Real time monitoring and controlling of Marine Sewage Treatment Plant Effluent

As on date around 56,000 vessels are moving in the World shipping fleet and it is growing every day. All these vessels were manned by seafarers who spend on an average of 6 months on-board. Their continuous stay onboard required the basic hotel service such as food, climate controlled Accommodation and all lavatory facilities. On top of this thousands of passenger ferries and cruise liners floating on the oceans also providing similar facilities for nature-calls of passengers. Discharge of these wastes from sewage system affects the marine environment, particularly in the confined water bodies similar to Baltic sea. One of the important requirements as per MARPOL (International conventions for the prevention of Pollution from ships,1973) by IMO is maintaining sewage treatment plant (STP) onboard [1]. This part has been specified in detail as ANNEX-IV - Prevention of Pollution by Sewage from ships[1]. Standards for Sewage treatment plant placed on-board is evaluated basis on the contents in the effluent from the plant after all processes completed. This evaluation is not performed on every STP fitted in so many numbers of vessels in service today. As a part of pre- building exercise STPs were chosen from list of type approved systems available. This type approval is issued by marine administrators by sample evaluation of one of the plant in the factory environment. This paper proposed the model STP in which the data from Real time monitoring the contents in the effluent can be used to regulate the air supplied to the plant. Different sensors such as microorganism detector, PH prob, Phosphorous sensor and Nitrogen detector of instant results types used for this purpose. To regulate the supplied air, frequency controlled motor is used in the supply-air Fan. This regulation of air will reduce the energy requirement of the overall process. Added with the regulation of air supply, real-time control on feed rate of dosing pump optimize the chemical use in the plant. Nitrogen and Phosphorus contents continues measurements and flowmeter readings from inlet and outlet of the plant ensure the effective performance of Full treatment module. This proposed model plant will be an energy efficient and real-time compliance to the international limitations stated in MARPOL.