September 4th, 2017     No Comments »

Lab Analysis 101

You are probably aware that your NPDES permit requires laboratory analysis of your wastewater. The results of which, are sent to the EPA.

But what are those lab tests? What do all those acronyms mean? And why are they important?

This month we are going to explain what all these tests are and what they mean for the environment.

Laboratory testing is done to assess the suitability of disposing water and wastewater into the environment. The analyses we perform, as required by the EPA, test different chemical, biological, and physical characteristics of water. There is a narrow range of conditions that aquatic and plant life need to survive. Wastewater has to fit within those parameters, in order to protect life in the bodies of water that are being discharged into.


Some manufacturing processes and pollutants can raise water temperatures above the acceptable range for some species. Elevated water temperature can also cause algae blooms which reduces oxygen levels for other aquatic life. Low dissolved oxygen can lead to fish kills and loss of other life in water environments.

Total Suspended Solids
Total Suspended Solids (TSS) are solids in water that can be trapped by a filter. TSS can be just about anything that is suspended in water. Most common are things such as silt, decaying plant and animal matter, industrial wastes, and sewage. Although some solids, like silt, are naturally occurring, high concentrations of suspended solids can cause many problems for stream health and aquatic life. High TSS can block light from reaching submerged vegetation. As the amount of light passing through the water is reduced, photosynthesis slows down. Reduced rates of photosynthesis causes less dissolved oxygen to be released into the water by plants. If light is completely blocked from bottom dwelling plants, the plants will stop producing oxygen and will die. As the plants are decomposed, bacteria will use up even more oxygen from the water. High TSS can also cause an increase in surface water temperature, because the suspended particles absorb heat from sunlight. This can cause dissolved oxygen levels to fall even further (because warmer waters can hold less dissolved oxygen), and can harm aquatic life in many other ways.


pH — Hydrogen

pH represents the effective concentration (activity) of hydrogen ions (H+) in water. Clean water, is the baseline or neutral state and supports life. It has a pH of 7. A pH of less than 7 is considered acid. A pH higher than 7 is considered alkaline. The pH of water can be measured with a pH meter, which is an electronic device with a probe. The probe contains an acidic aqueous solution enclosed by a glass membrane that allows migration of H+ ions. Numerous environmental pollutants can affect the pH of water. Carbon dioxide in the air can lead to “Acid Rain.” Dissolved calcium can make water alkaline. Decaying plants can raise acidity.

Dissolved Oxygen (DO)
Most aquatic habitats are occupied by fish or other animals requiring certain minimum dissolved oxygen concentrations in the water, to survive. Dissolved oxygen concentrations may be measured directly in wastewater, but the amount of oxygen potentially required by other chemicals in the wastewater is termed an ‘oxygen demand.’ Dissolved or suspended oxidizable organic material in wastewater will be used as a food source. Finely divided material is readily available to microorganisms whose populations will increase to digest the amount of food available. Digestion of this food requires oxygen, so the oxygen content of the water will ultimately be decreased by the amount required to digest the dissolved or suspended food. Oxygen concentrations may fall below the minimum required by aquatic animals if the rate of oxygen utilization exceeds replacement by atmospheric oxygen. Biochemical Oxygen Demand (BOD)Since all natural waterways contain bacteria and nutrients, almost any waste compounds introduced into such waterways will initiate biochemical reactions. Those biochemical reactions create what is measured in the laboratory as the biochemical oxygen demand (BOD) — the oxygen required by these organisms to survive.
Chemical Oxygen Demand

Oxidizable chemicals (such as reducing chemicals) introduced into a natural water will similarly initiate chemical reactions. Those chemical reactions create what is measured in the laboratory as the chemical oxygen demand (COD).

Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of pollution effect. The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygen demand of biodegradable pollutants plus the oxygen demand of non-biodegradable oxidizable pollutants.

Nitrogen is an important nutrient for plant and animal growth. Atmospheric nitrogen is less biologically available than dissolved nitrogen in the form of ammonia and nitrates. Availability of dissolved nitrogen may contribute to algal blooms. Ammonia and organic forms of nitrogen are often measured as Total Kjeldahl Nitrogen, and analysis for inorganic forms of nitrogen may be performed for more accurate estimates of total nitrogen content.

Total Phosphorus and Phosphate, PO−3

Phosphates enter the waterways through both non-point sources and point sources. Point sources are a specific effluent or runoff that can be traced, Non-point, is all the run-off that can’t be traced to its origin. The non-point sources of phosphates include: natural decomposition of rocks and minerals, storm water runoff, agricultural runoff, erosion and sedimentation, atmospheric deposition, and direct input by animals/wildlife; whereas: point sources may include: wastewater treatment plants and permitted industrial discharges. In general, the non-point source pollution typically is significantly higher than the point sources of pollution. Therefore, the key to sound management is to limit the input from both point and non-point sources of phosphate. High concentration of phosphate in water bodies is an indication of pollution and largely responsible for eutrophication (meaning ‘too many nutrients’; it chokes the life from plants and animals in a body of water).

Phosphates are not toxic to people or animals unless they are present in very high levels. Digestive problems could occur from extremely high levels of phosphate.

Chlorine Residual
Chlorine is widely used for bleaching and as a disinfectant. Remaining concentrations of oxidizing hypochlorous acid and hypochlorite ions (unoxidized chlorine, or the chlorine that hasn’t broken down yet) may be measured as chlorine residual to estimate effectiveness of disinfection, or to show its safe for discharge to aquatic ecosystems. While within the wastewater treatment plant chlorine can be helpful in reducing bacteria and other contaminants, once discharged into the environment, fish and other aquatic life can be poisoned if leftover chlorine is still active in the environment.
This concludes this month’s lesson on chemistry and laboratory analysis, if you made it this far, give yourself an A+!

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