Exam Question
(a) Sketch and describe Biological Sewage Treatment System. (6)
(b) How does the Biological Sewage Treatment Plant work (6)
(c) What is understood by the term BOD? What are the factors that affect BOD? (4)
Class 4 (4th Engineer)
MEKG
📅 Feb 2024
Reference Answer
### (a) Description of a Biological Sewage Treatment System
A Biological Sewage Treatment Plant (STP) is a type of Marine Sanitation Device (MSD) designed to treat raw sewage to a standard compliant with international regulations, specifically MARPOL Annex IV, before discharge into the sea. The fundamental principle is the use of aerobic microorganisms (bacteria) to decompose organic waste in a controlled environment.
**Core Concept:** The system mimics and accelerates natural biological decomposition. Raw sewage, which is rich in organic matter, serves as food for aerobic bacteria. By supplying a continuous flow of air (oxygen) into the treatment tank, an ideal environment is created for these bacteria to thrive and multiply. They consume the organic pollutants, converting them into harmless substances like carbon dioxide (CO₂), water (H₂O), and a stable, inert residue known as activated sludge.
**Main Components and Construction:**
A Biological Sewage Treatment Plant (STP) is a type of Marine Sanitation Device (MSD) designed to treat raw sewage to a standard compliant with international regulations, specifically MARPOL Annex IV, before discharge into the sea. The fundamental principle is the use of aerobic microorganisms (bacteria) to decompose organic waste in a controlled environment.
**Core Concept:** The system mimics and accelerates natural biological decomposition. Raw sewage, which is rich in organic matter, serves as food for aerobic bacteria. By supplying a continuous flow of air (oxygen) into the treatment tank, an ideal environment is created for these bacteria to thrive and multiply. They consume the organic pollutants, converting them into harmless substances like carbon dioxide (CO₂), water (H₂O), and a stable, inert residue known as activated sludge.
**Main Components and Construction:**
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