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MARPOL Annex IV & Sewage Treatment Plant

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"MARPOL Annex IV & Sewage Treatment Plant" by Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.

"MARPOL Annex IV & Sewage Treatment Plant" by Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.

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  • 1. MARPOL ANNEX IV AND SEWAGE TREATMENT PLANT Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 6/3/2014 1
  • 2. 2 MARPOL Annex IV “Regulations for the Prevention of Pollution by Sewage” • Entry into force: 27 September 2003. • The second of the optional Annexes, Annex IV contains requirements to control pollution of the sea by sewage. (A revised Annex was adopted in 2004.) Certificates issued under Annex IV: • International Sewage Pollution Prevention Certificate • Surveys: Initial & Renewal 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 3. Special Area for Annex IV: - Baltic Sea Date of entry into force: 1st Jan, 2013 6/3/2014 3 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 4. 4 SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 5. Sewage means - Drainage and other wastes from any forms of toilets and urinals - Drainage from medical premises ,wash tubs and scuppers located in these premises - Drainage from spaces containing living animals and other waste waters mixed with drainage as above 6/3/2014 5 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 6. Regulation 10: Standard discharge connections OD: 210 mm ID: as per pipe OD Bolt dia: 170mm Slots in flange: 4 hole 18mm Flange thickness: 16mm Bolts and nuts: 4 x 16mm 6/3/2014 6 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 7. REGULATION 11: DISCHARGE OF SEWAGE 1. Discharge of sewage into the sea is prohibited except when, The ship is discharging comminuted and disinfected sewage using a system approved by the organization at a distance of 3 nautical miles from the nearest land and that which is not comminuted or disinfected at a distance of 12 nautical miles from the nearest land 2. Sewage shall not be discharged instantaneously, but at a moderate rate when the ship is en route and doing a speed of not less than 4 knots. 3. Ship has in operation a sewage treatment plant or an approved sewage comminuting and disinfecting system with storage tank or a holding tank of adequate capacity certified by the organization, 4. Test results of the plant are laid down in the INTERNATIONAL SEWAGE POLLUTION PREVENTION certificate. The validity of this certificate shall not exceed more than 5 years. 5. It should not cause any discoloration of the surrounding waters nor produce visible floating solids 6/3/2014 7 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 8. 8 Legislation preventing the discharge of untreated waste overboard has been in place for some time with a requirement that it should be retrofitted where not already in use. American legislation defines three types of sewage treatment units. SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 9. Sewage systems Regulations. Legislation preventing the discharge of untreated waste overboard has been in place for some time with a requirement that it should be retrofitted where not already in use. American legislation defines three types of sewage treatment units. Type 1 A device capable of discharging effluent having no floating solids and a coliform count of less than 1000 per 100ml of effluent. Type II A device capable of discharging effluent with suspended solids not in excess of 150mg/litre and a coliform count of less than 200 per 100ml Type III A device to prevent the discharge overboard of treated or untreated waste. Ventilation systems are to be kept independent of other vents A log is to be kept of any discharge overboard from a holding tank 6/3/2014 9 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 10. 10 Human sewage is disposed of naturally by the action of bacteria the human digestive system. Most modern sewage systems encourage the growth of human bacteria by supplying Oxygen to the bacteria which helps the colony thrive and therefore literally eat the raw sewage. Most human sewage is 98% water so can be broken down effectively by this simple action. However the bacteria must be killed before the sewage effluent (water) is disposed overboard otherwise it would absorb all oxygen in the water. SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 11. 11 Historically Chlorine has been used for this role, but in many parts of the world chlorine damage is greater than sewage damage. The most common marine sewage system is called the “ AEROBIC ACTIVATED SLUDGE” system, and was pioneered by Hamworthy in 1914. SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 12. 12 ACTIVATED SLUDGE PROCESS The Hamworthy Super Trident Sewage Treatment Plant utilises the activated sludge process which was developed in England by Ardern and Lockett in 1914, and was so named because it involved the production of an activated mass of micro organisms capable of stabilising a waste aerobically. SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 13. 13 Basically the microbial population uses waste materials to obtain energy and grow. Waste consists mainly of several biochemical compounds (carbohydrates, proteins, nucleic acids and lipids) which contain mainly carbon, but also nitrogen, phosphorous and other elements in lesser amounts. Microbes consist of primary and secondary feeders who use the waste material for energy and growth. Primary feeders are bacteria, they use soluble waste molecules for food, secondary feeders such as protozoa are larger microbes and ingest particulate food, mostly bacteria that has grown on waste molecules SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 14. 14 Oxygen is provided to supply micro-organisms with the means to oxidise a portion of the organic compounds 'in the waste. A portion of the energy released during oxidation is converted to chemical energy which permits the organisms to use the remaining organic carbon as building blocks to synthesize the particular compounds needed for their structure and function. The amount of oxygen used during the process of obtaining energy and extracting organic carbon from the waste for growth is termed biochemical oxygen demand (BOD). SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 15. 156/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 16. 16 Principle Biological system require a steady and relatively constant flow of solid sewage so the bacteria can exist in sufficient quantity to maintain effluent discharge at the correct quality. sludge build up is a possible problem although extended residence in the aeration chamber greatly reduces the amount. For example, sewage with 80% solid waste is reduced to 20% of its original weight after 12 hours in the aeration tank. The process of aerobicity strips oxygen from the water and creates more water, carbon dioxide and bacteria. SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 17. 17 - The Trident sewage treatment unit shown above consists of three chambers. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 18. 18 1. Sewage enters into the primary chamber of aeration chamber via a coarse mesh filter where large solids are broken down. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 19. 19 -The aeration chamber is where the main biological action takes place. - Here air blowers mounted on the outside of the unit oxygenate and stir the effluent and bacteria mix via a series of pipes and nozzles. - The sewage remains in this aeration tank for some time.6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 20. 20 2. Incoming sewage displaces some effluent of the settling tank (or hopper) where under inactive conditions biological floc, activated sludge and bacteria, settle out and is returned to the aeration chamber via air lift pumps also driven by the blowers. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 21. 21 3. A second transfer pipe scum's the surface of the settling tank and returns it back to the aeration chamber. - This returned sludge contains the bacteria to digest the incoming sewage. Thus the importance of this floc return can be seen 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 22. 22 4. Effluent passing over from this chamber should be clean and ready for disinfecting in the chlorinating chamber. - The level in this chamber is controlled by a pump and float switch arrangement. typical chlorine levels at discharge is 5ppm. 5. Valves are fitted to the aeration and primary chambers to allow them to be pumped out and back flushed as necessary.6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 23. 23 The bacteria are susceptible to water conditions including temperature and the presence of toilet cleaning agents. In this way the system is fitted with by-pass valves so passing contaminated water overboard. Should the bacteria be killed it takes some time before a new colony forms. There are special 'feeds' which promote the reestablishment of these colonies SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 24. 24 GENERAL MAINTENANCE Daily: The air supply pressure should be checked to ensure it is within the limits specified in the handbook. Too high a pressure may indicate blocked distribution pipe work or air diffuser elements, Too Iow a pressure may indicate broken or leaking distribution pipe work, dirty compressor air inlet filter or compressor/motor failure. An investigation of the problem and any necessary remedial action will need to be carried out.
  • 25. 25 Maintenance of Aerobic treatment units. 1. Thorough , regular cleaning and inspection with particular attention being paid to areas behind internal division plates 2. Checks on alarms and trips 3. Checks on aeration equipment 4. Checks on transfer systems in the tanks 5. It is recommended that a low air pressure switch rather than a motor failed alarm be fitted to the air blower motor hence eliminating the danger of the fan belts snapping and going undetected. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 26. 26 The contents of the aeration compartment should be checked for quantity of suspended solids using the graduated cylinder supplied. Fill the cylinder to the 100ml level and allow to stand for 30 minutes. If the level of the settled sludge is above the 50ml level the unit should be desludged by pumping approximately 50% of the aeration tank contents overboard. If the aeration tank contents are very dark in colour, exhibit a tendency to float or settle very poorly and have a strong smell of raw sewage or "rotten eggs", then the tank can be assumed to have turned anaerobic. This is due to the loss of the activated mass of microbes, possibly due to a lack of air/oxygen or the high use of disinfectants in the toilets. SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 27. 27 The only solution is to drain and clean the tank and refill it with clean sea water or freshwater prior to putting it back on line. If for this or any other reason the tank has been completely drained and refilled then the effluent quality can be reduced until after an approximate 14 day conditioning period has elapsed. SEWAGE 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 28. 28 Physical-Chemical Sewage system This is based on the separation of the liquid element from the sewage flow. This is disinfected in a 5% chlorine for 30 minutes to kill off coliform bacteria and then discharged overboard in full MARPOL compliance. One problem with this system is the required space, Only a finite amount of space can be set aside for the storage of the solid part of the waste which can only be discharged in port or outside territorial waters when allowed. If these facilities are unavailable the system become inoperative. There is also the need to carry quantities of Calcium Hypochlorite for conversion to Sodium HypoChlorite for the disinfection of sewage flow. Calcium Hypochlorite requires very careful handling. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 29. 29 PHYSICAL CHEMICAL 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 30. Electrocatalytic Oxidation - Sewage is collected, macerated and passed through a electrolytic cell. - Electrolysis produces Sodium Hypochlorite which is used to oxidise organic material before discharge. Alternately dosing by chlorine may be used. - The effluent passes on through to a settling tank were the oxidation process is completed. These type of plants can be 50% smaller than biological types, this and the fact that pass through times are extremely short- typically 30 minutes compared to the several hours of the biological unit- are the main advantages of this system. - The discharge contains no solids and is totally free of coliform bacteria. A disadvantage of this system is due to the short exposure time in the oxidiser relatively high levels of chlorine are required to ensure destruction of the coliform bacteria. It is possible that this chlorine level can be present to some degree in the discharge. Dechlorination plant may be fitted6/3/2014 30 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 31. Electrocatalytic Oxidation 6/3/2014 31 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 32. Vacuum sewage systems 6/3/2014 32 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 33. Operation - Liquid flows from the aeration tank of an aerobic sewage tank to a coarse impeller centrifugal pump. - This delivers the liquid under pressure via an eductor and back to the tank. - The eductor reduces the pressure in the sewage system pipework to a set point after which the pump is stopped. - When the pressure in the pipework rises above a set value it is restarted. - The pipework consists of a network of mainly pvc pipes connected into separate zones- typically by deck- and brought down to a common manifold via isolating valves. These valves allow work on sections of the system whilst still maintaining others in use. - The toilets are connect to the system via a vacuum operated foot valve. Vacuum timers are also fitted which allow measured quantities of flushing water to be applied. Where toilets are connected in the same zone but exist at different heights non-returning valves may be fitted. In addition filter boxes may be fitted along with additional isolating valves to improve operation. 6/3/2014 33 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 34. Advantages: 1. Very little flushing water is required and the volume of sewage dealt with can be much reduced with the downsizing of relevant equipment and cost saving. 2. This has made them very popular for passenger vessels.Lloyds regulations state that the capacity of a sewage system for flushing water with conventional plant is 115 litres/ person/ day and 15 litres for vacuum systems. Disadvantages: 1. The main disadvantage is blockage due to drying and crystalisation of urea. Over a period of time this can be so severe as to completely close the pipes. Chemicals are on the market which can be added in very small doses which help remove and prevent this deposits but there success is not guarenteed. 2. In the event of vacuum failure a method must be in place to prevent dangerous gases passing back into the accommodation. 6/3/2014 34 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 35. The Hazards and regulations regarding the Sewage Systems - Raw sewage discharged into restricted waters will eventually overwhelm the self purification ability of the limited quantity of water. - In a closed dock the effect can be seen in a black sludgy water which when disturbed gives off an unpleasant smell possibly Hydrogen Sulphide. - When the quantity of sludge is reasonable aerobic bacteria digest the sewage breaking it down to simple compounds and Carbon dioxide using up Oxygen in the process. These compounds and Carbon dioxide promote plant life which returns oxygen to the water. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 35
  • 36. - When the quantity of Oxygen becomes so depleted that the aerobic bacteria can no longer function, anaerobic or bacteria not requiring Oxygen to function will take over. - The breakdown of the sludge is then associated with the same process of decay with foul smelling and dangerous gasses being produced. - Therefore the principal means of sludge conditioning on board is that of aerobic action, Types of sewage disposal. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 36
  • 37. There are four main types of sewage disposal systems fitted to ships: 1. Discharge from the toilet bowl into a common drain leading to overboard via storm valves 2. As above except common drain leads to a storage tank with or without aeration. Contents discharged ashore or at sea when appropriate. 3. Sewage treatment systems with sewage being collected and treated to produce an effluent suitable to discharge without effect on environment. 4. Vacuum collecting system where the drains are kept at a slightly negative absolute pressure , on flushing water, sewage and air are drawn into the drains being led to a collecting or treatment tank which is kept at atmospheric pressure. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 37
  • 38. Aerobic and anaerobic bacterial action When the sewage enters the drainage system it is acted upon by aerobic bacteria and is broken down, during this process the naturally occurring Aerobic Bacteria strip the water of oxygen and produce; more water, Carbon Dioxide, and more bacteria. If, however, there is insufficient oxygen for these bacteria then alternative bacteria dominates. These Anaerobic Bacteria produce Hydrogen Sulphide, Methane and Ammonia. These gasses are either highly toxic or flammable or both. In particular Hydrogen Sulphide is toxic to humans in concentrations down to 10ppm and its flammable vapours are heavier than air so may build up in lethal pockets in enclosed spaces. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 38
  • 39. Safety Parameters The generation by anaerobic bacteria these toxic and flammable gasses is present in all types of systems to some degree. The possibility of anaerobic action within a sewage treatment plant should be reduced as far as possible. Should these gasses be generated and allowed to enter the accommodation could lead to disaster. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 39
  • 40. The following are some methods which may help to reduce the risks: The fitting of proper ventilation in toilet spaces and the fitting of water traps can only be seen as secondary measures to reducing the risk. The primary concern is to eliminate the possibility of generating the gasses in the first place. Where sewage is stored in tanks for discharge, some method of maintaining an adequate level of oxygen in the water must be in place. Examples of these may be by direct air injection or by air entraining into the liquid whilst pumping through a nozzle. Where active aeration is not fitted then the contents of the storage tank should be changed within a maximum of a 24 hour period unless some other means of treatment is used.. The conditions in the tank should be closely monitored Where aerobic treatment plants are used then manufacturers operating instructions should be closely adhered to. A system of maintenance should be in place. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 40
  • 41. Tank Ventilation arrangements. Ventilation pipes should be in good condition and free from obstructions. They should be of a size to minimise pressure drop and ensure good gas clearance. They should be self draining to prevent blockage by water. Any flame gauze's or other fittings should be checked for cleanliness. Toilets, showers, washbasins, etc. The condition of drainage pipes should be checked regularly, as should the operation of the water seal or other fitted arrangements to prevent the back flow of gasses. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 41
  • 42. Accommodation ventilation arrangements The ventilation should be sufficient to ensure proper balance allowing each compartment to be correctly supplied. The ventilation system should be correctly maintained and checked for cleanliness. Air extraction is of vital importance and the cleanliness of grills should be checked, the opening under doors should not be blocked, vent louvers should be correctly position to ensure all spaces are properly vented. The forced ventilation equipment should be regularly checked and maintained. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 42
  • 43. Operational aspects Only approved toilet cleaning agents should be used, the use of excessive quantities of bleach should be avoided as this may kill the bacteria. . Complaints of foul or musty smells should be dealt with immediately as these may indicate anaerobic action. The dangers of these gases should be explained to all crew. 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 43
  • 44. Suspended solids The quantity of solid waste in the effluent is weighed. After drying on an asbestos mat filter element. Biological Oxygen demand (B.O.D.) Aerobic bacteria use Oxygen in the process of breaking down the sewage. At the end of the process the action of the bacteria reduces and so does the Oxygen demand. The effectiveness of a sewage treatment plant may be gauged by taking a one litre sample and incubating it for 5 days at 20oC. The amount of Oxygen consumed in milligrams per litre or ppm is termed the B.O.D. Coliform count It is possible that the effluent contain bacteria and viruses hazardous to health if it has not been properly treated at the final stage. An indication of this is a count of the Coliform bacteria which are found in the intestine. A coliform count in a 100ml sample incubated for 48 hrs at 35oC. Another test at the same temperature but over a 24 hour period produces a colony of bacteria. 6/3/2014 44 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh.
  • 45. ANY QUESTION? THANK YOU! 6/3/2014 Mohd. Hanif Dewan, Chief Engineer and Maritime Lecturer & Trainer, Bangladesh. 45