Essay about climate changes

Climate Change Essay

 

Climate change in the world can be caused by various activities. When climate change occurs; temperatures can increase a dramatically. When temperature rises, many different changes can occur on Earth. For example, it can result in more floods, droughts, or intense rain, as well as more frequent and severe heat waves. Oceans and glaciers have also experienced some changes: oceans are warming and becoming more acidic, glaciers are melting, and sea levels are rising. As these changes frequently occur in future decades, they will likely present challenges to our society and environment.

effects and causes

 

The warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level. The Earth’s average surface temperature has risen by 0.76° C since 1850. Most of the warming that has occurred over the last 50 years is very likely to have been caused by human activities. In its Fourth Assessment Report projects that, without further action to reduce greenhouse gas emissions, the global average surface temperature is likely to rise by a further 1.8-4.0°C this century, and by up to 6.4°C in the worst case scenario. Even the lower end of this range would take the temperature increase since per - industrial times above 2°C – the threshold beyond which irreversible and possibly catastrophic changes become far more likely.
The climate can affect every person and our health directly through increases in temperature. Such increases may lead to more extreme heat waves during the summer while producing less extreme cold spells during the winter. Particular segments of the population such as those with heart problems, asthma, the elderly, and the very young can be especially vulnerable to extreme heat. There can be extreme floods and droughts, hurricanes.

Nowadays there are so many factories that exhale really destructive substances and pollute the air. We all know very well that air is something we can’t live without. When we breathe the polluted air, we can get seriously ill. Ground-level ozone can damage lung tissue, and is especially harmful for those with asthma and other chronic lung diseases. Sunlight and high temperatures, combined with other pollutants such as nitrogen oxides and volatile organic compounds, can cause the ground-level ozone to increase.We cannot escape from the polluted air-it’s everywhere, even in our homes and we are breathing it non-stop. This can cause cancer and other serious diseases.

Another huge problem is that the sea levels are rising worldwide. Also the expansion of ocean water is caused by warmer ocean temperatures.. Mountain glaciers and small ice caps are melting as well as Greenland’s Ice Sheet and the Antarctic Ice Sheet. The temperature is rising which means that ice is melting faster and faster.

However, these are not the only problems. Another issue are the greenhouse gasses. They are gasses which trap heat in the atmosphere. Some greenhouse gases such as carbon dioxide occur naturally by natural processes and other are created and emitted solely through human activities. For example carbon dioxide is entering the atmosphere because of human activities like burning of fossil fuels (oil, natural gas, and coal). All vehicles exhale too much damaging substances. People have been trying to reduce them but the problem is still topical and I think we have to do something like ride a bike not a car to work or school, we should take the shortest route possible, and plan our drive so that we will not backtrack or travel out of our way.We also may choose a clean-burning fuel, which reduces ozone-forming pollutants and buy a car that produces fewer emissions or runs using an alternative fuel.The taxes of cars should be higher and most of the people will prefer to use the public transport and we will no longer have traffic jams and we will reduce the damaging emissions.

As a conclusion, I think that when it can not do both, The UN should prioritize combating climate change over reducing poverty. Of course, poverty is a big issue, which needs a solution but have you ever asked yourself why the poor countries like Bangladesh, Gambia, Zambia are poor and why so many people die? It’s because the climate doesn’t allow them to grow food and they can’t afford to buy it from other countries. The climate is a very important thing and if we don’t stop the changes soon, more and more plants and trees are going to die, we won’t have enough food and then not only will the third world countries suffer from hunger but so will the whole world. I think it is better to first stop the changes in climate and then gradually reduce the hunger in the poor countries. Because if we stop the changes, we are going to be healthier and everything around us will be cleaner and it will be how it actually should be. I believe harmony between nature and human beings will return.

Mendelian laws of inheritance

Mendelian laws of inheritance 

Mendelian laws of inheritance are statements about the way certain characteristics are transmitted from one generation to another in an organism. The laws were derived by the Austrian monk Gregor Mendel (1822–1884) based on experiments he conducted in the period from about 1857 to 1865. For his experiments, Mendel used ordinary pea plants. Among the traits that Mendel studied were the color of a plant's flowers, their location on the plant, the shape and color of pea pods, the shape and color of seeds, and the length of plant stems.
Mendel's approach was to transfer pollen (which contains male sex cells) from the stamen (the male reproductive organ) of one pea plant to the pistil (female reproductive organ) of a second pea plant. As a simple example of this kind of experiment, suppose that one takes pollen from a pea plant with red flowers and uses it to fertilize a pea plant with white flowers. What Mendel wanted to know is what color the flowers would be in the offspring of these two plants. In a second series of experiments, Mendel studied the changes that occurred in the second generation. That is, suppose two offspring of the red/white mating ("cross") are themselves mated. What color will the flowers be in this second generation of plants? As a result of these experiments, Mendel was able to state three generalizations about the way characteristics are transmitted from one generation to the next in pea plants.

Words to Know

Allele: One of two or more forms a gene may take.
Dominant: An allele whose expression overpowers the effect of a second form of the same gene.

 
Gamete: A reproductive cell.
Heterozygous: A condition in which two alleles for a given gene are different from each other.
Homozygous: A condition in which two alleles for a given gene are the same.
Recessive: An allele whose effects are concealed in offspring by the dominant allele in the pair.

Terminology

Before reviewing these three laws, it will be helpful to define some of the terms used in talking about Mendel's laws of inheritance. Most of these terms were invented not by Mendel, but by biologists some years after his research was originally published.
Genes are the units in which characteristics are passed from one generation to the next. For example, a plant with red flowers must carry a gene for that characteristic.
A gene for any given characteristic may occur in one of two forms, called the alleles (pronounced uh-LEELZ) of that gene. For example, the gene for color in pea plants can occur in the form (allele) for a white flower or in the form (allele) for a red color.
The first step that takes place in reproduction is for the sex cells in plants to divide into two halves, called gametes. The next step is for the gametes from the male plant to combine with the gametes of the female plant to produce a fertilized egg. That fertilized egg is called a zygote. A zygote contains genetic information from both parents.
For example, a zygote might contain one allele for white flowers and one allele for red flowers. The plant that develops from that zygote would said to be heterozygous for that trait since its gene for flower color has two different alleles. If the zygote contains a gene with two identical alleles, it is said to be homozygous.

Mendel's laws

Mendel's law of segregation describes what happens to the alleles that make up a gene during formation of gametes. For example, suppose that a pea plant contains a gene for flower color in which both alleles code for red. One way to represent that condition is to write RR, which indicates that both alleles (R and R) code for the color red. Another gene might have a different combination of alleles, as in Rr. In this case, the symbol R stands for red color and the r for "not red" or, in this case, white. Mendel's law of segregation says that the alleles that make up a gene separate from each other, or segregate, during the formation of gametes. That fact can be represented by simple equations, such as:
RR → R + R or Rr → R + r
Mendel's second law is called the law of independent assortment. That law refers to the fact that any plant contains many different kinds of genes. One gene determines flower color, a second gene determines length of stem, a third gene determines shape of pea pods, and so on. Mendel discovered that the way in which alleles from different genes separate and then recombine is unconnected to other genes. That is, suppose that a plant contains genes for color (RR) and for shape of pod (TT). Then Mendel's second law says that the two genes will segregate independently, as:
RR → R + R and TT → T + T
Mendel's third law deals with the matter of dominance. Suppose that a gene contains an allele for red color (R) and an allele for white color (r). What will be the color of the flowers produced on this plant? Mendel's answer was that in every pair of alleles, one is more likely to be expressed than the other. In other words, one allele is dominant and the other allele is recessive. In the example of an Rr gene, the flowers produced will be red because the allele R is dominant over the allele r.

Predicting traits

The application of Mendel's three laws makes it possible to predict the characteristics of offspring produced by parents of known genetic composition. The picture on page 1248, for example, shows the cross between a sweet pea plant with red flowers (RR) and one with white flowers (rr). Notice that the genes from the two parents will segregate to produce the corresponding alleles:
RR → R + R and rr → r + r
There are, then, four ways in which those alleles can recombine, as shown in the same picture. However, all four combinations produce the same result: R + r → Rr. In every case, the gene formed will consist of an allele for red (R) and an allele for "not red" (r).
The drawing at the right in the picture on page 1248 shows what happens when two plants from the first generation are crossed with each other. Again, the alleles of each plant separate from each other:
Rr → R + r
Again, the alleles can recombine in four ways. In this case, however, the results are different from those in the first generation. The possible results of these combinations are two Rr combinations, one RR combination, and one rr combination. Since R is dominant over r, three of the four combinations will produce plants with red flowers and one (the rr option) will product plants with non-red (white) flowers.
Biologists have discovered that Mendel's laws are simplifications of processes that are sometimes much more complex than the examples given here. However, those laws still form an important foundation for the science of genetics.

water pollution definition causes effects and prevention

                                            Water Pollution

Water pollution is the contamination of water bodies ( lakes, rivers, oceans and groundwater). Water pollution affects plants and organisms living in these bodies of water and in almost all cases the effect is damaging not only to individual species and populations, but also to the natural communities.

 

Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds. Point source pollution refers to contaminants that enter a waterway through a discrete conveyance, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain.
Non-point source pollution: Non-point source (NPS) pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. The leaching out of nitrogen compounds from agricultural land which has been fertilized is a typical example. Nutrient runoff in storm water from “sheet flow” over an agricultural field or a forest are also cited as examples of NPS pollution.
Contaminated storm water washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of NPS pollution. However, this runoff is typically channelled into storm drain systems and discharged through pipes to local surface waters, and is a point source. However where such water is not channeled and drains directly to ground it is a non-point source.

Types of Water Pollution:

There are two types of water pollution: Ground water pollution & Surface water pollution

i. Groundwater Pollution:

Considerable amount of Earth’s water is found in soil or under rock structures called aquifers. People use aquifers to obtain drinking water and build wells to access it. In case this water becomes polluted, it is called groundwater pollution. This is caused by pesticide contamination from the soil and this can infect the drinking water and lead to huge problems.
Groundwater refers to water collected under the Earth’s surface. The sources of groundwater are rain, snow, hail, sleet, etc. Water that falls on the Earth’s surface continues to travel downwards due to gravity, until a zone comes where it is saturated with water.
At this depth, the spaces between the soil and rock particles are filled up with water. This particular zone is known as the saturated zone. The topmost portion of the saturated zone is referred to as water table. The level of water table changes depending upon the season, it is highest in spring and lowest in summer.
Groundwater is connected to surface water such as rivers, streams and lakes. In fact, there is continuous exchange of water between surface water and groundwater. Groundwater pollution is a change in the properties of groundwater due to contamination by microbes, chemicals, hazardous substances and other foreign particles. It is a major type of water pollution. The sources of groundwater pollution are either natural (mineral deposits in rocks) or man-made.
Natural sources are less harmful compared to hazardous chemicals generated by human activities. Any chemical present on the surface can travel underground and cause groundwater pollution. The seepage of the chemical depends on the chemical type, soil porosity and hydrology.
One of the major sources of groundwater pollution is industries. Manufacturing and other chemical industries require water for processing and cleaning purposes. This used water is recycled back to water sources without proper treatment, which in turn, results in groundwater pollution.
It is also to be noted that solid industrial wastes that are dumped in certain areas also contribute to groundwater pollution. When rainwater seeps downwards, it dissolves some of these harmful substances and contaminates groundwater.
Another source of groundwater pollution is agriculture; the fertilizers, pesticide and other chemicals used in growing plants contaminate groundwater. Residential areas also generate pollutants (microorganisms and organic compounds) for groundwater contamination.
Groundwater pollutant can be divided into point source and non-point source based on the nature of disposal. The former refers to contaminants originating from a particular source such as sewage pipe or tank; whereas non-point source is spread over large areas (for example, pesticides and fertilizers).
It is very difficult and costly to treat contaminated groundwater. Hence, it is better to minimize the risk of groundwater pollution. Public awareness programs about the importance of groundwater and ways to minimize its contamination should be implemented.

ii. Surface Water Pollution:

These are the natural water resources of the Earth. These are found on the exterior of the Earth’s crust, oceans, rivers and lakes.
Water is an essential commodity for survival. We need water for drinking, cooking, bathing, washing, irrigation, and for industrial operations. Most of the water for such uses comes from rivers, lakes or groundwater sources. Water has the property to dissolve many substances in it, therefore, it can easily get polluted.
Pollution of water can be caused by “point sources” or “non- point sources”. Point sources are specific sites near water which directly discharge effluents into them. Major point sources of water pollution are industries, power plants, underground coal mines, offshore oil wells etc.
The discharge from non-point sources is not at any particular site, rather, these sources are scattered, which individually or collectively pollute water. Surface run-off from agricultural fields, overflowing small drains, rain water sweeping roads and fields, atmospheric deposition etc., are the non-point sources of water pollution.
Sources of Surface Water Pollution:

1. Sewage:
Emptying the drains and sewers in fresh water bodies causes water pollution. The problem is severe in cities.

2. Industrial Effluents:
Industrial wastes containing toxic chemicals, acids, alkalies, metallic salts, phenol's, cyanides, ammonia, radioactive substances, etc., are sources of water pollution.They also cause thermal (heat) pollution of water.

3. Synthetic Detergents:
Synthetic detergents used in washing and cleaning produce foam and pollute water.

4. Agrochemicals:
Agrochemicals like fertilizers (containing nitrates and phosphates) and pesticides (insecticides, fungicides, herbicides etc.) washed by rain-water and surface runoff pollute water.

5. Oil:
Oil spillage into sea-water during drilling and shipment pollute it.

6. Waste heat:
Waste heat from industrial discharges increases the temperature of water bodies and affects distribution and survival of sensitive species.

Sources and Types of Water Pollutants:

Pathogens:
Coli-form bacteria are a commonly used bacterial indicator of water pollution, although not an actual cause of disease. Other microorganisms sometimes found in surface waters which have caused human health problems include:
i. Burkholderia pseudomallei.
ii. Cryptosporidium parvum.
iii. Giardia lamblia.
iv. Salmonella.
v. Novovirus and other viruses.
vi. Parasitic worms (helminths).
High levels of pathogens may result from inadequately treated sewage discharges. This can be caused by a sewage plant designed with less than secondary treatment (more typical in less- developed countries. In developed countries, older cities with aging infrastructure may have leaky sewage collection systems (pipes, pumps, valves), which can cause sanitary sewer overflows. Some cities also have combined sewers, which may discharge untreated sewage during rain storms. Pathogen discharges may also be caused by poorly managed livestock operations.
Chemical and other contaminants: Contaminants may include organic and inorganic substances.
Organic water pollutants include:

i. Detergents.
ii. Disinfection by-products found in chemically disinfected drinking water, such as chloroform.
iii. Food processing waste, which can include oxygen-demanding substances, fats and grease.
iv. Insecticides and herbicides, a huge range of organohalides and other chemical compounds.
v. Petroleum hydrocarbons, including fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion by-products, from storm water runoff.
vi. Tree and bush debris from logging operations.
vii. Volatile organic compounds (VOCs), such as industrial solvents.
viii. Various chemical compounds found in personal hygiene and cosmetic products.

Inorganic water pollutants are:
i. Pre-production industrial raw resin pellets.
ii. Heavy metals including acid mine drainage, chemical waste as industrial by-products.
iii. Acidity due to industrial discharges like sulphur dioxide.
iv. Silt in surface runoff due to logging, slash and burn practices, construction sites or land clearing sites.
v. Fertilizers in runoff from agriculture including nitrates and phosphates.

Other agents:
i. The combustion of coal leads to the release of mercury in the atmosphere. This enters the rivers, lakes and groundwater. This is very hazardous for pregnant women and infants.
ii. Cattle and pig rearing causes a significant amount of nutrient-filled waste.
iii. Fertilizers having a large quantity of nitrogen and phosphorus cause a high biological oxygen demand in the water. The high amount of BOD is responsible for oxygen depletion in water bodies.
iv. Human settlement along the banks of rivers causes human, animal and industrial waste to be discharged into it.

Effect of Water Pollution:

i. Disorders:
Some pollutants like sodium can cause cardiovascular diseases, while mercury and lead cause nervous disorders.

ii. Toxic Substances:
DDT is toxic material which can cause chromosomal changes. Some of these substances like pesticides, methyl mercury etc., move into the bodies of organisms from the medium in which these organisms live. These substances tend to accumulate in the organism’s body from the medium food. This process is called bioaccumulation or bio concentration. The concentration of these toxic substances builds up at successive levels of food chain. This process is called bio magnifications.

iii. Water Pollution:
Fluoride pollution causes defects in teeth and bones, a disease called fluorosis while arsenic can cause significant damage to the liver and the nervous system. In addition to all these, organic compounds present in the polluted water facilitate the growth of algae and other weeds, which in turn use more oxygen dissolved in the water. This reduces the amount of oxygen dissolved in the water and the consequent shortage of oxygen for other aquatic life.

iv. Asbestos:
This pollutant is a serious health hazard and carcinogenic. Asbestos fibers can be inhaled and cause illnesses such as asbestosis, mesothelioma, lung cancer, intestinal cancer and liver cancer.

v. Mercury:
This is a metallic element and can cause health and environmental problems. It is a non-biodegradable substance so is hard to clean up once the environment is contaminated. Mercury is also harmful to animal health as it can cause illness through mercury poisoning.

vi. Phosphates:
The increased use of fertilizers means that phosphates are more often being washed from the soil and into rivers and lakes. This can cause eutrophication, which can be very problematic to marine environments.

vii. Oils:
Oil does not dissolve in water; instead it forms a thick layer on the water surface. This can stop marine plants receiving enough light for photosynthesis. It is also harmful for fish and marine birds.

viii. Petrochemicals:
This is formed from gas or petrol and can be toxic to marine life.

ix. Organic matter which reaches water bodies is decomposed by micro-organisms present in water. For this degradation, oxygen dissolved in water is consumed. Dissolved oxygen (DO) is the amount of oxygen dissolved in a given quantity of water at a particular temperature and atmospheric pressure.
Amount of dissolved oxygen depends on aeration, photosynthetic activity in water, respiration of animals and plants and ambient temperature.The saturation value of DO varies from 8-15 mg/L. For active fish species (trout and Salmon) 5-8 mg/L of DO is required whereas less desirable species like carp can survive at 3.0 mg/L of DO.Lower DO may be harmful to animals especially fish population. Oxygen depletion (deoxygenating) helps in release of phosphates from bottom sediments and causes eutrophication.

x. Addition of compounds containing nitrogen and phosphorus helps in the growth of algae and other plants which when die and decay consume oxygen of water. Under anaerobic conditions foul smelling gases are produced. Excess growth or decomposition of plant material will change the concentration of CO₂ which will further change pH of water. Changes in pH, oxygen and temperature will change many physicochemical characteristics of water.

xi. Lead in water may be released from water pipes as lead is used in plumbing. Lead poisoning affects kidneys reproductive system, liver, brain and central nervous system. It also causes anaemia and mental retardation in children.

xii. Nitrate ions present in the water are harmful to human health. From nitrogen fertilizers, nitrate ions seep into water bodies from where these may bioaccumulate in the bodies of the consumers. In the stomach nitrate is reduced to nitrite and is responsible for blue baby syndrome and stomach cancer.

Control of Water Pollution:

The following points may help in reducing water pollution from non-point sources.
(i) Judicious use of agrochemicals like pesticides and fertilizers which will reduce their surface run-off and leaching. Use of these on sloped lands should be avoided.
(ii) Use of nitrogen fixing plants to supplement the use of fertilizers.
(iii) Adopting integrated pest management to reduce greater reliance on pesticides.
(iv) Prevent run-off of manure. Divert such run-off to basin for settlement. The nutrient rich water can be used as fertilizer in the fields.
(v) Separate drainage of sewage and rain water should be provided to prevent overflow of sewage with rain water.
(vi) Planting trees would reduce pollution by sediments and will also prevent soil erosion.
For controlling water pollution from point sources, treatment of waste waters is essential before being discharged. Parameters which are considered for reduction in such water are: Total solids, biological oxygen demand (BOD), chemical oxygen demand (COD), nitrates and phosphates, oil and grease, toxic metals etc. Waste waters should be properly treated by primary and secondary treatments to reduce the BOD, COD levels up to the permissible levels for discharge.
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff (effluents) and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants. Its objective is to produce an environmentally-safe fluid waste stream (or treated effluent) and a solid waste (or treated sludge) suitable for disposal or reuse (usually as farm fertilizer).
Sewage is created by residential, institutional, and commercial and industrial establishments and includes household waste liquid from toilets, baths, showers, kitchens, sinks and so forth that is disposed of via sewers. In many areas, sewage also includes liquid waste from industry.
Sewage can be treated close to where it is created (in septic tanks, bio-fitter’s or aerobic treatment systems), or collected and transported via a network of pipes and pump stations to a municipal treatment plant.
Sewage collection and treatment is typically subject to local, state and federal regulations and standards. Industrial sources of wastewater often require specialized treatment processes (see Industrial wastewater treatment).
Conventional sewage treatment may involve three stages, called primary, secondary and tertiary treatment. Primary treatment consists of temporarily holding the sewage in a quiescent basin where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface. The settled and floating materials are removed and the remaining liquid may be discharged or subjected to secondary treatment.
Secondary treatment removes dissolved and suspended biological matter. Secondary treatment is typically performed by indigenous, water-borne micro-organisms in a managed habitat. Secondary treatment may require a separation process to remove the micro­organisms from the treated water prior to discharge or tertiary treatment.
Tertiary treatment is sometimes defined as anything more than primary and secondary treatment. Treated water is sometimes disinfected chemically or physically (for example, by lagoons and microfiltration) prior to discharge into a stream, river, bay, lagoon or wetland, or it can be used for the irrigation of a golf course, green way or park. If it is sufficiently clean, it can also be used for groundwater recharge or agricultural purposes.

i. Pre-treatment removes materials that can be easily collected from the raw wastewater before they damage or clog the pumps and skimmers of primary treatment clarifiers (trash, tree limbs, leaves, etc.).

ii. Screening:
The influent sewage water is screened to remove all large objects carried in the sewage stream. This is most commonly done with an automated mechanically raked bar screen in modern plants serving large populations, whilst in smaller or less modern plants a manually cleaned screen may be used.
The raking action of a mechanical bar screen is typically paced according to the accumulation on the bar screens and/or flow rate. The solids are collected and later disposed in a landfill or incinerated. Bar screens or mesh screens of varying sizes may be used to optimize solids removal. If gross solids are not removed they become entrained in pipes and moving parts.

iii. Grit removal:
Pre-treatment may include a sand or grit channel or chamber where the velocity of the incoming wastewater is adjusted to allow the settlement of sand, grit, stones, and broken glass. These particles are removed because they may damage pumps and other equipment. For small sanitary sewer systems, the grit chambers may not be necessary, but grit removal is desirable at larger plants.

iv. Fat and grease removal:
Fat and grease is removed by passing the sewage through a small tank where skimmers collect the fat floating on the surface. Air blowers in the base of the tank may also be used to help recover the fat as froth. In most plants however, fat and grease removal takes place in the primary settlement tank using mechanical surface skimmers.

v. Primary treatment:
In the primary sedimentation stage, sewage flows through large tanks, commonly called “primary clarifiers” or “primary sedimentation tanks.” The tanks are used to settle sludge while grease and oils rise to the surface and are skimmed off.
Primary settling tanks are usually equipped with mechanically driven scrapers that continually drive the collected sludge towards a hopper in the base of the tank where it is pumped to sludge treatment facilities. Grease and oil from the floating material can sometimes be recovered for saponification.
The dimensions of the tank should be designed to effect removal of a high percentage of the floatables and sludge. A typical sedimentation tank may remove from 60 to 65 per cent of suspended solids, and from 30 to 35 per cent of biochemical oxygen demand (BOD) from the sewage.

vi. Secondary treatment:
Secondary treatment is designed to substantially degrade the biological content of the sewage which is derived from human waste, food waste, soaps and detergent. The majority of municipal plants treat the settled sewage liquor using aerobic biological processes. To be effective, the biota requires both oxygen and food to live.
The bacteria and protozoa consume biodegradable soluble organic contaminants (e.g. sugars, fats, organic short-chain carbon molecules, etc.) and bind much of the less soluble fractions into floe. Secondary treatment systems are classified as fixed-film or suspended-growth systems.
Fixed-film or attached growth systems include trickling filters and rotating biological contactors, where the biomass grows on media and the sewage passes over its surface. Suspended-growth systems include activated sludge, where the biomass is mixed with the sewage and can be operated in a smaller space than fixed-film systems that treat the same amount of water.
However, fixed-film systems are more able to cope with drastic changes in the amount of biological material and can provide higher removal rates for organic material and suspended solids than suspended growth systems.

vii. Rotating biological contactors:
Rotating biological contactors (RBCs) are mechanical secondary treatment systems, which are robust and capable of withstanding surges in organic load. RBCs were first installed in Germany in 1960 and have since been developed and refined into a reliable operating unit.
The rotating disks support the growth of bacteria and micro-organisms present in the sewage, which break down and stabilize organic pollutants. To be successful, micro-organisms need both oxygen to live and food to grow. Oxygen is obtained from the atmosphere as the disks rotate. As the micro-organisms grow, they build up on the media until they are sloughed off due to shear forces provided by the rotating discs in the sewage.
Effluent from the RBC is then passed through final clarifiers where the micro-organisms in suspension settle as sludge. The sludge is withdrawn from the clarifies for further treatment. A functionally similar biological filtering system has become popular as part of home aquarium filtration and purification.
The aquarium water is drawn up out of the tank and then cascaded over a freely spinning corrugate fiber-mesh wheel before passing through a media filter and back into the aquarium. The spinning mesh wheel develops a bio film coating of microorganisms that feed on the suspended wastes in the aquarium water and are also exposed to the atmosphere as the wheel rotates. This is especially good at removing waste urea and ammonia urinated into the aquarium water by the fish and other animals.

viii. Biological aerated filters:
The removal of nitrogen is effected through the biological oxidation of nitrogen from ammonia (nitrification) to nitrate, followed by De-nitrification, the reduction of nitrate to nitrogen gas. Nitrogen gas is released to the atmosphere and thus removed from the water. Nitrification itself is a two-step aerobic process, each step facilitated by a different type of bacteria.
The oxidation of ammonia (NH₃) to nitrite (NO₃) is most often facilitated by Nitrosomonas spp. (nitroso referring to the formation of a nitroso functional group). Nitrite oxidation to nitrate (NO₃), though traditionally believed to be facilitated by Nitrobacter spp. (nitro referring the formation of a nitro functional group), is now known to be facilitated in the environment almost exclusively by Nitrospira spp.De-nitrification requires anoxic conditions to encourage the appropriate biological communities to form. It is facilitated by a wide diversity of bacteria.

ix. Secondary sedimentation:
The final step in the secondary treatment stage is to settle out the biological floe or filter material through a secondary clarifier and to produce sewage water containing low levels of organic material and suspended matter.

x. Tertiary treatment:
The purpose of tertiary treatment is to provide a final treatment stage to raise the effluent quality before it is discharged to the receiving environment (sea, river, lake, ground, etc.). More than one tertiary treatment process may be used at any treatment plant. If disinfection is practiced, it is always the final process. It is also called “effluent polishing.”

xi. Sand filtration removes much of the residual suspended matter. Filtration over activated carbon, also called carbon adsorption, removes residual toxins.

xii. Lagooning provides settlement and further biological improvement through storage in large man-made ponds or lagoons. These lagoons are highly aerobic and colonization by native macrophytes, especially reeds, is often encouraged. Small filter feeding invertebrates such as Daphnia and species of Rotifera greatly assist in treatment by removing fine particulates.

Sludge treatment & disposal: 

i. Anaerobic digestion:
Anaerobic digestion is a bacterial process that is carried out in the absence of oxygen. The process can either be thermophilic digestion, in which sludge is fermented in tanks at a temperature of 55°C, or mesophilic, at a temperature of around 36°C.
Though allowing shorter retention time (and thus smaller tanks), thermophilic digestion is more expensive in terms of energy consumption for heating the sludge. Anaerobic digestion is the most common (mesophilic) treatment of domestic sewage in septic tanks, which normally retain the sewage from one day to two days, reducing the BOD by about 35 to 40 percent.
This reduction can be increased with a combination of anaerobic and aerobic treatment by installing Aerobic Treatment Units (ATUs) in the septic tank. One major feature of anaerobic digestion is the production of biogas (with the most useful component being methane), which can be used in generators for electricity production and/or in boilers for heating purposes.
ii. Aerobic digestion:
Aerobic digestion is a bacterial process occurring in the presence of oxygen. Under aerobic conditions, bacteria rapidly consume organic matter and convert it into carbon dioxide. The operating costs used to be characteristically much greater for aerobic digestion because of the energy used by the blowers, pumps and motors needed to add oxygen to the process. Aerobic digestion can also be achieved by using diffuser systems or jet aerators to oxidize the sludge.
iii. Composting:
Composting is also an aerobic process that involves mixing the sludge with sources of carbon such as sawdust, straw or wood chips. In the presence of oxygen, bacteria digest both the wastewater solids and the added carbon source and, in doing so, produce a large amount of heat.
iv. Incineration:
Incineration of sludge is less common because of air emissions concerns and the supplemental fuel (typically natural gases or fuel oil) required to burn the low calorific value sludge and vaporize residual water.
Stepped multiple hearth incinerators with high residence time and fluidized bed incinerators are the most common systems used to combust wastewater sludge. Co-firing in municipal waste-to-energy plants is occasionally done, this option being less expensive assuming the facilities already exist for solid waste and there is no need for auxiliary fuel.
v. Sludge disposal:
When a liquid sludge is produced, further treatment may be required to make it suitable for final disposal. Typically, sludge’s are thickened (dewatered) to reduce the volumes transported off-site for disposal.
There is no process which completely eliminates the need to dispose of bio-solids. There is, however, an additional step some cities are taking to superheat sludge and convert it into small pelletized granules that are high in nitrogen and other organic materials.

Ecosystems - Essay on Ecosystem

Ecosystems

An ecosystem is a segment of nature consisting of a community of living beings and the physical environment both interacting and exchanging materials between them.

The two components of nature, organisms and the environment are not only highly complex and dynamic but also interdependent, mutually reactive and interrelated. Ecology deals with the various principles which govern relationships between organisms and their environment.

At about the same time the English naturalist, St. George Jackson Mivart coined the term hexicology, and defined as the study of the relations which exist between the organisms and their environment with respect to the nature of the locality, the temperature and the amounts of light, and their relations to other organisms as enemies, rivals, or accidental and involuntary benefactors. Thus, ecology is literally the study of organisms and their relationship with environment.

Scope and Importance:

Taylor (1936), in an attempt to define ecology, has very rightly pointed out that scope of ecology by stating that ecology is the science of all the relations of ecosystems, all organisms to all their environments.

Ecology plays an important role in agriculture crop rotation, weed control, management of grasslands, range management forestry, biological surveys, pest control, fishery biology, and in the conservation of soil, wildlife, forest, water supplies, water bodies like rivers, lakes and ponds,

Ecosystem is defined as a dynamic entity composed of a biological community and its associated abiotic environment. Often the dynamic interactions that occur within an ecosystem are numerous and complex.

Ecosystems are also always undergoing alterations to their bio-tic and antibiotic components. Some of these alterations begin first with a change in the state of one component of the ecosystem, which then cascades and sometimes amplifies into other components because of relationships.

Ecosystem Productivity:

The productivity in an ecosystem are of two kinds—primary productivity and secondary productivity. The primary productivity of an ecosystem is the rate at which organic matter is produced during photosynthesis. During the process of production and consumption, energy is passed along, or flows, from one organism to another. For example, solar energy is converted to chemical energy within the leaves of green plants. The leaves can then be eaten by some herbivore, and the herbivore may, in turn, be eaten by a carnivore.

Consider a hypothetical ecosystem that receives 1,000 Kilocalories of light energy in a given day. Most of this energy is not absorbed at all. Some is simply reflected back into space. Of the energy that is absorbed, most is stored as heat or used for evaporation of water. A small amount is assimilated by plants.

Energetic Efficiency :

The movement of energy through the community depends on the efficiency with which organisms consume their food resources and convert them into biomass. This efficiency is referred to as the food chain or ecological efficiency.

Ecological efficiency are determined by both internal, physiological characteristics of organisms and their external, ecological relationships to the environment. To understand the biological basis of ecological efficiency, one must dissect the individual link of the food chain into its component parts

India - My Country essay

India - My Country

India is a big country with second largest population and seventh largest land area in the world. The population of India is more than 1.2 billion.
There are 29 states mainly on the basis of linguistic lines. There are wide variety of languages and that of culture, festivals, dress and mode of living is even greater.There lies cultural unity among Hindus, Muslims, Sikhs, Christians, Buddhists and other communities in India.

Geography

On the north of India there are Himalayan mountain ranges. It protects India as its guardian. There is Indian Ocean, Bay of Bengal and Arabian Ocean in the south, south-east and south-west respectively.
The highest point in India lies in the Kanchenjunga mountains. The longest river is River Ganga.

National

India has a three-colored national flag. The three colors are saffron, white and green. The Ashok Chakra in the center of the India flag denotes righteousness.
The national anthem and song are “Jana Gana Mana” and “Vande Mataram” respectively. In the National Emblem, there are four lions standing back to back denoting courage and strength.

History

The civilization of Harappa and Indus Valley in India is believed to be more than 4000 years old. The Rig Vedic period started at around 1700 B.C. India was highly civilized and well developed by 500 B.C.  India witnessed a golden period under Gupta Empire during 320 A.D and 500 A.D. The Delhi Sultanate ruled from 1206 to 1526. The Mughal period was from 1526 to 1857. Bahadur Shah II was the last Mughal Emperor. The British ruled thereafter. India got its independence on 15th August, 1947.

Religion of India

Several religions originated from India such as Hinduism, Buddhism, Sikhism and Jainism. Islam, Christianity and other religions also found its place in India.

Language

As per Article 343 of the Constitution of India, India's official languages shall be Standard Hindi (the dialect known as khadi boli) written in the Devanagari script, and English.

These are the official languages of the Union of India.

There are many regional languages and several other local dialects. These languages mainly belong to Indo-Aryan and Dravadian family. There are 22 official languages in India.Currently there are 22 scheduled languages in India Assamese, Bengali, Bodo, Dogri, Gujarati, Hindi, Kannada, Kashmiri, Konkani, Maithili, Malayalam, Meitei (Manipuri), Marathi, Nepali, Odia, Punjabi, Sanskrit, Santali, Sindhi, Tamil, Telugu, Urdu

Festivals

The major Hindu Festivals are Diwali, Durga puja, Dussehra, Raksha Bandhan, Holi etc. The major Muslim festivals are Ramadan, Eid, Muharram, etc. The major Sikh festivals are Holla Mohalla, Vaisakhi, Guru Nanak Gurpurab, etc. The Christians celebrate Christmas, Good Friday, Easter, St. Valentine’s Day, etc.

Some Important Cities

New Delhi is the Capital city of India. The other metro cities are Kolkata, Mumbai, Chennai. The other major cities are Bangalore, Mysore, Chandigarh, Raipur, etc.

Indian Culture

Indian Culture has a rich history of more than four thousand years. The national culture of India aims for perfect blend of Hinduism, Islam, Buddhism, Christianity, Sikhism, and other wide variety of regional cultures.