Water Quality

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Division B Champion West Windsor-Plainsboro Community Middle School
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Water Quality was a Division B and Division C event that last ran in 2014, which tested students' ability to identify marine coral reef indicator organisms and to test students' knowledge on indicators affecting estuarine and marine water quality. Topics that may be included in the testing are aquatic ecology, the water cycle, nutrient cycling, aquatic chemistry, potable water treatment, waste water treatment, aquatic food chains and webs, community interactions, population dynamics, watershed resource management issues, sedimentation pollution, harmful species, marine biology and ecology, coral reef flora and fauna (as well as general ecology) and estuary ecology.


The Basics

Water quality includes the physical, chemical and biological characteristics of water. In countries around the world, especially in the U.S., standards are set to determine whether water is potable, or safe to drink, under the direction of the EPA. This year's Water Quality event deals with estuary and coral reef ecology, replacing the freshwater ecology of last year.

The Water Cycle

For more information on the Hydrologic Cycle (water cycle), please see the Hydrologic Cycle main page.

Marine Indicator Species

For a list of indicator species from years prior to 2014, please see Water Quality/Macroorganism List.

The teams must be able to identify several marine coral reef health indicator species. These species have been grouped into categories based on where they indicate unstable coral reefs (Global, Indo-Pacific and Atlantic) as well as what factor has caused this organism to disappear (overfishing, blast fishing, poison fishing, aquarium fish collecting, nutrient pollution and curio collection). Teams should be able to identify the organisms by sight and also by some of the organisms' characteristics.

Coral Reef Indicator Species
Global Indo-Pacific Atlantic
Banded Coral Shrimp (Stenopus hispidus)-AF Barramundi Cod (Cromileptes altivelis)-OF,BF,PF,AF Gorgonia-NP
Butterfly Fish (Chaetodon spp.)-OF,PF,AF Bumphead Parrotfish (Bolobometron muricatum)-OF,BF,PF,AF Flamingo Tongue Snail (Cyphoma gibbosum)-CC
Crown of Thorns Starfish (Acanthanser planci)-OF Giant Clam (Tridacna)-OF,CC Nassau Grouper (Epinephelus striatus)-OF
Fleshy Algae-NP Humphead Wrasse (Cheilinus undulatus)-OF,BF,PF,AF
Grouper >30 cm (Serranidae)-OF,BF,PF Sea Cucumber (Thelenota ananas, Stichopus chloronotus)-OF
Hard Coral-BF,PF,NP
Long-Spined Black Sea Urchin (Diadema spp.)-OF,NP
Moray Eel (Muraenidae)-OF,AF
Parrotfish >20cm (Scaridae)-OF,BF,PF,AF
Pencil Urchin-CC
Recently Killed Coral-BF,PF,NP
Snapper (Lutjanidae)-OF,BF
Sweetlips (Haemulidae)-OF,BF,PF,AF
Triton (Charonia spp.)-OF,CC

Each team is also responsible for knowing these same facts about the following plant and animal Invasive Species

Invasive Species
Plants Animals
Purple Loosestrife Lionfish
Eurasian Water Milfoil European Green Crab
Hydrilla Chinese Mitten Crab
Asian Carp
Zebra Mussel
Northern Snakehead

Human Impact

Wastewater Treatment

Treatment in the US costs $12 billion a year, and is expected to double in 10 years.

Septic-Tank Disposal Systems: This is the conventional method for treatment. A sewer line from the house leads to an underground septic tank in the yard. This tank is designed to separate solids from liquid, digest and store organic matter, and allow the treated sewage to seep into the surrounding soil. As the wastewater moves through the soil, it is further treated by the natural processes of oxidation and filtering.

This method can fail if the tank isn't pumped out when it's full of solids or if there is poor drainage in the surrounding soil.

Septic tank system.jpg

Wastewater Treatment Plants: Raw sewage is delivered to the plant through a network of sewer pipes. Following treatment, the wastewater is discharged into rivers, lakes, or the ocean.

Wastewater treatment.jpg

Wastewater treatment is divided into three categories: primary, secondary, and advanced. Primary and secondary treatment is required by law for all municipal plants in the US. When secondary treatment isn't enough to clean water, advanced (tertiary) treatment is used.

Potable Water Treatment

Potable water treatment is the process by which lake or river water is made drinkable by humans. There are six steps: Coagulation, Flocculation, Sedimentation, Disinfection, Filtration and Distribution.

Nutrient Cycles/Biogeochemical Cycles

This event covers nutrient cycles such as the carbon, nitrogen and phosphorous cycle for land and marine ecosystems.

Cycle Description Picture
Carbon Cycle The cyclic movement of carbon in different chemical forms from the environment to organisms then back to the environment. Ccycle.jpg
Nitrogen Cycle The cyclic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment. Ncycle.jpg
Phosphorus Cycle The cycle that involves the uptake of phosphorus by organisms. Phosphorus in the environment is mainly found in rocks, but natural weathering processes can make it available to biological systems. Phosphorus is an essential nutrient for plants and animals in the form of the ions PO43- and HPO42- . (phosphate ion, hydrogen phosphate ion, respectively) It is a constituent of DNA-molecules and RNA-molecules, which store energy,(in the form of ATP and ADP) and of fats of cell membranes. (lipids) Pcycle.jpg


A major part of Water Quality deals with the analysis of a particular body of water, such as a stream, for different properties. These properties include salinity, pH, alkalinity, phosphates, nitrates, turbidity, dissolved oxygen (DO), temperature, fecal coliform, total solids, and biological oxygen demand (BOD). Students should know acceptable levels of each of these factors for estuary ecosystems and how each of these factors rise and fall based on the characteristics of the body of water and what is entering the water. The Water Quality Index used to determine the overall quality of a certain body of water based on the above factors should not be used.


Salinity is a property of water, which describes its salt concentration. Salinity is measured by dissolved salts in parts per thousand (ppt). Fresh water has a ppt of <0.5, which means that there are 0.5 molecules of dissolved salt for every 1000 molecules of solution, or 1 molecule of salt per every 2000 molecules of solution. Brackish water has a ppt between 0.5 and 30, saline water has a ppt between 30 to 50, and brine has a ppt of >50. The only water safe for human consumption is fresh water. In ocean water, total salt content makes up 3.5% of ocean water, the other 96.5% being water. Of the dissolved salts in ocean water, 85% of the salts is sodium chloride (3% of all the water). The other 15% of the total salts are other salt ions such as Magnesium, Strontium etc. (.5 % of total ocean water)

Water salinity
Fresh water Brackish water Saline water Brine
<0.5 ppt 0.5-30 ppt 30-50 ppt >50 ppt

Constructing a Salinometer

In order to test salinity, your team must construct a homemade salinometer/hydrometer capable of measuring saltwater concentrations from 1-10%. Typically, this section will be worth about 5% of the test. The vast majority of salinometers are based on the principles of density and buoyancy. Since saline solutions contain dissolved NaCl, their densities are higher than that of distilled water. Due to the elevated density, the solution exerts a higher buoyant force, causing the hydrometer to float higher than in distilled water. There is a direct relationship between salinity and and buoyant force - the more saline the water, the higher your hydrometer will float.

To make a rudimentary salinometer, get a drinking straw and some clay. Place a ball of clay on one end of the salinometer, completely covering the opening of the straw. Then make some solutions of water and salt, with the salt concentration being between 0% and 10%, and mark the meniscus of the water solution on the straw with a permanent marker, Sharpie, etc. Repeat for any number of solutions for a more accurate calibration. The amount of clay and the length and diameter of the straw affect the distance between marks on the salinometer.

Note that this is not the only way in which to make a salinometer, and you may create and invent ways to do it yourself.


A new indicator this year for marine ecosystems only. This measures the amount of calcium carbonate in marine water, a nutrient necessary for coral reef growth. Aragonite itself is the mineralized form of calcium carbonate. Under normal conditions, aragonite saturation cannot exceed 1 Ω (the omega is used for the amount of Aragonite saturation), but under special conditions such as where the temperature is higher, the water can become supersaturated with Aragonite. The amount of Aragonite saturation optimal for coral reef growth is 4 Ω, which is found near the equator because the water is warmer and can therefore hold more Aragonite.


The pH is a measurement of the hydrogen ion concentration in a substance. It is a logarithmic scale that ranges from 0 to 14, meaning that a solution with a pH of 5 has 10 times the concentration of hydrogen ions as a solution with a pH of 6. A pH of 0 to 7 is acidic, and a pH of 7 to 14 is basic. A pH of 7 is neutral.

pH is an important water quality indicator because organisms can only tolerate water that is not too acidic nor too basic. The normal pH of rivers in the United States is 6.5 to 8.5, and values between 6.0 and 9.0 can support life for fish and invertebrates. This makes acid rain an important factor in water quality, since it will make water more acidic, and once the pH value approaches 6.0, negative effects begin to appear. The natural environment of an area can also affect pH. Limestone is a base when dissolved in water, so it can neutralize the effects of acids. Volcanoes, geysers, and hot springs will make water more acidic, as well as the presence of sulfur in nearby minerals.

Alkalinity is the ability of a solution to neutralize an acid. There are several ions that contribute to alkalinity, including bicarbonate, carbonate, hydroxide, and phosphate. Thus, limestone contributes to alkalinity, since its formula is calcium carbonate, and carbonate is one of the ions listed above.


Phosphates are able to enter waterways in a variety of natural ways such as rocks or normal animal and plant waste in the water. Human sources such as fertilizers, pesticides, industrial and cleaning compounds, septic tanks and wastewater from sewage treatment can increase the amount of phosphates in the water. The phosphates of a river or stream are usually measured in Parts Per Million (ppm).


Ammonia is oxidized to form nitrates. Some human sources that can add to the total amount of nitrate in the water are fertilizers, poorly functioning septic tanks, inadequately treated wastewater from sewage treatment plants, manure from farm livestock, animal wastes including fish and birds, storm drains, runoff from crop fields, parks, lawns, feedlots and car exhausts. Nitrates, like phosphates, are test in Parts Per Million (ppm).


Turbidity can be measured in nephelometric turbidity units (NTU) or Jackson Turbidity Units (JTU). A nephelometer measures the attenuation of light as it passes through a sample of water and is reported in NTU. The Jackson Candle Method is essentially the same thing, except it uses a candle viewed through a column of water (the longer the column of water, the lower the turbidity) and is reported in JTU. The standard of turbidity for drinking water is 0.5 NTU to 1 NTU. To test the turbidity of the water, people also use a Secchi Disk. When measuring, depth is usually reported in feet to the nearest tenth of a foot, or meters to the nearest tenth of a meter. Light can penetrate to a depth of about 2-3 times the Secchi Disk depth. Seasonal variations can change the turbidity of a lake and lake turnover can also change it because of nutrients being released.Other sources of turbidity include gasoline or oil from roads, benthic organisms stirring up sediments, industrial wastes, and urban runoff. Effects of turbidity include an increase in water temperature, decrease of photosynthetic rate, and more aesthetically displeasing water.

Dissolved Oxygen

Air is about 21% oxygen which is 210,000 ppm. Most surface waters contain between 5 and 15 ppm of dissolved oxygen. If a stream or river has below 5 ppm of dissolved oxygen, then that can put aquatic life under stress, and below 1-2 ppm for a few hours can kill large fish living in the river. Total dissolved oxygen levels should not be greater than 110% at any point. Two very important factors are temperature and atmospheric pressure. Lower temperatures and higher atmospheric pressure will result in higher levels of dissolved oxygen. When dissolved or suspended solids are present in the water, this can reduce the effectiveness of dissolving of oxygen in water and can be problematic for organisms living in the water. Dry periods can lower stream discharge and raise water temperatures. From night to day, DO will fluctuate dramatically. When algal blooms are present, they can cause large fluctuations in DO through the night especially in areas where there is not much current for aeration. The primary reasons for a fluctuation in the amount of DO because of humans is dumping, sediment erosion, or the release of water from a dam. DO enters the water by means of diffusion from the atmosphere, aeration from wind, waves, and as water moves over rocks and debris, and photosynthesis of aquatic plants.


If the temperature of the water increases, this increases the sensitivity of organisms to disease, parasites, and pollution. When small changes in temperature occur in the stream, these can adversely affect the reproductive systems of aquatic organisms such as macroinvertebrates or fish. Temperature change can be caused by many things such as: natural seasonal changes, anthropogenic activities, industrial thermal pollution as discharge of cooling water, or storm water runoff from heated surfaces like streets. Soil erosion increases water turbidity and this will also increase the temperature of the water. The removal of trees and brush from the side of the river will not only increase erosion, but it will also increase the amount of sunlight that hits a river or stream.

Fecal Coliform

Fecal Coliform bacteria are living organism entering streams. If a stream has a high number of fecal coliform bacteria, then the water has had an increase in the input of fecal matter. Fecal Coliform concentrations are reported in the following format: Number of bacterial colonies/100 mL of sample water. When Fecal Coliform counts are over 200 colonies/100 mL of sample water, there is a greater chance of pathogenic organisms being present. Water with high levels of fecal coliform bacteria are associated with the following diseases: Dysentery, Typhoid Fever, Gastroenteritis, and Hepatitis. The primary sources of Fecal Coliform bacteria are from failing/leaking septic systems, animal waste, and the discharge from a water treatment plant. Urbanization can also cause problems with fecal coliform bacteria levels because plant and animal wastes can be washed away by a storm into sewers and contaminate water. When the temperature of water is high and the total levels of nutrients are high, this promotes bacteria growth.

Total Solids

The total solids of the water measures the suspended and dissolved solids in the body of water. Suspended solids can be retained on a water filter and will settle to the bottom of a water column and include silt, clay, plankton, organic wastes, and inorganic precipitates. Dissolved solids pass through a water filter and include calcium, bicarbonate, nitrogen, phosphorus, iron, and sulfur and other ions in the water. Concentration of dissolved solids in stream water is important because it determines the flow of water in and out of the cells of aquatic organisms. Many of the dissolved solids (nitrogen, phosphorus, and sulfur) are essential nutrients for aquatic life. Low concentrations of total solids can limit growth of aquatic organisms, while elevated levels can lead to accelerated eutrophication of the water system and increase the turbidity of the water. Both of these consequences decrease the overall water quality of the water. Sources of elevated levels of total solids may result as a result of runoff from agricultural activities, dredging, mining, salt from streets in winter, fertilizers from lawns, water treatment plants, plant materials, soil particles and soil erosion, and decaying organic matter. High concentrations of suspended solids can reduce water clarity, increase turbidity, reduce photosynthesis levels by reducing the sunlight that reaches plants, increase water temperature due to increased absorption of light at the water surface, and bind with toxic chemicals or heavy metals.

Biochemical Oxygen Demand

The biochemical oxygen demand (BOD) measures how fast organisms use up the oxygen in the water. Aerobic microbes use oxygen to oxidize the organic matter in the water. BOD is tested using the means for testing dissolved oxygen, but the test is done over a period of time to determine the rate of oxygen being used. Oxygen used for decomposition processes rob other organisms of oxygen needed to live. Organisms with low tolerance may die off and be replaced by organisms with more tolerance for low oxygen levels.


You may bring in one two-sided page of resource notes and 2 non-programmable/graphing calculators. You must bring Class 4 eye protection. You must also bring a salinometer as well to measure saline solutions between 0 and 10% salinity within a range of 1% at regionals and .5% at states and nationals.

See Also

Water Quality/Macroorganism List