Discharging of sewage in sea or territorial waters in banned as it can drastically affect the marine life. In case the sewage is to be discharged, first it has to be treated with the help of a sewage treatment plant. STP is now mandatory on every ship, according to International legislature.

1. Basic Description of a Sewage Treatment
Plant on Ship
ekomeri.com · by ekomeri · October 26, 2015
Discharging of sewage in sea or territorial waters in banned as it can
drastically affect the marine life. In case the sewage is to be discharged, first
it has to be treated with the help of a sewage treatment plant. STP is now
mandatory on every ship, according to International legislature.
sewage-treatment-system sewage-treatment-system
 Introduction
The first question you would probably ask is , “Why to use a ship
sewage treatment plant if the waste is already biodegradable?”. The
question definitely isn’t wrong but the problem is that not all sewage
constituents are biodegradable and not all take the same time to
break down. Also, untreated sewage has solid particles which take a
lot of time to disintegrate. It is for this reason that a sewage treatment
plant is used.

2. Raw sewage in water needs oxygen to break down naturally. This
sewage when disposed to the sea absorbs excessive oxygen and thus
reduce the requisite amount of oxygen needed by the fishes and
marine plants. Bacterias present in the sewage produces hydrogen
sulfide gas which produces acrid smell. Human waste has E. Coli
bacterias which are found in the intestine. The amount of E.Coli
bacteria in a water sample indicates the sewage content of that
sample.
Sewage treatment plants on ships are of two types:
o Chemical sewage treatment plant
o Biological sewage treatment plant
 Chemical Sewage Treatment plant
basic-concept-of-sewage-treatment-system
Chemical treatment plant consists of a big storage tank which collects,
treates and stores the sewage for discharging it to the sea or to a
shore receiving facility. The sewage is first collected in a tank and the

3. liquid content is reduced. This can be done by flushing water from
wash basins and bathroom drains directly into the sea. The liquid
from any other sources is treated chemically to get rid of the color
and smell and then it is reused as flushing water in toilets. The
chemicals that are used assist in the process of breaking the solid
constituents and also in sterilization.
A mechanical instrument known as comminutor is used to help
breaking down of the solid particles to smaller ones. The liquid
sewage remains at the top and the solid particles settle down, which
are then discharged to a sullage tank. The liquid sewage is chemically
treated and is used for toilet flushing purposes. The sewage from the
sullage tank is discharged to the shore collecting facilities.
It is important to supply adequate quantity of chemical dosages to
prevent odour and corrosion due to high level of alkalinity.
 Biological Sewage treatment plant
Biological sewage treatment plant uses bacterias to facilitate the
process of breaking down of solid constituents. It generates an
oxygen rich atmosphere that aerobic bacterias utilizes to multiply and
disintegrate the sewage waste to convert it into sludge. The treated
sewage thus generated can be disposed off to any waters. The process
that takes place inside the plant is known as aeration process.
The whole plant is divided into three compartments namely,
o aeration compartment
o settling compartment
o chlorine treatment compartment.

4. Sewage enters the sewage treatment plant first through the aeration
compartment. Aerobic bacterias digests the sewage waste and reduce
it to small particles. A continuous supply of atmospheric oxygen is
provided to increase the rate of digestion process.The disintegrated
solid waste is then transferred to the settling compartment where the
solid constituents settle down under the effect of gravity. The liquid
at the top is then passed to the chlorine treatment compartment. In
this compartment the liquid water is treated with chlorine and other
chemicals to kill any surviving bacterias. Once done the water is then
discharged into the sea. The process of chlorination is facilitated with
the help of chlorine tablets. The sludge that settles down in the
settling compartment is removed and stored in a storage tank to later
discharge it to shore facilities or decontrolled areas.
The Original Posted by Raunekk / Bright Hub
ekomeri.com · by ekomeri · October 26, 2015