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Sewage and Waste Water Treatment

When we flush the toilet ashore, we do not have to bother about what happens next – the stuff disappears and this is someone else’s responsibility from now on. But that is not the case on board ship. To keep up treatment plant working properly everyone, not just the engineers has to understand what we cannot and what we cannot do with the sewage and grey water from the basins, showers and so on, which we produce. Everyone does not just mean ship’s crew – it includes anyone who comes on board, i.e. pilots, stevedores, even visitors from the shore office.

The reason we have regulations on how to deal with sewage is common sense, really. The stuff is not something you would like to have when your family is going to the beach for a day. What we are allowed to do with sewage is covered by the international regulations. The revised MARPOL Annex IV says there is no restriction on discharging sewage that passed through the approved treatment plant.

But, if your ship does not have an approved plant, as laid down in MARPOL, then you are not allowed to discharge any comminuted disinfected sewage closer than three miles to the nearest land. Even within that distance, it has to go into the holding tank, even if it has been through the treatment plant.

So, what does happen when we flush the lavatory and wash our hands? The waste goes to a treatment plant either using gravity and pumps or, in more modern systems, using a vacuum. Almost all treatment plants on ships work on what is called extended aeration. This simply means that air is blown through the sewage, which stimulates the production of the aerobic bacteria. Aerobic means existing in the presence of oxygen. Their job in life is to eat sewage.

In principle, this is how the aeration plant works. There are three compartments – aeration, settling and chlorine contact. Sewage flows or is pumped through a coarse filter to the aeration compartment and air is bubbled through series of diffusers. The air comes from low pressure compressors. The bacteria digest the sewage turning it into inert sludge, water, and CO2. Some of the sludge collects in the bottom of the compartment. The digested effluent together with the bacteria and the remaining sludge flow through another coarse screen into the settling tank. Sludge and bacteria sink to the bottom and recirculated to the aeration compartment.

Debris is skimmed from the surface. The clean effluent flows through a chlorinator into a contact tank. The chlorine kills any remaining harmful bacteria. Make sure you familiarize yourself with the local regulations. Some countries, Korea for example, insist on chlorination while others, such as Canada, forbid it.

Grey water from showers, sinks and so on, also flows into the contact tank and the resulting effluent which is now cleaned and harmless, is discharger overboard. The discharge is controlled by float switches located in the last chamber. The switches start the discharge pump which forces the fluid though a valve and overboard. There is an emergency overflow but it is very important to prevent sewage overflowing into the bilges because, if that happens, the oily water separator and the oil content monitor will not work.

This is the inlet filter on the front of the aeration compartment – it is a coarse screen designed to let human soil and toilet paper pass through it and nothing else. So please, no cigarette ends or packets, no condoms, no female sanitary products, no newspapers and no kitchen towels. Toilet paper is designed to dissolve, the kitchen towers are not.

Sewage and Waste Water Treatment - 3Grey water like sink waste does not go through the aeration process so there is one area in the ship where we have to be very careful – the galley. Too much grease can block pipes so those people who work here try to keep as much of it as possible out of the sink. Then, there is cooking oil. But there was a case in the United States when Port State inspectors sent down divers to investigate an oil spill on the ship in harbor – it turned out that someone emptied the entire contents of the deep fat fryer into the galley sink. If you need to get rid of the cooking oil, put it in a waste oil tank.

Of course, lavatories have to clean, too. Note that in the ship’s sewage treatment plant bacteria are our friends and not enemies. So we have to use special cleaners that do not kill aerobic bacteria. When you maintain your system, it is very important to inspect the outlet connection, particularly if your system uses vacuum technology instead of water and gravity to move the sewage the lavatories to the treatment plant. A break here on in any part of the piping will reduce the efficiency of the vacuum and has to be replaced.

There is another reason why this connection is important – it prevents any backflow of the sewage gases into the toilet compartment. But in case they do get in, it is essential to keep toilet and washing areas properly ventilated. Check extraction grills, louvers and ducts to make sure they are clean and not blocked with dirt; if there are fans installed, make sure they work.

The disinfectant tablets in the chlorinator also have to be checked regularly during routine rounds and their proper levels maintained. Make sure you keep sufficient spares as recommended by the manufacturer. From time to time the plant itself has to be cleaned and all build-up of sludge removed. Refer to the manual for the instructions. In principle, we shut the system down and empty it either partially or completely. We open up the compartments, inspect them and clean them.

We check the operation of the float switches and alarms, the condition of air diffusers and the compressor filters, belts and bearings. We replace any defective jointing. It is particularly important to check the compressors and the diffusers which supply air. If there is insufficient air, the aerobic bacteria die and are replaced by the opposite, anaerobic bacteria. They also digest sewage, but in the process they produce gases which are highly toxic, flammable and in some cases explosive – hydrogen sulfide, methane, Sewage and Waste Water Treatment - 4ammonia.

When you are cleaning the plant, do not go inside, wear the face mask, goggles and gloves at all times. Very rare, and in the really exceptional circumstances, when someone has to go inside the plant, remember that this is dangerous. Treated like any other entry into an enclosed space, do a proper risk assessment and take all the necessary precautions. Once the system is clean, you can re-fill and start it again and, as with any other maintenance work on board, keep a clear simple record of what you have done.

We normally clean the treatment plants when the ships Is drydocked or, sometimes, when in port. If cleaning is done in port, the sludge and the rest of the plant’s contents have to be discharge to proper facilities ashore. On rare occasions, we might have to clean the plant at sea because so long as we are far enough from land, untreated sewage can be discharged overboard. This is also an opportunity to use a bacteria killing cleaner so long as the system if flushed with sea water before the treatment plant is reconnected.

After starting the plant again, it takes between ten days and two weeks for aerobic bacteria to reestablish themselves. So, if you are cleaning it at sea, you must only completely de-sludge the system when the ship is going to be in unrestricted waters for that time.

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This set consists of two books on ship’s stability, in fact two editions of the world famous title. The latest fourth edition has been fully revised and updated and that is the reason why we decided to include both books. We are aware of the serious changes in the marine transportation of cargoes and design of ships intended to serve purpose. However, it shall be noted that the rules and regulations that pertain to the transportation of the movable bulk cargo remained more or less constant being working.

There are four main parts in this book. The opening chapter of the volume is dealing with the prerequisites for the calculations of the ship’s stability and trim as well as the hull strength. The first part is dealing with the transverse stability of the ship including inclining test, free surface effect and stability at large angles.

The second part addresses the longitudinal stability of the vessel while the third part covers the longitudinal hull strength. The final part will provide information on the modern application including usage of the shipboard computers calculating stability, practical aspects of ship stability etc. Some additional information is provided within several appendices to the main part.

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The material presented within this course was mainly intended to give ship Masters and Chief Engineers as well as officers some good training on the chemical tanker operations. It will be useful to all people assigned immediate responsibility for such operations including, but not limited to cargo loading and discharging, cargo handling, and caring of the cargo during transit period etc.

All critically important aspects have been covered, e.g. safety on board chemical tankers, protection of the marine environment, established operational practices and the obligations imposed by the applicable regulatory framework. The publication contains all course handouts and can be used in the classroom as well as for the self-study.

Twelve chapters of the coursebook cover absolutely all aspects of the operations, from chemistry and physics, associated hazards, design of the chemical tankers, and cargo contamination to the cargo handling systems used on board, shipboard safety, pollution prevention, ballasting and de-ballasting operations, ship-shore interface and others. The text is full of supplementary information including glossary of commonly user terminology.

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Here is a truly excellent compilation of stowage factors. The publication was prepared by the industry experts and is providing reader with the necessary information on the stowage factors. One of the most useful reference sources covering literally all classes of merchandise. This sixth edition of the volume has been significantly revised in order to include more useful data such as the stowage factors for bulk shipments of the ore cargo, sweet oil, containerships etc.

The stowage factors presented in the book are in cubic meters as well as cubic feet per ton. The information contained in this publication is the result of combined work of a team of experts and it took years to gather it all. All entries included in the volume are arranged in alphabetical order for easiest reference. There is a separate section addressing measurement and capacity of the shipping containers.

In short, the book is full of up-to-date and useful data arranged in such a way that would allow their immediate use on board any cargo ship so we do recommend having a copy at all times. Several supplementary tables are also there to give some additional data, such as tonnage conversion, salinity and draught adjustment etc.

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Weldability. Hot and Cold Cracking.

In the course of the welding cycle three events occur:

  1. 1. Filler metal and contiguous base metal are melted and resolidify to form a fused connection.
  2. 2. The heat effect of welding subjects the adjacent base metal to a thermal gradient ranging from above the base metal melting point to ambient temperature. The heat affected zone, HAZ, and deposited weld metal then cool to ambient temperature. As indicated in the picture, the variety of metallurgical structures produced in this heat affected zone includes those exposed to the various temperatures which produce resolidification of melted base metal, grain growth, grain refinement, or modification of metallurgical microstructure.
  3. 3. The solidification of molten metal, as well as the metallurgical phase changes, induce plastic flow and develop residual stresses which may exceed the yield point in magnitude; thus resulting in structural distortion


Hot Cracking

When cracking occurs at elevated temperatures, the crack is usually intergranular, meaning between grain boundaries. Such Weldability. Hot and Cold Cracking - 2cracking is associated with excessive solidification and cooling stresses acting on constituents present at the grain boundaries which are relatively weak at elevated temperatures. The weakened grain boundary may consist of specific low melting constituents such as sulfides in steel. In other cases the deposition of a weld bead of unfavorable geometry may impose excessive cooling stresses on the hot weld deposit which has relatively low strength at elevated temperature.

For example, in submerged arc welding, weld beads such as those shown in the picture, would tend to form a center section which solidifies last and remains at an elevated temperature after the surrounding metal has solidified and cooled. The low strength at the grain boundaries of the material at elevated temperature is inadequate to resist the thermal stresses, and hot cracking occurs. Such cracking, can usually be readily prevented by changing weld parameters to produce a bead of more favorable contour.


Cold Cracking - Hydrogen Cracks or Delayed Cracks


The role of hydrogen is an important consideration in the welding of ship steels. Hydrogen-bearing compounds such as water or organic compounds present on the filler metal surface, in electrode coverings, or on base metal surfaces may dissociate in the welding arc to form atomic hydrogen.

The atomic hydrogen penetrates and is highly soluble in molten steel weld metal and the zone of adjacent heat affected steel which has been transformed to a phase known as austenite; the austenite Weldability. Hot and Cold Cracking - 3forms when the heat affected zone of a steel is heated above a critical temperature, (approximately 900°C (1,640°F), for structural steels.

As the solidified weld metal and austenitized heat affected zone cool to ambient temperatures, they are transformed into non-austenitic phases which release most of the dissolved hydrogen from solution, since hydrogen is practically insoluble in these phases.

When hydrogen is released from solution in the presence of a hard zone in the microstructure and a high residual stress field, a condition known as hydrogen cracking may occur. Since the time of such cracking varies from immediate to several days or weeks after the completion of welding, the phenomenon is also known as delayed cracking.

The tendency for such cracking varies directly with the magnitude of:

  1. 1. hydrogen concentration,
  2. 2. local metal hardness,
  3. 3. residual stress.

Hydrogen delayed cracking is the most important and troublesome form of cracking encountered in welding of the higher strength ship steels.

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This is an excellent and world class publication, a truly must-have for all navigators of today; in fact, it will be interesting and useful not only to the ship masters but also to the owners, and anyone else involved in planning the voyage. The text of the publication will provide mariners with the clear and easy-to-use information and all required support so that they can properly calculate the best, meaning both shortest and economical, distance between any ports.

The content of the volume is presented in accordance with the market areas. The volume includes numerous and very informative data tables and illustrations, maps and lots of other supplementary information. According to the reviews received from different parts of the world, the publication shall be treated as one of the most valuable reference sources for the people in the shipping industry.

Note that it is becoming increasingly popular among the superyacht fleet owners, brokers and of course navigators who have already appreciated the comprehensiveness and user-friendliness of the volume – the author managed to collect enormous amount of useful information and arrange it in a maximum comfortable way. All ports regularly used for commercial shipping are covered.

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This publication was prepared by Frank Ward Sterling, Lieutenant of the United States Navy Fleet, back in 1942. Taking into account the date of the release, it is quite obvious that some of the latest technological developments in the field of boating cannot be reflected in this volume. However, the book covers all important aspects of the boat handling which have actually remained unchanged.

The volume will be of some interest to any boat owner and any person willing to get to the essentials of the boat navigation. The material is arranged in two halves covering boat navigation and seamanship. While the first part deals with the various navigational tools, records and publications, dead reckoning and positioning of the boat, the second one addresses soundings and tides, weather issues, rules of the road etc.

In short we would recommend all people planning their voyage on the boat to have a look into this book to ensure proper knowledge of the theory. The material is presented in a very understandable way and maybe that is why the publication is still used by many people notwithstanding the age of the book. In fact the explanations provided by the authors will make the topics understandable even to the people with no maritime background.

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The present volume is making one of the parts of the famous Reed’s series of book. The intention of the author is to provide a comprehensive professional coverage of the theoretical knowledge related to the naval architecture the one particularly required by the marine engineers.

The arrangement of the material contained in the book is very helpful to the reader – the author starts with the very elementary information and then step by step goes deeper. Throughout the content of the publication, the main emphasis is placed onto the essential theoretical principles.

The text is supplemented by the numerous illustrations of a very informative character, and such approach makes understanding much easier. We may assure you that all engineers who work systematically with this book will eventually find the time spent on the learning amply fully and adequately repaid since they will have a good understanding of all principles of the naval architecture and be able to apply their knowledge when handling their day to day operations.

The book definitely deserves attention of all marine engineers since the author concentrates on the maters specifically chosen to suit their needs with no excessive information.

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