WATER QUALITY ASSESSMENT AND POLLUTION CONTROL WMA 318 Prof. O. Martins and Dr O.Z. Ojekunle Dept of Water Res. Magt. & Agromet UNAAB. Abeokuta. Ogun State Nigeria email@example.com
PROPERTIES OF WATER • Water is a chemical compound of oxygen and hydrogen and in the gaseous state can be represented by the molecular formula H2O. The isotopes of hydrogen and three isotopes of oxygen exist in nature, and if these are taken into account, 33 varieties of water are possible. • The physical properties of liquid water are unique in a number of respects, and these departure from what might be considered as normal for such a compound are of the greatest importance with respect to both the existence of life on earth and the operation of many geochemical processes. • The boiling point and freezing point of water are both far higher than would be the theoretically expected, considering the low molecular weight of the compound, and the range of temperature over which water as a liquid is wider than might be expected. The reason for these and other departures from “normal” behaviour can be gained by more detailed consideration of the molecular structure of the compound.
MOLECULAR STRUCTURE OF WATER • The spheres representing the ions coalesce to some extent, and the molecule might be thought of as a sphere having two rather prominent bubbles of “blisters” attached to it. Te bonds connecting the hydrogen’s to oxygen describe an angle of 105o, so that the two hydrogen are relatively close together on one side of the molecule. • Although this representation of the molecule is somewhat empirical it helps to explain some of the abnormal features of the behaviour of water. The molecule has dipolar properties because the positive charge associated with the hydrogen are connected on one side of the molecule, leaving a degree of negativity on the opposite side. Forces of attraction thus exist between hydrogens of one molecule and the oxygen bonds. They hold molecule together in a fixed pattern in the solid state. In contrast to the orderly arrangement of molecules in crystal of ice, the molecules of liquid water are in a chaotic condition of disorder. Hydrogen bonds still remain an important force but their arrangement is continually shifting • The cohesive forces represented by the hydrogen bonds impact to liquid water is high heat of vaporization. The forces also tend to prevent the passage to electric currents and impart to the fluid its high dielectric constant. The attraction between molecules of a liquid is shown at a liquid surface by the phenomenon called Surface tension. The surface of water is 75.6 dynes per centimeter at 0oC and 71.8 dynes per centimeter at 25oC, which are very high values compared with the many other liquids
PROPERTIES OF WATER • Chemical Constitution of Water • 1 Ionic and Non Ionic • Ionic • Anion • Cations • 2 Major Anions • Bicarbonate, Chloride, Sulphate • Major Cations • Sodium, Potassium, Calcium, Magnesium • Non-Ionic • SiO2, Dissolved gases, oily Substance, Synthetic detergent, etc
CHARACTERISTICS OF WATER • Hardness • Carbonate (Temporary) Hardness CaCO3 • Non Carbonate (Permanent) Hardness CaSO4 • Concentration of Hydrogen-ion, which are expressed in pH units. It is the—Log10H+ • Specific Electrical Conductance • - Increases with temperature: values must therefore be related to the same temperature (2%) • Colour • Alkanity: Ability to neutralize acid; due to the presence of OH-, HCO3-, CO32-, • Acidity: Water with pH 4.5 is said to have acidity; caused by the presence of free mineral acids and carbonic acids • Turbidity: Measure of transparency of water column; indirect method of measuring ability of suspended and colloidal materials to minimize penetration of light through water. • Dissolved gasses: O2, N2, CO2, H2S, CH4, NH3, etc.
PHYSICAL CHEMICAL PARAMETER • Since water is not found in its pure in nature, it is important to determine its combined physical, chemical and biological characteristics. This is done through monitoring of water for its quality. • Physical chemical parameter analyzed in natural environments; Atmosphere (rainfall), hydrosphere (river, lakes, and oceans) and Lithosphere (Groundwater) are similar-
PHYSICAL CHEMICAL PARAMETER (Cont) • Temperature: Measurement is relevant • For Aquatic life • Control of waste treatment plants • Cooling purposes for industries • Calculation of solubility of dissolved gases • Identification of water source • Agriculture Irrigation • Domestic uses (Drinking, bathing) • Instrument of measurement is thermometer • pH: Controlled by CO2/HCO3-/CO32- Equilibria in natural water. Its values lie between 4.5 and 8.5. It is important • Chemical and biological properties of liquid • Analytical work • Measurement is done in the field. Most common method of determination is the electrometric method, involving a pH-meter. It is important to calibrate the meter with standard pH buffer solutions
PHYSICAL CHEMICAL PARAMETER (Cont) • Dissolved Oxygen: Water in contact with the atmosphere has measurable dissolved oxygen concentration. It values depends on • Partial pressure of O2 in the gaseous phase • Temperature of the water • Concentration of salt in the water (the higher the salt content in water, the lower the concentration of dissolved oxygen and the other gases). • Measurement is important in • Evaluation of surface water quality • Waste-treatment processes control • Corrosivity of water • Septicity • Photosynthetic activity of natural water
MEASUREMENT & RELATIONSHIP OF PHYSICAL CHEMICAL PARAMETERS • Temperature:Temperature affects the density of water, the solubility of constituents (Such as oxygen in water), pH, Specific conductance, the rate of chemical reactions, and biological activity of water. Continuous water quality sensor measure temperature with thermistor, which is a semiconductor having resistance that changes with temperature. Thermistor are reliable, accurate, and durable temperature sensors that require little maintenance and are relative inexpensive. The preferred water-temperature scale for most scientific work ids the Celcius scale. measure temperature to plus or minus 0.1 degree celcius (oC)
MEASUREMENT & RELATIONSHIP OF PHYSICAL CHEMICAL PARAMETERS (Cont) • Specific Conductance: Electrical conductivity is a measure of the capacity of water to conduct an electrical current and is a function of the types and quantities of dissolved substance in water. As concentration of dissolved ions increase, conductivity of the water increases. Specific conductance is the conductivity expressed in units of Microsiemen per centimeter at 25oC. Specific conductance are a good surrogate for total dissolved solids and total ions concentrations, but there is no universal linear relation between total dissolved solids and specific conductance. • Specific conductance sensors are of 2 types: contact sensors with electrodes and sensor without electrodes.
MEASUREMENT & RELATIONSHIP OF PHYSICAL CHEMICAL PARAMETERS (Cont) • Salinity: Although Salinity is not measured directly, some sondes include the capability of calculating and recording salinity based on conductivity measurement. Conductivity has long been a tool of estimating the amount of chloride, a principle component of salinity in water. Salinity is commonly reported using the Practical Salinity Scale (PSS), a scale developed to a standard potassium-chloride solution and based on conductivity, temperature and barometric pressure measurement. • Before developing the PSS, salinity was reported in part per thousand/million. Salinity expressed in the PSS is a dimensionless value, although by convection, it is reported as practical salinity unit.
MEASUREMENT & RELATIONSHIP OF PHYSICAL CHEMICAL PARAMETERS (Cont) • Dissolved Oxygen: Sources of DO in surface waters are primarily atmospheric reaeration and photosynthetic activity of aquatic plants. DO is an important factor in chemical reactions in water and in the survival of aquatic organisms. In surface water, DO concentration typically range from 2-10mg/l. DO saturation decreases as water temperature increases, and DO saturation increases with increased atmospheric pressure. Occasion of super saturation (greater than 100 percent DO saturation) often are related to excess photosynthetic production of oxygen by aquatic plants as a result of nutrient (nitrogen and Phosphorus) enrichment, sunlight and warm water temperature. • DO may be depleted in inorganic oxidation reaction or by biological and chemical processes that consume dissolved, suspended or precipitated organic matter. • The DO Solubility in saline environments is dependent on salinity as well as temperature and barometric pressure. DO in water that have specific conductance values of greater than 2000 microsiemens/centimeter should be corrected for salinity. • The newest technology for measuring DO is the Luminescent sensor that is based on dynamic fluorescence quenching.
MEASUREMENT & RELATIONSHIP OF PHYSICAL CHEMICAL PARAMETERS (Cont) • pH: The pH of aqueous solution is controlled by the interrelated chemical reactions that produce or consume hydrogen ions. The pH of a solution is a measure of the effective hydrogen-ion concentration. More specifically, pH is a measure that represents the negative base-10 logarithm of hydrogen-ion activity of a solution, in moles per liter. Solutions having a pH below 7 are described as acidic, and solutions with pH greater than 7 are described as basic or alkaline. Dissolved gases such as carbon dioxide, hydrogen sulphide and ammonia, apparently affect pH.Dagasification (for example, loss of carbon dioxide) or precipitation of a solid phase (for example, calcium carbonate) and other chemical, physical, and biological reactions may cause the pH of a water sample to change appreciably soon after sample collection. • The electrometric pH-measurement method, using a hydrogen-ion electrode, commonly is used in continuous water-quality pH sensors. • A correctly calibrated pH sensor can accurately measure pH to -+ 0.2 pH units; however, the sensor can be stretched, broken or fouled easily. If the streamflow rates are high, the accuracy of the pH measurement can be affected by streaming-potential effects.
MEASUREMENT & RELATIONSHIP OF PHYSICAL CHEMICAL PARAMETERS (Cont) • Turbidity: Turbidity is defined as an expression of the optical properties of a sample that cause light rays to be scattered and absorbed, rather than transmitted in straight lines through a sample. ASTM further describe turbidity as the presence of suspended and dissolved matter, such as clay, silt, finely divided organic matter, plankton, other microscopic organisms, organic acids, and dyes. Implicit in this definition is the fact that colour, either of dissolved materials or of particles suspended in the water also can affect turbidity. • Turbidity sensors operate differently from those for temperature, specific conductance, DO, and pH, which convert electrical potentials into the measurement of constituent of interest. Submersible turbidity sensors typically direct a light beam from light-emitting diode into water sample and measure the light that scatters or is absorbed by suspended particles in water. • Most commercially available sensors report data in Nephelometric Turbidity Units (NTU)/ with a sensor range of 0-1000 and an accuracy of -+5 percent or 2NTU, whichever is greater.
WATER QUALITY ASSESSMENT AND POLLUTION CONTROL WMA 318 PART 2
Note • For any water body to function adequately in satisfying the desired use, it must have corresponding degree of purity. • Drinking water should be of highest purity. As the magnitude of demand for water is fast approaching the available supply, • the concept of management of the quality of water is becoming as important as its quantity.
Contaminant • Are physical, chemical, biological or radiological substances found as unwanted residue in or on a substance. • Pathogens: Are micro organisms that can cause diseases e.g bacteria • Metals (Metals that are harmful in relatively small amounts are labeled toxic)
Disease caused by contaminants • Salmonella Typhi Typhoid fever • Vibro Cholera Cholera • Entameoba histolytica Amoeba Dysentery • Escherichia Coli (E. Coli) Gastroenterits • Enterovirus Polio • Hepatitis Infestious Hepatitis • Heavy Metal Cancer
Water Purification Process • Abstraction: Abstraction involves pumping and transportation of raw water, a process with high rate of electrical energy consumption. It occurs at the intake. • Screening: Is defined as the process whereby relatively large and suspended debris is removed from the water before it enters the plant. • Aeration: Aeration (Air Stripping) is a physical treatment process whereby air is thoroughly mixed with water to removed dissolved gasses and odour. • Coagulation: Addition of chemical to remove suspended solids. • Flocculation: A chemical flocculent, such as aluminium sulphate, is mixed rapidly with the water to remove mud. • Sedimentation: Also known as clarification- is the gravity-induced removal of particles. • Filtration: Involves the removal of suspended particles from water by passing it through a layer or bed of a porous granular material e.g sand. The filter water the passed through nozzles, the nozzles and sand in the filter beds must be cleaned periodically (This is known as back washing). • Chlorination: After filtration, the water looks much more cleaner than it was in the dam or river but it may not yet be healthy to drink because it may contain unseen micro-organism (bacteria) that are dangerous to the human body and can serious illness (such as diahorrea) • 4.5 liters – 1 Gallon. 1 Liter – 100cl. 1 m3 – 5 drums or 200 liter volume.
WATER QUALITY OBJECTIVES AND REQUIREMENT • A major advantage of the water quality objectives approach to water resources management is that it focuses on solving problems caused by conflicts between the various demands placed on water resources, particularly in relation to their ability to assimilate pollution. The water quality objectives approach is sensitive not just to the effects of an individual discharge, but to the combined effects of the whole range of different discharges into a water body. It enables an overall limit on levels of contaminants within a water body to be set according to the required uses of the water.
WQ Criteria • For some other water quality variables, such as dissolved oxygen, water quality criteria are set at the minimum acceptable concentration to ensure the maintenance of biological functions.
Examples of the development of national water quality criteria and guidelines in Nigeria • In Nigeria, the Federal Environmental Protection Agency (FEPA) issued, in 1988, a specific decree to protect, to restore and to preserve the ecosystem of the Nigerian environment. The decree also empowered the agency to set water quality standards to protect public health and to enhance the quality of waters
Background Information • FEPA approached this task by reviewing water quality guidelines and standards from developed and developing countries as well as from international organisations and, subsequently, by comparing them with data available on Nigeria's own water quality. • The standards considered included those of Australia, Brazil, Canada, India, Tanzania, the United States and the World Health Organization (WHO). These sets of data were harmonised and used to generate the Interim National Water Quality Guidelines and Standards for Nigeria
Background Information (Cont) • These sets of data were harmonised and used to generate the Interim National Water Quality Guidelines and Standards for Nigeria. These address drinking water, recreational use of water, freshwater aquatic life, agricultural (irrigation and livestock watering) and industrial water uses. The guidelines are expected to become the maximum allowable limits for inland surface waters and groundwaters, as well as for non-tidal coastal waters. They also apply to Nigeria's transboundary watercourses, the rivers Niger, Benue and Cross River, which are major sources of water supply in the country.
THE NATIONALENVIRONMENTAL STANDARDS AND REGULATIONS ENFORCEMENT AGENCY (NESREA) • Prior to the dumping of toxic waste in Koko village, in Delta State, in 1987, Nigeria was ill equipped to manage serious environmental crisis, as there were no institutional arrangement or mechanisms for environmental protection and enforcement of environmental laws and regulations in the country. • Arising from the Koko toxic episode, the Federal Government promulgated the Harmful Waste Decree 42 of 1988, which facilitated the establishment of the Federal Environmental Protection Agency (FEPA) through Decree 58 of 1988 and 59 (amended) of 1992. FEPA was then charged with the overall responsibility of environmental management and protection. It is on record that by the establishment of FEPA, Nigeria became the first in African country to establish a national institutional mechanism fir environmental protection.
NESREA (Cont) • In the wisdom of Government, FEPA and other relevant Departments in other Ministries were merged to form the Federal ministry of Environment in 1999, but without an appropriate enabling law on enforcement issues. This situation created a vacuum in the effective enforcement of environmental law standards and regulations in the country. • To address this lapse, the Federal Government in line with Section 20 of the 1999 constitution of the Federal Republic of Nigeria, established the National Environmental Standard and Regulations Enforcement Agency (NESREA), as a parastatal of the federal Ministry of Environment. By the NESREA Act 2007, the Federal Environmental Protection Agency Act Cap F10 LFN 2004 has been repealed (NESREA 2007).
Water quality criteria for individual use categories • Water quality criteria have been widely established for a number of traditional water quality variables such as pH, dissolved oxygen, biochemical oxygen demand for periods of five or seven days (BOD5 and BOD7), chemical oxygen demand (COD) and nutrients. Such criteria guide decision makers, especially in countries with rivers affected by severe organic pollution, in the establishment of control strategies to decrease the potential for oxygen depletion and the resultant low BOD and COD levels.
Development of criteria for Aquatic DO • Numerous studies have confirmed that a pH range of 6.5 to 9 is most appropriate for the maintenance of fish communities. • Low concentrations of dissolved oxygen, when combined with the presence of toxic substances may lead to stress responses in aquatic ecosystems because the toxicity of certain elements, such as zinc, lead and copper, is increased by low concentrations of dissolved oxygen. • High water temperature also increases the adverse effects on biota associated with low concentrations of dissolved oxygen.
Criteria for Aquatic Life DO • The water quality criterion for dissolved oxygen, therefore, takes these factors into account. Depending on the water temperature requirements for particular aquatic species at various life stages, the criteria values range from 5 to 9.5 mg/l, i.e. a minimum dissolved oxygen concentration of 5-6 mg/l for warm-water biota and 6.5-9.5 mg/l for cold-water biota. Higher oxygen concentrations are also relevant for early life stages. More details are given in Alabaster and Lloyd (1982) and the EPA (1976, 1986).
BOD Requirement • In Nigeria, the interim water quality criterion for BOD for the protection of aquatic life is 4 mg O2 l-1 (water temperature 20-33 °C), for irrigation water it is 2 mg O2 l-1 (water temperature 20-25 °C), and for recreational waters it is 2 mg O2 l-1 (water temperature 20-33 °C) (FEPA, 1991).
Drinking Water Criteria • Quality criteria for raw water generally follow drinking-water criteria and even strive to attain them, particularly when raw water is abstracted directly to drinking-water treatment works without prior storage. Drinking-water criteria define a quality of water that can be safely consumed by humans throughout their lifetime. Such criteria have been developed by international organisations and include the WHO Guidelines for Drinking waterQuality (WHO, 1984, 1993) and the EU Council Directive of 15 July 1980 Relatingto the Quality of Water Intended for Human Consumption (80/778/EEC), which covers some 60 quality variables. These guidelines and directives are used by countries, as appropriate, in establishing enforceable national drinking-water quality standards.
Irrigation • Poor quality water may affect irrigated crops by causing accumulation of salts in the root one, by causing loss of permeability of the soil due to excess sodium or calcium leaching, or by containing pathogens or contaminants which are directly toxic to plants or to those consuming them.
Irrigation • Even when the presence of pesticides or pathogenic organisms in irrigation water does not directly affect plant growth, it may potentially affect the acceptability of the agricultural product for sale or consumption. Criteria have been published by a number of countries as well as by the Food and Agriculture Organization of the United Nations (FAO)
Irrigation Criteria Takes into Account • Water quality criteria for irrigation water generally take into account, amongst other factors, such characteristics as crop tolerance to salinity, sodium concentration and phytotoxic trace elements. • The effect of salinity on the osmotic pressure in the unsaturated soil zone is one of the most important water quality considerationsbecause this has an influence on the availability of water for plant consumption. • Sodium in irrigation waters can adversely affect soil structure andreduce the rate at which water moves into and through soils. Sodium is also a specific source of damage to fruits. • Phytotoxic trace elements such as boron, heavy metals and pesticides may stunt the growth of plants or render the crop unfit for human consumption or other intended uses.
Livestock watering • Livestock may be affected by poor quality water causing death, sickness or impaired growth. Variables of concern include nitrates, sulphates, total dissolved solids (salinity), a number of metals and organic micropollutants such as pesticides. In addition, bluegreen algae and pathogens in water can present problems. • Some substances, or their degradation products, present in water used for livestock may occasionally be transmitted to humans. • The purpose of quality criteria for water used for livestock watering is, therefore, to protect both the livestock and the consumer.
Livestock Water Standard • Criteria for livestock watering usually take into account the type of livestock, the daily water requirements of each species, the chemicals added to the feed of the livestock to enhance the growth and to reduce the risk of disease, as well as information on the toxicity of specific substances to the different species
Recreational use • Recreational water quality criteria are used to assess the safety of water to be used for swimming and other water-sport activities. The primary concern is to protect human health by preventing water pollution from faecal material or from contamination by microorganisms that could cause gastro-intestinal illness, ear, eye or skin infections. • Criteria are therefore usually set for indicators of faecal pollution, such as faecal coliforms and pathogens. There has been a considerable amount of research in recent years into the development of other indicators of microbiological pollution including viruses that could affect swimmers. As a rule, recreational water quality criteria are established by government health agencies.
Amenity use • Criteria have been established in some countries aimed at the protection of the aesthetic properties of water. These criteria are primarily orientated towards visual aspects. They are usually narrative in nature and may specify, for example, that waters must be free of floating oil or other immiscible liquids, floating debris, excessive turbidity, and objectionable odours. The criteria are mostly non-quantifiable because of the different sensory perception of individuals and because of the variability of local conditions.
Commercial and sports fishing • Water quality criteria for commercial and sports fishing take into account, in particular, the bioaccumulation of contaminants through successive levels of the food chain and their possible biomagnification in higher trophic levels, which can make fish unsuitable for human consumption.
In India, the Central Pollution Control Board (CPCB) has developed a concept of designated best use.
A colour coding frequently used to depict the quality of water on maps
Suspended particulate matter and sediment • The attempts in some countries to develop quality criteria for suspended particulate matter and sediment aim at achieving a water quality, such that any sediment dredged from the water body could be used for soil improvement and for application to farmland. • Another goal of these quality criteria is to protect organisms living on, or in, sediment, and the related food chain. Persistent pollutants in sediments have been shown to be accumulated and biomagnified through aquatic food chains leading to unacceptable concentrations in fish and fish-eating birds. • NOTE: SEE VARIOUS TABLE FOR DATA
WATER QUALITY ASSESSMENT AND POLLUTION CONTROL WMA 318 PART 3
TYPES OF WATER • Water is commonly described either in terms of its nature, usage, or origin. The implications in these descriptions range from being highly specific to so general as to be non-definitive. Ground waters originate in subterranean locations such as wells, while surface waters comprise the lakes, rivers, and seas.
TYPES OF WATER (Cont) • Fresh Water (precisely less than 0.5%) • Fresh water may come from either a surface or ground source, and typically contains less than 1% sodium chloride. It may be either "hard" or "soft," i.e., either rich in calcium and magnesium salts and thus possibly forming insoluble curds with ordinary soap. Actually, there are gradations of hardness, which can be estimated from the Langelier or Ryznar indexes or accurately determined by titration with standardized chelating agent solutions such as versenates.
TYPES OF WATER (Cont) • Brackish Water • Brackish water contains between 0.5 or 1 and 2.5% sodium chloride, either from natural sources around otherwise fresh water or by dilution of seawater. Brackish water differs from open seawater in certain other respects. The biological activity, for example, can be significantly modified by higher concentrations of nutrients. Fouling is also likely to be more severe as a consequence of the greater availability of nutrients. • The main environmental factors responsible, singly or in combination, for these differences are the salinity, the degree of pollution, and the prevalence of silt.
TYPES OF WATER (Cont) • Seawater • Seawater typically contains about 3.5% sodium chloride, although the salinity may be weakened in some areas by dilution with fresh water or concentrated by solar evaporation in others. Seawater is normally more corrosive than fresh water because of the higher conductivity and the penetrating power of the chloride ion through surface films on a metal.The rate of corrosion is controlled by the chloride content, oxygen availability, and the temperature.
Saline • Water is classified as "saline" when it becomes a risk for growth and yield of crops. Saline water has a relatively high concentration of dissolved salts (cations and anions). Salt is not just "salt" as we know it - sodium chloride (NaCl) - but can be dissolved calcium (Ca2+), magnesium (Mg2+), sulfate (SO42-), bicarbonate (HCO3-), Boron (B), and other compounds. • Water can be both saline and sodic, or saline-sodic. If water has an EC greater than 4 (2 for horticulture) and a Sodium Adsorption Ration (SAR) greater than 12, it is considered saline-sodic • The concentration is usually expressed in parts per million (ppm) of salt. • If water has a concentration of 10,000 ppm of dissolved salts, then one percent (10,000 divided by 1,000,000) of the weight of the water comes from dissolved salts.