Total suspended solids ( TSS) is an important and practical indicator for assessing water quality in water and wastewater treatment . This indicator specifies the concentration of suspended, sparingly soluble solids in the water. The presence of these particles not only affects the appearance and clarity of the water but can also indicate chemical, microbiological, or organic contamination. This article discusses the definition of TSS, measurement methods, influencing factors, and the importance of TSS monitoring in water treatment plants.
Suspension flotation (SAF) and solution flotation (DAF)
Determination of total suspended solids (TSS)
In short, the total suspended solids (TSS) refers to the amount of suspended particles in water that cannot pass through a filter with very fine pores (usually 2 micrometers). These particles include organic matter such as plant debris, algae, and microorganisms, as well as minerals such as sand, clay, and metal particles. The TSS value
is typically expressed in milligrams per liter (mg/L) , which corresponds to the mass of suspended particles per liter of water sample.
The difference between TSS, TDS and SS
Total dissolved solids (TDS) is sometimes confused with other similar measurements such as total dissolved solids (TDS) or suspended solids (SS). The main difference between these measurements lies in the physical state of the particles:
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TSS (Total Suspended Solids): Suspended solids that are insoluble in water and can be separated by filtration .
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TDS (Total Dissolved Solids): The amount of dissolved particles (such as salts and minerals) in the water that passes through the filter.
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SS (suspended solids): In many sources, it is considered a synonym for PM.
In fact, TSS + TDS = TS (total solids) , which means that the sum of dissolved solids and suspended solids equals the total solids in the water.
Sources of suspended solids in water
Elevated concentrations of suspended solids in water can be caused by both natural and anthropogenic factors. The most common sources include:
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Soil erosion and surface runoff: Rain or snowmelt causes soil, sand and clay particles to be washed into rivers.
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Industrial activities: Wastewater containing suspended solids from factories, mines or textile factories.
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Municipal wastewater: domestic wastewater containing organic matter and microorganisms.
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Algae and natural organic substances: Excessive algae growth in water sources can also lead to an increase in the total content of organic substances.
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Construction and engineering projects: Excavation work, cutting and concreting can lead to an increase in the level of suspended solids in surface waters.
TSS measurement method
The total amount of suspended solids (TSS) is usually determined by filtration and gravimetric methods. The general procedure is as follows:
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A specific amount of water (usually 100 to 500 ml) is passed through a filter with a specific pore size.
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After the water has passed through, let the filter cartridge dry and then weigh it.
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The weight difference of the filter membrane before and after filtration indicates the mass of the suspended particles.
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The results are given in milligrams per liter (mg/L).
The standard method for measuring TSS under laboratory conditions is the APHA standard 2540 D.
The negative effects of high concentrations of suspended solids on water quality
High concentrations of suspended solids in water can have a variety of harmful effects, including:
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Reduced water clarity: The water becomes cloudy, which impairs its appearance.
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Reduces light penetration: In natural resources such as lakes and rivers, it prevents light from reaching aquatic plants.
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The processes of photosynthesis in algae and aquatic plants are changing.
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Increased microbial load: Suspended particles create a favorable environment for the growth of bacteria and microorganisms.
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Increased treatment costs: Suspended solids can clog filters and systems in wastewater treatment plants.
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Reduced dissolved oxygen (DO): The breakdown of organic matter into total dissolved solids (TDS) leads to a reduction in dissolved oxygen in the water, which results in the death of aquatic organisms.
The importance of controlling suspended solids in wastewater treatment plants
In water and wastewater treatment plants, monitoring total suspended solids (TSS) is crucial for ensuring water quality. High TSS levels in wastewater treatment typically indicate low efficiency of the sedimentation or aeration systems. Conversely, low TSS levels indicate effective purification. Minimizing TSS concentration is also
essential in drinking water treatment to ensure that the water meets requirements for appearance, hygiene, and taste.
Methods for reducing suspended solids in water and wastewater
Physical, chemical, and biological methods can be used to reduce suspended solids in water . The most important include:
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Sedimentation process: In this process, particles that are heavier than water settle and separate from the liquid phase.
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Coagulation and agglomeration: The addition of chemicals such as aluminum sulfate or electrolytic polymers can cause small particles to clump together into larger lumps, making them easier to settle.
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Filtration: The water is passed through a sand filter, carbon filter or membrane filter to remove suspended particles.
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DAF (Diffusion Air Flotation): Uses air bubbles to transport lighter particles to the water’s surface and collect them there.
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Biological treatment: In wastewater, microorganisms can decompose some of the suspended organic matter .
permissible TSS limit according to standard
The permissible concentrations of suspended solids vary depending on the type of water body (drinking water, wastewater, industrial or agricultural water). Generally speaking:
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Drinking water: less than 5 mg/l (high transparency)
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Wastewater from municipal sewage treatment plants: maximum concentration of 30 to 40 mg/l
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Industrial wastewater: Depending on the industry, the concentration ranges between 50 and 200 mg/l.
These limits must be adhered to in accordance with the standards of the US Environmental Protection Agency (EPA) and the World Health Organization (WHO).
Differences in total suspended solids (TSS) content in raw water and industrial wastewater
Natural raw water typically contains low concentrations of suspended solids (less than 20 mg/L), while industrial wastewater can have concentrations of up to several hundred mg/L. For example, suspended solids concentrations
are often very high in the food, textile, and paper industries , necessitating the use of complex treatment systems.
In conclusion
Total suspended solids (TSS) is one of the most important indicators of water quality and plays a key role in the purification process and in maintaining a healthy environment.
Accurate TSS measurements not only improve the efficiency of water treatment plants but also contribute to preventing water pollution and environmental problems.
Selecting suitable filtration systems, using effective coagulation and sedimentation processes, and continuous monitoring help keep TSS concentrations within acceptable limits and significantly improve water quality.