Perhaps you might ask why is there a need to use marine sewage treatment systems when the wastewater is biodegradable. This query is certainly not wrong. However, the problem is that not all of the materials in the sewage are biodegradable. Not every trash inside the sewage also takes the same time in order to be broken down to pieces. It has been the trend that there are a lot of untreated sewage materials that have solid particles and take a lot of time in order to disintegrate. It is for these reasons that it is required that every ship should have a marine sewage treatment facility.
Raw sewage in water has to have oxygen in order to break down naturally. When the sewage is disposed to the sea, it absorbs excessive oxygen, reducing the requirement of the amount of oxygen needed by the marine plants as well as the fishes. Bacteria that are inside the sewage produces gas known as hydrogen sulfide and has an acrid smell to it. The waste produced by human has E. Coli bacteria which are commonly found in the intestine. The amount of bacteria particularly E. Coli that is present in a water sample will indicate the amount of sewage content.
Two types of treatment plants in ships:
Chemical sewage treatment plant
Biological sewage treatment plant
Chemical Sewage Treatment plant
The chemical sewage treatment facility consists of big tanks that act as storage containers. These tanks collect then treats and then store the sewage for discharge into the ocean or to an offshore receiving plant. The sewage is collected and placed inside a tank where the liquid content is significantly reduced. Reducing the liquid is done by flushing the excess water from bathroom drains and wash basins directly to the sea. The liquid coming from other sources is then treated chemically in order to get rid of the smell as well as the color. The treated water is then reused as flushing water in comfort rooms. The chemicals used in the process will assist in the breakdown process as well as in sterilization.
In order to facilitate the breaking down of solid particles into smaller particles, a mechanical instrument called the comminutor is employed by the facility. The liquid sewage will remain at the top of the container while the solid materials settle to the bottom of the tank and are then discharged into a sullage tank. The liquid sewage is then treated and recycled as water in flushing toilets and similar functions. The sewage contained in the sullage tank is then discharged to collecting plants.