Recycling and reuse of wastewater will do away with the need of using fresh water. The extent to which the processes involved in wastewater treatment are cost effective and easy to follow will act as an impetus. Hence discussing about the processes involved in wastewater treatment and their relative merits and demerits becomes pertinent.
Like Sedimentation tanks, Septic tanks (Imhoff tanks) can play a major role in the process of removing solids from wastewater.
Designed by Karl Imhoff of Germany, an Imhoff tank is an improved septic tank in which the incoming sewage or influent is not allowed to get mixed up with the sludge produced. Also, the outgoing sewage or effluent is not allowed to carry with it any large amount of the suspended matter as in the case of a septic tank.
**Construction and operational features**
It is a double chamber tank, the upper chamber is called the sedimentation tank or flowing-through chamber, through which sewage flows at a very low velocity; the lower chamber is the digestion chamber in which anaerobic or septic decomposition occurs.
Solids of the sewage settle to the bottom of the sedimentation chamber through the sloping bottom walls (slope 5 vertical to 4 horizontal). They are made to fall in the digestion chamber through an entrance slot at the lowest point of the sedimentation chamber. The slot is trapped or overlapped in such a way that the gases generated in the digestion chamber cannot enter the sedimentation chamber.
A gas vent, also called scum chamber is provided with the digestion chamber to take care of the gases escaping to the surface. The chief gas is methane (CH ) having a considerable fuel value and may, therefore, be separately collected for use. In order to prevent particles of sludge or scum from penetrating into the sedimentation chamber, the sludge and scum must be maintained at a distance of at least 45 cm below and above the slots respectively. The free or clear zone is called neutral zone.
The digestion chamber is made up of two or three inverted cones called hoppers with sides sloping (1 : 1) so as to concentrate the sludge at the bottom of the hopper. The sludge is removed periodically through sludge-pipe, the flow being under a hydrostatic pressure of 1.2 to 1.8 m. All the sludge is not removed, only the lower layers which are completely decomposed are withdrawn, leaving some sludge to keep the tank seeded with anaerobic bacteria.
To permit uniform distribution of settled solids throughout the length of the digestion chamber, so as to utilize the storage capacity in the greatest measure, arrangements for reversing the direction of flow through the tanks are commonly made.
**Merits**
Imhoff tanks combine the advantages of both the septic and sedimentation tanks and, as such find use in case of small treatment plants requiring only preliminary treatment. They have better economy and give good results without skilled attention with minimum problems of sludge disposal.
**Demerits**
(i) Greater depth means greater costs and especially where excavation is to be done in quick sand or solid rock, they become uneconomical. (ii) Unsuitable to acidic wastewater exists. (iii) There's no adequate control over their operation. This makes them unsuitable for use in large treatment plants where separate sludge digestion tanks are preferred.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater Treatment is fast becoming popular, as it is comprehensive and well-researched. To learn all about wastewater treatment, click: http://www.all-about-wastewater-treatment.com .
This has also been published as: wastewater treatment plant on Wordpress
Friday, August 22, 2008
Tuesday, August 19, 2008
Water Quality and Pollution -- The Raison D'etre For Wastewater Treatment
Water as a chemical:
Pure water is a compound of hydrogen and oxygen. It is colorless, odorless and tasteless. It exists as liquid at ambient temperature.
Water - what it contains:
Water has both living and non-living organisms and substances in it. The living organisms can be further subdivided into macro- and micro- organisms. Macro organisms, which are biological, are those that are visible to the naked eye or can be seen through a microscope.
In contrast, microbiological micro-organisms are not visible even through a microscope.
Water quality criteria:
The quality of water is a function of several factors. These include its source, location, geological conditions, depth of water level, seasonal changes, domestic activity, agricultural activity, industrial activity, etc.
Excessive exploitation of natural resources and the use of technological advances with no concern for the ecology adversely affect air, water and land, alike.
The substances present in water can be classified as floating matter and suspended matter. Floating matter takes the form of leaves, twigs, dead organisms and algae. Examples of suspended matter present in water are silt, clay, decaying vegetable matter, bacteria, microorganisms, algae, insoluble iron, and manganese.
There are also dissolved impurities which include gases like carbon dioxide, hydrogen sulfide, etc., as well as chemical substances, minerals and salts.
Water sources and water quality:
Water quality differs according to the source. For instance, the turbidity in surface water is usually high, while ground water and sub-soil water on river beds are colorless and clear. Again, sub-soil water and ground water are more likely to have totally dissolved solids than surface water. The presence of hardness, alkalinity, fluoride, chloride and nitrate are all more likely in ground water than in surface level or sub-soil water. Bacteria and organic matter are more likely to be found in surface level water than in ground or sub-soil water.
Water pollution:
Water is essential for living, just like air. One may live without air for a few minutes. But, without water, one is sure to die within a few days. We all know about air pollution. Water pollution is also the gift of modern man to posterity.
How water gets polluted:
Pollution of water sources is caused by sewage and sullage from human settlements, dumping of solid wastes, wastewater from industries, and chemicals in agriculture. When foreign materials harmful to us are added, the water is sure to get polluted. Two readily such foreign materials that come readily to mind are industrial waste and sewage from cities.
Why we need good water:
We need good water for drinking by humans and animals, supporting aquatic life, generating electric power, irrigating crops in fields, and recreation such as water-based sports.
Thus the need for wastewater treatment can never be overemphasized.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater Treatment is fast becoming popular, as it is comprehensive and well-researched. To know more about wastewater treatment, click here: http://www.all-about-wastewater-treatment.com .
This has also been published as: wastewater treatment on Wordpress
Pure water is a compound of hydrogen and oxygen. It is colorless, odorless and tasteless. It exists as liquid at ambient temperature.
Water - what it contains:
Water has both living and non-living organisms and substances in it. The living organisms can be further subdivided into macro- and micro- organisms. Macro organisms, which are biological, are those that are visible to the naked eye or can be seen through a microscope.
In contrast, microbiological micro-organisms are not visible even through a microscope.
Water quality criteria:
The quality of water is a function of several factors. These include its source, location, geological conditions, depth of water level, seasonal changes, domestic activity, agricultural activity, industrial activity, etc.
Excessive exploitation of natural resources and the use of technological advances with no concern for the ecology adversely affect air, water and land, alike.
The substances present in water can be classified as floating matter and suspended matter. Floating matter takes the form of leaves, twigs, dead organisms and algae. Examples of suspended matter present in water are silt, clay, decaying vegetable matter, bacteria, microorganisms, algae, insoluble iron, and manganese.
There are also dissolved impurities which include gases like carbon dioxide, hydrogen sulfide, etc., as well as chemical substances, minerals and salts.
Water sources and water quality:
Water quality differs according to the source. For instance, the turbidity in surface water is usually high, while ground water and sub-soil water on river beds are colorless and clear. Again, sub-soil water and ground water are more likely to have totally dissolved solids than surface water. The presence of hardness, alkalinity, fluoride, chloride and nitrate are all more likely in ground water than in surface level or sub-soil water. Bacteria and organic matter are more likely to be found in surface level water than in ground or sub-soil water.
Water pollution:
Water is essential for living, just like air. One may live without air for a few minutes. But, without water, one is sure to die within a few days. We all know about air pollution. Water pollution is also the gift of modern man to posterity.
How water gets polluted:
Pollution of water sources is caused by sewage and sullage from human settlements, dumping of solid wastes, wastewater from industries, and chemicals in agriculture. When foreign materials harmful to us are added, the water is sure to get polluted. Two readily such foreign materials that come readily to mind are industrial waste and sewage from cities.
Why we need good water:
We need good water for drinking by humans and animals, supporting aquatic life, generating electric power, irrigating crops in fields, and recreation such as water-based sports.
Thus the need for wastewater treatment can never be overemphasized.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater Treatment is fast becoming popular, as it is comprehensive and well-researched. To know more about wastewater treatment, click here: http://www.all-about-wastewater-treatment.com .
This has also been published as: wastewater treatment on Wordpress
Monday, August 18, 2008
Why Must We Treat Waste Water?
It's not a widely published fact, but that's no reason why it should not be a widely acknowledged problem. The world's supply of fresh water is slowly running dry. Forty percent of the world's population is already reeling under the problem of scarcity.
Most of the diseases plaguing the world are water-borne. And while there is a child born every eight seconds in America, there is a life taken every eight seconds by some water-borne disease in other parts of the world.
Is it the lopsided distribution of fresh water that is causing climate change, or is it the climatic change that is causing this lopsided distribution? The fact is that there is a significant climate change, and as a consequence of this change, some regions are becoming drier while others are getting wetter. Some parts of the world are experiencing greater desertification, while others are suffering category 4 and 5 hurricanes.
According to the United Nations, water scarcity is amongst the most serious crises facing the world. And things are only getting worse.
Uzbekistan and Kazakhstan of the erstwhile USSR, Chile, Mexico, Paraguay, Argentina, Peru and Brazil in Latin America, parts of China and the Middle East especially Iran, and more than 25 countries of Africa are all suffering from varying degrees of desertification.
Global weather has gone awry. It is making poor countries poorer. Countries that are already facing drought and famine are getting less and less water. For how long can these countries run on dry?
Nowhere is the situation worse than in Africa. Almost 40 million people in 19 countries are facing imminent food shortage. Much of the livestock there will perish. The growing water shortage will make food scarcer, potable water less accessible and water-borne diseases even more rampant. And the number of people who will suffer all this is expected to touch more than 500 million by the 2025. And the global consequence: A greater dependence on international aid.
And this problem is not just limited to Africa. No one can tell which part of the globe will be next.
Blame this on nature. It's most convenient. But fact is, much of the blame belongs to increasing consumption and improper usage.
At every opportunity nature reminds us by what it does and what it doesn't, that it is one of the forces we have little control over. So there's no way we can stop the rain or start it. But what we can do is become more water-efficient - get more from every gallon of water. And the only way to do this is to recycle and reuse waste water. Water is the giver of life. It has no substitute. And every drop counts!
Many believe that the next world war is likely to be fought on the issue of water. Even though the world is two-thirds water, most of it is not potable, and much of it is not usable for any other purpose as well.
And we are busy consuming and contaminating whatever is left of it, as if it were a non-depletable resource. This article is one of several aimed at identifying ways to make the best use of water, an increasingly scarce resource, by recovering it from wastewater, whether we intend to reuse the water so recovered or let it just charge our ground water reserves.
This is aimed at a wide cross-section of people involved in taking corrective action across the world policy makers, administrators, municipal engineers & scientists, engineers & administrators in industries vested with the responsibility of wastewater treatment and management, industrial & residential property builders, academics, students and just about everyone who cares about posterity.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater is fast becoming popular, as it is comprehensive and well-researched. Read his blog at: http://www.all-about-wastewater-treatment.com .
This has also been published as: Wastewater on Tumblr
Most of the diseases plaguing the world are water-borne. And while there is a child born every eight seconds in America, there is a life taken every eight seconds by some water-borne disease in other parts of the world.
Is it the lopsided distribution of fresh water that is causing climate change, or is it the climatic change that is causing this lopsided distribution? The fact is that there is a significant climate change, and as a consequence of this change, some regions are becoming drier while others are getting wetter. Some parts of the world are experiencing greater desertification, while others are suffering category 4 and 5 hurricanes.
According to the United Nations, water scarcity is amongst the most serious crises facing the world. And things are only getting worse.
Uzbekistan and Kazakhstan of the erstwhile USSR, Chile, Mexico, Paraguay, Argentina, Peru and Brazil in Latin America, parts of China and the Middle East especially Iran, and more than 25 countries of Africa are all suffering from varying degrees of desertification.
Global weather has gone awry. It is making poor countries poorer. Countries that are already facing drought and famine are getting less and less water. For how long can these countries run on dry?
Nowhere is the situation worse than in Africa. Almost 40 million people in 19 countries are facing imminent food shortage. Much of the livestock there will perish. The growing water shortage will make food scarcer, potable water less accessible and water-borne diseases even more rampant. And the number of people who will suffer all this is expected to touch more than 500 million by the 2025. And the global consequence: A greater dependence on international aid.
And this problem is not just limited to Africa. No one can tell which part of the globe will be next.
Blame this on nature. It's most convenient. But fact is, much of the blame belongs to increasing consumption and improper usage.
At every opportunity nature reminds us by what it does and what it doesn't, that it is one of the forces we have little control over. So there's no way we can stop the rain or start it. But what we can do is become more water-efficient - get more from every gallon of water. And the only way to do this is to recycle and reuse waste water. Water is the giver of life. It has no substitute. And every drop counts!
Many believe that the next world war is likely to be fought on the issue of water. Even though the world is two-thirds water, most of it is not potable, and much of it is not usable for any other purpose as well.
And we are busy consuming and contaminating whatever is left of it, as if it were a non-depletable resource. This article is one of several aimed at identifying ways to make the best use of water, an increasingly scarce resource, by recovering it from wastewater, whether we intend to reuse the water so recovered or let it just charge our ground water reserves.
This is aimed at a wide cross-section of people involved in taking corrective action across the world policy makers, administrators, municipal engineers & scientists, engineers & administrators in industries vested with the responsibility of wastewater treatment and management, industrial & residential property builders, academics, students and just about everyone who cares about posterity.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater is fast becoming popular, as it is comprehensive and well-researched. Read his blog at: http://www.all-about-wastewater-treatment.com .
This has also been published as: Wastewater on Tumblr
Thursday, August 14, 2008
Waste Water Aspects To Ponder - Part Two
In a previous article, I listed some important factors you must take into account before you treat wastewater. These include the presence, in the wastewater, of acidity, alkalinity, hardness, and chloride, as well as the BOD and COD of wastewater. In this article, I have added substantially to the list. Before wastewater treatment begins, the following factors must also be considered.
Ammonia nitrogen:
This is derived from ammonium compounds and organic compounds in wastewater by aerobic or anaerobic digestion. Un-ionized ammonia is toxic to fish life. Free ammonia, in concentration above about 0.2 mg/l can cause fatalities to fish. Ammonia toxicity is not a problem in receiving waters with pH below 8.0. This can be estimated by distillation of wastewater at pH above 9. The ammonia liberated is neutralized in sulfuric acid. The excess sulfuric acid is back titrated with alkali. The estimation of ammonia can be done by any other methods like nesslerization or digestion.
Nitrate nitrogen:
Nitrate nitrogen in drinking water with high nitrate content often causes methemoglobinemia (blue-baby disease) in infants. The maximum concentration should not be allowed to exceed 45 mg/l. Nitrate is reduced to nitrite in digestive system which, in turn, attacks the hemoglobin in infants resulting in methemoglobinemia. Nitrate nitrogen can be estimated by measuring the optical density at 220 nm and 275 nm in spectrophotometer.
Nitrite:
Nitrite can also interact with amine chemically or enzymatically to form nitrosoamines which are carcinogens. This is measured by colorimetric determination using sulfanilamide.
Sulfate:
Sulfate is one of the major anions occurring in natural waters. Sulfates form hard scales in boilers and heat exchangers. Sulfate assumes significance in water and wastewater, as it is associated with odor and sewer-corrosion problems resulting from the reduction of sulfate into hydrogen sulfide under anaerobic conditions. Sulfate in water or wastewater can be estimated by precipitation with barium chloride, acidified with hydrochloric acid.
Phosphates:
Most of the synthetic detergents designed for the household applications contain large amounts of polyphosphates as builders. Many of them contain 12-13% phosphorous or over 50% poly-phosphates. The organisms involved in the biological processes of wastewater treatment require phosphorous for reproduction and synthesis of new cellular material. Phosphorous in wastewater causes eutrophication, which affects transportation in sea/lakes. The presence of phosphorous in wastewater needs to be controlled before it is discharged into the receiving water bodies. Phosphorous present in wastewater can be estimated through colorimetric technique, by adding acidified ammonium molybdate solution to form a molybdophosphate complex.
Nutrients:
Wastewater often contains large amounts of the nutrients like nitrogen and phosphorus in the form of nitrate and phosphate, which promote plant growth. In severe cases, excessive nutrients in receiving waters cause algae and other plants to grow quickly depleting oxygen in the water. Deprived of oxygen, fishes and other aquatic organisms die, emitting foul odors. Nutrients from wastewater have also been linked to ocean "red tides" that poison fishes and cause illness in humans.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on wastewater treatment is fast becoming popular, as it is comprehensive and well-researched. Read his blog at: http://www.all-about-wastewater-treatment.com .
This has also been published as: ammonia nitrogen on Hubpages
Ammonia nitrogen:
This is derived from ammonium compounds and organic compounds in wastewater by aerobic or anaerobic digestion. Un-ionized ammonia is toxic to fish life. Free ammonia, in concentration above about 0.2 mg/l can cause fatalities to fish. Ammonia toxicity is not a problem in receiving waters with pH below 8.0. This can be estimated by distillation of wastewater at pH above 9. The ammonia liberated is neutralized in sulfuric acid. The excess sulfuric acid is back titrated with alkali. The estimation of ammonia can be done by any other methods like nesslerization or digestion.
Nitrate nitrogen:
Nitrate nitrogen in drinking water with high nitrate content often causes methemoglobinemia (blue-baby disease) in infants. The maximum concentration should not be allowed to exceed 45 mg/l. Nitrate is reduced to nitrite in digestive system which, in turn, attacks the hemoglobin in infants resulting in methemoglobinemia. Nitrate nitrogen can be estimated by measuring the optical density at 220 nm and 275 nm in spectrophotometer.
Nitrite:
Nitrite can also interact with amine chemically or enzymatically to form nitrosoamines which are carcinogens. This is measured by colorimetric determination using sulfanilamide.
Sulfate:
Sulfate is one of the major anions occurring in natural waters. Sulfates form hard scales in boilers and heat exchangers. Sulfate assumes significance in water and wastewater, as it is associated with odor and sewer-corrosion problems resulting from the reduction of sulfate into hydrogen sulfide under anaerobic conditions. Sulfate in water or wastewater can be estimated by precipitation with barium chloride, acidified with hydrochloric acid.
Phosphates:
Most of the synthetic detergents designed for the household applications contain large amounts of polyphosphates as builders. Many of them contain 12-13% phosphorous or over 50% poly-phosphates. The organisms involved in the biological processes of wastewater treatment require phosphorous for reproduction and synthesis of new cellular material. Phosphorous in wastewater causes eutrophication, which affects transportation in sea/lakes. The presence of phosphorous in wastewater needs to be controlled before it is discharged into the receiving water bodies. Phosphorous present in wastewater can be estimated through colorimetric technique, by adding acidified ammonium molybdate solution to form a molybdophosphate complex.
Nutrients:
Wastewater often contains large amounts of the nutrients like nitrogen and phosphorus in the form of nitrate and phosphate, which promote plant growth. In severe cases, excessive nutrients in receiving waters cause algae and other plants to grow quickly depleting oxygen in the water. Deprived of oxygen, fishes and other aquatic organisms die, emitting foul odors. Nutrients from wastewater have also been linked to ocean "red tides" that poison fishes and cause illness in humans.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on wastewater treatment is fast becoming popular, as it is comprehensive and well-researched. Read his blog at: http://www.all-about-wastewater-treatment.com .
This has also been published as: ammonia nitrogen on Hubpages
Wednesday, August 13, 2008
Wastewater -- Details To Ponder
There are some important things you must take into account before you begin wastewater treatment.
Acidity:
Can water be acidic in taste? Most natural water, domestic wastewater and many industrial wastewater are buffered by a carbon dioxide-bicarbonate system. Acid waters are of concern because of their corrosive characteristics and the expense involved in removing or controlling the corrosion-producing substances. Mineral acids are measured by titration to a pH of about 3.7.
Alkalinity:
When will the water be alkaline in taste? The alkalinity of natural water is primarily due to the salts of weak acids. Although, weak or strong bases may also contribute. Natural water contains appreciable amounts of carbonate and hydroxide alkalinity. Higher alkaline waters are usually unpalatable. Alkalinity is measured volumetrically by titration with N/50 or 0.020 NH2SO4.
Hardness:
Water is more often hard. Do you agree? Hardness is caused by metallic ions that are capable of reacting with soap to form a precipitate. Calcium bicarbonate, magnesium sulfate, strontium chloride, ferrous nitrate and manganese silicate are the major sources for hardness in wastewater. Hardness is determined using ethylene-di-amine tetra acetic acid (EDTA) or its sodium salts as the titrating agent.
Chloride:
Chloride is a major contributor to the 'total dissolved solids' in water/wastewater. The chloride content of water/wastewater increases as its mineral content increases. Chlorides at a concentration above 1000 mg/l give a salty taste, which is objectionable to many people. Chloride concentration of wastewater is estimated by Mohr's method using silver nitrate with potassium chromate as an indicator.
Biochemical Oxygen Demand (BOD):
The strength of wastewater is judged by BOD. This is defined as the amount of oxygen required by bacteria while stabilizing the organics in wastewater under aerobic conditions, at a particular time and temperature. This can be referred as BOD5, which accounts for 70% of the total BOD. The measurement of BOD is based on the principle: determination of dissolved oxygen content of water/wastewater on the first day and dissolved oxygen content on the fifth day ('5' in BOD5 indicates this). The difference in dissolved oxygen concentrations between first day and fifth day is expressed as BOD of wastewater.
Chemical Oxygen Demand (COD):
What does COD of wastewater mean? This reflects the concentration of organic compounds present in wastewater. This measures the total quantity of oxygen required for oxidation of organics into carbon dioxide and water. The oxidation of organics in wastewater is carried out by the action of strong oxidizing agents. Generally, acidified potassium dichromate is used as an oxidizing agent for the determination of COD. Silver sulfate is used as the catalyst for the oxidation of organics in wastewater during the determination of COD. Mercuric sulfate is added to control the interference of chloride in the estimation of COD. The method consists of adding a known concentration of potassium dichromate (added with silver sulfate and mercuric sulfate) into wastewater containing organic compounds to be oxidized in the heating condition. After oxidation, the excess potassium dichromate is back titrated with ferrous ammonium sulfate.
Importance of COD:
Estimation of COD expresses the total concentration of organics present in the waste water. This measures approximately the theoretical oxygen demand of wastewater. The determination accounts for about 95% of the organic concentration in wastewater. This forms about 1.43 times the BOD of wastewater. BOD to COD ratio reveals the treatability of wastewater. If the ratio of BOD/COD is above 0.5, the wastewater is considered to be highly biodegradable. If the ratio is less than 0.3, the wastewater is deemed to undergo a chemical treatment before the routine biological treatment.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on waste water is fast becoming popular, as it is comprehensive and well-researched. Read his blog at: http://www.all-about-wastewater-treatment.com .
This has also been published as: wastewater on Wordpress
Acidity:
Can water be acidic in taste? Most natural water, domestic wastewater and many industrial wastewater are buffered by a carbon dioxide-bicarbonate system. Acid waters are of concern because of their corrosive characteristics and the expense involved in removing or controlling the corrosion-producing substances. Mineral acids are measured by titration to a pH of about 3.7.
Alkalinity:
When will the water be alkaline in taste? The alkalinity of natural water is primarily due to the salts of weak acids. Although, weak or strong bases may also contribute. Natural water contains appreciable amounts of carbonate and hydroxide alkalinity. Higher alkaline waters are usually unpalatable. Alkalinity is measured volumetrically by titration with N/50 or 0.020 NH2SO4.
Hardness:
Water is more often hard. Do you agree? Hardness is caused by metallic ions that are capable of reacting with soap to form a precipitate. Calcium bicarbonate, magnesium sulfate, strontium chloride, ferrous nitrate and manganese silicate are the major sources for hardness in wastewater. Hardness is determined using ethylene-di-amine tetra acetic acid (EDTA) or its sodium salts as the titrating agent.
Chloride:
Chloride is a major contributor to the 'total dissolved solids' in water/wastewater. The chloride content of water/wastewater increases as its mineral content increases. Chlorides at a concentration above 1000 mg/l give a salty taste, which is objectionable to many people. Chloride concentration of wastewater is estimated by Mohr's method using silver nitrate with potassium chromate as an indicator.
Biochemical Oxygen Demand (BOD):
The strength of wastewater is judged by BOD. This is defined as the amount of oxygen required by bacteria while stabilizing the organics in wastewater under aerobic conditions, at a particular time and temperature. This can be referred as BOD5, which accounts for 70% of the total BOD. The measurement of BOD is based on the principle: determination of dissolved oxygen content of water/wastewater on the first day and dissolved oxygen content on the fifth day ('5' in BOD5 indicates this). The difference in dissolved oxygen concentrations between first day and fifth day is expressed as BOD of wastewater.
Chemical Oxygen Demand (COD):
What does COD of wastewater mean? This reflects the concentration of organic compounds present in wastewater. This measures the total quantity of oxygen required for oxidation of organics into carbon dioxide and water. The oxidation of organics in wastewater is carried out by the action of strong oxidizing agents. Generally, acidified potassium dichromate is used as an oxidizing agent for the determination of COD. Silver sulfate is used as the catalyst for the oxidation of organics in wastewater during the determination of COD. Mercuric sulfate is added to control the interference of chloride in the estimation of COD. The method consists of adding a known concentration of potassium dichromate (added with silver sulfate and mercuric sulfate) into wastewater containing organic compounds to be oxidized in the heating condition. After oxidation, the excess potassium dichromate is back titrated with ferrous ammonium sulfate.
Importance of COD:
Estimation of COD expresses the total concentration of organics present in the waste water. This measures approximately the theoretical oxygen demand of wastewater. The determination accounts for about 95% of the organic concentration in wastewater. This forms about 1.43 times the BOD of wastewater. BOD to COD ratio reveals the treatability of wastewater. If the ratio of BOD/COD is above 0.5, the wastewater is considered to be highly biodegradable. If the ratio is less than 0.3, the wastewater is deemed to undergo a chemical treatment before the routine biological treatment.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on waste water is fast becoming popular, as it is comprehensive and well-researched. Read his blog at: http://www.all-about-wastewater-treatment.com .
This has also been published as: wastewater on Wordpress
Thursday, August 7, 2008
How To Eliminate Solid Impurities From Wastewater
Sewage treatment has taken on a different dimension today, against the backdrop of the risk of fresh water sources running dry. Wastewater is constituted of storm-water, water used for varied purposes, and sewage, enveloping the community.
Most urban social groups produce sewage from both domestic and nondomestic origins. Unless duly processed, wastewater can cause illness or disease to the community and damage the environment.
Here I have discussed solids removal from wastewater. How can we remove solids sinking to the bottom from the sewage?
Easy. Via a settling tank. It is made up of the following units:
(a) Sedimentation tanks: either chemical or plain precipitation
(b) Septic (Imhoff) tanks
(c) Sludge digestion tanks
**Sedimentation tanks**
This process is implemented with the aim of eliminating suspended organic and mineral matter from wastewater. After it has been subjected to go past screens and abrasive particles chamber. These are the units in which sedimentation takes place. The less heavy sewage solids of organic origin, which settle down in the sedimentation tanks, are labelled as sludge. Meanwhile the wastewater that has been partly cleared by the settling in of the solid particles is called the effluent. Both sludge and effluent should be further treated to render them lasting and not objectionable.
The settling down of the solids can be due to flocculation, gravity, or aggregation of sewage-particles. If coagulating chemicals are not deployed in the sewage, the tanks are termed as ordinary sedimentation tanks. Otherwise, if chemicals are made use of for bringing the finer congealed and suspended solids into masses of large volume, these are then termed chemical precipitation tanks. Chemicals addition is resorted to, to hasten the settling down process. The chemicals used are alum, lime, ferric chloride, ferric sulphate, chlorinated copper etc.
**Types of sedimentation tanks**
Sedimentation is effected in either vertical-flow or horizontal-flow tanks. The horizontal-flow tanks are normally rectangular while the others are normally circular.
In a 4 walled right angled tank, sewage flows in steadily at one side and flows out at the opposite end, generally above a small breakwater. Slush is withdrawn physically and dumped into sludge-digestion tanks. The scum formed at the surface is withdrawn by the mechanical scraper, with the assistance of a second blade termed skimmer, via a scum receptacle.
In the case of a circular and upward-flow tank, sewage flows in at the centre, rises upwardly to be pulled out by steadily flowing over a weir on the boundary. That is assembled on the surface. Such tanks are particularly designed to avail of the theory of flocculation. By the aid of which, fine congealed granules are gathered into wooly masses of large size, that are settled with ease as slush on the bottom of the tank.
Mechanical blades gather the slush, accumulating it at the centre, from which place it is withdrawn for further treatment. The sediment removed effluent running over the weir in the outlet is accumulated in a pipe in the outlet for further treatment.
When only primary sewage is to be processed in the tanks being considered, They might well be ordinarily labelled as primary settling tanks or primary clarifiers.
Meanwhile when sewage is marked for treatment at a second level, as in trickling filters or aeration tanks, similar tanks may therefore be labelled as secondary settling tanks or secondary clarifiers.
**Design criteria for primary sedimentation tank**
As with the sedimentation tanks in water supply, the volume treatable is decided as per the space of incoming sewage and the required settling of solids period. The factors are:
(i) period of detention: 1 to 3 hours. Longer periods result in higher efficiency than shorter periods, but too lengthy a period may cause septicemia and should not be allowed.
(ii) velocity of flow: about 30 cm square/min.
(iii) surface loading: you might see that the overall range of surface loading from thirty-thousand to forty-thousand l / m / day is in conformity withconforms with that used in case of horizontal & vertical flow sedimentation tanks.
(iv) depth of liquid of settling tanks cleaned mechanically should not be less than 2.1 m. And for the final clarifier for clarified sludge, 2.4 meters or above.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on "Wastewater Treatment" is fast becoming popular, as it is comprehensive and well-researched.
To learn all about diseases caused by wastewater, click: http://www.all-about-wastewater-treatment.com .
This has also been published as: methods of cleaning water on Zimbio
Most urban social groups produce sewage from both domestic and nondomestic origins. Unless duly processed, wastewater can cause illness or disease to the community and damage the environment.
Here I have discussed solids removal from wastewater. How can we remove solids sinking to the bottom from the sewage?
Easy. Via a settling tank. It is made up of the following units:
(a) Sedimentation tanks: either chemical or plain precipitation
(b) Septic (Imhoff) tanks
(c) Sludge digestion tanks
**Sedimentation tanks**
This process is implemented with the aim of eliminating suspended organic and mineral matter from wastewater. After it has been subjected to go past screens and abrasive particles chamber. These are the units in which sedimentation takes place. The less heavy sewage solids of organic origin, which settle down in the sedimentation tanks, are labelled as sludge. Meanwhile the wastewater that has been partly cleared by the settling in of the solid particles is called the effluent. Both sludge and effluent should be further treated to render them lasting and not objectionable.
The settling down of the solids can be due to flocculation, gravity, or aggregation of sewage-particles. If coagulating chemicals are not deployed in the sewage, the tanks are termed as ordinary sedimentation tanks. Otherwise, if chemicals are made use of for bringing the finer congealed and suspended solids into masses of large volume, these are then termed chemical precipitation tanks. Chemicals addition is resorted to, to hasten the settling down process. The chemicals used are alum, lime, ferric chloride, ferric sulphate, chlorinated copper etc.
**Types of sedimentation tanks**
Sedimentation is effected in either vertical-flow or horizontal-flow tanks. The horizontal-flow tanks are normally rectangular while the others are normally circular.
In a 4 walled right angled tank, sewage flows in steadily at one side and flows out at the opposite end, generally above a small breakwater. Slush is withdrawn physically and dumped into sludge-digestion tanks. The scum formed at the surface is withdrawn by the mechanical scraper, with the assistance of a second blade termed skimmer, via a scum receptacle.
In the case of a circular and upward-flow tank, sewage flows in at the centre, rises upwardly to be pulled out by steadily flowing over a weir on the boundary. That is assembled on the surface. Such tanks are particularly designed to avail of the theory of flocculation. By the aid of which, fine congealed granules are gathered into wooly masses of large size, that are settled with ease as slush on the bottom of the tank.
Mechanical blades gather the slush, accumulating it at the centre, from which place it is withdrawn for further treatment. The sediment removed effluent running over the weir in the outlet is accumulated in a pipe in the outlet for further treatment.
When only primary sewage is to be processed in the tanks being considered, They might well be ordinarily labelled as primary settling tanks or primary clarifiers.
Meanwhile when sewage is marked for treatment at a second level, as in trickling filters or aeration tanks, similar tanks may therefore be labelled as secondary settling tanks or secondary clarifiers.
**Design criteria for primary sedimentation tank**
As with the sedimentation tanks in water supply, the volume treatable is decided as per the space of incoming sewage and the required settling of solids period. The factors are:
(i) period of detention: 1 to 3 hours. Longer periods result in higher efficiency than shorter periods, but too lengthy a period may cause septicemia and should not be allowed.
(ii) velocity of flow: about 30 cm square/min.
(iii) surface loading: you might see that the overall range of surface loading from thirty-thousand to forty-thousand l / m / day is in conformity withconforms with that used in case of horizontal & vertical flow sedimentation tanks.
(iv) depth of liquid of settling tanks cleaned mechanically should not be less than 2.1 m. And for the final clarifier for clarified sludge, 2.4 meters or above.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on "Wastewater Treatment" is fast becoming popular, as it is comprehensive and well-researched.
To learn all about diseases caused by wastewater, click: http://www.all-about-wastewater-treatment.com .
This has also been published as: methods of cleaning water on Zimbio
Tuesday, August 5, 2008
Everything You Wish To Know Regarding Elimination of Suspended Solids From Sewage Water, Employing I
Recycling and reusing wastewater will do away with the indispensability of consuming virgin water. The extent to which the procedures comprising wastewater treatment are cost efficient and easily followed will give a kick start to using water treatment. Hence talking about the procedures occurring in sewage treatment and their pros and cons, becomes relevant.
Like Sedimentation tanks, Septic tanks (Imhoff tanks) can be largely instrumental in the process of removing solids from wastewater.
Conceived by Karl Imhoff of Germany, an Imhoff tank is a bettered septic tank in which the sewage flowing in is not assigned to get blended with the mud brought forth. Also, the outgoing sewage or effluent is not assigned to transmit any substantial quantity of the suspended matter as with a septic tank, featureswise.
**Building and Functional features**
It comprises a double chamber tank. The upper chamber is termed the accumulation of gravel tank or a stream or current chamber, through which sewage flows at a very low speed; the bottom chamber comprises the decomposing chamber where oxygenless or infected disintegration happens.
Solid matters in the sewage settle to the bottom of the flowing-through chamber beyond the slanting lower walls (slope 5 vertical to 4 horizontal). They are propelled to drop in the digestion chamber beyond an elongated aperture at the bottommost part of the upper chamber. The aperture is provided with an airtrap by which the gaseous fluids produced in the bottom chamber cant escape into the upper chamber.
A gas vent, also called, scum chamber is provided with the bottom chamber to remove the vapors going up to the surface. The main gas is methane having a sizeable calorific value and may, therefore be separately collected for use. To avert pieces of scum or mud from penetrating into the top chamber, the mire and scum must be maintained at a space of minimum 45 cm below and above the slots, respectively. The clear or zone free of obstructions is termed neutral zone.
The digestion chamber is made up of two or three cones turned upside down termed hoppers, with sides sloping (1 : 1) so as to accumulate the mire at the bottom of the hopper. The mud is withdrawn now and then through a sludge-pipe, the stream being kept under a water pressure of 1.2 to 1.8 m. All of the mud is not removed, only the lower layers which have rotted completely. Some mud is kept behind to maintain the tank laced with anaerobic bacteria.
To permit uniform distribution sunk solid matter over all areas of the bottom chamber, so as to make use of the ample storage capacity in the greatest measure, preparations for changing the line of flow at every part of the tanks, are normally put forth.
**Merits**
Imhoff tanks combine the advantages of both the septic and sedimentation tanks and, thereby find use in small size plants requiring only preliminary treatment. They are more economical and give satisfactory results in the absense of close attention and with least problems of getting rid of slush.
**Demerits**
(i) Installing the Imhoff tanks at greater depth spells lack of economy specially where foundations are to be laid in quick sands or solid rocks.
(ii) The above tanks are unsuitable to acidity in wastewater
(iii) Full control is not there over their operation. This makes them unsuitable for using in large size plants where distinct mud digestion tanks are chosen.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater Treatment is fast becoming popular, as it is comprehensive and well-researched.
To learn all about wastewater treatment, click: http://www.all-about-wastewater-treatment.com .
Keywords: wastewater treatment, recycling wastwater, reusing wastwater, recycling and reusing wastewater, removing solids from wastewater, eliminating suspended solids from wastewater, Imhoff tank, Karl Imhoff
This has also been published as: recycling wastwater on Tumblr
Like Sedimentation tanks, Septic tanks (Imhoff tanks) can be largely instrumental in the process of removing solids from wastewater.
Conceived by Karl Imhoff of Germany, an Imhoff tank is a bettered septic tank in which the sewage flowing in is not assigned to get blended with the mud brought forth. Also, the outgoing sewage or effluent is not assigned to transmit any substantial quantity of the suspended matter as with a septic tank, featureswise.
**Building and Functional features**
It comprises a double chamber tank. The upper chamber is termed the accumulation of gravel tank or a stream or current chamber, through which sewage flows at a very low speed; the bottom chamber comprises the decomposing chamber where oxygenless or infected disintegration happens.
Solid matters in the sewage settle to the bottom of the flowing-through chamber beyond the slanting lower walls (slope 5 vertical to 4 horizontal). They are propelled to drop in the digestion chamber beyond an elongated aperture at the bottommost part of the upper chamber. The aperture is provided with an airtrap by which the gaseous fluids produced in the bottom chamber cant escape into the upper chamber.
A gas vent, also called, scum chamber is provided with the bottom chamber to remove the vapors going up to the surface. The main gas is methane having a sizeable calorific value and may, therefore be separately collected for use. To avert pieces of scum or mud from penetrating into the top chamber, the mire and scum must be maintained at a space of minimum 45 cm below and above the slots, respectively. The clear or zone free of obstructions is termed neutral zone.
The digestion chamber is made up of two or three cones turned upside down termed hoppers, with sides sloping (1 : 1) so as to accumulate the mire at the bottom of the hopper. The mud is withdrawn now and then through a sludge-pipe, the stream being kept under a water pressure of 1.2 to 1.8 m. All of the mud is not removed, only the lower layers which have rotted completely. Some mud is kept behind to maintain the tank laced with anaerobic bacteria.
To permit uniform distribution sunk solid matter over all areas of the bottom chamber, so as to make use of the ample storage capacity in the greatest measure, preparations for changing the line of flow at every part of the tanks, are normally put forth.
**Merits**
Imhoff tanks combine the advantages of both the septic and sedimentation tanks and, thereby find use in small size plants requiring only preliminary treatment. They are more economical and give satisfactory results in the absense of close attention and with least problems of getting rid of slush.
**Demerits**
(i) Installing the Imhoff tanks at greater depth spells lack of economy specially where foundations are to be laid in quick sands or solid rocks.
(ii) The above tanks are unsuitable to acidity in wastewater
(iii) Full control is not there over their operation. This makes them unsuitable for using in large size plants where distinct mud digestion tanks are chosen.
Author Bio:
Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater Treatment is fast becoming popular, as it is comprehensive and well-researched.
To learn all about wastewater treatment, click: http://www.all-about-wastewater-treatment.com .
Keywords: wastewater treatment, recycling wastwater, reusing wastwater, recycling and reusing wastewater, removing solids from wastewater, eliminating suspended solids from wastewater, Imhoff tank, Karl Imhoff
This has also been published as: recycling wastwater on Tumblr
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