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Glossary of Technical Terms Used in Environmental Health & Safety: suspended solids (SS)

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suspended solids (SS)

Suspended Solids (SS) in Environmental & Water Treatment: The Unseen Particles That Matter

Suspended solids (SS) refer to the solid particles that are suspended in a liquid, typically water. These particles are too large to be dissolved, but they are small enough to remain suspended in the water column. They can be organic or inorganic, natural or man-made, and range in size from microscopic to visible.

Why do SS matter in environmental and water treatment?

  • Aesthetic Issues: SS cause cloudiness and turbidity in water, making it undesirable for drinking, recreational use, and industrial processes.
  • Health Concerns: Some SS may carry pathogens like bacteria, viruses, and parasites, posing health risks to humans and animals.
  • Environmental Impacts: SS can settle and accumulate in waterways, impacting aquatic life, clogging drainage systems, and contributing to eutrophication.
  • Industrial Processes: SS can interfere with industrial processes, clogging pipes, fouling equipment, and affecting product quality.

Measuring Suspended Solids

The most common method for determining SS is filtration. A known volume of water is passed through a filter with a pore size of 0.45 microns or less. The residue retained on the filter represents the total suspended solids (TSS).

Filtering with a Glass Wool Mat or 0.45 Micron Filter Membrane

  • Glass Wool Mat: This method is suitable for collecting larger SS, typically those greater than 10 microns. The glass wool provides a porous surface that traps the particles.
  • 0.45 Micron Filter Membrane: This method is more precise and captures a wider range of SS, including those smaller than 10 microns. The filter membrane is made of a material like cellulose ester or nylon, and its small pore size allows for the collection of a broader spectrum of suspended particles.

Examples of Solids Captured by Filtration:

  • Organic Matter: Leaves, twigs, algae, plankton, fecal matter
  • Inorganic Matter: Silt, clay, sand, minerals
  • Man-made Materials: Plastic particles, fibers, industrial byproducts

Removing Suspended Solids:

Several methods are used to remove SS from water, including:

  • Sedimentation: Allowing heavier particles to settle to the bottom of a tank.
  • Filtration: Passing water through a porous medium like sand, gravel, or membranes.
  • Coagulation and Flocculation: Adding chemicals to cause small particles to clump together, making them easier to remove.
  • Centrifugation: Using centrifugal force to separate solid particles from the liquid.

Conclusion:

Monitoring and controlling SS is critical for maintaining healthy aquatic environments and ensuring the safety and quality of water for various purposes. Understanding the types of SS present, their impact, and appropriate removal techniques is crucial for responsible environmental and water management. By implementing effective SS removal strategies, we can improve water quality and protect both human health and the environment.

Test Your Knowledge

Suspended Solids Quiz

Instructions: Choose the best answer for each question.

1. Which of the following is NOT a reason why suspended solids (SS) are important in environmental and water treatment?

a) They can cause cloudiness and turbidity in water. b) They can carry pathogens like bacteria and viruses. c) They can contribute to eutrophication. d) They can enhance the taste and odor of water.

Answer

d) They can enhance the taste and odor of water.

2. What is the most common method for determining suspended solids (SS)?

a) Spectrophotometry b) Titration c) Filtration d) Chromatography

Answer

c) Filtration

3. Which of the following is NOT an example of a solid captured by filtration for SS analysis?

a) Leaves b) Silt c) Dissolved salts d) Plastic particles

Answer

c) Dissolved salts

4. What is the primary purpose of coagulation and flocculation in SS removal?

a) To increase the density of particles for easier sedimentation. b) To dissolve particles into the water. c) To prevent the formation of new particles. d) To make the water taste better.

Answer

a) To increase the density of particles for easier sedimentation.

5. Which of the following methods is NOT typically used to remove suspended solids from water?

a) Sedimentation b) Distillation c) Filtration d) Centrifugation

Answer

b) Distillation

Suspended Solids Exercise

Instructions: You are working as a water treatment plant operator. You have collected a sample of water from a nearby river and need to determine the total suspended solids (TSS) content.

Materials:

  • Water sample from the river
  • Beaker
  • Filter paper (0.45 micron pore size)
  • Filter funnel
  • Drying oven
  • Desiccator
  • Analytical balance

Procedure:

  1. Weigh a clean, dry filter paper using the analytical balance. Record the weight.
  2. Using a beaker, carefully pour a known volume of the river water sample through the filter paper.
  3. Allow the water to drain completely.
  4. Carefully remove the filter paper from the funnel and place it in a drying oven at 105°C until constant weight is achieved (meaning the weight doesn't change significantly after repeated weighings).
  5. Once the filter paper is dry, let it cool in a desiccator before weighing it again on the analytical balance.

  6. Calculate the TSS using the following formula:

    TSS (mg/L) = [(Weight of filter paper + residue) - (Weight of filter paper)] / Volume of water sample (L) * 1000

Questions:

  1. What is the purpose of using a desiccator after drying the filter paper?
  2. Why is it important to achieve constant weight during the drying process?
  3. What are some possible sources of error in this experiment?
  4. What are some potential implications of a high TSS reading for the water treatment plant?

Exercise Correction

1. **Purpose of Desiccator:** A desiccator is used to cool the filter paper in a dry environment, preventing it from absorbing moisture from the air and increasing its weight. This ensures accurate weight measurement of the filter paper and residue. 2. **Importance of Constant Weight:** Achieving constant weight during drying ensures that all moisture has been evaporated from the filter paper and residue. This is essential for accurate determination of the TSS. 3. **Sources of Error:** * **Incomplete Drying:** If the filter paper is not completely dry, the TSS reading will be higher than the actual value. * **Filter Paper Not Clean:** If the filter paper was not clean before use, it could contribute to a higher TSS reading. * **Loss of Residue:** Some of the residue might be lost during the filtering or drying process, leading to a lower TSS reading. * **Inaccurate Volume Measurement:** An inaccurate measurement of the water sample volume will lead to an inaccurate TSS calculation. 4. **Implications of High TSS:** * **Increased Treatment Costs:** High TSS requires more extensive treatment processes to remove suspended solids, increasing the cost of water treatment. * **Potential Health Risks:** High TSS can indicate the presence of harmful pathogens that need to be removed to ensure safe drinking water. * **Equipment Fouling:** High TSS can lead to clogging of pipes and filters, requiring regular maintenance and cleaning, leading to downtime and increased maintenance costs.

Books

  • Water Quality: An Introduction by Davis and Cornwell (Focuses on general water quality concepts including SS, treatment methods, and regulations.)
  • Water Treatment: Principles and Design by Metcalf & Eddy (Comprehensive coverage of water treatment technologies, including those specifically targeting SS removal.)
  • Environmental Engineering: A Global Perspective by Tchobanoglous, Burton, and Stensel (A broad overview of environmental engineering, including chapters on water quality and treatment processes related to SS.)

Articles

  • "Suspended Solids: A Review of Measurement and Removal Techniques" by [Author Name] (Search for recent review articles on the topic of SS for a comprehensive overview of the field.)
  • "Impact of Suspended Solids on Aquatic Ecosystems" by [Author Name] (Focuses on the ecological consequences of SS in different aquatic environments.)
  • "Evaluation of Coagulation-Flocculation for Removal of Suspended Solids from Wastewater" by [Author Name] (An example of a research article exploring specific treatment methods for SS removal.)

Online Resources

  • U.S. Environmental Protection Agency (EPA): [EPA Website Link] (Extensive information on water quality regulations, treatment methods, and research related to SS.)
  • World Health Organization (WHO): [WHO Website Link] (Guidance on safe drinking water and the role of SS control.)
  • Water Environment Federation (WEF): [WEF Website Link] (Professional organization dedicated to water quality and treatment, offering resources on SS and related topics.)

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