IMO D-2 Standard

The IMO Ballast Water Management Convention

The International Maritime Organization’s Ballast Water Management Convention was adopted in 2004 and entered into force in September 2017. It applies to all ships that carry ballast water on international voyages.

Regulation D-2 sets the discharge standard — the maximum number of living organisms permitted in treated ballast water at the point of discharge.

D-2 discharge standard

Organism category	Maximum permitted
Organisms ≥ 50 μm (e.g., zooplankton)	< 10 per cubic metre
Organisms 10–50 μm (e.g., phytoplankton)	< 10 per millilitre
Indicator microbe: E. coli	< 250 CFU per 100 mL
Indicator microbe: Intestinal enterococci	< 100 CFU per 100 mL
Indicator microbe: Toxicogenic V. cholerae	< 1 CFU per 100 mL

The UV intensity proxy

UV-based BWTS systems demonstrate treatment efficacy through sustained UV intensity rather than direct organism counting. Under the IMO G8 guidelines for UV systems, a minimum operational intensity of:

252 W/m²

correlates with achieving the D-2 organism limits under normal operating conditions. This value is defined in the codebase as THRESHOLDS.UV_INTENSITY.IMO_MIN.

How the dashboard checks D-2 compliance

The Compliance tab compares the most recent UVR_INTENSITY reading against the 252 W/m² threshold in real time:

IMO D-2 = COMPLIANT  if UVR_INTENSITY >= 252
IMO D-2 = NON-COMPLIANT  if UVR_INTENSITY < 252

This is a live check on the latest telemetry record — not a stored compliance log. For a historical record of intensity values, use the Data Export tab to download timestamped telemetry.

Record-keeping obligations

Ships must maintain a Ballast Water Record Book documenting every ballasting and deballasting operation. The dashboard supports this in two ways:

• Audit Trail (Compliance tab) — shows the last 8 system events: PROCESS_START, PROCESS_STOP, and ALARM_TRIGGERED, each with a timestamp and location.
• CSV Export (Data Export tab) — provides a full timestamped record of UVR_INTENSITY, operation_type, and location for every telemetry reading within the selected date range.

Tip

For regulatory submissions, export a CSV filtered to the voyage date range and include the columns: timestamp, operation_type, location, and UVR_INTENSITY. This provides the core evidence trail for each ballasting event.

Important limitation

Caution

This dashboard provides operational monitoring only. It does not constitute an official type-approved BWTS compliance certificate and does not replace statutory surveys, port state control inspections, or the certified BWTS logbook entries required by the convention.

References

• IMO MEPC.173(58) — Ballast Water Management Convention
• IMO MEPC.G8 — Guidelines for approval of BWTS using UV radiation
• IMO D-2 Compliance Monitoring — product page