Dissolved Oxygen - Quia

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Dissolved Oxygen

When doing any water sampling test, it is important to record certain

Background Information

Dissolved oxygen (DO) is essential to healthy streams and lakes.  The dissolved oxygen level can be an indication of how polluted the water is and how well the water can support aquatic plant and animal life.  Generally, a higher dissolved oxygen level indicates better water quality.  If dissolved oxygen levels are too low, some fish and other organisms may not be able to survive.  Much of the dissolved oxygen in water comes from oxygen in the air that has dissolved in the water.  Some of the dissolved oxygen in the water is a result of photosynthesis of aquatic plants.  On sunny days, high DO levels occur in areas of dense algae or plants due to photosynthesis.  Stream turbulence may also increase DO levels because air is trapped under rapidly moving water and the oxygen from the air will dissolve in the water. 

Water temperature also affects DO levels.  Colder water can hold more oxygen in it than warmer water.  A difference in DO levels may be seen at the test site if tested early in the morning when the water is cool and then later in the afternoon on a sunny day when the water temperature has risen.  A difference in DO levels may be seen between winter water temperatures and summer water temperatures.  Similarly, a difference in DO levels may be apparent at different depths of the water if there is a significant change in water temperature. 

Species such as sludge worms, blackfly larvae, and leeches are more tolerant of low dissolved oxygen levels so those species are more likely to be found in warm waters.  Species that need high levels of dissolved oxygen include pike, trout, bass, salmon, mayfly nymphs, stonefly nymphs, and caddisfly larvae so those will be more likely found in colder waters.

Low DO levels may be found in areas where organic material (dead plant and animal matter) is decaying.  Bacteria require oxygen to decompose organic waste, thus, deplete the water of oxygen.  Areas near sewage discharges sometimes have low DO levels due to this effect.  DO levels will also be low in warm, slow moving waters.  

Dissolved oxygen levels are often measured in parts per million (ppm) but sometimes are given in terms of Percent Saturation.  Percent Saturation is the amount of oxygen dissolved in the water sample compared to the maximum amount that could be present at the same temperature.  For example, water is said to be 100 % saturated if contains maximum amount of oxygen at that temperature.  A water sample that is 50 % saturated only has half the amount of oxygen that it could potentially hold at that temperature.  For this project, results will be reported in ppm but if you wish to determine the Percent Saturation, you can use this DO Percent Saturation chart.  Sometimes water can become supersaturated with oxygen because of rapidly tumbling water.  This usually lasts for a short period of time but can be harmful to fish and other aquatic organisms. 

Test Procedure

To perform the dissolved oxygen test, use a dissolved oxygen test kit.  Follow the instructions provided with the kit.  Record results in parts per million (ppm).  Some important points to remember are: 

• Try to sample the water away from the bank and below the water surface level. 

• Be careful not to get any air bubbles in the sample during collection; it may result in a false high reading. 

• Allow the water to gently fill the DO sample bottle from bottom to top. Put a lid on the bottle while it is under water.  

• Test the DO level immediately. Biological activity in the sample and exposure to air can quickly change the DO level. 

What to Expect

At 20 oC (room temperature) and standard atmospheric pressure (sea level), the maximum amount of oxygen that can dissolve in fresh water is 9 ppm.  If the water temperature is below 20 oC, there may be more oxygen dissolved in the sample.  Generally a dissolved oxygen level of 9-10 ppm is considered very good.  At levels of 4 ppm or less, some fish and macroinvertebrate populations (e.g. bass, trout, salmon, mayfly nymphs, stonefly nymphs, caddisfly larvae) will begin to decline.  Other organisms are more capable of surviving in water with low dissolved oxygen levels (i.e sludge worms, leeches). 

DO Percent Saturation values of 80-120 % are considered to be excellent and values less than 60% or over 125% are considered to be poor. 

Biological Oxygen Demand

Background Information

Microorganisms such as bacteria are responsible for decomposing organic waste.  When organic matter such as dead plants, leaves, grass clippings, manure, sewage, or even food waste is present in a water supply, the bacteria will begin the process of breaking down this waste.  When this happens, much of the available dissolved oxygen is consumed by aerobic bacteria, robbing other aquatic organisms of the oxygen they need to live.  Biological Oxygen Demand (BOD) is a measure of the oxygen used by microorganisms to decompose this waste.  If there is a large quantity of organic waste in the water supply, there will also be a lot of bacteria present working to decompose this waste.  In this case, the demand for oxygen will be high (due to all the bacteria) so the BOD level will be high.  As the waste is consumed or dispersed through the water, BOD levels will begin to decline.  


Nitrates and phosphates in a body of water can contribute to high BOD levels.  Nitrates and phosphates are plant nutrients and can cause plant life and algae to grow quickly.  When plants grow quickly, they also die quickly.  This contributes to the organic waste in the water, which is then decomposed by bacteria.  This results in a high BOD level. 

When BOD levels are high, dissolved oxygen (DO) levels decrease because the oxygen that is available in the water is being consumed by the bacteria.  Since less dissolved oxygen is available in the water, fish and other aquatic organisms may not survive. 

Test Procedure

The BOD test takes 5 days to complete and is performed using a dissolved oxygen test kit.  The BOD level is determined by comparing the DO level of a water sample taken immediately with the DO level of a water sample that has been incubated in a dark location for 5 days.  The difference between the two DO levels represents the amount of oxygen required for the decomposition of any organic material in the sample and is a good approximation of the BOD level.  

Take 2 samples of water and record the DO level (ppm) of one immediately using the method described in the dissolved oxygen test.  Place the second water sample in an incubator in complete darkness at 20 oC for 5 days.  If you don't have an incubator, wrap the water sample bottle in aluminum foil or black electrical tape and store in a dark place at room temperature (20 oC or 68 oF).  After 5 days, take another dissolved oxygen reading (ppm) using the dissolved oxygen test kit.  The BOD level is determined by subtracting the Day 5 reading from the Day 1 reading.  Record your final BOD result in ppm. 

What to Expect

A BOD level of 1-2 ppm is considered very good.  There will not be much organic waste present in the water supply.  A water supply with a BOD level of 3-5 ppm is considered moderately clean.  In water with a BOD level of 6-9 ppm, the water is considered somewhat polluted because there is usually organic matter present and bacteria are decomposing this waste.  At BOD levels of 100 ppm or greater, the water supply is considered very polluted with organic waste.  

Generally, when BOD levels are high, there is a decline in DO levels.  This is because the demand for oxygen by the bacteria is high and they are taking that oxygen from the oxygen dissolved in the water.  If there is no organic waste present in the water, there won't be as many bacteria present to decompose it and thus the BOD will tend to be lower and the DO level will tend to be higher. 

At high BOD levels, organisms that are more tolerant of lower dissolved oxygen (i.e. leeches and sludge worms) may appear and become numerous.  Organisms that need higher oxygen levels (i.e. caddisfly larvae and mayfly nymphs) will not survive. 

Carbon Dioxide

Background Information

Carbon dioxide in the water is in the form of a dissolved gas.  Aquatic plant life depend on carbon dioxide in the water in order to survive.  However, higher levels of carbon dioxide in the water make it difficult for fish to use the limited amount of oxygen in the water.  Usually as the dissolved oxygen levels decrease, the carbon dioxide levels increase. 

Test Procedure

To perform the carbon dioxide test, use a carbon dioxide test kit.  Follow the instructions provided with the kit.  Record results in parts per million (ppm). 

What to Expect

Surface waters should have a carbon dioxide level less than 10 ppm. 


Background Information

pH measures the relative acidity of the water.  A pH level of 7.0 is considered neutral.  Pure water has a pH of 7.0.  Water with a pH level less than 7.0 is considered to be acidic.  The lower the pH, the more acidic the water.  Water with a pH greater than 7.0 is considered to be basic or alkaline.  The greater the pH, the greater its alkalinity.  In the US, the pH of natural water is usually between 6.5 and 8.5.  Fresh water sources with a pH below 5 or above 9.5 may not be able to sustain plant or animal species. 

Industries and motor vehicles emit nitrogen oxides and sulfur oxides into the environment.  When these emissions combine with water vapor in the atmosphere, they form acids.  These acids accumulate in the clouds and fall to earth as acid rain or acid snow.  Acid rain damages trees, crops, and buildings.  It can make lakes and rivers so acidic that fish and other aquatic organisms cannot survive. 

Test Procedure

To perform the pH test, use a pH test kit or pH paper.  Follow the instructions provided with the kit.  pH must be measured immediately at the test site because changes in temperature affect pH value.  Try to take the water sample at a location away from the bank and below the water surface.  pH is recorded with a number value only, there are no units associated with the pH value.  

What to Expect

A pH reading between 6.5-7.5 is considered to be excellent; the water is neutral.  A pH level between 6-6.4 or 7.6-8.0 is considered to be good.  A pH level between 5.5-5.9 or 8.1-8.5 is considered to be fair.  If the water's pH level is less than 5.5 it is very acidic and is at a level where fish and other organisms may find it impossible to survive.  A pH level greater than 8.6 is considered to be very alkaline and this is not good either. 


Background Information

Nitrogen is an element needed by all living plants and animals to build protein.  In aquatic ecosystems, nitrogen is present in many forms.  It can combine with oxygen to form a compound called nitrate.  Nitrates may come from fertilizers, sewage, and industrial waste. They can cause eutrophication of lakes or ponds.  Eutrophication occurs when nutrients (such as nitrates and phosphates) are added to a body of water.  These nutrients usually come from runoff from farmlands and lawns, sewage, detergents, animal wastes, and leaking septic systems.  High levels of nutrients in a body of water may cause plant life and algae to flourish. As the plants grow, they can choke out other organisms.  Algae blooms may eventually cover the water's surface.  These large plant populations produce oxygen in the upper layers of the water but when the plants die and fall to the bottom, they are decomposed by bacteria which use a lot of the dissolved oxygen in the lower layers.  Bodies of water with high levels of nitrates usually have high BOD levels due to the bacteria consuming the organic plant waste and subsequent low DO levels. 

Test Procedure

Perform the nitrate test using a nitrate-nitrogen test kit.  Follow the instructions provided with the kit.  Concentrations of nitrates are usually expressed as nitrate-nitrogen (NO3-N) and not as nitrate (NO3).  For this project, nitrate measurements should be reported as nitrate-nitrogen (ppm).  

What To Expect

A nitrate-nitrogen reading of less than 1.0 ppm is considered to be excellent.  A reading between 1.1-3 ppm is considered to be good.  A reading between 3.1-5ppm is fair, and a reading greater than 5 ppm is considered to be poor. 

Ammonia Nitrogen

Although Ammonia nitrogen is part of the nitrogen cycle, NH3 is the principal form of toxic ammonia. In time, Ammonia nitrogen will break down into nitrate nitrogen and eventually into nitrites that are absorbed and used by plant. It has been reported toxic to fresh water organisms at concentrations ranging from 0.53 to 22.8 mg/L. Toxic levels are both pH and temperature dependent. Toxicity increases as pH decreases and as temperature decreases. Plants are more tolerant of ammonia than animals, and invertebrates are more tolerant than fish. Hatching and growth rates of fishes may be affected. In the structural development, changes in tissues of gills, liver, and kidneys may also occur. Toxic concentrations of ammonia in humans may cause loss of equilibrium, convulsions, coma, and death.

Ammonia levels in excess of the recommended limits may harm aquatic life. Ammonia toxicity is thought to be one of the main causes of unexplained losses in fish hatcheries.  Although the ammonia molecule is a nutrient required for life, excess ammonia may accumulate in the organism and cause alteration of metabolism or increases in body pH. Different species of fish can tolerate different levels of ammonia but in any event, less is better. Rainbow trout fry can tolerate up to about 0.2 mg./l while Hybrid striped bass can handle 1.2 mg/l.

Fish may suffer a loss of equilibrium, hyperexcitability, increased respiratory activity and oxygen uptake, and increased heart rate. At extreme ammonia levels, fish may experience convulsions, coma, and death. Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0 mg/l. Trout appear to be most susceptible of these fish and carp the least susceptible.

At higher  levels (>0.1 mg/liter NH3) even relatively short exposures can lead to skin, eye, and gills damage. Slightly elevated ammonia levels falling within the acceptable range may adversely impact aquatic life. Fish may experience a reduction in hatching success; reduction in growth rate and morphological development; and injury to gill tissue (i.e., hyperplasia), liver, and kidneys. Hyperplasia-the gill filaments are swollen and clumped together, reducing the fish's ability to 'breath'.

Elevated levels can also lead to ammonia poisoning by suppressing normal ammonia excrement from the gills. If fish are unable to excrete this metabolic waste product there is a rise in blood-ammonia levels resulting in damage to internal organs.  The fish response to toxic levels would be lethargy, loss of appetite, laying on the pond bottom with clamped fins, or gasping at the water surface if the gills have been affected. Because this response is similar to the response to poor water quality, parasite infestations and other diseases.


Background Information

Phosphorus is usually present in natural waters as phosphate.  Phosphates are present in fertilizers and laundry detergents and can enter the water from agricultural runoff, industrial waste, and sewage discharge.  Phosphates, like nitrates, are plant nutrients.  When too much phosphate enters a water, plant growth flourishes.  Phosphates also stimulate the growth of algae which can result in an algae bloom.  Algae blooms are easily recognized as layers of green slime, and can eventually cover the water's surface.  As the plants and algae grow, they choke out other organisms.  These large plant populations produce oxygen in the upper layers of the water but when the plants die and fall to the bottom, they are decomposed by bacteria which use a lot of the dissolved oxygen in the lower layers.  Bodies of water with high levels of phosphates usually have high BOD levels due to the bacteria consuming the organic plant waste and subsequent low DO levels.  

Test Procedure

Test for phosphates by using a phosphate test kit.  Follow the instructions provided with the kit.  It is important that the vials or test tubes used in the test be extremely clean.  Preferably they should be rinsed with distilled or demineralized water prior to the test.  Record your results for the phosphate test in ppm. 

What to Expect

A reading of 1.0 ppm or less is considered excellent.  A phosphate level between 1.1-4 ppm is good.  A level between 4.1-9.9 ppm is fair, and a level greater than 10 ppm is poor. 


Background Information

Turbidity refers to how clear or how cloudy the water is.  Clear water has a low turbidity level and cloudy or muddy water has a high turbidity level.  High levels of turbidity can be caused by suspended particles in the water such as soil, sediments, sewage, and plankton.  Soil can get in the water by erosion or runoff from nearby lands.  Sediments can be stirred up by too much  activity in the water, either by fish or humans.  Sewage is a result of waste discharge and high levels of plankton may be due to excessive nutrients in the water. 

If the turbidity of the water is high, there will be many suspended particles in it.  These solid particles will block sunlight and prevent aquatic plants from getting the sunlight they need for photosynthesis.  The plants will produce less oxygen thereby decreasing the DO levels.  The plants will die more easily and be decomposed  by bacteria in the water, which will reduce the DO levels even further. 

Suspended particles in the water also absorb additional heat from sunlight which will result in warmer water.  Warm water is not able to hold as much oxygen as cold water so DO levels will decrease, especially near the surface.  

Suspended particles are also destructive to many aquatic organisms.  They can clog the gills of fish and interfere with their ability to find food.  They can also bury bottom dwelling creatures and eggs.  Suspended particles can transport pollutants through the water. 

Test Procedure

There are several ways to measure turbidity.  One way is with a Secchi disk which is slowly lowered into the water until it is no longer visible, then raised until just visible, and lowered to just no longer visible.  The depth at which the Secchi disk is no longer visible the second time is recorded in meters.  A Secchi disk is usually more appropriate for deep waters of lakes, ponds, and rivers. 

For shallow waters, a turbidity test kit that has a image at the bottom of a clear tube can be used. This is the recommend method for this project.  Sample water that is collected can be  added to the tubes to determine the turbidity level.  The turbidity level is measured in Jackson Turbidity Units (JTU).  This method does not require students to go out into deeper water. 

If using a meter to measure turbidity, the meter will most likely report in NTUs, (Nephelometric Turbidity Unit).  NTU and FNU (Formazin Nephelometric Unit) are the USEPA-designated units of turbidimetric measurement.  They are based on use of a detector (meter) placed at 90° from the incident beam to detect scattered light, and are interchangeable units.

A clear mountain stream might have a turbidity of around 1 NTU, whereas a large river like the Mississippi might have a dry-weather turbidity of around 10 NTUs. These values can jump into hundreds of NTUs during runoff events. Therefore, the turbidity meter to be used should be reliable over the range in which you will be working.

So, if using a Secchi disk for this testing parameter, please submit the results using units of meters.  If using a turbidity test kit, submit the results in JTUs, and if using a meter, please report results in NTUs.

Unfortunately, there is not easy way to convert these units.  

What to Expect

A turbidity reading of 0-10 JTU  or NTU is considered normal.  A Secchi depth less of less than 1 meter indicates a high concentration of suspended solids. 

Coliform Bacteria

Background Information

If coliform bacteria are present in the water supply it is an indication that the water supply may be contaminated with sewage or other decomposing waste.  Usually coliform bacteria are found in greater abundance on the surface film of the water or in the sediments on the bottom.  

Fecal coliform, found in the lower intestines of humans and other warm-blooded animals, is one type of coliform bacteria.  The presence of fecal coliform in a water supply is a good indication that sewage has polluted the water.  Testing can be done for fecal coliform specifically or for total coliform bacteria which includes all coliform bacteria strains and may indicate fecal contamination. 

Test Procedure

Depending on the level of your students and your experience with this type of test, you may opt to do a total coliform test or a fecal coliform test.  The total coliform test is simpler but does not give a quantitative result; the test just indicates the presence or absence of coliform bacteria (yes/no). 

If a fecal coliform test is performed, please report your results as number of fecal coliform colonies per 100 ml sample of water.  

What to Expect

The presence of coliform bacteria may be an indication of a polluted water supply but it would  be necessary to do further tests in order to identify the specific bacteria present and the level of contamination. 

Recommended fecal coliform bacteria counts are: 

|Drinking water less than 0 colonies per 100 mL sample of water  |

|Swimming less than 200 colonies per 100 mL sample of water  |

|Boating/Fishing less than 1000 colonies per 100 mL sample of water  |


Background Information

In most streams, the energy available to organisms is stored in plants and made available to animal life either in the form of leaves and algae that are eaten by macroinvertebrates.  In turn, the macroinvertebrates are a source of energy (food) for larger animals such as fish, which are a source of energy (food) for birds, raccoons, and humans. 

Besides being an important link in the food chain, macroinvertebrates can also serve as an indicator of water quality.  Some stream-bottom macroinvertebrates cannot survive in polluted  water while others can survive or even thrive in polluted water.  A healthy ecosystem supports diversity of organisms, so in a healthy stream, the stream-bottom community will include a  variety of pollution-sensitive macroinvertebrates.  Conversely, an unhealthy stream will support only a few types of nonsensitve macroinvertebrates. 

In this project, macroinvertebrate sampling is coupled with chemical water quality sampling.  The reason for this is quite simple.  The process of identifying stream pollution with water analysis alone is time intensive and can only provide information for the time of sampling. Even the presence of fish may not provide information about a pollution problem because fish can move away to avoid polluted water and then return when conditions improve.  However, most stream-bottom macroinvertebrates cannot move to avoid pollution. A macroinvertebrate sample may provide more information about pollution or overall water quality that is not present at the time of sample collection.   

Useful stream-bottom macroinvertebrate data are easy to collect without expensive equipment. 

Test Procedure

The two most common methods to sample macroinvertebrates include the kick net or the dip net methods.  The kick net is most efficient for sampling streams with rocky or gravel stream beds where the velocity of the water will move the dislodged organisms into the net.  The dip net method can be used in a variety of habitats and used like the kick net or used for scooping through the water. 

The first step is to select a sampling site to ensure that the appropriate equipment is obtained.  Find a riffle that is typical of the stream. A good riffle for sampling will have cobble-sized stones, fast-moving water, and a depth of 3 to 12 inches. Select a 3-foot by 3-foot area within the riffle for sampling.

Position the kick net at the downstream end of the sampling area and proceed slowly walking upstream.  The net should be stretched out to its full 3-foot width with the bottom edge lying firmly against the stream bed. No water should wash under or over the net.  If needed, small rocks can be used to weigh down the bottom edge of the net.  A "kick" is a stationary sampling accomplished by using the toe or heel of a boot and dislodging the upper layer of the stream bed one meter at a time.  If larger substrate is encountered, such as a large piece  of wood, the object should be picked up and rubber by hand or small brush to dislodge the attached organisms. 


NOTE: To avoid losing macroinvertebrates that should be part of the sample, do not stand in or disturb the sampling area before the kick seine is in place.  

Lift the kick seine out of the water with a forward scooping motion.  The object is to avoid losing any macroinvertebrate specimens while the seine is lifted.  This will be easier if one person holds the top of the kick seine handles while the other person holds the bottom of the handles. 

Carry the kick seine to the stream bank and spread it out flat on a piece of white plastic. Carefully examine the net and  the collected debris for macroinvertebrates.  Look carefully as many specimens will be small and hard to see.  Using tweezers or fingers, place all the specimens in white containers filled with stream water. Sort them into different types as you remove them from the net, and place each type in a separate container.  Ice cube trays are very effective for this process.

NOTE: If your plan is to transport the sample back to your "lab" before sorting and identification, you can place the contents of the kick seine (including the debris) into a bucket that is partly filled with stream water.  If you put a lid on the bucket (recommended), you should leave some air space above the water in the bucket to allow mixing of oxygen. 

Once the macroinvertebrates are collected and sorted, they can be identified by using the Save Our Streams Macroinvertebrate Identification Key.  

Record and submit the results to the project data base.

What to Expect

The Guidelines established by the Save Our Streams Program will be followed for this project.  Save Our Streams identifies three groups of macroinvertebrates based on their  sensitivity to pollution: pollution sensitive, somewhat pollution tolerant and pollution tolerant.  The Save Our Streams method involves collecting a sample of macroinvertebrates from the stream, identifying the organisms and rating the water quality.  Water quality ratings of excellent, good, fair, and poor are based on the pollution tolerance levels of the organisms found and the diversity of organisms in the sample.  A stream with excellent water quality  should support organisms from all three pollution tolerance groups. 

Indicators of good water quality 

Mayfly larvae 

Caddisfly larvae 

Stonefly larvae 

Gilled snails 

Riffle Beetle - adult


Water Peeny


Indicators of fair water quality 


Riffle Beetle - larva


Cranefly larvae 





Watersnipe Fly

Whirligig Beetle - larva


Clam or Mussel 

Indicators of poor water quality 

Midge fly larvae 

Blackfly larvae 


Aquatic worms 

Lung snails 

Iron and manganese are non-hazardous elements that can be a nuisance in a water supply. Iron and manganese are chemically similar and cause similar problems. Iron is the most frequent of the two contaminants in water supplies; manganese is typically found in iron-bearing water.

Sources of Iron and Manganese in Drinking Water

Iron and manganese are common metallic elements found in the earth's crust. Water percolating through soil and rock can dissolve minerals containing iron and manganese and hold them in solution. Occasionally, iron pipes also may be a source of iron in water.

Indications of Iron and Manganese

In deep wells, where oxygen content is low, the iron/manganese-bearing water is clear and colorless (the iron and manganese are dissolved). Water from the tap may be clear, but when exposed to air, iron and manganese are oxidized and change from colorless, dissolved forms to colored, solid forms.

Oxidation of dissolved iron particles in water changes the iron to white, then yellow and finally to red-brown solid particles that settle out of the water. Iron that does not form particles large enough to settle out and that remains suspended (colloidal iron) leaves the water with a red tint.  Manganese usually is dissolved in water, although some shallow wells contain colloidal manganese (black tint).  These sediments are responsible for the staining properties of water containing high concentrations of iron and manganese. These precipitates or sediments may be severe enough to plug water pipes.

Iron and manganese can affect the flavor and color of food and water. They may react with tannins in coffee, tea and some alcoholic beverages to produce a black sludge, which affects both taste and appearance. Manganese is objectionable in water even when present in smaller concentrations than iron.

A problem that frequently results from iron or manganese in water is iron or manganese bacteria. These nonpathogenic (not health threatening) bacteria occur in soil, shallow aquifers and some surface waters. The bacteria feed on iron and manganese in water. These bacteria form red-brown (iron) or black-brown (manganese) slime in toilet tanks and can clog water systems.   If you are having problems with iron, manganese, and/or occassional sulfur odors we typically recommend testing for the Option 1 Package and the Option 3 Nuisance Bacteria Package.

Potential Health Effects

The regulations regarding iron and manganese in drinking water were established as secondary standards, which means the limits were set because of nuisance problems and aesthetic concerns.  It has come to my attention that a portion of the public may be suitable to Iron Overload  or Hemochromatosis.  The symptoms of hemochromatosis vary and can include: chronic fatigue, arthritis, heart disease, cirrhosis, cancer, diabetes, thyroid disease, impotence, and sterility. 

Iron may also form iron oxide which would reduce available oxygen levels for fish and other aquatic life.

Sulfates and Hydrogen Sulfide

Sulfates are a combination of sulfur and oxygen and are a part of naturally occurring minerals in some soil and rock formations that contain groundwater. The mineral dissolves over time and is released into groundwater.

Sulfur-reducing bacteria, which use sulfur as an energy source, are the primary producers of large quantities of hydrogen sulfide through the process of decomposition. These bacteria chemically change natural sulfates in water to hydrogen sulfide. Sulfur-reducing bacteria live in oxygen-deficient environments such as deep wells, plumbing systems, water softeners and water heaters. These bacteria usually flourish on the hot water side of a water distribution system.

Hydrogen sulfide gas also occurs naturally in some groundwater. It is formed from decomposing underground deposits of organic matter such as decaying plant material. It is found in deep or shallow wells and also can enter surface water through springs, although it quickly escapes to the atmosphere. Hydrogen sulfide often is present in wells drilled in shale or sandstone, or near coal or peat deposits or oil fields.

Indications of Sulfate and Hydrogen Sulfide


Sulfate minerals can cause scale buildup in water pipes similar to other minerals and may be associated with a bitter taste in water that can have a laxative effect on humans and young livestock. Elevated sulfate levels in combination with chlorine bleach can make cleaning clothes difficult.  Sulfur-oxidizing bacteria produce effects similar to those of iron bacteria. They convert sulfide into sulfate, producing a dark slime that can clog plumbing and/or stain clothing. Blackening of water or dark slime coating the inside of toilet tanks may indicate a sulfur-oxidizing bacteria problem. Sulfur-oxidizing bacteria are less common than sulfur-reducing bacteria.

Hydrogen Sulfide

Hydrogen sulfide gas produces an offensive "rotten egg" or "sulfur water" odor and taste in the water. In some cases, the odor may be noticeable only when the water is initially turned on or when hot water is run. Heat forces the gas into the air which may cause the odor to be especially offensive in a shower. Occasionally, a hot water heater is a source of hydrogen sulfide odor. The magnesium corrosion control rod present in many hot water heaters can chemically reduce naturally occurring sulfates to hydrogen sulfide.

Potential Health Effects


Sulfate may have a laxative effect that can lead to dehydration and is of special concern for infants. With time, people and young livestock will become acclimated to the sulfate and the symptoms disappear. Sulfur-oxidizing bacteria pose no known human health risk.  The Maximum contaminate level is 250 mg/L.

Hydrogen Sulfide

Hydrogen sulfide is flammable and poisonous. In ponds, sulfate and sufides indicate bacterial decomposition; which is an aerobic process. Excessive amounts of decomposition can lead to the depletion of oxygen levels. High temperatures or frozen layers over a pond or stream can heighten the loss of oxygen leading to the death of plants, fish, and other aquatic life. As more species die, more bacterial occurs, thus depleting even more oxygen creating a vicious cycle. Unless something is done to interrupt the cycle or introduce oxygen by natural or artificial means, the action of the bacteria could cause eutrophication; literally meaning the ‘death’ of a lake.

Usually, in humans, it is not a health risk at concentrations present in household water, except in very high concentrations. While such concentrations are rare, hydrogen sulfide's presence in drinking water when released in confined areas has been known to cause nausea, illness and, in extreme cases, death. Water with hydrogen sulfide alone does not cause disease. In rare cases, however, hydrogen sulfide odor may be from sewage pollution which can contain disease-producing contaminants.   Therefore, testing for bacterial contamination and Sulfate Reducing Bacteria is highly recommended.

5 Facts about Copper based Algaecides

Here's a situation that pond owners run into time and time again-we'll use Dan as our example. Dan loves the pond on his property; he loves to look out over the fish swimming around, frogs leaping into the water from the edge, and birds fly in to rest.

With the best interests of his pond in mind, and hoping to get rid of a little excess algae, he contracts a 'pond company' manage his pond. When the company arrives for their first 'treatment, ' Dan walks out to observe and is surprised by what he sees-two men wearing protective suits, gloves, and a mask are navigating a boat around his pond, spraying an unnaturally deep blue liquid all across the surface.

When Dan inquires about what they're spraying, they respond with "copper sulfate, it's a chemical algaecide." Concerned about his pond and the wildlife living in it, Dan then asks if it's safe, prompting the pond company to respond, "uhh sure, it's perfectly safe..."

Dan then asks the next logical question, "then why are you both wearing hazmat suits?"

Encounters like this are leading pond owners nationwide to give up use of harsh chemicals to manage their pond. Just like Dan, they are gaining the awareness that chemical treatments are not really 'treating' at all-they are actually devastating your pond's natural ecosystem. And this is only one of many reasons why pond owners are avoiding algaecides:

1. Algaecides Cost You a Bunch of Money:

a. Algaecides themselves are costly, costing as much as 80% more than safe, environmentally friendly alternatives. Not only are they expensive, but many states also require algaecides to be applied by a licensed technician because they are so dangerous.

So, in addition to paying for expensive chemicals, you also have to pay for a professional to apply them roughly every two weeks. Pond owners sometimes pay thousands and thousands of dollars to control algae, unaware that cheaper, more environmentally friendly options exist.

2. You Can Never Stop Using Algaecides:

a. In order for algaecide to be effective, it must be in your pond in a specific concentration that is tough to maintain. Algaecides are weakened as water flows in and out of your pond, and they also leach into and accumulate in the soil.

If you want to maintain algae prevention, you can never stop applying the chemical. Unless you use a eco-friendly pond management alternative, quitting use of algaecides will lead to much larger algae blooms than you began with, because:

3. Algaecides Don't Treat the Causes of Algae in Your Pond:

a. Algae require nutrients to grow, just like we need food, and these nutrients are constantly flowing into your pond from the surrounding environment. If you take care of these nutrients, you get rid of the algae. Algaecides do nothing to affect the nutrient, as they only treat the visible symptoms of the overall problem by killing the algae itself.

This algae, in turn, sinks to the bottom of your pond and decays, releasing its nutrient to fuel even larger algae blooms in the future. The more algae you kill with chemicals, the more decaying matter will build up in your pond-sometimes leading to the need to dredge (remove sludge) at a huge expense. Not only that, but as the algae decays it sucks the oxygen out of the water, potentially leading to severe fish kills.

4. Algaecides are Extremely Toxic to Your Health:

a. Copper sulfate is readily absorbed through the skin, and has been classified by the EPA as being in toxicity class I - highly toxic -requiring the signal words "DANGER - POISON" on its container. According to the Extension Toxicology Network, accidental ingestion just gram quantities of copper sulfate can lead to some very nasty and deadly effects. Having such hazardous chemicals sprayed onto your property is an absolutely unnecessary risk.

5. Algaecides Damage Both Your Pond and its Surrounding Environment:

a. Algaecides upset the natural balance of the water body: phytoplankton, the base of the food chain, are greatly reduced and no longer support small aquatic life; sediment-dwelling insects are killed by the accumulating poison; and plants, serving as both fish food and habitat, are killed by algaecide's photosynthesis disruption.

After your pond's ecosystem has been debilitated, the highly water-soluble algaecide is flushed out during a rain event, becoming a hazard for downstream organisms. This can stress and sometimes be lethal to many types of fish, and can negatively affect animals that drink the water by bioaccumulating in their heart, liver, brain, kidneys, and muscles.

These terrible consequences are leading governmental bodies to consider banning on algaecide use. The City of Naples, Florida has banned copper sulfate because it heavily pollutes Naples Bay, and the European Union has considered prohibiting its use because it is "not compatible with sustainable ecosystems."


Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water. Water which has been treated with chlorine is effective in preventing the spread of disease.

The chlorination of public drinking supplies was originally met with resistance, as people were concerned about the health effects of the practice. The use of chlorine has greatly reduced the prevalence of waterborne disease as it is effective against almost all bacteria and viruses, as well as amoeba.

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Chlorination is also used to sanitize the water in swimming pools and as a disinfection stage in sewage treatment.


Disinfection by chlorination can be problematic, in some circumstances. Chlorine can react with naturally occurring organic compounds found in the water supply to produce dangerous compounds, known as disinfection byproducts (DBPs). The most common DBPs are trihalomethanes (THMs) and haloacetic acids. Due to the carcinogenic potential of these compounds, federal regulations in the United States of America require regular monitoring of the concentration of these compounds in the distribution systems of

municipal water systems. However, the World Health Organization has stated that the "Risks to health from DBPs are extremely small in comparison with inadequate disinfection."

There are also other concerns regarding chlorine, including its volatile nature which causes it to disappear too quickly from the water system, and aesthetic concerns such as taste and odor.

What is Alkalinity?

Alkalinity is the water's capacity to resist changes in pH that would make the water more acidic. This capacity is commonly known as "buffering capacity." For example, if you add the same weak acid solution to two vials of water - both with a pH of 7, but one with no buffering power (e.g. zero alkalinity) and the other with buffering power (e.g. an alkalinity of 50 mg/l), - the pH of the zero alkalinity water will immediately drop while the pH of the buffered water will change very little or not at all.  The pH of the buffered solution would change when the buffering capacity of the solution is overloaded.

Alkalinity refers to the capability of water to neutralize acid. This is really an expression of buffering capacity. A buffer is a solution to which an acid can be added without changing the concentration of available H+ ions (without changing the pH) appreciably. It essentially absorbs the excess H+ ions and protects the water body from fluctuations in pH. In most natural water bodies in Pennsylvania the buffering system is carbonate-bicarbonate ( H2CO3, HCO3, and CO3). 

Alkalinity of natural water is determined  by the soil and bedrock through which it passes. The main sources for natural alkalinity are rocks which contain carbonate, bicarbonate, and hydroxide compounds. Borates, silicates, and phosphates also may contribute to alkalinity. Limestone is rich in carbonates, so waters flowing through limestone regions or bedrock containing carbonates generally have high alkalinity - hence good buffering capacity. Conversely, areas rich in granites and some conglomerates and sandstones may have low alkalinity and therefore poor buffering capacity.

The presence of calcium carbonate or other compounds such as magnesium carbonate contribute carbonate ions to the buffering system. Alkalinity is often related to hardness because the main source of alkalinity is usually from carbonate rocks (limestone) which are mostly CaCO3. If CaCO3 actually accounts for most of the alkalinity, hardness in CaCO3 is equal to alkalinity. Since hard water contains metal carbonates (mostly CaCO3) it is high in alkalinity. Conversely, unless carbonate is associated with sodium or potassium which don't contribute to hardness, soft water usually has low alkalinity and little buffering capacity. So, generally, soft water is much more susceptible to fluctuations in pH from acid rains or acid contamination.

How alkalinity affects aquatic life

Alkalinity is important for fish and aquatic life because it protects or buffers against rapid pH changes. Living organisms, especially aquatic life, function best in a pH range of 6.0 to 9.0. Alkalinity is a measure of how much acid can be added to a liquid without causing a large change in pH. Higher alkalinity levels in surface waters will buffer acid rain and other acid wastes and prevent pH changes that are harmful to aquatic life. 

Acid shock may occur in spring when acid snows melt, thunderstorms, natural discharges of tannic waters, "acid rain", acidic dryfall, and other discharges enter the stream. If increasing amounts of acids are added to a body of water, the water's buffering capacity is consumed. If additional buffering material can be obtained from surrounding soils and rocks, the alkalinity level may eventually be restored. However, a temporary loss of buffering capacity can permit pH levels to drop to those harmful to life in the water.

The pH of water does not fall evenly as acid contamination proceeds. The natural buffering materials in water slow the decline of pH to around 6.0. This gradual decline is followed by a rapid pH drop as the bicarbonate buffering capacity is used up. At a pH of 5.5, only very weak buffering materials remain and pH drops further with additional acid. Sensitive species and immature animals are affected first. As food species disappear, even larger, resistant animals are affected.

For protection of aquatic life the buffering capacity should be at least 20 mg/L. If alkalinity is naturally low, (less than 20 mg/L) there can be no greater than a 25% reduction in alkalinity.


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