CE 264 Unit 2_2024.pdf

1 INTRODUCTION TO ENVIRONMENTAL QUALITY ENGINEERING CE 264 H.M.K. Essandoh/ M. Appiah-Brempong 2 Pollution Water pollution Air pollution Land pollution  Pollution 3  Pollution can be defined as an undesirable change in the...

1 INTRODUCTION TO ENVIRONMENTAL QUALITY ENGINEERING CE 264 H.M.K. Essandoh/ M. Appiah-Brempong 2 Pollution Water pollution Air pollution Land pollution  Pollution 3  Pollution can be defined as an undesirable change in the physical, chemical or biological characteristics of the air, water or land that can harmfully affect health, survival, or activities of humans or other living organisms.  Under this definition, pollution does not necessarily have to cause physical harm.  It may merely interfere with human activities, e.g. a lake may be considered polluted if it cannot be used for boating activities.  Pollution 4  The term ‘undesirable change’, requires value judgements.  An alteration may be judged favourable by some; or the undesirable effect may be considered acceptable when compared with the favourable effect  e.g. an affluent country may ban the use of DDT as a pesticide because of a judgement that the risks (especially to non-human organisms) outweigh the benefits.  At the same time, a country with insufficient food production or a country where malaria affects much of the population may decide that the advantages of using DDT to kill crop pests or malaria- carrying mosquitoes outweigh the risks of its undesirable effects.  Types of Pollution – Classification of pollutants 5  One classification of pollutants puts pollutants into three divisions:  The first type of pollutants include those substances that occur naturally in nature, but as a result of human activity are found in unusually large concentrations e.g. CO2.  The second type of pollutants are the toxic compounds that are released into the environment as a result of anthropogenic activities. These compounds are not found naturally in the environment e.g. mercury, zinc, arsenic, selenium etc.  The third type of pollutants occur when substances which are not themselves toxic are released into the environment as a result of human activity.  Types of Pollution – Classification of pollutants 6  Another classification of pollutants is given based upon the pollutant’s susceptibility to degradation  By this classification there are two types of pollutants  Non-degradable Pollutants  Degradable Pollutants  Non-degradable Pollutants  These are pollutants not broken down by natural processes. E.g. lead, mercury, some plastics etc  Degradable pollutants 7  Degradable Pollutants  These are the pollutants that can be decomposed, removed, consumed and thus reduced to acceptable levels either by natural processes or by human- engineered systems.  There are two classes of degradable pollutants  Rapidly degradable pollutants – these decompose quickly e.g. human sewage, animal and crop wastes.  Slowly degradable pollutants – these decompose slowly but eventually are either broken down completely or reduced to harmless levels, e.g. DDT, radioactive materials (strontium-90, plutonium-239 etc.).  Air pollution 8  Air pollution refers to the accumulation of substances in the atmosphere that can cause harmful health effects to living things or can negatively affect the public welfare.  Negative effects of public welfare include the economic impact or damage to crops or property, such as buildings or works of arts.  Air pollution is the result of human activities as well as naturally occurring phenomenon.  Transportation, power and heat generation, industrial processes and the burning of solid wastes are the major sources of pollution due to human activities.  Volcanic eruptions and naturally occurring fires such as those caused by lightning storms are natural causes of air pollution.  Air pollution 9  For anyone living in a crowed city it is hard to envision a world without smog.  The word smog is a relatively recent term describing a type of pollution associated with urban settings and smokestack industries.  Smog is a blend of the two words smoke and fog and it was first used by the French physician, Dr. H. A. des Voeux.  One of the greatest risk to human health and the environment is air pollution.  Air pollution 10  The list of health problems brought on or aggravated by air pollution includes:  lungdiseases, such as chronic bronchitis and pulmonary emphysema;  cancer, particularly lung cancer;  neural disorders including brain damage;  bronchial asthma and the common cold which are most persistent in places with highly polluted air and eye irritation.  Air pollution 11  Environmental problems resulting from air pollution include  damage to crops and vegetation  acid rain which eventually increases the acidity of some lakes making them unconducive for the survival of fish and other aquatic life  global warming and destruction of the stratospheric ozone layer which can potentially have devastating effects on our planet.  Air pollution 12  In addition to ozone, common pollutants that were among the first to be regulated include: carbon monoxide, airborne particulates, sulfur dioxide, lead, nitrogen oxides, asbestos, beryllium, mercury, vinyl chloride, arsenic, radionuclides, benzene and coke oven emissions.  Carbon monoxide – odourless gas produced from incomplete combustions  Sulfur dioxide – produced from combustion of coal, fuel oil and diesel fuel.  Nitrogen dioxide – Produced from combustions, motor vehicles, industrial boilers and heaters.  Particulate matter – produced from diesel soot and smoke produced from wood burning. Can also be produced from photochemical reactions among polluting gases, primarily sulfur oxides and nitrogen oxides resulting in corrosive sulfate or nitrate ions.  Common Air Pollutants Health concern Ozone (0.12 ppm) Respiratory tract problems, asthma, eye irritation, nasal congestion, premature aging of lung tissue 13 Particulate matter (150 µg/m3) Eye and throat irritation, bronchitis, lung damage Carbon monoxide (10 mg/m3) Cardiovascular, nervous and pulmonary problems, Sulfur Dioxide (0.03 ppm) Respiratory tract problems, permanent lung damage Lead (1.5 µg/m3) Retardation and brain damage Nitrogen Dioxide (100 µg/m3) Respiratory illness and lung damage Hazardous Air Pollutants Asbestos ( - ) Variety of lung disease especially lung cancer Beryllium Primary lung disease; affects liver, spleen, etc. Mercury Damages brain, kidneys and bowels Vinyl chloride (26 µg/m3)* Lung and liver cancer Arsenic Causes cancer Radionuclides Causes cancer Benzene Leukemia Coke Oven Emissions Respiratory Cancer Values quoted in the brackets represent the guideline values – California, USA  Land pollution 14  Historically, land has been the recipient of most wastes including those removed from the air and water.  Pollution of the land / soil not only threatens the future use of the land but also the quality of the surrounding air, surface water and groundwater.  Pollutants on the surface of the land or in the soil frequently move to the surrounding air and water, particularly groundwater.  Sometimes this contamination is the result of a direct application, say of pesticides or fertilizers, onto the land; improper storage, handling or disposal of toxic substances.  Land pollution 15  Industrial waste, if not properly treated and handled can imperil both public health and the environment.  Leaks from underground storage tanks and chemical spills also contribute to contamination of the land and groundwater.  If not properly disposed, common household wastes can cause environmental problems ranging from foul-smelling smoke from burning trash to breeding grounds for rats, flies and mosquitoes.  Even at properly managed waste disposal sites, land contamination can contribute to air and water pollution because small quantities of toxic substances may be dumped with other household wastes.  Land pollution 16  Rainwater seeping through these buried wastes may form leachate.  Leachate is the liquid that results when water moves through any non- water media and collects contaminants.  Examples would include water as it trickles through either wastes or soils where agricultural pesticides or fertilizers have been applied.  This leachate can then percolate down through the soil and may result in contamination of the groundwater.  Land pollution 17  Other organic wastes such as garbage and paper products decompose and can form explosive methane gas which, as a result of being lighter than air, tends to rise through the soil and into the atmosphere.  Instances of houses near municipal landfills collecting explosive levels of methane gas in crawl spaces or basements have been documented.  The main sources of land pollution are municipal waste disposal, illegal hazardous waste disposal, abandoned hazardous waste sites and underground tanks.  Water pollution 18  Water pollution is a harmful modification of water caused by the addition of substances likely to modify its quality, aesthetic aspect and use for human purposes.  The polluting agent may be physical, chemical or biological in nature and cause discomfort, nuisance or contamination  Water has very unusual characteristics, which makes it very ideal for the survival of living things  Dissolves many more substances than any solvent in the world. Hence it is easily polluted  Water can be seriously polluted through anthropogenic activities  Water pollution 19  List human activities that can pollute water  Water Pollution 20  Major water pollutants:  Sewage (blackwater: wastewater from toilets and greywater: wastewater from bathrooms and kitchens)  Fertiliser  Offshore drilling produced water  Radioactive wastes  The oceans are also being polluted through  its use as a dumping ground for wastes and nuclear testing  polluting it with oil (oil tankers and oil drilling exploration)  The oceans are also threatened by over exploitation of its resources  Water pollution 21  Point sources of pollution Pollutional loads discharged at a specific location from pipes outfalls, and conveyance methods from either municipal wastewater treatment plants or industrial waste treatment facilities  Nonpoint sources of pollution Sources of pollution that originate from multiple sources over a relatively large area 22  Water Pollution - effects 23  Consuming contaminated water can cause all kinds of illnesses depending on the source/type of contamination  Effects of water pollution include:  Human genetic and reproductive damage caused by radioactive chemicals, pesticides and industrial chemicals  Waterborne diseases such as cholera, dysentery, typhoid, and diarrhoea  Damage to plant and animal life  Eutrophication, which is the overgrowth of aquatic plants in water bodies as a result of pollution by nitrogen and phosphorus  Nuisance and aesthetic insult  Property damage caused by muddy and corrosive waters  Water Pollution - control 24  Treating industrial waste prior to discharge into water bodies  Enacting and enforcing National laws to reduce pollution (EPA guidelines)  Reducing phosphates content in detergents  Oil spills controlled by chemical foams and absorption pads  Research into the finding of oil eating bacteria 25 Basic Water microbiology and Public Health Basic water microbiology Public significance of diseases associated with excreta Water related diseases  Introduction 26  The constituents of wastewater and natural untreated water that often impair the quality and thus make water unwholesome for human consumption include micro-organisms (e.g. bacteria, viruses, algae, fungi etc) and hazardous chemical constituents e.g heavy metals like As, Cd, Hg, etc; some poly-aromatic hydrocarbons like pesticides – DDT, lindane etc.  These contaminants have the capacity of adversely affecting the health of consumers.  The most important aspect of drinking water is its micro-biological quality.  Very important is the types of microoganisms that are pathogenic.  Microbiological contaminants 27  Bacteria  Bacteria are single-cell organisms consisting of a protoplasm enclosed by a unit cell membrane.  Several types of bacteria including coccus, bacillus, vibrio and spirillum exist and are sized between 0.5 and 5 μm.  Within the protoplasm is a centrally positioned nuclear region which bears the genetic material known as chromatin.  Also present in the cytoplasm are other organelles like mitochondria, ribosomes and vacuoles.  The mitochondria helps with the respiration and metabolic activities of the cell to produce chemical energy required for multiplication and other activities.  The ribosomes are needed for the production of proteins whiles the vacuoles engage in excretory processes.  Most bacteria multiply by binary fission.  Bacteria 28  Bacteria are the cause of most sanitary problems because some of them are pathogenic. They can therefore cause diseases.  Their generation time (i.e. time taken to divide into two daughter cells) is very short e.g. as short as 20 minutes.  In sewage treatment and in some cases of water treatment processes (nitrification – nitrosomonas and nitrobacter), some bacteria are advantageous because they can stabilize organic matter.  C5H7O2N + 5 O2 → H2O + 4 CO2 + NH4+ + HCO3-  Bacteria 29  Bacteria cells can combine to form chains.  A capsule of bacteria cells can be found surrounded by a slime layer consisting of degradation products of the cell wall (polysaccharides). Some have flagella for locomotion.  The major source for pathogenic organisms is fecal matter originating from domestic sewage.  The number of organisms that are present in sewage varies enormously.  Bacteria 30  In water quality surveys quantitative values for the pathogenic organisms mentioned are normally not determined  Values are rather often determined for faecal coliforms, e.g. Escherichia coli (E. coli), sometimes streptococcus faecalis and spores of Clostridium perfringens.  Next to these, values for bacterial counts at 20 and 37°C representing the temperature at which these bacterial / pathogens are cultured are found  Coliforms and fecal coliforms 31  The organisms which are used as indicators of water pollution are Coliform bacteria  Coliform species are regularly found in unpolluted soils and water.  The standard test for coliforms cannot be said to indicate specific faecal pollution.  Especially in warm polluted waters the coliform number in water can increase quite significantly.  Coliforms and fecal coliforms 32  The coliforms are commonly rod-shaped bacterium, not thought of as disease causing bacteria.  Pathogenic bacteria in wastes and polluted waters are usually much lower in numbers and much harder to isolate and identify than coliforms which are usually in high numbers in polluted waters.   Many coliform bacteria live in the soil and these organisms may be the source of those that appear in water especially surface water.  Coliforms and fecal coliforms 33  In recent years coliform bacteria are replaced in water analysis by faecal coliforms.  Faecal coliforms are more specific and live in the intestinal tract of humans and many other animals.  E. Coli is exclusively faecal and constitutes over 90% of the coliform flora of the human intestine.  E. coli are the main part of faecal coliform; more time- consuming to detect. The faecal coliforms e.g. the E.coli must still be taken as the most sensitive and specific indicator of faecal pollution currently available.  Coliforms and fecal coliforms 34  Faecal Streptococci are occasionally used as indicator organisms especially when confirmation of dubious E.coli results is required.  Animals generally excrete much more high numbers of faecal streptococci than humans  Hence the ratio of faecal coliforms to faecal streptococci, can indicate whether pollution is derived from animal or human source (ratio of more than 4 = human source pollution).  Spores of Clostridium perfringens: - spore of C. perfringens is sometimes used for detection of intermittent pollution.  Coliforms and fecal coliforms 35  Indicator organisms are present in large numbers in the faeces of man.  The presence of these organisms in water may be interpreted to mean that such water has been contaminated with faecal matter, possibly coming from carriers of diseases/ pathogenic organisms.  E.coli 105 – 106 / ml  Streptococcus faecalis 103 – 105 / ml  Spores of clostridium perfringens 102 – 104 / ml  Coliforms and fecal coliforms 36  Organisms which might be injurious to health are in general always present in smaller numbers than E. coli.  This implies that E.coli (and faecal coliforms) is a good indicator for the probable presence of harmful organisms.  Organisms which are a hazard to health mostly originate from excrements.  E. Coli itself belongs to the coliform group and is harmless.  Besides E.coli, the bacteria of the coliform group are used as well in order to simplify the examinations in the laboratory.  Fungi 37  Fungi are microscopic plants, multicellular, lacking in chlorophyll, which is a photosynthetic pigment which permits the conversion of sunlight energy into chemical energy.  Fungi are found in biological treatment plants and polluted water utilizing organic matter.  They can be responsible for tastes and odours in water  Algae 38  Algae are microscopic plants, multicellular, lacking definite stems and leaves as is the case of higher plants.  They are present normally in surface water (river, lake, reservoirs) because they need sunlight.  Algae utilize CO2 (HCO3-), NH4 (NO2-, NO3-), PO43- and elements in minor amounts to produce cells and oxygen.  Algae can carry out photosynthesis (utilization of sunlight energy) and do not depend on oxidation of organic matter to survive.  Algae produce oxygen in the presence of light converting inorganic materials in water into organic matter.  In absence of light the algae exert oxygen demand.  Classes of Algae 39  Blue-green algae – (cyanophyceae or myxophyceae) e.g. microcystis anabaena, aphanizomenon, oscilatoria.  Green algae (chlorophyceae) e.g. chlorella, palmella, scenedesmus.  Diatoms (bacillariophyceae) e.g. asterionella, melosira, synedra, tabellaria.  Flagellates (chrysophyceae, euglenophyceae) e.g. chlamydomonas, euglena, pandorina,  Classes of Algae 40 The importance of algae for water quality is large because of  Their formation of taste and odour compounds, toxic substances  Their influence on the oxygen balance of the water (supersaturation of O2; anaerobic conditions)  Their contribution to the organic matter content of the water and the turbidity (clogging of filters).  Viruses 41  A virus particle consists of nucleic acid, DNA or RNA covered by a protein coat called a capsid.  The combined nucleic acid and capsid called the nucleocapsid can either be naked or enclosed by a membrane.  Among the enclosed virus are the influenza virus and herpes.  Virus are extremely host-specific and within a given host also tissue – and cell-specific.  Viruses 42  Virus differ from micro-organisms in the ff properties.  They may contain only one kind of nucleic acid RNA or DNA (note: there has been discovered however virions with both nucleic acid).  Only the nucleic acid is necessary (but not sufficient) for their reproduction.  They are unable to reproduce outside living cells.  Reproduction occurs within the host cell since they depend on the host cell for the replication of its nucleic acid and synthesis of its protein coat.  This process usually leads to the death of the host cell. Plants, animals and micro-organism e.g. bacteria are host for viruses size about 100 nm in length.  In using a bacterium as a host, the virus is known as phage 43  Human health can be compromised when pathogens exist in the water supply  Different kinds of microorganisms can live in water for a long time  Some of them directly pose a risk to the health of its consumers, while other pathogens are related to insects that live part of their life in the water.  Many water related diseases are caused by these pathogens.  Examples are cholera, typhoid and diarrhoea (WHO website).  Diseases related to water are classified into four groups: water-borne, water-washed, water-based, and water-related insect vector diseases  Public significance of diseases associated with excreta and water related diseases Classification of water and related diseases 44 Disease Disease Cholera Guinea worm Waterborne Water-based Infectious hepatitis Schistosoma Paratyphoid (Bilharzia) Typhoid Amoebic dysentery Malaria Bacillary dysentery Waterborne Onchocerciasis or water – Water related Gastroenteritis Yellow fever insect vector washed Sleeping sickness Ascaris Conjuctivitis Water - Diarrhoea diseases washed Leprosy Scabies  Water quality and health- Water washed diseases 45  Water washed diseases are caused by water scarcity where people cannot wash themselves, their clothes or home regularly (there is therefore poor personal hygiene).  Trachoma is the main cause of preventable blindness in the developing world, with four million sufferers, an estimated 500 million at risk and six million permanently blinded.  It is common in areas that are hot, dry and dusty and where there is not enough water for people to wash regularly.  Trachoma is spread, especially among young children, by flies, fingers and clothing coming into contact with infected eyes, spreading the infection to other people's eyes.  Water washed diseases 46  Effect on health  The infection causes a sticky eye discharge with soreness and swelling of the eyelids.  After repeated infections scarring of the inner eyelids occurs which can lead to trichiasis where the eyelashes turn inwards.  These then rub on the eye, scarring the cornea and causing blindness.  Prevention  Trachoma can be prevented through regular hand and face washing with a good supply of clean water, along with hygiene education to help prevent flies from breeding.  Scabies 47  Scabies occurs in areas where there is a lack of water and people are unable to wash themselves, their clothes, bedclothes or houses regularly.  It is caused by the scabies mite which infests the surface layer of the skin.  The mite can spread from one person to another through personal contact  Scabies 48  Effect on health  Scabies causes itchy sores and lesions mainly between the fingers, wrists, elbows, breasts and pubic areas.  In younger sufferers more areas, including baby's feet and the head, can be infected.  Because sufferers often scratch the sores and lesions they become prone to other bacterial infections.  Prevention  Washing regularly with soap and keeping clothes, bedclothes and houses clean prevents scabies.  Waterborne diseases 49  These are diseases spread by Infected contamination of water (or person hands) by human feaces or urine. Susceptible Pathogens in  Infection occurs in a manner as person excreta shown in the figure  Preventive measures  Improve quality of drinking water Consumption Contaminated  Prevent casual use of untreated of untreated water source water or unimproved sources of water  Water based diseases 50  Water based diseases are diseases whose causative pathogen spend part of its life cycle in aquatic animals such as water snails.  The most well-known example is schistosomiasis.  Its pattern of disease transmission includes a part of the pathogen (worm) life cycle in an intermediate host (as miracidia in snails).  The eggs of the worms are released into water bodies through the waste of an infected person.  Water based diseases 51  After the eggs of the worm hatch, they release miracidia which penetrate freshwater snails  The miracidia develop into cercaria which leave the snail host.  These larvae can only survive for 48 hours in water.  The larvae can, however, penetrate the skin of human beings and then migrate through the body, where they can multiply.  Infectious cycle of schistosomiasis 52 worm in bladder wall Cercariae develops and Eggs in urine moves within veins and In man arteries Eggs hatch into Skin penetration miracidia In water Cercariae leave Miracidia enter snail snail  Water based diseases 53  It is unfortunate that schistosomiasis is often spread by irrigation schemes which tend to provide suitable habitats for the snail host as wells as increasing the likelihood of contact with the water by agricultural workers.  Preventive measures  Desistfrom the use of or contact with any water resource known to have the infection.  Control snail population and prevent people or inhabitants from defecating in surface waters.  Water – related insect vector diseases 54  These are diseases spread by insects that breed or feed near open surface waters eg. malaria.  Preventive measures include:  Avoiding suitable habitats for insect like shallow stagnant water pools, regions around the edges of lakes and irrigation canals.  Control by the use of insecticides, although this measure has the possibility of creating some water quality problems.  Biological control measure like the introduction of fish species that prey on the larvae of the insect could be adopted.  Study the life cycle and transmission of the following diseases 55  Waterborne diseases  Water-based diseases  cholera,  Dracunculiasis (Guinea worm),  typhoid,  Schistosomiasis (bilharzia), and other helminths.  amoebic dysentery  bacillary dysentery.  Water-related diseases  dengue,  Water-washed diseases  Filariasis (elephantiasis),  scabies,  malaria,  trachoma and  Onchocerciasis (river blindness),  flea, lice and tick-borne  Trypanosomiasis (sleeping diseases. sickness)  yellow fever. 56 Water quality Water resources, use and consumption Water quality parameters Water quality and public health Raw water quality and pollution Raw water quality and application requirements  Water resources, use and consumption 57  Water resources include  surface water  groundwater  rain water  sea / ocean  moisture  wastewater can also be reused as a source of water  These are in constant circulation  Water is in constant motion through the hydrological cycle  Water use 58  About 66% of the human body is made up of water  Depending on the human body, about 3 – 10 litres of water / day is required for normal functioning.  Uses of water include – cooking, recreation, laundry, drinking gardening, transportation, waste disposal, fire fighting, industrial applications etc.  Factors that influence the use of water include: Cultural habits, pattern and standard of living, utility fee for water, quality of water, proximity of water source.  Water consumption 59  Water use and consumption are normally expressed in litres per capita (head) per day (l.c.d).  l.c.d is useful for making rough estimates of a community’s water demand  In the selection of the type of water supply / source, finance, location, size of community, geographical conditions and the available water source are normally the major considerations.  Typical Domestic Water Usage 60 Type of water supply Water consumption (l.c.d) Range Typical Communal water point (e.g. village well, public stand-post) at considerable distance (>1000 m) 5 – 10 7 at medium distance (500 – 1000m) 10 – 15 12 Village well walking distance < 250m 15 – 25 20 Communal standpipe walking distance < 250m 20 – 50 30 Yard connection (tap placed in house-yard) 20 – 80 40 House connection single tap 30 – 60 50 multiple taps 70 – 250 150 61 Source Water incidence Amount of water (103 km3) % of total water % of fresh water World oceans 1 300 000 97.220 - Salt lakes and inland seas 100 0.008 - Icebergs and polar ice 28 500 2.136 77.63 Water in the atmosphere 13 0.001 0.035 Water in plants and living organisms 1.13 0.0001 0.003 Fresh water lakes 120.3 0.009 0.335 Water courses 1.34 0.0001 0.003 Soil and subsurface water 67 0.005 0.178 Groundwater 8290 0.62 21.800 Total Fresh water 36,700 2.77 100 62  Water and wastewater quality parameters 63  The very notion of water quality is linked to the intended use of the water: swimming, drinking and cooking, irrigation, industrial process water etc.  Whatever we use it for, its quality must be preserved.  As the natural content of water varies considerably we must define average conditions for natural and safe waters.  Above a predestined threshold, water will be declared polluted. 64 Parameter WHO GH Std GH EPA Authority pH 8.5 5.5 – 8.5 6.9 (ww) Temperature Turbidity (NTU) 5 5 Dissolved oxygen Colour (mg Pt/l); (TCU) 15 15 Total suspended solids (TSS, mg/L) 0 Total dissolved solids (TDS, mg/L) 1000 1000 Biochemical oxygen demand (BOD5, mg/L) Chemical oxygen demand (COD, mg/L) Volatile solids Coliforms (No. /100ml) 0 0 Fecal coliforms (No./100ml) 0 0 65 Parameter WHO GH std bd GH EPA Heavy metals Fe (mg/l) 0.3* 0.3* Mn (mg/l) 0.4 As (μg/l) 10 Ca (mmol/l) 2.5(EU) Mg (mg/l) 30 (EU) Cr (mg/l) 0.05 Zn (mg/l) 5 Na (mg/l) 200 Pb (mg/l) 0.05 Se (mg/l) 0.01 66 Parameter WHO GH std bd GH EPA Pesticides 250 250 Chloride (mg/l) Alkalinity Total hardness(mmol/l) 5 Total hardness(mg/l) 500 500 (mg/l as CaCO3) 500 SO42- (mg/L) 250 67 Parameter WHO GH std bd GH EPA Eutrophic compounds NH4+ (mg/l) 0.5*(EPA) NO3- 45 10 NO2- 0.1 PO43- SiO2 Organic compounds PAH Odour Colour 68 Water Chemistry Water and wastewater quality parameters  Water Quality 69  As precipitated water encounters the atmosphere and the environment, its quality changes through interactions with:  Gases in the air  Soil and rock– contaminants  Anthropogenic activities eg mining, agriculture and irrigation, industries e.g. dyeing and tanning  Water and wastewater quality parameters 70  Water is characterised in terms of its physical, chemical and biological composition.  Water quality parameters include chemical, physical, and biological properties  A parameter is a measurable factor eg temperature  Water and waste quality parameters can be measured or tested in the laboratory to determine the characteristics of the water  Classification of water/wastewater quality parameters 71 Class Parameter Physical Total solids (TS), Total suspended solids (TSS) and Total dissolved solids (TDS), turbidity, Temperature, colour, odour. Chemical Organic: Carbohydrates, proteins, lipids, fats, oils, grease, BOD5, COD, TOC. Inorganic: pH, Alkalinity, grit, heavy metals, nutrients (N, P), chlorides, sulphur, hydrogen sulphide, gases. Microbiological Bacteria, algae, protozoa, viruses, coliforms, helminths  Turbidity 72  Turbidity is a measure of clarity of the water.  It is the tendency of water to scatter light at 90 degrees angle from the initial light path.  Turbidity is caused by suspended solids in the water  Measured in Nephlometric Turbidity Units (NTU)  Solids in water 73  Total solids content is composed of  floating matter  settleable matter  colloidal matter and  matter in solution  Solids 74  Coarse materials are usually removed before a sample is analysed for solids  Solids may be classified according to particle size as  suspended solids (> 1µm),  colloidal solids (0.001 - 1µm) and  dissolved solids (< 0.001 µm)  Solids are however, typically divided into suspended and dissolved solids through a 0.45µm glass fibre filter paper 75  Solids in Wastewater 76  Conductivity 77  Electrical conductivity (EC) is ability for a water sample to transmit electrical current. S.I. unit is Siemens/metre.  It’s commonly used to quantify TDS in a water sample as it is easy to determine on-site  EC is useful in wastewater reuse applications since high dissolved solids adversely affects reuse potential  In agricultural reuse, high TDS levels deteriorate the soil structure and decline soil production rates  In industrial use scaling and corrosion may occur  Temperature 78  Temperature affects a number of important water quality parameters:  Gas solubility decreases with increase in temperature  Solids solubility generally increase with increase in temperature  Rate of chemical reaction  Biological reaction rates: most organisms have a distinct temperature range within which they perform best  Temperature 79  Bacterial action increases with increase in temperature resulting in accelerated depletion of DO levels in streams.  An increase in temperature with decrease in quantity of DO can cause serious problems in surface waters.  A sudden change in temp. can result in high rate mortality in aquatic life  Abnormally high temperature fosters growth of undesirable water plants and wastewater fungus  pH 80  The hydrogen ion concentration is an important quality parameter both for natural waters and wastewater  Odour 81  Odours, especially in wastewater, result from hydrolysis and fermentation of organic matter, which produces ammonia, reduced sulphur and other malodorous compounds  Odorous compounds in raw wastewater Odorous compound Odour Amines Fishy Ammonia Ammoniacal Diamines Decayed flesh Hydrogen sulphide Rotten eggs Mercaptans (e.g. methyl & ethyl) Decayed cabbage Mercaptans (eg T-butyl & crotyl) Skunk Organic sulphides Rotten cabbage Skatole (C9H9N) Faecal matter 82 83  Colour 84  Colour in water can result from the result of decay of organic matter  Degradation products such as humic acids tend to produce a slightly brownish colour  Industrial wastewaters may impose more distinct colours  In streams, colour interferes with the transmission of sunlight and therefore reduces photosynthesis  Colour 85  Colour may be true or apparent  True colour is caused by dissolved substances in the water (eg humic acids)  It is the colour after particulate matter has been removed (usually by filtration through a 0.45 micrometer pore size filter).  Apparent colour is the colour that is actually seen.  Its results from a combination of dissolved and suspended solids/particulate matter in the water or turbidity  Hardness 86  There are 2 types of hardness in water  Carbonate hardness (temporary hardness)  Non- carbonate hardness (permanent hardness)  The most abundant multivalent metallic ions in natural water normally responsible for hardness are Ca and Mg.  Other cations like Fe2+, Mn2+, Sr2+ and Al3+ also contribute to the hardness but to a little extent.  Carbonate hardness is that associated with carbonates and bicarbonates in the water  Non-carbonate hardness is hardness not generated by carbonates but by other anions in the water, mainly sulphate, and also chloride (eg. salts such as magnesium chloride, calcium sulphate in water)  Hardness 87  Carbonate hardness is sensitive to heat and precipitates readily Ca(HCO3)2 → CaCO3 + CO2 + H2O  The impact of hardness is that it wastes soap.  In solution the lathering does not occur until all of the hardness ions are precipitated thereby softening the water.  e.g. 2 NaCOOC17H33 + Ca2+ → Ca2+(COOC17H33)2 + 2Na+  The precipitate formed adheres and stains dishwashers, clothes, tubs, dishes and may remain in the pores of the skin making the skin feel rough and uncomfortable.  Hardness 88  Changes in pH in the water distribution may result in deposits of precipitates.  HCO3 begins to convert to the less soluble carbonates at pH above 9.  Unit of measurement: mg/L as CaCO3  Ranges of hardness  Soft : < 50 mg/l as CaCO3  Moderately hard : 50 – 150 mg/L as CaCO3  Hard : 150 – 300 mg/L as CaCO3  Very Hard : > 300 mg/L as CaCO3  Alkalinity 89  Alkalinity is a total measure of the capacity of water to neutralize acids.  Alkalinity is not a pollutant and is different from pH.  pH measures the strength of an acid or base.  Alkalinity indicates a solution's power to react with acid and to buffer its pH, the power to keep its pH from changing.  Alkalinity is important for fish and aquatic life because it protects or buffers against pH changes (keeps the pH fairly constant) and makes water less vulnerable to acid rain.  The main sources of natural alkalinity are rocks, which contain carbonate, bicarbonate and hydroxide compounds.  Dissolved oxygen 90  Biodegradable organic matter, mostly of domestic origin, removes DO.  This is because the micro-organisms present in water consume the organics as food (substrate) and utilize oxygen to accomplish respiration.  The more the organics present, the larger the demand on oxygen.  Aquatic animals, including organisms in sediment remove DO.  Plants add DO during the day via photosynthesis but remove it at night by respiration.  Dying and decaying plants diminish DO.  Dissolved oxygen 91  In summer periods in temperate countries and in tropical countries, the increased water temperature reduces DO solubility.  Tributaries draining into or wastewater discharging into a river bring their own oxygen supplies that affect DO of the river on mixing.  Low river flows slow the rate of oxygen transfer into the water from the atmosphere.  Biodegradable and refractory organics 92  Wastewater is characterised by a considerable amount of organic matter  Major categories of organic matter by weight are:  Carbohydrates (30 – 50 %)  Fats (10 %)  Proteins (40 – 60 %)  Biodegradable and refractory organics 93  It is not possible to measure all individual organic compounds in wastewater  Common parameters to quantify organic matter in terms of oxygen demand are:  Theoreticaloxygen demand (ThOD)  Chemical oxygen demand (COD)  Total oxygen demand (TOD)  Biochemical oxygen demand (BOD)  Total organic carbon (TOC)  Theoretical oxygen demand (ThoD) 94  ThOD can be used only when the chemical equation of the organic compound is known  Overall balanced chemical oxidation equation for complex compounds  Phosphorus and sulphur compounds are commonly neglected in ThOD calculations without creating serious errors because they occur in relatively small amounts in most organic compounds  Chemical Oxygen Demand (COD) 95  The chemical oxygen demand (COD) is the amount of oxygen required to chemically oxidise the wastewater organic matter by potassium dichromate, to inorganic end products. −2 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡:ℎ𝑒𝑎𝑡  𝑜𝑟𝑔𝑎𝑛𝑖𝑐 𝑚𝑎𝑡𝑡𝑒𝑟 𝐶𝑎 𝐻𝑏 𝑂𝑐 + 𝐶𝑟2 𝑂7 + 𝐻+ 𝐶𝑟 3+ + 𝐶𝑂2 + 𝐻2 𝑂  Chemical Oxygen Demand (COD) 96  COD test is more accurate and faster than BOD  Easy to perform by technical and non-technical personnel  Many non-biodegradable organic compounds exert an oxygen demand  Does not oxidise ammonia  Does not yield 100 % of the stoichiometric ThOD calculation  Interference from high concentrations of chloride ions  Biochemical oxygen demand (BOD) 97  BOD determines the oxygen consumption of microorganisms during biodegradation of organic matter.  Most widely used parameter to quantify organic pollution because it best reflects the actual process taking place in nature  The test is based on the measurement of dissolved oxygen involved in the biochemical oxidation of organic matter present in the water.  BOD 98  Biochemical oxygen demand (BOD) 99  After 5 days oxidation is 60 – 70% complete  Process is 95-99 % complete within 20 days (total or ultimate BOD)  20°C used is the average value for slow moving streams in temperate climates  Different results would be obtained at different temperatures because biochemical reaction rates are dependent on temperature  Depending on microorganisms availability in the tested water, two procedures for the BOD measurement are used  An unseeded test is used for samples with sufficient number of microorganisms eg wastewater sample  A seeded test is used for samples with an inadequate number of microbes  Biochemical oxygen demand (BOD) 100 If the wastewater contains an adequate number of bacteria:  Select a volume of the sample, Vs, based on the estimated BOD value  Add to the BOD bottle (300-Vs) mL of unseeded dilution water (the unseeded dilution water should be saturated with oxygen and should contain essential nutrients N, P, K, Fe etc.)  Measure the initial and the final (after 5 days) dissolved oxygen (DO)  Biochemical oxygen demand (BOD) 101  The BOD is calculated by: D1 − D2 BOD5 = P  D1: dissolved oxygen of diluted sample immediately after preparation, mg/L  D2: dissolved oxygen of diluted sample after 5-day incubation at 20°C, mg/L  P: fraction of wastewater sample volume to total combined volume, P = Vs/VB.  VB: volume of the BOD bottle (usually VB = 300 mL)  Vs: volume of the sample  Biochemical oxygen demand (BOD) 102  The wastewater does not contain an adequate number of bacteria ➔ seeded BOD test:  Seed the dilution water with seed organisms (the seeded dilution water should be saturated by oxygen and should contain essential nutrients N, P, K, Fe etc.)  Fill a 1st BOD bottle with VB = 300mL of the dilution water  Select a volume of the sample, Vs, based on the estimated BOD value  Add to the 2nd BOD bottle (VB -Vs) of seeded dilution water  Measure the initial and the final (after 5 days) DO in both bottles  Biochemical oxygen demand (BOD) 103  The BOD is calculated by: (D1 − D2 ) − (B1 − B2 ) f BOD5 = P VB: volume of the BOD bottle (usually VB = 300 mL) Vs: volume of the sample D1: dissolved oxygen of diluted sample immediately after preparation, mg/L D2: dissolved oxygen of diluted sample after 5-day incubation at 20oC, mg/L B1: dissolved oxygen of seed control before incubation, mg/L B2: dissolved oxygen of seed control after incubation, mg/L f : fraction of seeded dilution water volume in sample to volume of seeded dilution water in seed control, f = (VB-Vs)/VB P: fraction of wastewater sample volume to total combined volume, P = Vs/VB.  Biochemical oxygen demand (BOD) 104  Measurable BOD using various dilutions of samples 105  BOD measurement: Example 106  The following information is available for a seeded 5-day BOD test conducted on a wastewater sample. 15 mL of the waste sample was added directly into a 300 mL BOD incubation bottle. The initial DO of the diluted sample was 8.8 mg/L and the final DO after 5 days was 1.9 mg/L. The corresponding initial and final DO of the seeded dilution water was 9.1 and 7.9 mg/L, respectively.  What is the BOD5 of the wastewater sample?  BOD measurement: Example 107  Use the case of seeded BOD test: (D1 − D2 ) − (B1 − B2 ) f BOD5 = P f = (300-15)/300 = 0.95 P = 15/300 = 0.05 BOD5 = [(8.8-1.9) – (9.1-7.9)x0.95]/0.05 BOD5 = 115.2 mg/L  BOD measurement: Example The following information is available for a seeded 5-day BOD test conducted on a wastewater sample. Fifteen mL of the waste sample was added directly into a 300 mL BOD incubation bottle. The initial DO of the diluted sample was 8.8 mg/L and the final DO after 5 days was 1.9 mg/L. The corresponding initial and final DO of the seeded dilution water was 9.1 and 7.9 mg/L, respectively. What is the BOD5 of the wastewater sample? (D1 − D2 ) − (B1 − B2 ) f Use the case of seeded BOD test: BOD5 = P f = (300-15)/300 = 0.95 P = 15/300 = 0.05 BOD5 = [(8.8-1.9) – (9.1-7.9)x0.95]/0.05 BOD5 = 115.2 mg/L 108  Biochemical oxygen demand (BOD) 109  The BOD test assumes organic matter oxidation follows 1st order kinetics 𝑑𝐵𝑂𝐷  = −𝑘𝐵𝑂𝐷 𝑑𝑡  Integrate within limits [UBOD, BODr] and [0, t]  𝐵𝑂𝐷𝑟𝑒𝑚𝑎𝑖𝑛𝑖𝑛𝑔 = 𝑈𝐵𝑂𝐷(𝑒 −𝑘𝑡 )  𝐵𝑂𝐷𝑡 = 𝑈𝐵𝑂𝐷 1 − 𝑒 −𝑘𝑡 UBOD is the ultimate carbonaceous BOD  Biochemical oxygen demand (BOD) 110  The amount of BOD exerted (removed) at any time is the difference between BOD existing at the initial time and the BOD remaining at any time.  𝐵𝑂𝐷𝑡 = 𝑈𝐵𝑂𝐷 − 𝐵𝑂𝐷𝑟  Substituting 𝐵𝑂𝐷𝑟 = 𝑈𝐵𝑂𝐷(𝑒 −𝑘𝑡 ) into the above  𝐵𝑂𝐷𝑡 = 𝑈𝐵𝑂𝐷 − (𝑈𝐵𝑂𝐷 𝑒 −𝑘𝑡 )  𝐵𝑂𝐷𝑡 = 𝑈𝐵𝑂𝐷 1 − 𝑒 −𝑘𝑡  5 day BOD for example would be given by:  𝐵𝑂𝐷5 = 𝑈𝐵𝑂𝐷 1 − 𝑒 −5𝑘 111 Biochemical oxygen demand (BOD)  The rate coefficient, k, is affected by temperature  𝑘 𝑇 = 𝑘20 (𝜃)(𝑇−20)  For untreated wastewater, k is about 0.12 to 0.46 day-1, typically 0.23 day-1 at 20°C  θ = 1.056 between 20 and 30°C  Example 112  Calculate BOD at 30°C after 3 days when BOD5 is 300 mg/L  Nitrification in the BOD test 113  Non-carbonaceous matter such as ammonia is produced during the hydrolysis of proteins  A number of bacteria are able to oxidise ammonia to nitrite (NO2-) and subsequently to nitrate (NO3-)  Nitroso-bacteria (Nitrosomonas): NH4+ + 1.5O2 → NO2- + 2H+ + H2O  Nitro-bacteria (Nitrobacter): NO2- + 0.5O2 → NO3  Total oxidation reaction: NH4+ + 2O2 → NO3- + 2H+ + H2O  Nitrification in the BOD test 114  O2 demand associated with the oxidation of ammonia to nitrate is called the nitrogenous BOD (NBOD)  Nitrification is usually observed to occur from 5 to 8 days after the start of the BOD incubation period (low reproductive rate)  If a sufficient amount of nitrifying bacteria is present initially, the interference could be significant  Assignment 115  Determine the 1-day BOD and ultimate first-stage BOD of a wastewater whose 5-day, 20°C BOD is 200mg/L. The reaction constant, k, is 0.23d-1  Nutrients – nitrogen and phosphorus 116  Common forms of nitrogen are  Organic nitrogen  Ammonia/ammonium (NH4+ NH3)  Nitrite (NO2-)  Nitrate (NO3-)  Gaseous N  Nitrogen Organic nitrogen (proteins; urea) Bacterial decomposition and hydrolysis Ammonia Organic nitrogen Organic nitrogen Assimilation nitrogen (bacterial cells) (net growth) O2 Lysis and autooxidation Nitrosomonas Nitrification Nitrite (NO2-) O2 Nitrobacter Denitrification Nitrate (NO3-) Nitrogen gas (N2) 117 Organic carbon  Nutrients – nitrogen Distribution of ammonia and ammonium ion as a function of pH 100 100 + NH4 NH3 80 80 Ammonium ions are + favoured at percent NH 3 percent NH 4 60 60 decreasing pH 40 40 NH4+, % NH3, % 20 20 Ammonia is favoured 0 0 at high pH 5 6 7 8 9 10 11 12 13 14 pH 118  Nitrogen Various forms of Nitrogen Form of nitrogen Abbreviation Definition Ammonia gas NH3 NH3 Ammonium ion NH4+ NH4+ Total ammonia nitrogen TAN NH3 + NH4+ Nitrite NO2- NO2- Nitrate NO3- NO3- Total inorganic nitrogen TIN NH3 + NH4+ + NO2- + NO3- Total Kjeldahl nitrogen TKN Organic N + NH3 + NH4+ Organic nitrogen Organic N TKN – (NH3 + NH4+) Total nitrogen TN Organic N + NH3 + NH4+ + NO2- + NO3- The TKN test quantifies the total nitrogen in raw municipal sewage 119 as there is hardly any oxidised nitrogen available  Nutrients – nitrogen and phosphorus 120  The presence of high levels of nitrates in drinking water can cause nitrate poisoning  The most common cause of blue baby syndrome or methemoglobinemia is water contaminated with nitrates.  When an infant drinks nitrate-rich water, the body converts the nitrates into nitrites.  These nitrites bind to the hemoglobin in the body, forming methemoglobin, which is unable to carry oxygen  The infant suffocates due to inadequate oxygen in the blood  Phosphates 121  Phosphorus is introduced into the environment from human activities such as:  human and animal wastes,  detergents  fertilizers,  industrial wastes  human disturbance of the land and its vegetation (e.g phosphate mining)  Phosphorus from natural resources, such as:  forest fires and fallout from volcanic eruptions, is insignificant when compared to human-caused enrichments of water.  Phosphates 122  Phosphates are commonly used in detergents  The breakdown of phosphorus complexes in phosphate detergent wastewater, creates freely available phosphates which may contribute to an oversupply of phosphate in waterways and cause an imbalance of the aquatic ecosystem  Phosphates in excess amounts can have a significant impact on water quality.  Phosphates 123  Phosphate has two different forms in our environment:  organic phosphate, which is a part of living plants and animals, their by-products and their remains;  inorganic phosphate, which can be bound to soil particles or are found in laundry detergents.  Phosphorous is usually present in natural waters as phosphate (PO4--P).  Nutrients – nitrogen and phosphorus 124  N and P are essential nutrients which help plants to grow, however excess in water can induce eutrophication of surface waters and nitrates can also contaminate groundwater  Eutrophication – the enrichment of water bodies (lakes, rivers, reservoirs) with nutrients usually phosphates (mainly) and nitrogen compounds, (silicates to a lesser extent) resulting in increased plant biomass (algal blooms, macrophytes or floating aquatic weeds).  Nitrogen and phosphorus 125  Eutrophication is a natural process (natural eutrophication) but can be accelerated by human influence (Cultural eutrophication) Degree of Eutrophication Level of nutrients Oligotrophic low Mesotrophic moderate Eutrophic high Hypertrophic very high  Eutrophication 126 Trophic [P] [Chl] secchi μg/l μg/l m Oligo < 10 < 2.5 >6 Meso 10 – 35 2.5 – 8 3–6 Eu 35 – 100 8 – 25 1.5 – 3 Hyper > 100 > 25 < 1.5  Adverse effects of algae 127  Occurrence of very turbid and coloured water.  Give rise to unstable oxygen conditions by photosynthesis and respiration of algae  Can cause overstrained oxygen economy due to degradation of dead algae, leading to anaerobic conditions at the sediment – water interface  Some algae can form gels which can clog rapid sand filters  Blue green algae if prevalent are capable of forming toxins.  Adverse effects of algae and aquatic weeds 128  Adverse effects of algae especially for water supply  Increase of coagulant demand  Flotation of flocs in settling basins  Clogging and impaired passage of water through filter  Bacterial aftergrowth in distribution system  Adverse effects of aquatic weeds  Clogging of intake screens for water supply or hydropower production  High evapo-transpiration  Interferences with transportation  Interference with fisheries: fish population and harvesting of fish  Some aquatic weeds 129  Sulphate 130  Occurs naturally in water supplies and present in wastewater  Required in synthesis of proteins and released in their degradation  Sulphate is reduced to sulphide under anaerobic conditions  Combines with hydrogen to form H2S Organic matter + SO4-2 → S-2 + H2O + CO2 (bacteria)  S-2 + 2H+ → H2S  Oil and grease 131  In streams oil and grease:  Interfere with natural re-aeration: Coats surfaces of water bodies and affects O2 transfer  Are toxic to certain species of fish and aquatic life  Create a fire hazard when present on the water surface in sufficient amounts  Destroy vegetation along the bank with consequent erosion  Oil and grease 132  Affect water reuse potential: Render boiler feed and cooling water unusable  Impart taste and odour to water  Create unsightly film on surface of water  Lower recreational and bathing potential of streams  Flouride 133  Flouride is an inorganic anion  It is alleged to impart benefits to humans  However recent finds bring up some controversy  WHO – Europe – Rate of decrease of cavities in teeth of children in regions with / without – same  The claim of F- being beneficial has not held up independent scientific scrutiny.  Flouride 134  High [F-] → more brittle and fragile bones, increased bone mass density but reduce strength of the bone at the same time due to F- caused defects in the bone structure.  F- + Al in drinking water → accumulates in brain → neurotoxic morphological changes.  A study in China has shown that even accepted levels of F- in water (0.88 mg/l) may affect children’s intelligence  High F- is also a contributing factor to a bone cancer condition of osteosarcoma.  May cause elevation in blood sugar possibly exacerbating diabetes.  Fluoride defects: dental and skelletal fluorosis 135 Mottling of teeth  Fluoride defects 136  Heavy metals 137  Heavy metals are ubiquitous, persistent and toxic pollutants.  Copper, zinc, chromium, cadmium, nickel, iron, lead, mercury and silver are the metals commonly classified as heavy metals  Tin, selenium, aluminium, molybdenum, cobalt, manganese and arsenic are also sometimes included in this categorization.  Trace quantities of heavy metals, Hg, Pb, Cd, Cr, Cu, Ni can be found in domestic wastewater.  Heavy metals 138  Most of metals are classified as priority pollutants. This means that they are regulated and a set of analytical test methods have been developed  Excessive quantities interfere with the beneficial use of water because of toxicity  The adverse effects of heavy metals on human health are well documented.  Birth defects, cancer and a number of chronic diseases have all been linked to heavy metals  Iron and Manganese 139  Consumer complaints – dark brown to black precipitates, stain laundry and porcelain fixtures  Coating and darkening of filters in treatment plants  Concentration as low as 0.02 mg/l could form coating in distribution mains, service lines, meters  Chronic exposure to manganese concentration beyond 0.5mg/l could give rise to a disease condition similar to Parkinsonism.  Iron and Manganese 140  WHO health-based guideline for manganese occurrence in drinking water is pegged at 0.4 mg/l (WHO guideline 2004)  In 2011 this guideline was withdrawn because Mn levels in drinking water in many countries exceeded this limit  WHO guideline value of 0.1 mg/l has been recommended for Mn for drinking water sources based on its staining properties  Arsenic 141  Long term exposure to drinking water with [As] > 10 μg/l  Can cause cancer of the skin, lungs, urinary bladder, kidney, etc  Skin pigmentation  Hardening and laceration of soles of feet.  Retardation in the intelligence of children.  In Ghana – upsurge in the incidence of cancer especially breast, meanwhile patronage of groundwater as drinking water source is on the increase.  Lead 142  Lead  Anaemia,  mental retardation  Heavy metals – toxicity Name (formula) Concern Cadmium (Cd) A carcinogen, soluble compounds highly toxic, toxic by inhalation of dust or fume, long term- concentrates in the liver, kidneys, pancreas and thyroid, hypertension suspected effect Chromium (Cr) Hexavalent chromium compounds carcinogenic and corrosive on tissue, long term- skin sensitisaton and kidney damage Lead (Pb) Toxic by inhalation or ingestion of dust and fumes, long term- brain and kidney damage, birth defects Mercury (Hg) Highly toxic by skin absorption and inhalation of fume or vapour, long term – toxic to central nervous system , may cause birth defects Arsenic (As) Highly toxic to mammals and aquatic species. When ingested, it is readily absorbed from the gastrointestinal tract, the lungs, and to a lesser extent from the skin, and is distributed throughout the body. Recently, arsenic in water supplies has 143 been linked to arsenical dermatosis and skin cancer. 144 RAW WATER QUALITY AND APPLICATION REQUIREMENTS  INDUSTRIAL WATER Maximum conc. of constituents in raw waters for various industrial operations (mg/l) Characteristic Boiler Cooling Textile Pulp and Chemical Petroleum water water Plants paper industry 145 Silica 150 50 - 50 - 85 Aluminum 3 3 - - - - Iron 80 14 0.3 2.6 10 15 Manganese 10 2.5 1.0 - 2 - Calcium - 500 - - 250 220 Magnesium - - - - 100 85 Ammonia - - - - - 40 Bicarbonate 600 600 - - 600 480 Sulfate 1400 680 - - 850 900 Chloride 19000 600 - 200 500 1600 Nitrate - - - - - 8 Dissolved 35000 1000 150 1080 2500 3500 solids Suspended 15000 5000 1000 - 10000 5000 solids Hardness 5000 850 120 475 1000 900 Alkalinity 500 500 - - 500 500 Color 1200 - - 360 500 25  Agriculture Water 146  Water Quality for irrigation (tropical conditions) TDS - < 400 mg/l – poor drainage saline soil inadequate water supply < 1000 mg/l – good drainage proper irrigation management < 2000 mg/l – salt resistant crops - good drainage - low sodium adsorption ration (S.A.R.) E.C. < 100 mS/m (25˚C) SAR < 10 - poor drainage < 18 - good drainage  Agriculture Water 147 Water Quality for irrigation (tropical conditions) Boron < 1.25 mg/l - sensitive crops < 4 mg/l – tolerant crops Coliforms < 100 per 100 ml if water is to be used for unrestricted irrigation SAR (meq/l)= [Na+] [Ca2+] + [Mg2+] 2 The porosity of Na – clay is lower than for Ca – clay. This means that the permeability for air and water is lower.  Quality requirements for fishing in tropical streams 148 CO2