CHAPTER FOUR:
HYDROBIOLOGY (WATER QUALITY)
Dadi -Mamud Naomi John and Hamzat Aliyu
4.1 HYDROBIOLOGY
Hydrobiology is primarily an ecological science. The living conditions in water are determined by the physicochemical and characteristics of the body of water. Many of these features—for example, the chemical composition of the water (in particular, the composition and amount of biogenic elements and dissolved gases, the nature of bottom sediments, and the transparency of the water) are strongly influenced by aquatic organisms and are often determined by their life processes. Hydrobiology studies the role of living phenomena in the context of the aggregate of interdependent processes of the aquatic medium. Modern hydrobiology can be viewed as a sub-discipline of ecology but the sphere of hydrobiology includes taxonomy, economic biology, industrial biology, and physiology etc. Limnology and is divided into lotic system ecology (flowing waters) and lentic system ecology (still waters). One of the significant areas of current research is eutrophication. Special attention is paid to biotic interactions in plankton assemblage including the microbial loop, the mechanism of influencing water blooms, phosphorus load and lake turnover. Another subject of research is the acidification of mountain lakes. Long-term studies are called for changes in the ionic composition of the water of rivers, lakes and reservoirs in connection with acid rain and fertilization. Much of the early work of hydrobiologists concentrated on the biological processes utilizes in sewage treatment and water purification especially slow sand filters. Other historically important work sought to provide biotic indices for classifying waters according to the biotic communities that they supported. This work continues to this day in Europe in the development of classification tools for assessing waterbodies for the EU water framework directive Field of research interests. Hydrobiology also involved Marine biology and biological oceanography which is the study of marine organisms their behaviors and interactions with the environment and the associated fields of chemical, physical, and geological oceanography to understand marine organisms. As growing global population stresses the ability of our society to produce food, water, and shelter, there was to continue to look to the oceans to help sustain our basic needs. And advances in technology, combined with demand, to improve our ability to derive food, drinking water, energy sources, waste disposal, and transportation from the ocean.
It is important for the future generations to build upon our existing knowledge of the ocean and its potential to help meet the needs of the world and its inhabitants since hydrobiology is a very broad area, so most researchers can select a particular area of interest and specialize in it. Specializations can be based on a particular species, group, behavior, technique, or ecosystem.
4.2 Introduction
Hydrobiology is greatly concerned with establishing a scientific basis for the rational exploitation of biological resources of the waters. This is bound up in many ways with the requirements of the marine and freshwater fishing industries, farm pond fishery, and the use of aquatic invertebrates and mammals (food-fish hydrobiology). Other practical applications of hydrobiology and stimuli to its development are the biological questions related to the use of the continental surface freshwater for drinking purposes and industrial supply, the protection of natural water against pollution, the self-purification of polluted water, and the biological methods of treating waste waters (sanitary hydrobiology). Hydro-biological methods are used to evaluate the extent of water pollution through the presence of certain indicator organisms (the so-called biological analysis of water quality). Hydrobiology studies the role of aquatic organisms as agents of self-purification. The concerns of technical hydrobiology are the related problems pertaining mainly to biological interference with the water supply and operation of ships apparatus and hydraulic structures, and the pipes and water supply lines of electrothermal power plants; the overgrowth of aquatic plants in reservoirs, and the damage to ships and port. New problems continue to arise, such as the need to determine the effect of plankton on the absorption and scattering of sound—information indispensable to specialists in underwater acoustics. Navigational hydrobiology is the study of biological interference (for example, bioluminescence) with naval activities; agricultural hydrobiology includes the study of the role of hydrobionts in the fertilization of rice paddies and the possibilities of fish breeding in these waters. The field of sanitary hydrobiology studies the effect upon aquatic organisms and their communities of the toxic substances in industrial effluent, the mechanism of the biological self-purification of water, and other matters relating to the pressing problem of supplying man’s growing need for pure water.
Life on Earth depends upon water. Water comprises 70% of earth surface. It serves different functions ranging from its transport function through serving as solvent for most chemicals to serving habitat to many organisms. Many' organisms also depend on water for certain stages of their life. For instance, some insects and amphibians use water as their breeding sites while it serves as an agent of dispersal for many plant seeds and fruits. The biological diversity of aquatic areas is neglected world- wide, even in coral reefs that rival tropical rain forests in their extraordinary diversity of life Water is a critical issue for the survival of all living organisms. Some can use salt water but many organisms including the great majority of higher plants and most mammals must have access to freshwater to live. Some terrestrial mammals, especially desert rodents appear to survive without drinking but they do generate water through the metabolism of cereal seeds and they also have mechanisms to conserve water to the maximum degree.
4.3 Water Quality Parameters
Water quality analysis is important to preserve and protect the natural ecosystem. A number of physico-chemical and biological methods have been carried out in water quality management. A study of different water parameters is very important for understanding of the metabolic events in aquatic ecosystem. The quality of surface water such as rivers, lakes and reservoir depend on their physical, chemical and biological prosperities. Water quality parameters were assessed in the determination of the water quality of Reservoirs. These parameters include:
Nitrate
Inorganic nitrate (NO3-) and nitrite (NO2-) are water soluble (as a result of their interaction with the positively charged portions of polar water molecules) and commonly exist as salts of nitric acid and nitrous acid, respectively. Nitrates are a form of nitrogen, which is found in several different forms in terrestrial and aquatic ecosystems. These forms of nitrogen include ammonia (NH3), nitrates (NO3), and nitrites (NO2). Nitrates are essential plant nutrients, but
in excess amounts they can cause significant water quality problems. Together with phosphorus, nitrates in excess amounts can accelerate eutrophication, causing dramatic increases in aquatic plant growth and changes in the types of plants and animals that live in the stream. This, in turn, affects dissolved oxygen, temperature, and other indicators. Excess nitrates can cause hypoxia (low levels of dissolved oxygen) and can become toxic to warm-blooded animals at higher concentrations (10 mg/L) or higher) under certain conditions. The natural level of ammonia or nitrate in surface water is typically low (less than 1 mg/L)
Nitrate generally, as a compound occurs naturally and also has many human-made sources. They are found in some lakes, rivers, and groundwater. You cannot taste, smell, or see nitrate in water. Consuming too much nitrate can be harmful. Nitrate is the most highly oxidized form of nitrogen compounds commonly present in natural waters. Other significant sources of nitrate are chemical fertilizers, decayed vegetable and animal matter, domestic effluents, sewage sludge disposal to land, industrial discharge and leachates from mines can contaminate stream, river, lake, and ground water. Unpolluted natural water contains minute amount of nitrate. Health effect of nitrate is can affect how blood carries oxygen and cause methemoglobinemia (also known as a blue baby syndrome). Bottle-fed babies under six months old are at the highest risk of getting methemoglobinemia. This illness can cause the skin to turn a bluish color and result in serious illness or death. (APHA, 2013).
pH
The pH of a solution is measured as negative logarithm of hydrogen ion concentration. At a given temperature, the intensity of the acidic or basic character of a solution is indicated by pH or hydrogen ion concentration. pH values from 0 to 7 are diminish acidic, 7 to 14 increasingly alkaline and 7 is neutral. Measurement of pH is one of the most important and frequently used tests, as every phase of water and wastewater treatment and waste quality management is pH dependent. The pH of natural water usually lies in the range of 4 to 9 and mostly, it is slightly basic because of the presence of bicarbonates and carbonates of alkali and alkaline earth metals. pH value is governed largely by the carbon dioxide/ bicarbonate/ carbonate equilibrium. It may be affected by humic substances, by changes in the carbonate equilibrium due to the bioactivity of plants and, in some cases, by hydrolysable salts, (WHO, 2004). The effect of pH on the chemical and biological properties of liquid makes its
etermination very important. It is used in several calculations in analytical work and its adjustment to an appropriate value is absolutely necessary in many of the analytical procedures. In dilute solution, the hydrogen ion activity is approximately equal to the concentration of hydrogen ion (Matos et al., 2010).
Dissolved Oxygen (DO)
All living organisms are dependent upon oxygen in one form or the other to maintain the metabolic processes that produce energy for growth and reproduction. Aerobic processes which need free oxygen for wastewater treatment are of great interest. In a study titled Variation in concentration of dissolved oxygen and hydrogen concentration at the surface of tropical reservoir: a case study of lower Usuma reservoir in Bwari, Abuja Dissolved oxygen is required for respiration by most aquatic animals and apart from this, dissolved oxygen combined with other important elements such as Carbon, Sulphur, Nitrogen and Phosphorous that could have been toxicants in the absence of oxygen in the waterbodies to form carbonate, sulphate, nitrate and phosphate respectively that constitute the required compounds for aquatic organisms for survival (Araoye, 2008). Sensitivity to low levels of dissolved oxygen is species specific; however, most species of fish are distressed when DO falls to 2 mg/l. Mortality usually occurs at concentrations less than 2 mg/l and usually larger fishes are affected by low DO than smaller fishes. The depletion of oxygen in aquatic environment has many effects on biota particularly fishes which include mortality, reduced growth rate, impaired reproductive activity and also fish become more susceptible to diseases (Dankishiya et al.,2013).
Dissolved Oxygen (DO) is also important in precipitation and dissolution of inorganic substances in water. DO levels in natural waters and wastewaters depend on physical, chemical and biological activities in waterbody. The solubility of atmospheric oxygen in freshwater ranges from 14.6mg/L at 0°C to about 7.0mg/L at 35°C under normal atmospheric pressure (WHO, 2015). Since it is poorly soluble gas, its solubility directly varies with the atmospheric pressure at any given temperature. Analysis of DO is a key test in water pollution control and wastewater treatment processes. The following illustrations reveal the importance of DO as a parameter:
i. It is necessary to know the DO level to assess quality of raw water and to keep a check on stream pollution.
ii. In wastewaters, dissolved oxygen is the factor that determines whether the biological changes are brought about by aerobic or anaerobic organisms.
iii. DO test is the basis of BOD test which is an important parameter to evaluate pollution potential of wastes
iv. DO is necessary for all aerobic biological wastewater treatment processes
v. Oxygen is an important factor in corrosion. DO test is used to control the amount of oxygen in boiler feed waters either by chemical or physical methods (APHA, 2013).
Hardness
Water hardness is a traditional measure of the capacity of water to precipitate soap. Hardness of water is not a specific constituent but is a variable and complex mixture of cations and anions. Total hardness is defined as the sum of the calcium and magnesium concentration, both expressed as CaCO3, in mg/l. The degree of hardness of drinking water has been classified in terms of the equivalent CaCO3 concentration as follows:
Soft 0-60 mg/L
Medium 60-120mg/L
Hard 120-180mg/L
Very hard > 180mg/L
When total hardness is numerically greater than that of total alkalinity expressed as CaCO3, the amount of hardness equivalent to alkalinity is called carbonate hardness. The amount of hardness in excess of total alkalinity expressed as CaCO3 is non-carbonate hardness. Non-carbonate hardness is caused by the association of the hardness-causing cations with sulphate, chloride or nitrate and is referred to as “permanent hardness”. This type of hardness, however, cannot be removed by boiling (APHA, 2014).
Biochemical Oxygen Demand (BOD)
The Biochemical Oxygen Demand (BOD) is an empirical standardized laboratory test which measures oxygen requirement for aerobic oxidation of decomposable organic matter and certain inorganic materials in water under controlled conditions of temperature and incubation period. The quantity of oxygen required for above oxidation processes is a measure of the test. The test is applied for fresh water sources (rivers, lakes), wastewater (domestic, industrial), polluted receiving water bodies, marine water (estuaries, coastal water)
and also for finding out the level of pollution, assimilative capacity of water as well as performance of waste treatment plant (APHA, 2014).
Therefore, biological oxygen demand represented the amount of biodegradable organic matter present in water. The greater the BOD, the more rapidly oxygen is depleted in the stream. This means less oxygen is available to higher forms of aquatic life. The consequences of high BOD are the same as those for low dissolved oxygen: aquatic organisms become stressed, suffocate, and die. World Health Organization recommended a limit of less than 5.0 mg/l as ideal for water bodies.
Conductivity
Conductivity is the capacity of water to carry electrical current and it varies both with number and types of ions in the solutions which, in turn, is related to the concentration of ionized substances in the water. Most dissolved inorganic substances in water are in the ionized form and hence contribute to conductance (NIS, 2007). The higher the salinity and conductivity levels, the lower the DO levels in the water, which can cause issues for some aquatic plants and animals. Some aquatic life can tolerate salinity changes, however, most cannot, and will either die or become seriously sick.
Conductivity of water is important because it tell how much dissolved substances, chemicals, and minerals are present in the water. Higher amounts of these impurities will lead to a higher conductivity. Even a small amount of dissolved salts and chemicals can heighten the conductivity of water. Conductivity of water might indicate that a pollutant has entered the water. For drinking water, the electrical conductivity should be less than 1 mS/cm.
Phosphate (PO4)
Phosphorous occurs in natural waters and in wastewater almost solely in the form of various types of phosphates. These forms are commonly classified into orthophosphates and total phosphates. These may occur in soluble form, in particles of detritus or in the bodies of aquatic organisms. Various forms of phosphate find their way into wastewater, effluents and polluted water from a variety of sources. Larger quantities of the same compounds may be added when the water is used or other cleaning, since these materials are major constituents of many commercial cleaning preparations. Orthophosphates applied to agricultural or residential cultivated land as fertilizers are carried into surface waters with storm run-off and
to a lesser extent with melting snow. On the other hand, Organic phosphates are formed primarily by biological processes. They are contributed to sewage by body wastes and food residues. An analysis to determine the presence of phosphates in water and wastewater analysis has great significance. Phosphate in small concentration are used in water supplies to reduce scale formation; to increase carrying capacity of mains; to avoid corrosion in water mains; to remove iron and manganese in micro quantities and in coagulation especially in acid conditions. The presence of phosphate in large quantities in freshwaters, however, indicates pollution through sewage and industrial wastes. It promotes growth of nuisance causing micro-organisms. Though phosphate possesses problems in surface waters, its presence is necessary for biological degradation of wastewaters. Phosphorus is an essential nutrient for the growth of organisms and it helps for the primary productivity of a body of water (NIS, 2007).
Sodium
Sodium ranks sixth among the elements in order of abundance and is present in most natural water. The levels may vary from less than 1 mg Na/L to more than 500 mg Na/L. Relatively high concentrations may be found in brines and hard water softened by the sodium exchange process.
The ratio of sodium to total cations is important in agriculture and human pathology. Soil permeability can be harmed by a high sodium ratio. Persons afflicted with certain diseases require water with low sodium concentration. A limiting concentration of 2 to3 mg/L is recommended in feed water destined for high-pressure boilers. When necessary, sodium can be removed by the hydrogen-exchange process or by distillation. Sodium compounds are used in many applications including caustic soda, fertilizers and water treatment chemical (WHO, 2015).
Although it is generally agreed that sodium is essential to human life, there is no agreement on the minimum daily requirement. However, it has been estimated that a total daily intake of 120–400 mg will meet the daily needs of growing infants and young children, and 500 mg those of adults. . On the basis of existing data, no firm conclusions can be drawn concerning the possible association between sodium in drinking-water and the occurrence of hypertension. No health-based guideline value is therefore proposed. However, sodium may affect the taste of drinking-water at levels above about 200 mg/litre.
Potassium (K)
Potassium ranks seventh among the elements in order of abundance, yet its concentrations in most drinking water seldom reaches 100mg/L. Potassium is an essential element in both plant and human nutrition and it occurs in groundwater as a result of mineral dissolution (APHA, 2013).
Carbon dioxide (CO2)
Aquatic vegetation and phytoplankton requires carbon dioxide for photosynthesis. It is produced as a result of respiration and decomposition. It gets dissolved in water and forms carbonic acid that affects water pH. Photosynthesis is the major cause for drain of carbon dioxide.
Heavy Metals
Studies on heavy metals in rivers, lakes, fish and sediments have constituted a major environmental focus especially during the last decade and heavy metals contamination of freshwater and sediment have been identified as a serious pollution resulting from industrialization. Protecting sediment quality is an important part of restoring and monitoring the biological integrity of our nation’s water as well as protecting aquatic life, wildlife and human health. Heavy metals are produced from a variety of natural and anthropogenic sources. In fluvial environments, however, metal pollution can result from direct atmospheric deposition, geologic weathering or through the discharge of agricultural, municipal, residential or industrial waste products.
Cadmium (Cd 2+)
Cadmium occurs in sulphide minerals that also contain zinc, lead or copper. The metal is used in electroplating, batteries, paint pigments and in alloys with various other metals. Cadmium is usually associated with zinc. It is highly toxic and has been implicated in some cases of poisoning through food. Minute quantities of cadmium are suspected of being responsible for adverse changes in arteries of human kidneys. It also generally causes cancers in laboratory animals and has been linked epidemiologically with certain human cancers. A cadmium concentration of 200μg/L is toxic to certain fishes. It may enter water as a result of
industrial discharges or the deterioration of galvanized pipe. The FAO-recommended maximum level for cadmium for irrigation water is 10μg/L/ (USEPA2012) drinking water standard for Cadmium is 0.005mg/L. BIS desirable limit is 1mg/L (WHO, 2004).
Chromium (Cr 3+)
Chromium is found chiefly in chrome-iron ore. Chromium is used in alloys, in electroplating and in pigment. Chromium salts are used extensively in industrial processes and may enter a water supply through discharge of wastes. Chromate compounds frequently are added to cooling water for corrosion control. Chromium may exist in water supplies in both the hexavalent and the trivalents state although the trivalent form rarely occurs in potable water. The USEPA regulates total chromium in drinking water and has set a Maximum Contaminant Level of 0.1 mg/L. The World Health Organization (WHO) guideline is 0.05 mg/L for total chromium.
Copper (Cu 2+)
Copper occurs in nature in its native state, the most important of which are those containing sulphide and those with oxides or carbonates. Copper salts are used in water supply systems to control biological growth of reservoirs and distribution pipe sand to catalyze in oxidation of manganese. Corrosion of copper-containing alloys in pipe fitting may introduce measurable amounts of copper into the water in a pipe system. FAO recommends maximum level for irrigation water is 200μg/L. USEPA drinking water standard for chromium and copper is 1 mg/L. permissible limit for copper is 0.05 mg/L (APHA, 2014).
Iron (Fe 2+)
Iron occurs in minerals as hematite, taconite and pyrite. It is widely used in steel and other alloys. Elevated iron levels in water can cause stains in plumbing, laundry and cooking utensils and can impart objectionable taste and colour in foods.
Iron is an essential element for photosynthesis, DNA synthesis, and many other cellular functions for plants. With regard to fish, it is an integral component of proteins involved in cellular respiration and oxygen transfer. Aquaponic systems are often iron deficient due to low amounts of iron in commercial fish feeds Iron in water has many effects on aquatic life
both good and bad. Iron (Fe) occurs naturally in water at a rate of roughly 1-3 parts per billion (ppb) in ocean water, about 1 part per million (ppm) in river water and 100ppm in groundwater. Iron comes from various minerals in the soil, which is why groundwater contains the highest iron concentrations. Iron levels in water vary depending on several factors and can affect aquatic populations, behavior and health.
Iron is vital to the life of all aquatic creatures, especially mollusks and green plants. Iron promotes enzyme growth and gives blood its red color. Iron binds to oxygen and travels with it in the blood, transporting the carbon dioxide out. Green plants use iron for nitrogen binding. Phytoplankton, some of the smallest ocean creatures, depend so heavily on iron that the amount of iron present in water limits the amount of phytoplankton that can survive. At normal levels, iron is not deadly to any aquatic animals, but at higher levels when iron does not dissolve in water, fish and other creatures cannot process all the iron they take in from water or their food. The iron can build up in animals' internal organs, eventually killing them. Higher levels of iron in fish and aquatic plants also has negative effects on the people or creatures consuming them.
To protect freshwater aquatic life, the short-term maximum guideline for total iron is 1 mg/l and for dissolved iron is 0.35 mg/L.
Lead (Pb 2+)
Lead in a water supply may come from industrial smelter discharges and mine or from dissolution of plumbing and plumbing fixture. Tap water that is not suitably treated may contain lead resulting from an attack on lead service pipes, lead interior plumbing, brass fixtures and fittings on solder pipe joints chiefly from galena (Pb). It is used in batteries, ammunition, solder, piping, pigments, insecticides and alloys. Lead also was used in gasoline for many years as an anti-knock agent in the form of tetraethyl lead.
Lead is a highly toxic metal in aquatic environment and its accumulation in fish tissues causes oxidative stress, neurotoxicity, and immune alterations (Lee et al. 2019). The WHO-recommended limit for lead levels in surface water is 0.01mg l.
Zinc (Zn 2+)
Zinc is an essential and beneficial element for human growth. Its concentration above 5mg/L can cause a bitter astringent taste in water. The zinc concentration in water varies from 0.06 to 7.0 mg/L with a mean concentration of 1.33 mg/L. Zinc most commonly enters domestic water supply from deterioration of galvanized iron and dezincification of brass. In such cases lead and cadmium also may be present because they are impurities of the zinc used in galvanizing. Zinc in water also may result from industrial waste pollution.
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