How to Keep Bilge Water Clean
Dirty Boat Water Has Negative Impacts on the Marine Environment
May 11, 2009
When a major oil spill happens in the harbour or ocean, most marine pollution authorities are usually quick to respond to clean these up. But small spills resulting from careless refuelling or pumping oily bilge water overboard can have significant negative effects on the marine environment.
MARPOL Regulations on Diposing of Bilge Water
New Zealand is party to the international MARPOL marine regulations. These mean that oil and petroleum products must not be discharged anywhere within New Zealand's territorial waters or within the Exclusive Economic Zone, being 200 nautical miles out to sea.
The regulations require that any bilge water discharged must contain less than 15mg of oil per litre of water, and only if the boat is moving and the oil is not cargo. It is doubtful that water from even the cleanest of bilges would meet this requirement. What these regulations essentially mean is that all bilge pumps should have some type of specialist oil filter fitted, but just how realistic is that for most people to install on small boats?
Options for Keeping Discharged Bilge Water Clean
Whilst it can be difficult to avoid oil being discharged with bilge water, it is still worthwhile being vigilant. There are a number of ways to make sure oil leakages into the harbour and ocean waters are reduced.
- Keep the boat engine well maintained so that it does not leak oil or fuel, and therefore the bilge water will be cleaner.
- Try to stop any rain or sea water leaking into the boat, so there is less need to pump out any water.
- Always use a drip tray or keep a piece of sorbent material underneath the engine to soak up accidental leaks.
- Before pumping the bilge, soak up any floating oil with sorbent material (newspaper, rags or paper towels in an emergency).
- Never mix detergent with oily bilge water, this mixture can be even more toxic than oil alone, and is very difficult to clean up. Try using an enzyme-based bilge cleaner which is less polluting.
- With automatic bilge pumps, always make sure there no floating oil in the bilges.
- For bigger boats, install a bilge water filter that will help remove most contaminants.
- Do not pump oily bilge water overboard – use a marine bilge pump out service (where available)
Many marinas and ports have facilities where old bilge water can be disposed of properly and it is good to use these.
Report all spills to the local authorities – the sooner they hear about oil spills the better the chance there is of minimising damage to the marine environment.
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