Water quality and stream sanitation basics: Identify the correct statements about dilution, self-purification, photosynthesis, and grab sampling in wastewater studies.
-
ADilution factor = ratio of diluting water quantity to sewage quantity
-
BAutomatic purification of polluted water is termed the self-purification phenomenon
-
CPhotosynthesis in receiving waters occurs only in the presence of sunlight
-
DGrab sample is commonly taken at the surface where turbulence provides representative mixing
-
EAll the above
Answer
Correct Answer: All the above
Explanation
Introduction / Context:Sanitation engineering combines laboratory testing with stream processes and basic biology. Clear terminology ensures correct interpretation of field and lab results when assessing wastewater impacts and treatment performance.
Given Data / Assumptions:
- Dilution and receiving water behavior influence observed concentrations.
- Self-purification integrates biodegradation and re-aeration.
- Photosynthesis by algae/macrophytes requires light.
- Grab sampling aims for a representative snapshot with adequate mixing.
Concept / Approach:
Each statement reflects standard practice: dilution factor compares volumes; self-purification describes natural recovery; photosynthesis is light-dependent; and for quickly collected grab samples, locations with turbulence (surface/baffles/mixers) are often chosen to better represent the bulk flow at that instant (site-specific judgment still applies).
Step-by-Step Solution:
Define dilution factor = V_diluent / V_sewage for bioassays or mixing studies.Recognize stream self-purification via BOD decay and atmospheric re-aeration.Acknowledge photosynthesis depends on solar radiation; depth and turbidity limit it.Select grab sample point where turbulence improves representativeness; avoid dead zones.Verification / Alternative check:
Use composite sampling for time-averaged quality; apply DO sag modeling to validate self-purification behavior.
Why Other Options Are Wrong:
In this set, all individual statements are valid; therefore “All the above” is correct.
Common Pitfalls:
Confusing dilution with decay; sampling in unmixed zones; interpreting photosynthetic DO spikes as sustained recovery.
Final Answer:
All the above