Volume of wastewater discharge:
Wastewater is a combination of excreta, flushing water and other gray-water or sullage and is much diluted depending on the per capita water uses. The personal water consumption alone is between 200 and 300 liters per day. When the industrial and energy production usage is added to the equation, fresh water usage exceeds 5,000 liters per day on a per capita basis.
The volume of wastewater discharge can be reduced substantially through conservation of water. This is a good idea for a number of reasons:
# It lowers monthly water bills
# It can also reduce the money that homeowners and communities spend for wastewater treatment.
# Increased efficiency of wastewater treatment plant and savings on energy costs.
# Significant reduction in wastewater flows also can save on personnel costs, such as overtime, and can eliminate or
postpone the need to upgrade or expand facilities. It lowers sewer charges and taxes for homeowners. Water conservation also directly benefits homeowners with onsite systems. Simply by reducing water use, homeowners can extend the life of their systems for many years, prevent system failures, and minimize maintenance costs, potentially saving hundreds of dollars.
# Water conservation also indirectly helps in maintaining the water quality. Excessive water drawing (exceeding the water holding capacity of the soil) from ground sources allows ground water contamination from neighboring areas or sea. So, avoid unnecessary water drawing from ground sources.
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When water becomes wastewater:
The potable water becomes wastewater after it gets contaminated with natural or synthetic microbiological compounds that arises out of human activities, commercial and industrial sources. They may be accompanied with surface water, ground water and storm water. Wastewater is sewage, storm-water and water that have been used for various purposes around the community. Unless properly treated, wastewater can harm public health and the environment. Most communities generate wastewater from both residential and nonresidential sources.
Residential wastewater:
Although the word sewage usually brings toilets to mind, it is actually used to describe all types of wastewater generated from every room in a house. In the U.S, sewage varies regionally and from home to home. They are based on factors such as the number and type of water-using fixtures and appliances, the number of occupants, their ages, and even their habits, such as the types of food they eat. However, when compared to the variety of wastewater flows generated by different nonresidential sources, household wastewater shares many similar characteristics overall. There are two types of domestic sewage: black-water or wastewater from toilets, and gray water, which is wastewater from all sources except toilets. Black-water and gray-water have different characteristics, but both contain pollutants and disease causing agents that require treatment.
Nonresidential wastewater:
Nonresidential wastewater in small communities is generated by diverse sources like offices, businesses, Super markets, restaurants, schools, hospitals, farms, manufacturers, and other commercial, industrial, and institutional entities. Storm-water is a nonresidential source and carries trash and other pollutants from streets, as well as pesticides and fertilizers from yards and fields.
Because of the different nonresidential wastewater characteristics, communities need to assess each source individually or compare similar types of nonresidential sources to ensure that adequate treatment is provided. For example, public restrooms may generate wastewater with some characteristics similar to sewage, but usually at higher volumes and at different peak hours. The volume and pattern of wastewater flows from rental properties, hotels, and recreation areas often vary seasonally as well.
Laundries differ from many other nonresidential sources because they produce high volumes of wastewater containing lint fibers. Restaurants typically generate a lot of oil and grease. It may be necessary to provide pretreatment of oil and grease from restaurants or to collect it prior to treatment. For example, by adding grease traps to septic tanks.
Wastewater from some nonresidential sources also may require additional treatment. For example, storm-water should be collected separately to prevent the flooding of treatment plants during wet weather. Screens often remove trash and other large solids from storm sewers. In addition, many industries produce wastewater high in chemical and biological pollutants that, can overburden onsite and community systems. Dairy farms and breweries are good examples. Communities may require these types of nonresidential sources to provide their own treatment or preliminary treatment to protect community systems and public health.
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The viruses of greatest significance in the water borne transmission of infectious diseases are essentially those that multiply in the intestine of humans and are excreted in large numbers in the feces of infected individuals.
Although viruses cannot multiply outside the tissues of infected hosts, some enteric viruses appear to have a considerable ability to survive in the environment and remain infective.
Discharges of sewage and human excreta constitute the main source of human enteric viruses in the aquatic environment. With the various analytical methods currently available, wide variations are found in the numbers of viruses present in sewage.
The numbers of viruses and the species distribution will reflect the extent to which the population is carrying them. It may reduce the number of viruses by the population.
Sewage treatment may reduce the number of viruses 10-1000-fold, depending on the nature and extent of the treatment given. However, it will not eliminate them entirely, and the sludge produced during sewage treatment will often contain large numbers. As sewage mixes with receiving water, viruses are carried downstream. They remain detectable for varying periods of time, depending on the temperature, the degree to which they are absorbed onto sediments, the depth to which sunlight penetrates into the water, and other factors. Consequently, enteric viruses can be found in sewage polluted water at the intakes to water-treatment plants.
The relationship between the occurrence of viruses in water and risks to health is not a simple one. Viruses are replicating infectious agents that are among the smallest of all microorganisms. In essence, they are nucleic acid molecules that can enter cells and replicate in them, and code for proteins. They are capable of forming protective shells around them. Viruses pathogenic to humans can occur in polluted water. Some of the diseases attributed to them are listed below:
The nature of viruses:
| Virus Family | Members | No.of serotypes | Diseases caused |
|---|---|---|---|
| Picorna-viridae | Human polioviruses | 3 | Paralysis, meningitis, fever |
| Human echoviruses | 32 | Meningitis, respiratory disease, rash, fever, gastroenteritis | |
| Human coxsackie Viruses a1-22,24 | 23 | Enteroviral vesicular pharyngitis, respiratory disease, meningitis, enteroviral vesicular stomatitis with exanthem (hand, foot and mouth disease) | |
| Human coxsackile viruses b1-6 | 6 | Myocarditis, congenital heart anomalies, rash, fever, meningitis, respiratory disease, epidemic myalgia (pleurodynia) | |
| Human enteroviruses 68-71 | 4 | Meningitis, encephalitis, respiratory disease, rash, acute enteroviral haemorrhagic conjunctivitis, fever | |
| Hepatitis A virus | 1 | Hepatitis A | |
| Reo-viridae | Human reoviruses | 3 | Unknown |
| Human rotaviruses | 5 | Gastroenteritis, diarrhea | |
| Adeno-viridae | Human adenoviruses | 41 | Respiratory disease, conjunctivitis, gastroenteritis |
| Parvo-viridae | Adeno-associated viruses | 4 | Latent infection following integration of DNA into the cellular genome |
| Calici-viridae | Human caliciviruses | 5 | Gastroenteritis in infants and young children. |
| Small round structured viruses (including norwalk virus) | 14 | Gastroenteritis, acute viral gastroenteropathy (winter vomiting disease) | |
| Hepatitis E virus | Hepatitis E | ||
| Unknown | Astroviruses | 1 | Gastroenteritis, neonatal necrotizing enterocolitis |
| Papova-viridae | Papillomaviruses | 2 | Planter warts |
| Pathogen | Disease |
|---|---|
| Bacteria campylobacter jejuni | Gastroenteritis |
| Enteropathogenic escherichia coli | Gastroenteritis |
| Legionella pneumophila | Acute respiratory illness |
| Salmonella | Typhoid, paratyphoid, salmonellosis |
| Shigella | Becillary dysentery |
| Vibrio cholerae | Gastroenteritis |
| Protozoa cryptosporidium | Diarrhea |
| Entamoeba histolytica | Amoebic dysentery |
| Giardia lamblia | Diarrhea |
| Naegleriafowleri | Meningoencephalitis |
| Enteroviruses | Respiratory illness |
| Enteroviruses | Eye infection |
| Adenovirus | Gastroenteritis |
| Astrovirus | Gastroenteritis |
| Calicivirus | Gastroenteritis |
| Coxsackievirus A | Myocarditis, meningitis, respiratory illness |
| Echovirus | Meningitis, diarrhea, fever, respiratory illness |
| Hepatitis A virus | Infectious hepatitis |
| Norwalk virus | Diarrhea, vomiting, fever |
| Poliovirus | Meningitis, paralysis |
| Rotavirus | Diarrhea, vomiting |
Recognition of seawater in ground water:Ground water samples taken from where there is seawater intrusion may have a chemical composition different from a simple proportional mixing of seawater and ground water. The popular belief is that, increase of total dissolved solids or chlorides alone is a valuable parameter to determine the extent of intrusion. However, the chloride-bicarbonate ratio (ratio of chlorides to the sum of carbonates and bicarbonates) is more important, which is definitely a pointer to the intrusion as given below:
| Type of water | Cl/CO3 + HCO3 |
|---|---|
| Normal good ground water in aquifer | 1 |
| Slightly contaminated ground water | 1 to 2 |
| Moderately contaminated ground water | 2 to 5 |
| Injuriously contaminated ground water | 5 to 10 |
| Highly contaminated ground water (near sea shore) | 10 to 20 |
| Sea water | 200 |
Classification of infective diseases in relation to water supplies:
I. Water borne diseases (fecal-oral):
(a) by bacterial organisms: cholera, typhoid, paratyphoid, dysentery, diarrhea, weil’s disease (leptospirosis) and tuberculosis
(b) by phage virus or bacteriophages: infectious hepatitis, jaundice and poliomyelitis
(c) by protozoan: amoebic dysentery, ascarsis and amoebic meningo cephalitis (fatal encephalitis usually acquired while swimming in ponds)
Preventive measures: improve quality of drinking water. Prevent causal use of the unhygienic sources.
II. Water washed diseases:
Scabies, skin diseases, typhus fever, leprosy, trachoma, conjunctivitis and bacillary dysentery
Preventive measures: increase water quantity for (washing/cleaning) use. Improve accessibility and reliability of domestic water supply.
III. Water based diseases:
Schistosomiasis (liver fluke), dracunculosis (guinea worm disease)
Preventive measures: control snail populations; filter the water through a fine mesh cloth to remove larvae/cyclops/snail. Disinfect contaminated water.
IV. Water related diseases (by vector organisms):
Malaria, filaria, dengue fever, sleeping sickness (African sleeping sickness)
Preventive measures: destroy breeding sites of insects. Decrease the need to visit breeding sites. Use mosquito nets.
Water borne diseases of biological origin
| S.No | Disease | Causative agent/Type of organism/Life cycle (pathogenicity) | Clinical features |
|---|---|---|---|
| 1. | Dracunculiasis (guinea worm infestation) | Dracunculus Medinensis / Nematode worm / Adult stage in human host larval stage in fresh water crustaceans cyclops | A stinging / burning sensation heralds the appearance of a blister, which ruptures to form an ulcer when the site of the skin is placed in water. The symptom appears when the female worm reaches the skin surface and is ready to discharge her larvae. Occasionally, there may be generalized symptoms of rticaria, nausea, vomitting and dyspnoea when the blister first appears. |
| 2. | Schistosomiasis [group of diseases lschistosome dermatitis (swimmer's itch), katayamafever, urinary schistosomiasis, intestinal schistosomiasis, hepatic schistosomiasis] | schistosoma haematobium, s. mansoni, s. japonicum, s. intercalatum, s. mekongi / Trematode flatworms / For s. mekongi (usage of only lowercase characters suggested) host is dog - for other species host is man - eggs are passed in the urine or faeces - in fresh water, the first larval stage, a miracidium penetrates body of freshwater snail - within the snail miracidia multiplies asexually to form numerous sporocysts - after 4 to 6 weeks released from snail as free swimming cercariae - cercaria penetrates the skin of man | Schistosome dermatitis (swimmer's itch): it is caused due to the penetration of the free swimming cercariae through the skin. It is an itchy popular skin rash, which occurs within about 24 hours. The eruption is probably allergic in nature. Katayama fever: this occurs about 4 to 6 weeks after infection, usually due to s.japonicum or s.mansoni and rarely to s.haematobium. There is an acute onset of fever, headache and cough. There is also enlargement of the liver, spleen and the lymph nodes. Examination of the blood film shows eosinophilia. Occasionally, katayama fever results in death. Urinary schistosomiasis, especially when the infestation is light, is frequently asymptomatic. Painless haematuria is usually the first sign. Terminal haematuria, passing small amounts of blood at the very end of micturition is characteristic. More serious disease is due to damage of the bladder and kidneys, as a result of obstruction to the flow of urine. Severe contraction of the bladder can occur, with fibrosis and calcification. Intestinal schistosomiasis can also be asymptomatic in light infestations. Patients may complain of fatigue, abdominal pain and diarrhoea, which can be bloody. Anaemia is common due to the blood loss. There is polyp and ulcer formation, which can occasionally cause bowel obstruction. Hepatic schistosomiasis can occur when there is a heavy infestation. This usually presents as a symptomless hepatomegaly, with or without enlargement of the spleen. In advanced cases portal hypertension may develop, with massive enlargement of the spleen and the appearance of oesophageal varices, which can bleed repeatedly. |
| 3. | Giardiasis | giardia lambia (g.duodenalis)/Protozo / g. lambia exists in two forms. The trophozoites found adherent to the mucous membranes of the upper small intestines - passed along the intestines - passed in the faeces - in the new host passes into the duodenum - produces two daughter trophozoites which then colonize the small bowel. | In symptomatic patients, the predominant feature is the acute onset of diarrhoea, which is often explosive, abdominal cramps, bloating and flatulence. There is no blood or pus in the stool, which is often pale and at times almost white in color. Malaise is common and sulphuric belching is quite characteristic. Untreated, the acute illness usually lasts for at least 10 days and often for much longer (4-12 weeks). During this illness patients often lose considerable weight. |
| 4. | Cryptosporidiosis | c. parvum (above 20 species are now known, of which c. Parvum pathogenic for humans) / protozoa / oocyst is ingested and passes through the stomach -excystation occurs with release of four motile sporozoites - sporozoites attach to the epithelial cell wall - sporozoite matures into a trophozoite -divides forming a meront and releases merozoites - microgametes and macrogametes formed and fertilize - zygotes formed and matured as oocyst - oocyst is the infective stage and is passed in the faeces. | Diarrhoea stools, watery and offensive and contain mucus or slime, but rarely pus or blood cells. Patients may also complain of mild abdominal pain and a few also have a mild fever. Symptoms usually last from 2 to 26 days. In individuals suffering from aids, the disease is much more severe and more persistent. Illness can last for several months or until death. |
| 5. | Cyclospora | Cyclospora cayetanensis / Protozoa / life cycle not known | Diarrhoea, abdominal pain, nausea, vomiting and anorexia. Flatulence and bloating are also features. The diarrhoea is characteristically prolonged, lasting from one to eight weeks. |
| 6. | Naegleria (free-living amoebo flagellate) | naegleria fowleri / Amoeboflagellates / n. Fowleri has three stages in its life cycle - in trophozoite stage (found in mud and surface of vegetation) the organism feeds and multiplies - motile biflagellate stage is found in surface layers of water - finally, the organisms are found as cysts - both trophozoite and biflagellate forms are potentially infectious for humans - infection occurs during swimming - pathogens penetrate through the nose - enters cerebrospinal fluid - finally penetrates and feed on brain. | Primary amoebic menigoencephalitis (pam). Initial symptoms are headache and a slight fever. Vomiting, stiff neck, increasing fever and severe headache leads to coma. |
| 7. | Illness caused due to cyanobacteria | Cyanobacteria / Algae (but truly prokaryote bacteria)/Illness related to cyanobacteria is mediated by toxins - toxins include hepatotoxins, neurotoxins and lipopolysaccharides. | Clinical presentation of disease that implicates cyanobacteria is wide. The commonest clinical presentation is a self limiting diarrhoea, which lasts for a few days. Erythematous skin rashes are also commonly described. |
| 8. | Cholera and other vibrios (gram.negative, neotile, comma shaped bacilli) | Vibrio cholerae / Bacilli/the infectious dose is high i.e. 106 to 108 organisms. If gastric acidity is neutralized, then the infectious dose falls to as low as 103 organisms. The organism proliferates in small intestine - penetrates mucus barrier to attach to the mucosal surface - colonizes the lining of gut -secretes a potent enterotoxin - intracellular level of cyclic adenosine monophosphate (camp) increases - increased secretion of chloride and inhibition of sodium uptake. | Painless watery diarrhoea. In mild cases, faeces are passed 2-3 times per day for 5-7 days. In a typical severe case, passage of copious water stool can be continuous. Within a matter of a few hours the stool becomes colorless, known as rice-water stool. The life threatening effects of cholera are due to the rapid depletion of body fluids. Shock can develop within 4 - 12 hours, with death soon after. Complications include renal or cardiac failure due to the dehydration of the body. Metabolic acidosis due to loss of bicarbonate in the stool. |
| 9. | Typhoid and paratyphoid | Salmonella typhi and salmonella paratyphi/ bacilli / Infectious dose is below 1000 and possibly 10 organisms. After passing through the stomach, the organism penetrates the lining of the small bowel - then passes to the mesenteric lymph nodes and multiplies - the organisms are then released into the blood stream -any organ can be infected, gall bladder is mainly infected - again intestine is affected, perforation of intestine occurs - increase in the excretion of infective agent in the stool. | Diarhoea, watery stool with blood, colicky abdominal pain and fever. Nausea and mild vomiting. |
| 10. | Shigellosis (bacillany dysentery) | Shigella dysenteriae, shigella flexneri, shigella boydii, shigella sonnei/ bacilli/ can cause disease in healthy adults with the administration of fewer than 200 viable organisms. The disease is produced by invasion and subsequent destruction of the superficial mucosa. | Diarrhoea accompanied by vomiting and leading to dehydration. Then fever, meningism and severe abdominal pain may occur/ diarrhoea mostly mucous with varying amounts of blood/ cholera type illness with watery diarrhoea or with a gangrenous form. May be associated with severe abdominal pain and the passage of stools containing altered blood and necrotic mucosa (lining of the bowel wall). |
| 11. | Campylobacterios | Campylobacter spp/ bacilli/ these are sensitive to stomach -acid and infection is enhanced by the buffering effect of foods. | Diarrhoea with watery and occasionally bloody. Pus in the faeces. Cramping abdominal pain and can mimic appendicitis, acute crohn's disease and ulcerative colitis. Fever and malaise are also features. |
| 12. | Escherichia coli | Escherichia coli/ bacilli/ adhere to gut wall and produce toxins. | Urinary tract infections, meningitis and septicaemia. Cause dehydrating diarrhoea in children. It is a common cause of traveller's diarrhoea. In infants can cause fever and watery mucoid diarrhoea. |
| 13. | Yersinia infections | Yersinia pestis/ bacilli/ infective dose is high, up to 109-infection of the terminal ileum leads to ulceration and inflammation of the mesenteric lymph nodes. | Affects children under five years. It causes fever, diarrhoea and abdominal pain which lasts for about one to three weeks. |
| 14. | Plesiomonas infections | Plesiomonas shigelloides/ bacilli/ pathogenic mechanism not known. | Gastroenteritis. Mild to severe mucoid and bloody diarrhoea. In some cases bacteraemia, osteomyelitis, septic arthritis and meningitis. |
| 15. | Aeromonas infections | Aeromonas hydrophila, aeromonas caviae, aeromonas sobria/ bacilli/ pathogenesis unclear. | To start with mild, self limiting diarrhoea then develop fever, abdominal pain and bloody diarrhoea. |
| 16. | Pseudomonas infections (aerobic, non- spore forming, gram negative bacilli) | Pseudomonas aeruginosa/ bacilli/pathogenesis differs with the syndrome and source of infection. | Respiratory infection, bacteraemia, meningitis and brain abscess, and ear, eye, bone and joint, urinary tract, gastrointestinal, and skin and soft-tissue infections. The most water-related skin rash is folliculitis. |
| 17. | Melioidosis | Burkholderia pseudomallei/ bacilli/causes purulent abscesses, which can affect several body systems. | Asymptomatic infections. Clinically melioidosis may present as an acute localized suppurative lesion, an acute pulmonary or septicaemic illness or as a chronic suppurative infection. |
| 18. | Legionnaire's disease | Legionella pneumophila/ bacilli/ enters the lung by direct inhalation of aerosols. | Pneumonia, pontiac fever (self limiting, influenza like illness characterised by malaise, myalgia, fever, chills and headache. |
| 19. | Leptospirosis | Leptospira interrogans, l.biflexa, l.parva/ obligate aerobes/ gains access to the bloodstream, either through intact mucous membrane, conjunctivae or damaged skin. Bacteraemia then carries the organisms to sites throughout the body including the liver, kidneys, csf and eye. Multiplication at these sites is then responsible for end-stage disease. | Non-specific flu-like illness, which lasts for three to seven days. Sudden onset of high fever, prostration, rigors and muscle pains headache, photophobia and abdominal pain. |
| 20. | Mycobacterial disease | Mycobacteria ulcerans, m. Avium (usage of the same case suggested), m.gordonae, m.marinum/ bacilli/ the skin diseases follow inoculation of the bacterium into the skin. Other infections follow from inhalation. | Tuberculosis and leprosy. |
| 21. | Tularaemia | Francisella tularensis/ bacilli/ infection through skin abrasion or by inhalation. Initially, organisms reproduce at the site of entry for three to five days. From here, they are spread to regional lymph nodes, followed by bacteraemia. Disseminated infection can affect several organs, causing focal necrotic lesions and granulomas. | Clinical disease can be either of the cutaneous-lymphatic type where a nodular, suppurative or ulcerative lesion develops at the site of entry. In the typhoidal presentation the main feature is high fever with occasional pneumonitis. |
| 22. | Helicobacter infections | Helicobacter pylori/ bacilli/ pathogenesis not known. | Nausea and abdominal pain which lasts for 3 - 14 days. Gastritis develops hypochlorhydria may persist for up to a year. In most patients, infection persists for several years or more. |
| 23. | Viral hepatitis | Hepatitis A, hepatitis B/ virus/ acquired orally - virus passes through the stomach, where it replicates in the lower intestine before being carried to the liver, where most replication occurs. Virus is shed from the liver in the bile, from which it contaminates the faeces. Liver damage occurs at the point when circulating antibody appears in the blood. | Jaundice. Initial symptoms are non-specific, and include malaise, lassitude, myalgia, arthralgia and fever. Inflammation of the liver, darkening of the urine and pale or clay colored stools. |
| 24. | Viral gastroenteritis | Rotaviruses (a, b & c)/ virus/ rotaviruses replicate in the villus epithelial cells of the small intestine and causes a loss of the absorptive cells. | Fever, vomiting and diarrhoea. |
| 25. | Enterovirus infections including poliomyelitis | (1) polio virus (2) coxsakie viruses A (3) coxsackie viruses B (4) echoviruses (5) enteroviruses/ virus/ infection follows the ingestion of faecally contaminated material. Initial site for replication is the submucosal tissue of the pharynx or distal small intestine. From the gut, virus may then spread directly to regional cervical or mesenteric lymph nodes or via the blood to various reticuloendothelial tissues such as liver, spleen, other lymph nodes and the bone marrow. Replication may then cease. | (1) aseptic meningitis, encephalitis, paralytic-poliomyelitis. (2) aseptic meningitis, encephalitis, paralytic disease, hand, foot & mouth disease; ulcerative stomatitis, lymphonodular pharyngitis, acute catarrh; pneumonitis, hepatitis; conjunctivitis, splenomegaly. (3) aseptic menigitis, paralytic disease, pericarditis, myocarditis, hepatitis, conjunctivitis, splenomegaly. (4) paralytic disease, respiratory -enteric disease, gastroenteritis, conjunctivitis. (5) paralytic poliomyetitis, epidemic conjunctivitis. |
| 26. | Adenoviral infections | Adenovirus a,b,c,d,e&f/ virus/ virus infects the cell, replicates to produce up to a million new viruses and then kills the cell by lysis to release new infective particles. | Gastroenteritis, pharyngitis and conjunctivitis. |
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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 oransims can be futher subdivided into macra- and micro- oprganisms. Macro organisms, which are biological, are those that are visible to the naked eye or can be seen through a microscope.
In contrast, microbiologoical 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 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.
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In a previous blog, I have 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 blog, 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.
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Acidity:
Alkalinity:
alkalinity. Higher alkaline waters are usually unpalatable. Alkalinity is measured volumetrically by titration with N/50 or 0.020 NH2SO4.
Hardness:
Biochemical Oxygen Demand (BOD):
Chemical Oxygen Demand (COD):
Importance of COD:
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