When it comes to marine sewage treatment systems, the primary system involves the removal of solid through a physical method. For the secondary treatment, the organic matters are forced to decompose through the help of bacteria and the effluent is sterilized after with the help of chlorine. After the final chlorination, the sewage water is then released to the sea. Once the secondary treatment is done on the sewage water, there are only a few potential pollutants left like organic chemicals which are non-biodegradable, heavy metals and nutrients. In order to take away all these remaining pollutants, the advance sewage treatment is utilized. There are many forms of advanced sewage treatment available. There are those that were proven and tested while some are found to be complex as well as expensive. The types depend on the design and the size.
Marine sewage treatment systems have three processing methods such as biological, mechanical and chemical. There are various sewage treatments but the ones commonly used are the combination of the three like chemical-biological, mechanical-biological and mechanical-chemical. The treatment is made up of these stages:
- The first stage is the accumulation of the waste water and then its management. During this stage, the waste water collected which is a combination of galley water, black water and grey water is temporarily stored inside tanks before the processing begins.
- The second stage is the pre-treatment of the waste water. This is done in order to protect the rest of the phases needed for the process of purification. Since the sewage has grease and solid waste in its composition, it should be treated before it became a problem in the succeeding processes. The solid contained is reduced with the help of the pre-treatment process. Less oxidation is also needed once the waste water is exposed to effective treatment. The method used in pretreatment is mechanical.
- The third step is the oxidation of the waste water. In this stage, the organic load is reduced by around 50% and the rest will undergo oxidation. Oxidation can either be biologically or chemically.
- The fourth step is the clarification and filtration of the waste water. At this process, the sludge is removed from the waste water and returned to the tank.
- Lastly, the waste water is disinfected in order to make sure it is pure. After this process, the waste water quality improves.