Water Quality Parameters & Sampling
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Questions and Answers

What is a common effect of hydraulic surges on treatment systems?

  • They decrease flow rate.
  • They have no impact on performance.
  • They can lead to incomplete treatment. (correct)
  • They improve treatment efficiency.

    • Which of the following compounds contains carbonate ions?

  • Calcium carbonate (CaCO3) (correct)
  • Hydrogen sulfide (H2S)
  • Sodium sulfide (Na2S)
  • Sodium bicarbonate (NaHCO3)

    • What issue can arise from periods of no flow in a treatment system?

  • Increased treatment efficiency.
  • Decreased solids accumulation.
  • Stagnation leading to increased solids accumulation. (correct)
  • Consistent effluent quality.

    • Which characteristic is NOT associated with distilled or deionized water?

    <p>It has high conductivity.</p> Signup and view all the answers

    What role do independent third-party certifiers play in systems performance?

    <p>They assess system performance in controlled settings.</p> Signup and view all the answers

    What is the oxidation state of nitrogen in nitrate (NO3-)?

    <p>+5</p> Signup and view all the answers

    Which of the following statements is true regarding the formation of hydrated ferric oxide?

    <p>It is formed when ferric ions are exposed to air.</p> Signup and view all the answers

    Which of the following is the lowest oxidation state of nitrogen in water or wastewater?

    <p>Nitrogen gas (N2)</p> Signup and view all the answers

    What is the main characteristic of groundwater mentioned in relation to its oxygen content?

    <p>It is often anoxic and low in oxygen.</p> Signup and view all the answers

    Which form of nitrogen is not involved in the nitrogen cycle according to the information provided?

    <p>Unreacted nitrogen gas (N2)</p> Signup and view all the answers

    What does CBOD5 measure in water quality assessment?

    <p>The amount of oxygen required for microbial decomposition of organic matter</p> Signup and view all the answers

    Which of the following statements about grab sampling is true?

    <p>It reflects the performance of a specific point in time if collected correctly.</p> Signup and view all the answers

    What is a primary disadvantage of using grab samples to evaluate wastewater treatment performance?

    <p>They can be easily contaminated and unreliable.</p> Signup and view all the answers

    How are composite samples collected for water quality analysis?

    <p>By collecting discrete samples over a set period, typically 24 hours.</p> Signup and view all the answers

    What is the significance of comparing water quality results against established standards?

    <p>To assess the suitability for designated uses and treatment requirements.</p> Signup and view all the answers

    What characteristic does not classify a parameter as unstable?

    <p>Total nitrogen</p> Signup and view all the answers

    Why is it essential to measure physical, chemical, and biological characteristics of water promptly after collection?

    <p>Parameters can change, affecting accuracy if delayed.</p> Signup and view all the answers

    Which statement correctly describes total suspended solids (TSS)?

    <p>It measures the particulate matter suspended in water that can affect clarity and quality.</p> Signup and view all the answers

    Which factor makes residential treatment plants challenging to evaluate using grab sampling?

    <p>Intermittent periods of no flow followed by hydraulic surges.</p> Signup and view all the answers

    Sulfides in water are characterized by containing which ion?

    <p>Sulfide ion (S2-)</p> Signup and view all the answers

    What is the primary function of silver nitrate in the argentometric method?

    <p>To react with halide ions to form a precipitate</p> Signup and view all the answers

    How does increasing the concentration of carbonate ions affect the solubility of ferrous ions?

    <p>It decreases the solubility of ferrous ions</p> Signup and view all the answers

    Which of the following minerals is NOT associated with iron?

    <p>Halite</p> Signup and view all the answers

    What role does potassium chromate play in the argentometric method?

    <p>It serves as an indicator for titration endpoint</p> Signup and view all the answers

    According to Le Châtelier's principle, what happens when the carbonate ion concentration is decreased?

    <p>The equilibrium shifts to the right, increasing ferrous ion concentration</p> Signup and view all the answers

    In which of the following environments can iron concentrations be expected to be high?

    <p>Streams with higher dissolved iron levels</p> Signup and view all the answers

    What is the typical effect of ferrous ions on food consistency?

    <p>They impart objectionable tastes and color to foods</p> Signup and view all the answers

    What can be inferred about the solubility of ferrous ions when the concentration of carbonate ions is increased?

    <p>Ferrous ion solubility decreases as ferrous carbonate precipitates</p> Signup and view all the answers

    What does the ultraviolet UV technique measure in relation to nitrate?

    <p>Absorbance at 220 nm</p> Signup and view all the answers

    What is one effect of elevated iron levels in water?

    <p>Causes stains in plumbing</p> Signup and view all the answers

    What is the purpose of acidifying the sample with 1N HCL?

    <p>To prevent interference from hydroxide or carbonate</p> Signup and view all the answers

    What is the primary challenge in determining nitrate levels?

    <p>Complex procedures and potential interference</p> Signup and view all the answers

    What role does the second measurement at 275 nm serve in the process?

    <p>Corrects the NO3— value</p> Signup and view all the answers

    How is empirical correction related to organic matter in water?

    <p>It varies based on organic matter composition</p> Signup and view all the answers

    Under what condition is the NO3— calibration curve effective according to Beer’s law?

    <p>Up to 11 mg N/L</p> Signup and view all the answers

    What interference may arise during the measurement of nitrate?

    <p>Presence of hydroxide</p> Signup and view all the answers

    Study Notes

    Water Quality Parameters & Sampling

    • Experiment 1 focuses on characterizing and determining physical and chemical water quality parameters.
    • On-site measurements of parameters are crucial to maintain accuracy.
    • Indicators of treatment plant performance include CBOD5, TSS, and TN.
    • CBOD5 measures oxygen needed by microorganisms to decompose organic matter over five days at 20°C. Standard methods (20th edition, section 1060B) detail collection and sampling procedures.
    • Grab sampling collects all material at once, reflecting conditions at a single point in time. Suitable for well-mixed surface waters but less so for wastewater streams due to fluctuating flow.
    • Composite sampling collects multiple samples over time (e.g., 24 hours), providing a better representation of overall treatment plant performance, despite being more costly and time-consuming. This is especially important for residential treatment plants with varying flow patterns.
    • Unstable parameters (pH, dissolved oxygen, chlorine residual, nitrites, temperature) require immediate analysis using grab sampling.

    Argentometric Method for Halide Ion Determination

    • The argentometric method is used to determine the concentration of halide ions (Cl-, Br-, I-) in a sample.
    • The method involves titrating a sample with a standard solution of silver nitrate (AgNO3) until the end point is reached.
    • Potassium chromate acts as an indicator, changing color when all halide ions have reacted.

    Iron in Water

    • Iron occurs in various forms in water (ferrous, ferric) and concentration levels vary in different sources (sea water, soil, streams, groundwater).
    • Ferrous iron (Fe2+) solubility is controlled by carbonate concentration, and follows Le Châtelier's principle. Increased carbonate concentration decreases ferrous iron solubility; decreased carbonate concentration increases it.
    • Ferric iron (Fe3+) forms from oxidation of ferrous iron, often forming red, insoluble hydrated ferric oxide through hydrolysis. It’s not significantly soluble unless the pH is very low or complex-forming ions are present.
    • Elevated iron causes staining in plumbing and utensils. Acceptable limits vary according to the end use of water (e.g., irrigation, drinking). The UN FAO suggests 5 mg/L for irrigation; the U.S. EPA sets a secondary drinking water standard MCL of 0.3 mg/L.

    Nitrate Determination by UV Spectrophotometry

    • Experiment 6 focuses on determining nitrate (NO3-) content in water using UV spectrophotometry.
    • Forms of nitrogen in water are ordered by decreasing oxidation state: nitrate, nitrite, ammonia, organic nitrogen, and nitrogen gas.
    • UV spectrophotometry measures nitrate absorbance at 220 nm. A second measurement at 275 nm corrects for interference from organic matter. This correction is empirical and may vary between water sources. The method is rapid but may be affected by the concentration of organic matter, particularly at NO3- concentrations above 11mg/L.
    • Acidification with 1N HCl prevents interference from carbonates and hydroxides. Sample filtration removes suspended particles that could skew results. Chloride ions do not interfere with the determination.

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    Related Documents

    Water Quality Parameters Laboratory Manual PDF

    Description

    This quiz explores essential water quality parameters and sampling techniques, focusing on physical and chemical indicators vital for treatment plant performance. It covers methods like grab and composite sampling, detailing their applications and implications in real-world scenarios. Understand the significance of metrics such as CBOD5, TSS, and TN in maintaining water quality standards.

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