The Mystery, Sorry History, of Waste Water

Since as long as people have used the water for transportation there has been the need to rid vessels of all the waste that human bodies emit on a daily basis.

In the early days a simple wooden platform over the side of the ship sufficed and this, of course, has given us many off-the-cuff sayings we use today… such as “don’t sh#@ into the wind as it will come back to haunt you”.  

Time moved on and when this simple method became unacceptable, a bucket was introduced and, instead of producing isolated meals for fish, the fish ended up having banquets! When paying passengers came along, toilets on board became (slightly) more sophisticated, but required waste to be stored until there was a suitable time for it to be dumped. There is one thing all these methods have in common and that is 'the feeding of fish'.

Shore based disposal was introduced when people started to notice the marine environment was being affected in areas where this waste was pumped out and, I guess, started to think about what happens to a ship’s waste.  If we’re honest about it, a ship disposing of untreated sewage in a deep ocean does have very little impact on the grand scheme of things, which is reiterated in the MARPOL rules for discharge at sea but, in enclosed seas and near coastal areas, the impact on local marine life is more evident. To this end, the IMO and MARPOL regulations have become ever more stringent, almost year on year. 

The marine industry as a whole is pretty good at looking after that which supports and sustains it, and has developed systems for use on board that ‘treat’ waste water to a satisfactory level for discharge into the big blue. There are many brands of equipment, all of which must have a compliance and approval certificate.

There are two main ways in which waste water is treated and there are several ways of making either process work. 

The earliest sewage treatment used on board was biological, using bacteria to break down waste. Early systems used a specific type of wood or bark and, although they were efficient when they worked, they were prone to failure when the toilet and grey water systems were used in a manner that didn’t support the bacteria. The everyday cleaning products you would use at home, particularly those containing bleach, kill the bacteria that these biological systems depend on and the system will soon stop working and block up. Once these systems stop, or in essence die, a major problem is that other, unwanted bugs grow…you know, you’ve seen them in your tooth brush holder, in the soap, your coffee cup…

Note to all the budding new stewards /esses out there: check first with the engineer before using domestic cleaning products on board! 

As biological systems developed, there was a proliferation of cleaning products that could be safely used. The most popular and best line that I have come across is Gamazyne, but your local chemical supplier will surely have something similar. 

Once, after a refit during a particularly hot summer in Savannah, Georgia, I recall opening up the motor yacht Migaea (she was sealed up for hull painting in the dry dock) and finding literally millions of flies everywhere, even in sealed light fixtures. The standard fix for these unwanted bugs is to introduce yet another bug.. a very hungry and vivacious fly.

We were warned that when these boxes of buzzing flies arrived that, while their average lifespan was only four to five days, they could live for up to two weeks after feeding well. So we had to keep plugs in sinks and showers for the whole two weeks in case they escaped. Untrained and mishandling could have resulted in an even bigger problem...

The second treatment option is one that I like to refer to as a chemical incinerator, which does pretty much as the name suggests. Toilet waste is deposited in the holding take where it is aerated (oxygen is passed through using air bubbles) before being transferred in a metered dose to a treatment tank. Here it is cycled through a macerator pump and choline, either in liquid form (sodium hypochlorite) or as a diluted bleach solution which is injected into the flow as it passes through a fine filter  installed in the system. What passes through the filter flows into a second tank and what doesn’t is diverted back into the process.

It doesn’t take long for the material to break down and be transferred to the second tank and when that’s full it overflows into a third tank where it is mixed with more sea water and discharged overboard via a specially designed filter which strips the residue choline from the water. 

Sstrict IMO regulations have set this discharge value so low that it has almost zero effect on the water that it is discharged into and, in my many years of experience, its colour is such that you cannot distinguish it from the surrounding water, even in pristine, clear blue ocean. 

One of the selling points of the chemical systems is that in open sea we can use sea water to make the sodium hypochlorite in a device known as an “Auto Clor”. This is done by passing high voltage electricity through the salt water, a process also used in salt water swimming pools to clean the water ashore. Hence we are using nothing but sea water itself and putting back the elements we took out. The latest IMO rules still require us to strip any potential over chlorination... As always the governing bodies covering their posteriors costs the end user more money. 

There are several different approaches to this from a number of different manufacturers but the principle is the same. Yachtprojects International is the European and UK distributor of parts and service for the Headhunter Inc product line and further information can be found on our website www.yachtprojects.net.