The IMO 2020 global sulphur cap, limiting sulphur content in marine fuel to 0.5 percent globally and 0.1 percent in Emission Control Areas, fundamentally changed the fuel economics of ocean shipping. Vessel operators faced a choice between switching to more expensive low-sulphur fuel oil, converting to LNG propulsion, or installing exhaust gas cleaning systems, commonly called scrubbers, that remove sulphur oxide and particulate matter from engine exhaust while continuing to burn less expensive high-sulphur heavy fuel oil. A significant portion of the global fleet, including vessels operating in and through Philippine waters, chose the scrubber route.
Operating a scrubber system correctly is not simply a matter of running the equipment. The wash water that a scrubber uses to clean exhaust gases accumulates a concentrated load of soot, heavy metals, polycyclic aromatic hydrocarbons, and other combustion-related contaminants. How that wash water is managed, and particularly how it is filtered before discharge or recirculation, affects both the environmental performance of the scrubber system and its operational reliability over the vessel’s service life.
How Scrubbers Work and Why Wash Water Filtration Matters
An exhaust gas cleaning system works by bringing engine exhaust gases into contact with seawater or treated freshwater in a scrubber tower, where the water absorbs sulphur dioxide and captures particulate matter from the exhaust stream. The result is cleaned exhaust discharged to atmosphere, meeting the IMO 2020 sulphur limits, and wash water that now carries everything the scrubber removed from the exhaust.
Open-loop scrubbers discharge this wash water directly to sea after passing it through the scrubber’s sludge separator, subject to IMO and port-specific wash water quality limits. Closed-loop scrubbers recirculate the wash water through a treatment circuit, discharging only a small bleed stream. Hybrid systems can operate in either mode depending on local regulations and operating conditions.
In all these configurations, wash water filtration serves two purposes. First, it removes the particulate content, soot, scale, and other solid material, from the wash water to the level required by discharge standards or required for recirculation system reliability. Second, it protects the downstream components of the wash water treatment circuit, heat exchangers, pumps, and in closed-loop systems the chemical treatment and UV treatment components, from the abrasive and fouling effects of that particulate content.
The Particle Challenge in Scrubber Wash Water
Scrubber wash water carries a different and in some ways more demanding particle load than either ballast water or lube oil. Soot particles from heavy fuel oil combustion are fine, poorly filterable by coarse strainers, and have a high tendency to agglomerate and deposit on filter surfaces rather than remaining in suspension for consistent capture. Heavy metals, particularly from the combustion of high-sulphur heavy fuel oil, are present in dissolved or colloidal form rather than as discrete particles, requiring different treatment approaches for their removal. Scale from seawater heating in the scrubber adds a mineral deposition challenge similar to that in geothermal brine service.
Effective scrubber wash water filtration requires a filter design that handles this heterogeneous particle mix without rapidly blocking, that operates continuously without manual service interruptions that would require shutting down the scrubber or bypassing filtration, and that maintains consistent performance across the variation in wash water quality that different fuels, engine loads, and sea water quality conditions produce.
Bollfilter’s Marine Exhaust Gas Cleaning System Filtration
Bollfilter produces dedicated filtration solutions for marine exhaust gas cleaning systems, drawing on its broader marine filtration expertise. The automatic backflushing filter technology that Bollfilter applies to ballast water, lube oil, and fuel oil service in the marine industry applies directly to scrubber wash water service, with the self-cleaning mechanism maintaining filter performance through the high particle loads that active scrubber operation generates without requiring manual intervention during normal operation.
Correct sizing for scrubber wash water service requires matching the filter to the wash water flow rate of the specific scrubber system, the particle load expected from the specific fuel grade and combustion conditions, and the discharge quality requirements the vessel must meet under the applicable regulation, which varies between IMO minimum requirements and more stringent requirements imposed by specific port states or operating areas.
Philippine Regulatory Context for Scrubber Operations
Vessels calling at Philippine ports operating open-loop scrubbers are subject to Philippine port state authority oversight for compliance with IMO wash water discharge requirements. Vessels whose scrubber wash water does not meet applicable discharge quality standards face port state control action that can range from operational restrictions to detention. Maintaining the wash water filtration and treatment system in effective operating condition is therefore a compliance matter, not simply an equipment reliability consideration.
The growing adoption of scrubber systems across the global fleet calling Philippine ports, including vessels on the major international shipping routes that pass through Philippine waters, makes scrubber wash water filtration a genuinely relevant supply and service requirement for the Philippine maritime sector. Ultra Power’s distribution of Bollfilter’s marine filtration range, including filtration solutions for exhaust gas cleaning systems, positions Ultra Power to support this requirement as the scrubber-equipped fleet calling Philippine ports continues to grow.
Ultra Power distributes Bollfilter’s full marine filtration range in the Philippines. For vessel operators running scrubber systems, ship managers specifying EGCS installation on newbuilds or retrofits, and port operators managing vessels calling with scrubber systems, understanding the wash water filtration requirement and specifying appropriate automatic filtration that maintains compliance across the vessel’s scrubber operating life is the technical foundation that makes a scrubber investment work as intended.
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