. Their combined vapour pressures can easily reach the external pressure before the vapour pressure of either of the individual components cross it. Hence the boiling point of the mixture would be lesser than the boiling point of either of the components.

Now, let us assume that water is one of the components in the immiscible mixture. Then we can bring that mixture to a boil at under 100 0C in one atmosphere ( Boiling Point of water at 1 ATM = 100 0C ) if we keep the pressure constant at 1 ATM. In other words, we can lower the operating pressure needed to boil the mixture by introducing steam.

The main concept behind steam distillation is that we use steam to help create the pressure needed to balance the operating pressure. We must be careful to only employ components that are immiscible with water while using steam.

Steam Distillation Process

Consider a binary mixture where component A is a high-boiling component and component B is a non-volatile component. Let’s say A is insoluble in water. We feed the mixture into the column. Using a steam coil, we raise the feed mixture’s temperature. A sparger forces the steam through another steam line. Steam enters the column through the feed mixture and adds to the vapour pressure. When it reaches the working pressure, it causes the creation of vapours of A at a significantly lower temperature. The non-volatile component is eliminated as residue but remains in the feed. Steam and Component A is routed via a condenser where they are easily separated after condensation.

Steam Distillation Advantages

We frequently use steam distillation since it has various advantages over other extraction methods. They are as follows:

  1. the process produces organic compounds devoid of solvents;
  2. Additional separation procedures are not necessary;
  3. It has a huge processing capacity on an industrial scale;
  4. Inexpensive equipment

Shall we wrap up?

Conclusion

In this blog, we saw the process of steam distillation, its advantages and its applications.