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Glossaire des Termes Techniques Utilisé dans Environmental Health & Safety: suspended solids (SS)

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suspended solids (SS)

Solides en Suspension (SS) dans le Traitement de l'Environnement et de l'Eau : Les Particules Invisibles Qui Importent

Les solides en suspension (SS) désignent les particules solides qui sont en suspension dans un liquide, généralement de l'eau. Ces particules sont trop grosses pour être dissoutes, mais suffisamment petites pour rester en suspension dans la colonne d'eau. Elles peuvent être organiques ou inorganiques, naturelles ou artificielles, et varient en taille du microscopique au visible.

Pourquoi les SS sont-elles importantes dans le traitement de l'environnement et de l'eau ?

  • Problèmes esthétiques : les SS provoquent la turbidité et la turbidité de l'eau, la rendant indésirable pour la consommation, les activités récréatives et les processus industriels.
  • Préoccupations pour la santé : certains SS peuvent transporter des agents pathogènes comme les bactéries, les virus et les parasites, posant des risques pour la santé des humains et des animaux.
  • Impacts environnementaux : les SS peuvent se déposer et s'accumuler dans les cours d'eau, affectant la vie aquatique, obstruant les systèmes de drainage et contribuant à l'eutrophisation.
  • Processus industriels : les SS peuvent interférer avec les processus industriels, obstruant les tuyaux, encrassant les équipements et affectant la qualité des produits.

Mesure des solides en suspension

La méthode la plus courante pour déterminer les SS est la filtration. Un volume d'eau connu est passé à travers un filtre avec une taille de pores de 0,45 micron ou moins. Le résidu retenu sur le filtre représente les solides totaux en suspension (TSS).

Filtration avec une natte de laine de verre ou une membrane filtrante de 0,45 micron

  • Natte de laine de verre : cette méthode convient à la collecte des SS plus gros, généralement celles supérieures à 10 microns. La laine de verre fournit une surface poreuse qui piège les particules.
  • Membrane filtrante de 0,45 micron : cette méthode est plus précise et capture une plus large gamme de SS, y compris celles inférieures à 10 microns. La membrane filtrante est faite d'un matériau comme l'ester de cellulose ou le nylon, et sa petite taille de pores permet la collecte d'un spectre plus large de particules en suspension.

Exemples de solides capturés par filtration :

  • Matière organique : feuilles, brindilles, algues, plancton, matières fécales
  • Matière inorganique : limon, argile, sable, minéraux
  • Matériaux artificiels : particules de plastique, fibres, sous-produits industriels

Élimination des solides en suspension :

Plusieurs méthodes sont utilisées pour éliminer les SS de l'eau, notamment :

  • Sédimentation : permettre aux particules plus lourdes de se déposer au fond d'un réservoir.
  • Filtration : faire passer l'eau à travers un milieu poreux comme le sable, le gravier ou les membranes.
  • Coagulation et floculation : ajouter des produits chimiques pour faire agglomérer les petites particules, les rendant plus faciles à éliminer.
  • Centrifugation : utiliser la force centrifuge pour séparer les particules solides du liquide.

Conclusion :

La surveillance et le contrôle des SS sont essentiels pour maintenir la santé des milieux aquatiques et garantir la sécurité et la qualité de l'eau à diverses fins. Comprendre les types de SS présents, leur impact et les techniques d'élimination appropriées est crucial pour une gestion responsable de l'environnement et de l'eau. En mettant en œuvre des stratégies efficaces d'élimination des SS, nous pouvons améliorer la qualité de l'eau et protéger à la fois la santé humaine et l'environnement.

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.)

Search Tips

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