Water Lab

Alkalinity is a way to measure water’s ability to resist change in pH or its "Buffering Capacity". Alkalinity helps prevent or reduce drastic changes in pH when exposed to acidic influxes that would normally cause a decrease in pH.

Alkalinity is measured in the lab by mixing 50mL of the sample with 1 drop of sodium thiosulfate and 5 drops of methyl red indicator and titrating with .02N sulfuric acid. The amount of acid used as a titrant in millimoles per liter or meq/L (milliequivalents per liter) is Alkalinity's unit of measurement.

Alkalinity is dependent upon concentrations of carbonate, bicarbonate, hydroxide, borate, phosphate, and silicates. It is important to measure alkalinity to determine the stream or rivers ability to neutralize acid from rainfall or wastewater pollution.

Citation

PH of water. (2013). Retrieved from Fundamentals of environmental measurements website.

Biological oxygen demand measures the amount of oxygen that bacterial consume when breaking down organic material that is present in water. BOD is important to monitor when assessing water quality because it is a way to identify the amount of organic matter available for organisms to break down.

A high BOD reading might indicate that there are increased amounts of organic materials, such as wastewater or animal waste from runoff, entering a water system.

A decrease in dissolved oxygen in an aquatic ecosystem can lead to anaerobic conditions which harm some aquatic species. This test is completed by adding nutrient broth to the water sample, measuring the initial amount of oxygen present in the water, sealing the sample, incubating for five days, and reading the final amount of oxygen present.

The initial and final readings are used to measure the loss of oxygen as a result of the bacteria breaking down the nutrients. The formula used to calculate BOD is:

BOD = and gives a BOD reading in units of mg/L.

Citation

Real Tech Inc. (2017). Biochemical oxygen demand.

Chemical oxygen demand is a measure of the amount of organic material and inorganic material in a water sample. Chemical oxygen demand is important to measure when assessing water quality because it measures the amount of organic material present in the water sample which can be an indicator of increased wastewater disposal. Higher COD values indicate higher organic matter present in the aquatic environment.

The difference between COD and BOD is that COD uses chemicals to measure the amount of oxygen used to oxidize the organic and inorganic matter. Conductivity is measured by using potassium dichromate to oxidize the organic and inorganic matter and then the sample is usually incubated for 2 hours at a high temperature. After incubation, a Ferrous ammonium sulfate (FAS) solution is used to titrate until the endpoint is reached. The amount of FAS solution used to reach the endpoint is used to calculate the COD in units of mg/L.

Citation

Real Tech. (2017). Chemical oxygen demand.

Conductivity is a measure of water’s ability to conduct electricity. Conductivity is an indication of the salinity of the water, or the concentration of ions that are dissolved in the water such as sodium, chloride, calcium, and magnesium.

As the conductivity reading increases, it is indicating more ions dissolved in the water.  Conductivity is important because aquatic species are extremely sensitive to the salinity of water and too many dissolved ions can lead to the death of sensitive aquatic life. Factors that affect conductivity include the water temperature, as water temperature increases, conductivity increases. Conductivity is measured using a probe that contains electrodes located close together and measures the ability of electrical current to flow between the electrodes. Most probes correct the measurement to a 25C temperature and gives the reading in parts per thousand.

Citation

Staff, F. (2010). What is conductivity?

Dissolved oxygen is the measure of the oxygen present in the water and one of the most important water quality parameters. Dissolved oxygen affects the health of fish, invertebrates, bacteria and plants that inhabit streams and bodies of water because they live through respiration of the oxygen that is in the water.

Microbial decomposition, a process crucial to the health of aquatic ecosystems, would not occur without the presence of oxygen in the water. Oxygen enters water through the mixing and aeration of the water, in natural and manmade ways as well as from photosynthesis of aquatic plants.

Dissolved oxygen and water temperature have a negative linear relationship. As temperature increases, dissolved oxygen tends to decrease. Dissolved oxygen is measured in the field using a dissolved oxygen probe the indicator units of milligrams per liter (mg/L) are recorded.

Citation

Fondriest Environmental Inc. (2013). Dissolved oxygen. Retrieved from Fundamentals of environmental measurements website.

Fecal Coliform is a measure of fecal matter present in the water sample. Coliform bacteria are present in the intestinal tract of warm-blooded mammals and measuring fecal coliform is a good indication of fecal contamination from non-point sources. Fecal coliform increases with increased rainfall due to increased transportation of fecal coliform present in soil surrounding water ecosystems.

Coliform is measured in the lab by filtering the water onto a grid paper and then putting it in a petri dish containing MC broth. The sample is incubated for 12 hours and then the cultures are counted using a microscope and the count is used to calculate fecal coliform in units of Cfb/100mL.

Citation

Hardness is a measure of the minerals in the water, mainly calcium and magnesium. Hardness is measured in the lab by combining 50mL of the water sample, a hardness indicator, and a buffer and then titrating with EDTA to the endpoint. The amount of EDTA used is then used to calculate the hardness value. Hardness is important when monitoring the pH of a water system.

Water that has a high pH usually has a high hardness value and water that has a low pH usually has a low hardness value. This relationship is because minerals in water act as a buffer that reduces the amount of acid in the water.

Factors that influence hardness levels include amounts of dissolved salts of calcium, magnesium and iron in the river. Hard water can lead to the precipitation of mineral deposits affecting other systems that transport or store water as well as affecting the plant and animal life in the water by either causing the water to become eutrophic or oligotrophic.

Citation

Calcium and water hardness. (n.d.).

pH is a measure of the concentration of hydrogen ions in the water samples. A high concentration of hydrogen ions causes water to be more acidic and a lower concentration causes the water to be more basic. pH is measured in the field using a pH meter and ranges from 0-14 with the lower values representing higher concentrations of hydrogen ions and the higher numbers representing a lower concentration of the hydrogen ions.

pH is important because increased acidity can stress aquatic organisms, increase the solubility of harmful chemicals in the water, and potentially change the entire ecosystem of a body of water. For instance, if pH increases slightly, there is a chance of eutrophication resulting in increased nutrients and plant life but a decrease in dissolved oxygen.

Effects of pH change usually are demonstrated when levels below 5.0 or above 9.6 are reached.  Drastic change can seriously impact aquatic organisms that rely on dissolved oxygen to survive. pH can be affected by many factors, some of which include interactions with surrounding rock, acid rain, wastewater discharge, decomposing pine needles, dissolved carbon dioxide levels, agricultural runoff, industrial runoff and mining operations.

Citation

PH of water. (2013). Retrieved from Fundamentals of environmental measurements website.

Total suspended solids are a measurement of the portion of inorganic and organic solids retained by a filter paper after filtration and a period of drying.

To measure TSS, a fixed volume of water is filtered through a pre-weighed filter paper which is then dried out and weighed again in the lab. The difference in the weight of the filter paper is used to calculate TSS.

There is a positive correlation between turbidity level and total suspended solids because both tests are dependent on the concentration of particles in the water. Factors such as rainfall and flow rate can affect TSS because they can increase the concentration of solids that are in the water at certain times.

This parameter is taken by inserting a vial of the sample water into a turbidimeter while field sampling. This instrument tests for suspended and colloidal matter by measuring the way that light is refracted through the sample. The higher the turbidity reading or Nephelometric Turbidity Units (NTU), the higher the concentration of particles in the sample.

Turbidity is an expression of relative clarity of the water that could be influenced by the presence of clay, silt, microscopic organisms, and organic and inorganic matter and tends to have higher readings during increased rainfall.

Turbidity is dependent upon size, shape and refractive index of particles.  Increased turbidity readings in streams is an indicator of increased sedimentation and siltation which can have harmful effects on aquatic life. The best way to reduce increased turbidity is stream-bank erosion prevention and land use management to decrease sediment transportation from runoff.

Citation

USGS. (2016).