Exam Question

### (a) General Arrangement of an Oil Monitoring System
An Oil Discharge Monitoring and Control System (ODMCS) is a mandatory system under MARPOL Annex I designed to prevent marine pollution by controlling the discharge of oily water from a ship's machinery space bilges or a tanker's cargo ballast tanks. The system operates on the principle of measuring the oil content in the effluent and automatically stopping the discharge if the concentration exceeds the statutory limit (e.g., 15 ppm for machinery bilges).
**Principle of Operation (Light Absorption Method):**
The most common measurement principle, as referenced in the provided text, is **direct light absorption or scattering**.