A common question that arises when studying the clarity or quality of water is what the difference between turbidity and total suspended solids. Total suspended solids and turbidity are of the main parameters for water quality. This study investigated whether turbidity could produce a satisfactory. PDF | This article confirms the existence of a strong linear relationship between turbidity and total suspended solids (TSS) concentration.
To determine TSS, you need to run sample liquid through a filtering process where the sample is filtered, dried, and weighed. The best meter we have found measures both TSS and turbidity is made by Hach.
It is a portable hand-held meter complete in a carry case which measures turbidity, suspended solids, and sludge blanket level. More information on this product can be found here. These numbers can vary depending of the type of particles present and are provided as a guide only. What is the difference between turbidity and TSS?
It is worth noting that measuring turbidity from a sample allows you to get an instantaneous reading of NTUs meaning you can take the reading directly from out in the field. Measuring TSS on the other hand, is a manual and drawn out process requiring a precise technique and measurements that often have to be conducted back in a laboratory. While portable meters are available as mentioned earlier, they are expensive and depending on the application, may or may not be worth the investment.
It is worth considering the regularity of testing required and whether testing needs to be done on-site or can be taken back to a laboratory to go through the filtering process. Put simply, turbidity looks at how well a light passes through liquid and TSS is a quantitative expression of suspended particles. Even though turbidity and TSS compliment each other, they are both influenced differently. Turbidity and TSS do overlap in the measurement of some particles as shown in the illustration below but as mentioned, they do actually differ making it extremely difficult to form any kind of correlation between the two.
The big question we often get asked is: The conversion cannot be broken down into a formula where you simply fill in your parameters and out spits the TSS conversion. Unfortunately, it is much more complicated and we are unable to find any suitable resource to support in correctly working out a unique conversion formula. While turbidity and total suspended solids often overlap, there are a few outlying factors that only contribute to one or the other.
Turbidity is determined by the amount of light scattered off of these particles 6. While this measurement can then be used to estimate the total dissolved solids concentration, it will not be exact. In addition, turbidity measurements may be affected by colored dissolved organic matter 5.
While this dissolved matter is not included in TSS measurements, it can cause artificially low turbidity readings as it absorbs light instead of scattering it 8. Total suspended solids, on the other hand, are a total quantity measurement of solid material per volume of water 6.
This means that TSS is a specific measurement of all suspended solids, organic and inorganic, by mass. TSS includes settleable solids, and is the direct measurement of the total solids present in a water body. As such, TSS can be used to calculate sedimentation rates, while turbidity cannot 1,6.
Water clarity is strictly relative to sunlight penetration. While this is usually determined by the amount of suspended solids in water, it can also be affected by CDOM and other dissolved solids Water clarity is the most subjective measurement of the these three parameters, as it is usually determined by human observation 5. Is this water clear, or murky, or just slightly opaque? Human observation of clarity allows for personal perception and judgement. A sediment-laden river flows into Tuscaloosa Lake.
These suspended particles can come from soil erosion, runoff, discharges, stirred bottom sediments or algal blooms 1. While it is possible for some streams to have naturally high levels of suspended solids, clear water is usually considered an indicator of healthy water 9, A sudden increase in turbidity in a previously clear body of water is a cause for concern. Excessive suspended sediment can impair water quality for aquatic and human life, impede navigation and increase flooding risks 7.
Water Chemistry Suspended solids can increase the temperature of water as they absorb additional heat from the sun. This can also cause dissolved oxygen levels to drop below the thermocline, creating hypoxic conditions. In terms of water quality, high levels of total suspended solids will increase water temperatures and decrease dissolved oxygen DO levels 1.
This is because suspended particles absorb more heat from solar radiation than water molecules will. This heat is then transferred to the surrounding water by conduction. Warmer water cannot hold as much dissolved oxygen as colder water, so DO levels will drop In addition, the increased surface temperature can cause stratification, or layering, of a body of water 3.
Turbidity, Total Suspended Solids & Water Clarity
When water stratifies, the upper and lower layers do not mix. As decomposition and respiration often occur in the the lower layers, they can become too hypoxic low dissolved oxygen levels for organisms to survive. Photosynthesis Production Suspended solids, particularly algae, can block sunlight from reaching submerged plants.
This can cause dissolved oxygen levels to drop, as the plants rely on respiration consuming oxygen instead of photosynthesis. Turbidity can also inhibit photosynthesis by blocking sunlight. Halted or reduced photosynthesis means a decrease in plant survival and decreased dissolved oxygen output 9.
The higher the turbidity levels, the less light that can reach the lower levels of water. This reduces plant productivity at the bottom of an ocean, lake or river Underwater vegetation die-off has two main effects. First, as photosynthetic processes decrease, less dissolved oxygen is produced, thus further reducing DO levels in a body of water The subsequent decomposition of the organic material can drop dissolved oxygen levels even lower.
Second, seaweed and underwater plants are necessary food sources for many aquatic organisms.
What is the difference between Turbidity and TSS?
As they die off, the amount of vegetation available for other aquatic life to feed on is reduced. This can cause population declines up the food chain Erosion Bank erosion along a river can be cause by runoffflooding or strong water flow. An increase in turbidity can also indicate increased erosion of stream banks, which may have a long-term effect on a body of water 3.
Erosion reduces habitat quality for fish and other organisms. These suspended particles can also clog fish gills and affect growth rates Erosion can contribute to shallower, filled-in lakes and streams as some of the suspended particles settle out These settleable solids can suffocate benthic organisms and fish eggs 1.
In addition, the sediment may smother insect larvae and other fish food sources When this occurs in rivers and channels, the increased sediment loads can reduce navigability for ships and boats 7.
In cases of excessive sedimentation, settleable solids from erosion and runoff can even halt freight passage completely. Contamination Wastewater effluent can carry pathogens and other contaminants into a water body if it is not treated properly. EPA Pollutants such as dissolved metals and pathogens can attach to suspended particles and enter the water 2.
This is why an increase in turbidity can often indicate potential pollution, not just a decrease in water quality. Contaminants include bacteria, protozoa, nutrients e.
Several of these pollutants, especially heavy metals, can be detrimental and often toxic to aquatic life The addition of nutrients can encourage the development of harmful algal blooms. When the suspended solids concentration is due to organic materials, particularly sewage effluent and decaying organic matter, the presence of bacteria, protozoa and viruses are more likely.
These organic suspended solids are also more likely to decrease dissolved oxygen levels as they are decomposed Human Concerns These microbes and heavy metals can impact not only aquatic organisms, but drinking water as well 2.
Organic suspended solids, such as decomposing matter or sewage effluent often naturally include high levels of microorganisms such as protozoa, bacteria and viruses Such pathogens contribute to waterborne diseases like cryptosporidiosis, cholera and giardiasis In industrial processes, turbidity can contribute to clogged tanks and pipes The particles can also scour machines, potentially damaging them.
What Contributes to Suspended Solids? Turbidity is caused by include organic materials such as algae, and inorganic materials such as silt and sediment.
Suspended solids in a body of water are often due to natural causes. These natural solids include organic materials such as algae, and inorganic materials such as silt and sediment. Some algae, such as phytoplankton, are regular occurrences, especially in the ocean. Inorganic materials can easily become suspended due to runoff, erosion and resuspension from seasonal water flow. However, when suspended solids exceed expected concentrations, they can negatively impact a body of water. Excess over background amounts are often attributed to human influence, whether directly or indirectly Pollution may contribute to either organic or inorganic suspended solids, depending on the source.
Algae, sediment and pollution will affect water quality in different ways depending on the quantity present. Algae Different algae can float in the water or be found rooted on a riverbed. Some, like kelp and seaweed, look like underwater plants. Algae are plantlike, photosynthesizing organisms that can thrive in both freshwater and saltwater These organisms come in different sizes, from microscopic phytoplankton to giant sea kelp forests Both the phytoplankton and seaweed forms of algae will consume nutrients in the water and can increase dissolved oxygen levels through photosynthesis.
When they die, however, the organic material is decomposed by microbes in the water column. This decomposition process can decrease dissolved oxygen levels to below normal levels In particular, cyanobacteria, or blue-green algae, have floating mechanisms that keep them at the surface, blocking sunlight from the water These phytoplankton contribute to the total suspended solids concentration, while rooted vegetation or attached streambed-mat forms of algae do not.
However, if these rooted algae become detached usually when the algae dies or if it is forcefully removedthen their mass becomes part of the suspended solids measurement 6. Algal blooms can coat the surface of the water and prevent light from penetrating. An algal bloom occurs when an excessive amount of algae grows quickly across the surface of a body of water. These blooms usually occur due to an influx of nutrients such as nitrogen and phosphorus due to agricultural runoff or decomposition, though warmer water temperatures and longer daylight hours also contribute to their growth Floating algal blooms can block sunlight, release toxins, and deplete oxygen levels in a body of water While some algae growth occurs naturally often seasonallyexcessive growth is often attributed nutrient pollution.
Turbidity monitoring can be used to determine if an increase in suspended solids is natural or due to agricultural runoff 6. Runoff and Erosion Sediment is comprised of any solid material that can be transported by water, wind or ice It is usually defined as the soil particles including silt, clay and sand that are deposited on the bottom of a body of water These particles are usually classified by size from smallest clay is less than 0. Silt falls in between, ranging from 0.
Sediment particles can be fine silt or clay, sand and even gravel. However, not all sediment is suspended. The amount and size of suspended sediment is dependent on water flow The faster the flow, the larger the particle that can be suspended.
Higher flow rates can also support a higher concentration of suspended solids. Particles larger than 0. Most of the suspended sediment that remains colloidal solids consists of fine sand, silt, and clay The majority of suspended sediment present in water bodies comes from runoff and erosion 6.
If the land surrounding a body of water has only sparse vegetation, the topsoil can easily be washed away into the water 3. Highly vegetated areas will absorb most of the runoff, keeping the body of water clearer. Runoff causes erosion, washing soil and other particulates into a body of water. In addition to collecting suspended particles from runoff, rivers and streams can slowly erode soft riverbanks due to the constant water flow. An increase in river volume and flow due to rain or other causes can increase the rate of erosion On the other side of the spectrum, bedrock-based streams may not have much sediment available to suspend.
The local geology will determine natural turbidity levels based on normal flow rates, soil type, land structure and vegetation 6. If the surrounding land is altered by agriculture, construction or other soil-disturbing use, it can accelerate erosion and runoff, increasing turbidity 3. Pollution Pollution ranges from large garbage to microplastics, flecks of metal or asphalt, and chemical dyes.
Any potentially harmful substance that is added to the environment by humans, whether directly or indirectly, is considered pollution This can vary from bacteria riding along on a sewage plant discharge, to coal and iron ore particulates that float in from a mining zone.
If these pollutants are larger than 2 microns, they will contribute to the total suspended solids concentration. Some of the more common suspended solid pollutants are pathogens bacteria, protozoa, helminthsmicrobeads from exfoliating soapswastewater effluent, sewage, airborne particulates, and road particles e. Colored wastewater discharge and dyes are pollutants that will affect turbidity, but not suspended solids. Nutrients like nitrate and phosphorus are often considered pollutants, but as they are a dissolved substance, they do not contribute directly to the suspended solids concentration Instead, they are an indirect contributor as they fuel algal blooms, which do affect TSS and turbidity.
These dissolved nutrients, along with dissolved metals, chemicals, and refractory organics, will impact the quality of a body of water Nitrate and phosphorus can cause eutrophication excessive plant and algae growth which in turn causes low dissolved oxygen levels due to plant respiration and microbial decomposition. Refractory organics are often carcinogenic, while heavy metals and other chemicals can be toxic to aquatic organisms While these contaminants can enter the water as a dissolved substance, many of them ride along on grains of soil or other larger pieces of pollution e.
When this is the case, they can be picked up in suspended sediment samples. Chemical dyes will affect turbidity readings as the colored molecules will affect light absorption, but they will not be included in a suspended solids measurement.
Factors that Influence Turbidity Suspended solids can be comprised of organic and inorganic materials such as sediment, algae, and other contaminants. However, there are specific factors that can affect turbidity levels in a body of water. These are water flow, point source pollution, land use and resuspension.
Water Flow and Weather Stream flow and turbidity are often directly related; as water flow increases, so will turbidity levels. Turbidity and water flow are causally related High flow rates keep particles suspended instead of letting them settle to the bottom.
Thus in rivers and other naturally-occurring high flow environments, turbidity can be a constant presence 2. In these areas, it is important to monitor for changes in turbidity at the same point each time to ensure that the data is not affected by a lower or higher water velocity Weather, particularly heavy rainfall, also affects water flow, which in turn affects turbidity.
Rainfall can increase stream volume and thus stream flow, which can resuspend settled sediments and erode riverbanks 1. Heavy rainfall will cause turbidity to spike, as this storm event graph shows. This is due to increased water flow and increased sediment from runoff.
Rain can also directly increase the level of total suspended solids through runoff. As water flows over a surface, it can pick up particles and deposit them in a body of water 2. Runoff can also wash away topsoil, and contribute to riverbank erosion 3. If the flow rate increases enough, it can resuspend bottom sediments, further raising TSS concentrations 2. In areas of dry, loose soil or earth-disturbed sites e. The addition of new particles will increase the suspended solids concentration.
- What is the difference between Turbidity and TSS?
However, wind will generally not increase turbidity levels in the water alone. In wave-dominated estuaries and coastal areas, turbidity is naturally low In comparison, tidal areas, where the water flow is strong enough to resuspended bottom sediments, have high natural turbidity levels. Wind-driven turbidity increases only occur in shallow zones where waves are tall enough to resuspend sediment Tides, wind, and rain can influence turbidity levels due to their effect on water flow and introduced sediment loads 9.
Tributaries can also alter turbidity. When a freshwater stream or river enters a saltwater estuary, the change in water flow can cause turbidity levels to increase. This mixing area is often called a turbidity maximum zone These zones tend to have little aquatic vegetation due to the high suspended solids concentrations.
Estuaries are often subject to tidal influences as well, which can pull in sand and sediment from the shoreline and resuspended bottom sediments Turbid rivers can carry their suspended sediments into the ocean. Point-source pollution can increase turbidity through the addition of suspended solids and colored effluent wastewater to a body of water.
For water quality, common examples include discharge pipes from factories and wastewater treatment plants. In addition, farms can also fall under the category of point-source pollution These sources can release harmful pathogens bacteria and chemicals into the water, in addition to suspended solids. Here is an example of point source pollution. NOAA Ocean Service Many factories, wastewater treatment plants, and sewage treatment plants discharge effluent into local water bodies or sewer systems.
Sometimes this water is treated or filtered before it is discharged, but sometimes it is not The EPA has created several guidelines for effluent discharge, but they are all based on the technology used, and not the final impact on the local water body While most wastewater treatment plants include a settling period in the treatment process, this does not affect colloidal nonsettleable solids When this wastewater is discharged, these suspended solids may still be present unless treated with additional filters.
In addition, colored effluent cannot be trapped by a filter. While dyes and colored dissolved organic material CDOM are not included in a suspended solids measurement, they will contribute to turbidity readings due to their effects on light absorption.
Farms that are identified as point sources often allow fertilizer and animal waste to enter local bodies of water. Most agricultural pollution is due to runoff, and not a specific discharge. While this runoff is not intentional, it can be detrimental to water quality as these pollutants are untreated Animal wastes can increase pathogen concentrations in the water, while the fertilizer can contribute to eutrophication and excessive algal growth.
Land Use Construction sites loosen soil that could run off into a body of water. NCDOTcommunications via Flickr A major factor in increased turbidity and total suspended solids concentrations is due to land use.Total suspended solid (Tss)
Construction, logging, mining and other disturbed sites have an increased level of exposed soil and decreased vegetation Agricultural areas are also considered disturbed areas after they are tilled Land development, whether it is agricultural or construction, disturbs and loosens soil, increasing the opportunities for runoff and erosion