Turbidity and TSS: water clarity explained

  • Turbidity and TSS are two separate but comparable measurements of water clarity
  • Turbidity is determined by evaluating the light-scattering qualities of the water and determining how clear or translucent it is
  • TSS refers to any particles suspended in the water column, including silt, algae, sediment, and other substances (both organic and inorganic)

Turbidity and TSS are two distinct yet interconnected measurements related to water clarity. Researchers frequently use terms like turbidity and total suspended solids (TSS) to describe water quality. However, it’s essential to clarify the differences between these two parameters. While both offer insights into water clarity, they have distinct characteristics and measurement methods.


Turbidity is an optical parameter understood as a specific medium’s clarity. We can also refer to turbidity by examining the water’s light-scattering characteristics and determining how clear or translucent it is. The unit for measuring turbidity is a Nephelometric Turbidity Unit (NTU). Usually, a larger NTU score indicates more suspended solids, organic debris, algae, and other minute particles that cause the liquid to become hazy or murky are present. Researchers can identify these particles by testing turbidity.

Generally, higher NTU measurements suggest less clear water, whereas low readings indicate clearer liquid. NTU values typically range from 1 to 4000, with 1 denoting the purest clarity and 4000 denoting transparencies like milk. For example, a fairly good NTU reading for tap water would be less than 1.

Researchers can measure turbidity in two ways: turbidimetry or nephelometry. Both methods test and record light (of a known intensity) as it passes through a medium. Turbidimetry counts measure how much light is attenuated. In contrast, nephelometry measures how much light is scattered.

Total Suspended Solids (TSS)

Total suspended solids (TSS) include any particles suspended in the water column, like silt, algae, sediment, and other substances (both organic and inorganic). These particles can be separated from the water during the filtering process because they are big enough not to pass through the filter. Generally, suspended particles absorb heat from the sun, thus raising the water’s temperature when dissolved oxygen levels are too low. Conversely, if dissolved oxygen levels are too high, this can be fatal to aquatic life. Researchers measure TSS in mg/L, ppm, g/L , and %.

A sample liquid must be filtered, dried, and weighed after filtering to determine TSS. Researchers use the formula given below for determining TSS in mg/L:

TSS formula

Researchers can measure TSS with portable instruments. However, they can be fairly expensive. Generally, people regard Hach as the best metre for measuring TSS. Another good thing about these portable instruments is that they can also measure turbidity.

Turbidity vs TSS

The primary purpose of turbidity monitoring is to assess water clarity. Highly turbid water is opaque and frequently called cloudy or murky; this appearance is due to a significant number of particles dispersed throughout the water. In this respect, turbidity and TSS relate to one another, yet it’s crucial to distinguish them despite their resemblance. Turbidity is solely a gauge of relative clarity. So, although it cannot precisely measure the solids, turbidity can show variations in the water’s TSS concentration.

Although they don’t measure the same thing, TSS and turbidity are comparable because they both measure the liquid’s clarity. Determining turbidity from a sample enables you to obtain an immediate reading of NTUs, allowing you to take measurements while still in the field. On the other hand, TSS measurement is a laborious, manual operation that frequently necessitates making measurements back in a lab. As was already noted, portable metres are available, but they are expensive and may or may not be worthwhile investments depending on their intended use. Therefore, it is important to consider how frequently testing is necessary and whether testing may be performed off-site or in a laboratory for filtration.

Importance of determining both parameters

Turbidity measurement is beneficial and practical, even though it is an optical parameter. Determining turbidity is one of the simplest and least expensive ways to assess a water source’s health. Discharges, erosion, runoff, algal blooms, or disturbed sediments are a few potential reasons for excessive turbidity. Suspended particles can enter a body of water in a variety of ways. These factors will impact a body of water. For example, high TSS levels in turbid water can raise water temperatures, lower dissolved oxygen levels, and inhibit photosynthesis, which can cause underwater plants to die off and disrupt the ecosystem’s food chain. Additionally, erosion and runoff cause the increase in contamination of a water body, harming aquatic life and resulting in toxic algal blooms.

TSS is a crucial indicator of water quality for wastewater treatment processes and environmental safety. Technicians must remove a significant amount of suspended organic and inorganic debris using filtering, settling, or flotation techniques before releasing wastewater into the environment.

Real-time monitoring solution

Water quality data contain critical facts to support decision-making in water resource management. Therefore, continuous, real-time data on water quality are essential to ensure sufficient water resources. In addition, higher data collecting frequency improves comprehension of the factors that affect water quality.

Knowing this need, LG Sonic deployed a Monitoring Buoy that provides a complete overview of your water quality by collecting key parameters every 10 minutes. This integrated real-time water quality monitoring system can measure key water quality parameters, including TSS, Turbidity, and beyond.