Sea is blue, plastic is grey – so keep them apart

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ACO Marine insists that grey water waste must be controlled in the same way as sewage.

Grey water is waste water that comes from household use such as clothing, dishes, bathing, except toilet water, known as black water. Grey water is considered to be more harmful to the environment that sewage. Black water is organic, while grey water may contain different chemicals, greases and even plastics.

According to Mark Beavis, MD of ACO Marine, research shows that small parts of plastic may be found in even presumably clean water. Cleaning liquids, hair and skin products contain a lot of such substances. Some countries, like Great Britain, have already decided to reject the manufacture of toilet items and cleaning products which contain plastic particles.

MARPOL strictly regulates black water waste however there are no international regulations as to grey water discharge. Some areas have rules handling different wastes from vessels, but they just correspond to the requirements of the market.

Currently, plastic pollution draws main attention of media, however grey water also contains a lot of other environmentally harmful substances. Thus, this issue has to be handled effectively before the waste water discharge.

Though MEPC 227(64) establishes requirements for limitation of the discharge of oils, IMO does not provide any standards for the separation of grease from galley water. Earlier there was a thought of using just ordinary grease traps. However, such small boxes are still limited in handling different substances that can get though the discharge barrier.

All vessels produce grey water which they can legally discharge overboard. The amount of these harmful substances depends on the type of the vessel. For example, on cruise ships this problem is really intense. To determine a wastewater treatment system, a lot of factors should be taken into account, such as a number of people on board, operational periods of galley and laundry, water temperature and density, etc.

Beavis also mentions that greases and fat oils are the most difficult to deal with effectively. Moreover, they cause a failure of wastewater treatment. Since there are no specific standards, ship operators are advised to think thoroughly over characteristics and dimensions of the grease separation system.

ACO Marine offers special separators manufactured from high-density polyethylene composite which can be operated manually and automatically. While having the same performance standards as more common stainless-steel models, they are more cost-effective and lighter units.

The amount of waste from the vessels is quite small in comparison with the quantities of harmful substances that get in the sea from rivers and other sources. The shipping industry already follows the environmentally positive strategy of reducing its CO2 emissions. Likewise, they should set up more effective and feasible limitations to grey and black wastewater discharge.