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Water Quality Parameters 101

Thursday, February 23rd, 2017

Maintaining a healthy gulf is an important goal for the State of Mississippi. In our previous blog, “Improving water quality on the Mississippi Gulf Coast”, we discussed different types of pollution that can impair water quality, but how can you tell if a water body is impaired? There are numerous water quality indicators that are used to determine the health of a water body. Some of these measurements can be taken on site, while others are collected and analyzed in a laboratory. After the samples have been analyzed, the data is used to assess the health of the body of water by comparing it to a specific water quality standard that is set by the State. More information on Mississippi’s water quality standards can be found here.

On-site Parameters

MDEQ field technician takes water quality measurements on the Mississippi Coast.

On-site parameters are taken and recorded directly at the site. There are several parameters that fit this category, including temperature, pH, dissolved oxygen (DO), and turbidity. Temperature is an important parameter as it affects so many different aspects of water quality, including biological and chemical reactions, solubility of chemical species, and density of the water. It can be affected not only by the season but also by groundwater, discharges, and weather. pH represents how alkaline or acidic a water body can be and is measured on a scale from 0-14. A pH of 7 is balanced or neutral. Lower than 7 means that the water is acidic, and higher than 7 is alkaline or basic. The pH of water can have a negative impact on the aquatic life in a water body if it is too acidic or too basic. DO is a measurement of how much oxygen is dissolved in the water and is typically measured in milligrams per liter (mg/L) or percent saturation. Aquatic organisms cannot live without oxygen, so this parameter is one of the most significant indicators of water quality. DO can enter a water body in two ways: turbulence from wind or waves or photosynthesis of plant material which creates oxygen as a by-product. Turbidity is measured in Nephelometric Turbidity Units (NTU’s) and is an assessment of the ability of light to pass through water. It is caused by suspended solids floating in the water. Suspended solids occur naturally in water and include silt, clay, and organic particles such as algae. Increased suspended solids can be from erosion or effluent discharges. High turbidity can signify that there is not enough light to reach plant life in the water body, which can affect the photosynthesis process and, therefore, minimize the amount of DO produced.

Lab Parameters

Some parameters need to be sampled and preserved at the site and analyzed at a laboratory, including nitrogen, phosphorus, and fecal bacteria. Nitrogen and Phosphorus are plant nutrients, measured in mg/L. High concentrations of these nutrients can cause extreme growth of plants and algae in water bodies, which can lead to low DO levels that negatively impact aquatic animal life. These nutrients can enter water body systems via fertilizers, wastewater discharge, car washes, and agricultural runoff. Lab results reveal the amounts of total nitrogen and total phosphorus, as well as a breakdown of their many forms, to give a clear picture of potential nutrient issues. Fecal bacteria naturally occur in the intestines of humans and animals. They enter water body systems through outflow of wastewater treatment plants, septic systems, storm water runoff, and animal waste. They serve as an indicator of other microorganisms that can cause harm to human health. Fecal bacteria are measured in the lab by incubating a sample for 24 hours and counting how much bacteria grew in that amount of time, usually in organisms/100 mL.

These examples are just a few of the types of water quality parameters that are used to assess water bodies. Identifying an impaired water body is a complicated process that is taken very seriously by the State of Mississippi. In our FAQs section of the Beach Outfalls Challenge website, we have provided water quality data for a few beach monitoring sites in Gulfport, MS, to give you can idea of what the water quality is like on the Mississippi Gulf Coast.

A successful Beach Outfalls Challenge could help improve water quality and benefit the ecology of the Mississippi Sound, as well as remedy harm to natural resources harmed by the Deepwater Horizon oil spill. MDEQ is looking for practical, implementable, eco-restoration solutions that will improve water resources. Do you have a great idea? Registration for the Beach Outfalls Challenge is now open! Learn more about the Beach Outfalls Challenge by visiting the ABOUT Page of our website. CLICK HERE to receive periodic updates about the Beach Outfalls Challenge.

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