Mine drainage pollution from the Lackawanna River entering the Susquehanna River near Pittston, Pa. (above); Water quality monitoring equipment (below)
Susquehanna River Basin Commission
4423 North Front Street, Harrisburg, PA 17110
phone (717) 238-0423; fax (717) 238-2436
pH is a measure of water's acidity/basicity. The range goes from 0–14, with 7 being neutral. A pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates basicity. pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic. Since pH can be affected by chemicals in the water, pH is an important indicator of water that is changing chemically. pH is reported in "logarithmic units," like the Richter scale which measures earthquakes. Each number represents a 10-fold change in the acidity/basicity of the water. Water with a pH of 5 is ten times more acidic than water having a pH of six.
The EPA recommends that public water suppliers maintain pH levels between 6.5 and 8.5. Water with a low pH or acidic water can leach metal from pipes leaving a metallic or sour taste in the water. Acidic drinking water can also stain laundry, leave blue-green stains in sinks and drains, and damage pipes and fixtures. Basic water or water with a pH greater than 7 contains alkaline minerals. These minerals can cause scale build-up on pipes and fixtures. The minerals can also give water an alkaline taste and make coffee bitter. Water suppliers use a variety of chemical additions to control pH levels in their finished water.
Turbidity is the amount of particulate matter that is suspended in water. Turbidity monitors measure the scattering effect that suspended solids have on light: the higher the intensity of scattered light, the higher the turbidity. Material that causes water to be turbid includes:
Turbidity makes the water cloudy or opaque, and is reported in nephelometric turbidity units (NTU). During periods of low flow (base flow), many rivers are a clear green color, and turbidities are low, usually less than 10 NTU. During a rainstorm, particles from the surrounding land are washed into the river making the water a muddy brown color, indicating water that has higher turbidity values. Also, during high flows, water velocities are faster and water volumes are higher, which can more easily stir up and suspend material from the stream bed, causing higher turbidities. Turbidity has far reaching impacts on water treatment plants. The particles that make the water turbid provide food and shelter for pathogens and can carry nutrients, heavy metals and other toxins. If the particles are not removed correctly, they can cause unpleasant tastes and odors in the finished water. To ensure proper treatment, larger qualities of chemicals are needed to remove the additional particles from the water, and filters need to be cleaned or back-flushed more frequently, which increases operational costs.
Water temperature is very important to fish and other aquatic life, as well as for swimmers, fishermen, and industries. Temperature affects the ability of water to hold oxygen and affects chemical reactions used in the treatment process.
Total organic carbon is the measure of organic carbon, carbon-based molecules derived from living organisms, in the water. Organic carbon can come from decaying plant and animal matter or petroleum-based products. Organic carbon can be found in pesticides, fertilizers and many other products. Organic carbon reacts with the chlorine used to disinfect the water. The byproducts of this reaction are known as disinfection byproducts (DBP) and are carcinogenic. TOC monitors are used to detect organically-based chemical contaminants.
Specific conductance is a measure of the ability of water to conduct an electrical current. It is highly dependent on the amount of dissolved solids (such as salt) in the water. Pure water, such as distilled water, will have a very low specific conductance, and sea water will have a high specific conductance. Rainwater often dissolves airborne gasses and airborne dust while it is in the air, and thus, often has a higher specific conductance than distilled water. Specific conductance is an important water quality measurement because it gives a good idea of the amount of dissolved material in the water.
High specific conductance indicates high dissolved solids concentration; dissolved solids can affect aquatic life, as well as the suitability of water for domestic, industrial, and agricultural uses. At higher levels, drinking water may have an unpleasant taste or odor or may even cause gastrointestinal distress. Additionally, high dissolved solids concentration can cause deterioration of plumbing fixtures and appliances. Relatively expensive water treatment processes, such as reverse osmosis, are needed to remove excessive dissolved solids from water.
The oxygen dissolved in lakes, rivers, and oceans is crucial for the organisms and creatures living in it. As the amount of dissolved oxygen drops below normal levels in waterbodies, the water quality is harmed and creatures begin to die off. Indeed, a waterbody can "die," a process called eutrophication.
A small amount of oxygen, up to about ten molecules of oxygen per million of water, is actually dissolved in water. This dissolved oxygen is breathed by fish and zooplankton and is needed by them to survive.
Rapidly moving water, such as in a mountain stream or large river, tends to contain a lot of dissolved oxygen, while stagnant water contains little. Bacteria in water can consume oxygen as organic matter decays. Thus, excess organic material in our lakes and rivers can cause an oxygen-deficient situation to occur. Aquatic life can have a hard time in stagnant water that has a lot of rotting, organic material in it, especially in summer, when dissolved oxygen levels are at a seasonal low. Although dissolved oxygen is not often used in day-to-day operations of water suppliers, it is still of great value in characterizing the overall health of rivers.
Data platform for remote stations (above); Total organic carbon analyzer (below)
***During the winter season, data transmission schedules to the web site may be reduced for select stations to conserve power, since the stations are powered by solar panels which can be affected by snow/ice conditions and shorter daylight hours. In addition, water quality observations may be affected at times by ice buildup and/or blockages.