Particles in Water - Properties and Processes

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There are different origins: mineral substance dissolution, erosion, organic matter decomposition, farming wastes and wastewater. The different kinds of colloids: The hydrophobic colloids are responsible for water coloration and basically they have an organics origin with a R-NH 2 or R-OH part. These electronegative parts create hydrogen links with the water molecules.

CP3 - Center for Particulate Products and Processes

This layer opposes itself to the colloid meeting and is a stabilization factor. The hydrophilic colloids are from mineral origins.

At their surface are concentrated negative charges which bring about an impossible agglomeration. Colloid elimination: In order to remove colloids from water the best solution is to perform like a first step a particle coagulation with a coagulant agent. The aim of this step is to destabilize the colloid electrostatic charge to promote the meeting and their future agglomeration during the flocculation step.

Toggle navigation. It may even disappear completely from the bottom water, making life for fish and many other plants and animals impossible in this part of the pond. Because this area is separated from the surface waters, fertilizers or feed materials falling to the pond floor are no longer available for the plankton or the fish. In cooler weather, heavy cool rains or strong winds can cause this water stratification to break up.

The whole water mass then turns over , bringing the cooler, oxygen-poor bottom waters to the surface of the pond and sometimes killing the fish. In some cases, the nutrients and feed materials brought up from the bottom water can also cause excessive plankton growth. Such a thermometer is very fragile. To carry it around, you should keep it in a protective case. You can easily make one from a piece of bamboo in which you place some cotton wool. To measure the temperature of surface waters , for example in the feeding canal at the pond water inlet or in the pond itself next to the outlet structure, proceed as follows.

Note: you can use the same method with a bucket full of water, but be careful to measure the temperature immediately after the water is collected. It you have to measure water temperatures often, it may be best to tie a sampling bottle to a pole with the bulb of the thermometer permanently attached just inside the bottle as shown in the illustration. Read the temperature as soon as you have filled the sampler with surface water. To measure the temperature of water from a greater depth , for example bottom water in a pond near the outlet structure, you need a better water sampler such as the one described earlier see Section 2.

Then proceed as follows. Whenever you need to closely follow temperature changes in your pond for management purposes , such as fish propagation see Section 9. The best time to do this is shortly after sunrise , when the air temperature is near its minimum value , and again shortly after midday , when the air temperature is near its maximum value , see graph below. You can calculate the average daily temperature of the water and list thermal fluctuations in a table para.

If you have a maximum-minimum thermometer , you will need to read the pond water temperature only once a day to obtain both the minimum and maximum temperatures. First, secure the thermometer in the pond, within easy reach by: driving a wooden pole into the pond bottom, slightly angled from vertical, within easy reach of the outlet structure the top of the pole should be above water ; fixing a nail near the top of this pole, and attaching a string from the nail to the top of the thermometer; hanging the thermometer about 50 cm below the water surface, at a safe distance from the wooden pole.

To record the extreme daily water temperatures , proceed as follows.

Physical processes

Note this down as the minimum temperature for that day. Note this down as the maximum temperature for the previous day. Note : you can also measure the temperature each evening. In this case, the minimum and maximum temperatures will both be for that day.


If you have several ponds of about the same size and depth, fed with a common water supply, it is sufficient to obtain the minimum and maximum temperatures in one of these ponds only. You can then calculate the average daily temperature of the water and show thermal fluctuations on a graph , as explained below.

Note : in a shallow pond not much more than 1 m deep, it is sufficient to measure the water surface temperature. In a pond deeper than 1.

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This method gives you a good estimate of the temperatures in which your fish live. Note : if, for a deeper pond, you have also measured one water temperature near the bottom, you should calculate two average temperatures: the surface water average , as explained above; and the bottom water average , from the minimum and maximum temperatures observed near the bottom.

The overall average of the pond water is then estimated by dividing by two the sum of the surface and bottom water average temperatures. To guide your management practices, you can show on a graph the variations of daily water temperature over a period of time. Mark it with exact dates to avoid any error.

For example, you may be interested in showing the fluctuations of: the minimum water temperatures , at the bottom of the graph; the maximum water temperatures , at the top of the graph; the average water temperatures , in the middle of the graph. When this information is plotted on a graph, you can easily follow the changes in water temperature that are affecting your fish stocks. It is possible to take some action to improve, within certain limits, the water temperature in fish ponds. But remember that: the larger the pond , the more stable its average water temperature will be, whereas in very small ponds of only a few hundred square metres, temperature conditions can change very rapidly, for example during a rainstorm or because of a strong, cold wind; the smaller the pond , the easier it will be to change its average water temperature through management.

If you wish to increase the average water temperature of your pond, for example for early spawning of warmwater fish or for prolonged growth or survival over winter months, you can do so in the following way.

by Gregory, John

Be careful, however, not to mix the layers while doing so. The most important gas dissolved in water is oxygen O 2. As you have already learned, dissolved oxygen DO is essential to most living organisms for their respiration.

Oxygen is also necessary for dead organic matter to be broken down during the process called decomposition. The oxygen dissolved in water has two sources: atmospheric oxygen; photosynthesis. The atmospheric oxygen in contact with the water surface is an unlimited source of oxygen; unfortunately, its passage into water, its diffusion and its subsequent dissolving into water is a very slow process.

You will learn how to improve this process by using aerators later in this section.

The major source of dissolved oxygen in ponds is photosynthesis see Section 2. Remember that this process depends on the amount of light available to the plants and therefore: oxygen production decreases during cloudy days; it completely stops at night; it gradually decreases as water depth increases and light levels diminish, the rate of the decrease depending on the water turbidity see Section 2. Measuring DO content in water 5. You can measure how much oxygen is dissolved in water either by chemical methods or by electrical methods.

Chemical methods usually rely on the use of simple kits, which can be bought from specialized suppliers. They contain all the chemicals and small equipment necessary to determine the DO content with sufficient accuracy for pond management purposes. Instructions should be closely followed. The measurement is taken on a small water sample obtained with the water sampler described above see Section 2.

Electrical methods are based on the use of an oxygen meter , a rather expensive device which can be bought from specialized suppliers. It has the advantage that the DO content can be measured directly from the water, at any depth. The DO content is read from a scale. Instructions should be accurately followed.

Contrasting student and scientific views

You should take particular care to calibrate i. Remember : when measuring DO content, you should always measure the water temperature simultaneously , so that you will be able to relate the DO measurement to this temperature. Apply the method described below. To estimate the average DO content of the water in a shallow pond at a certain time, you should obtain a series of water samples. The simplest but less accurate way is to obtain water samples from one station only but at different depths , as follows.

Solvent properties of water

Do not take water samples near growing aquatic plants or beneath a heavy cover of algae blown against the shore, as these samples would not be typical of the conditions in the rest of the pond. If your pond is large and deep, such as a barrage pond , you may need more water samples to obtain a better estimate of the average DO content of water in the pond. You should, if needed: add one sampling station at the shallow end of the pond; obtain at each station four samples instead of three, at depths equal to 0. In some cases see below , you may wish to obtain the DO content of the upper layers of the pond only.

Properties of Water - Hydrogen Bonding in Water - Biology - Biochemistry

For this you should take samples in this upper layer only, and calculate the averages as before. As for all other gases, the maximum quantity of oxygen that water can hold, the oxygen solubility in water , depends on three factors. The maximum quantity of oxygen which a particular body of water can normally hold is called the percent saturation value. Under certain circumstances, it may happen that the pond water contains more than this percent saturation value. It is then said that there is supersaturation of the water with oxygen, a phenomenon which may happen, for example, in the afternoon when photosynthesis has been very active.

If the DO content of surface water is measured equal to 8. The oxygen saturation value of the water is therefore equal to 8. It is often easier to use the following graphical method , which gives you a quick estimate of the oxygen saturation value good enough for freshwater pond management purposes. Note: if you can, make a copy of the blank graph so that you can use it again. Remember: if the DO saturation value is higher than percent, there is oxygen supersaturation in the water. GRAPH 1 Graph for the determination of oxygen saturation values in fresh water at sea level Levels of dissolved oxygen that fish require The oxygen requirements of fish are determined by three basic factors : fish species; size of the fish; and water temperature.

In addition, there may be some variation due to physiological factors such as activity, feeding and digestion, sexual maturation and spawning. As you have already learned see Section 2. Fish such as catfish, which are used to slow-moving water bodies, can tolerate lower levels than fish used to fast-moving water. For a particular species, younger fish require higher oxygen levels than adults. At higher water temperatures, the fish will consume more oxygen for their respiration.

2.4 Pond water temperature

This factor can be very important, because when temperature rises, water holds less oxygen see the first chart on page 2. When actively feeding and later, when digesting their food , fish will require much more oxygen than usual. You will learn more about DO requirements of fish in Section Two types of fluctuation in oxygen level can be found in fish ponds: daily fluctuations , both in surface water and in deeper water; seasonal fluctuations , mostly observed in deeper ponds.

In surface water , the daily fluctuation of the DO content is related to the hour cycle of day and night. On clear days, DO production is higher than on cloudy days.