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102 while inspecting a. vessel found the gravity tank filled with polluted Chi- cago river water because of the care- lessness of the watchman in opening the valve leading to the tank while washing down decks. And even if the duty of collecting drinking water is (2. COOnIIG ~Tarthr ToD t1thig Warer Tarr THE MARINE REVIEW waters. This may occur when the vessel never goes far from shore, as in running between Chicago and Mil- waukee, or when it is in clean water for too short a time to fill its tanks. This situation is aggravated by the fact that the engineer in the engine eb - a THermosrar Controlled , valves Myecror t Cooling Water Ouiler water FIG. 1-DRAWING OF APPARATUS FOR DISINFECTING WATER BY STEAM JET, EQUIPPED WITH DEVICES TO MAKE IT AUTOMATIC AND es FOOLPROOF IN OPERATION performed with vigilance, such care can be, and most likely often is, nullified by leaky valves, the defects of which cannot be detected except by means of the drip valve described above. ‘Filling Tanks from Shore-—When drinking-water tanks are filled from shore, this is done either by carrying the water through a fire hose directly from the hydrant to the tank or by connecting the hose to the distribu- tion system. In most cases vessels that fill their tanks from shore have the pipe systems so arranged that they can also fill through a sea cock directly from the lake, protecting this line from contamination with the valves and drip pipe previously de- scribed. As a further protection on some vessels the wheels for operating the valves are removed, so that there will be no accidental opening of this connection. Opportunities for Contamination.— The opportunities for contaminating the drinking water aboard lake car- riers are as follows: 1. Contamination suction pipe while lying in polluted water, due to faulty seating of valves, failure to close valves, or the use of a general service pump. _2. Since in most of the vessels the engine rooms and sea cocks are aft of amidships and since there is usual- ly more or less sewage discharged from toilets in the forward part of the boat, it is possible that some of this fecal matter discharged from the bow is sucked in through the sea cock, _ 3. Accidental or intentional taking of supplies near shore or in unsafe of sea cock or room cannot tell at all times exactly where the vessel is; also by the fact that many ship captains and engineers are not acquainted with all the places where it. is unsafe to take water. There is also the likelihood that en- gineers and other employes may for- get to close the sea. cock, as the vessel approaches a polluted harbor. 4. There is also more or less pos- sibility of picking up sewage in the wake of other vessels, as for example where one vessel is towing another. That this method of contamination is a real one has been brought out by testimony before the international joint commission on remedies for the vogue, TODISIVVOUTION SYST CL? March, 1917 from the Great Lakes, it is obvious that it is an impossibility for any vessel operating on the Great Lakes, using the methods at present in to obtain a drinking water which shall be at all times free from. contamination. lt is, therefore, necessary, in order always to furnish a safe water for drinking purposes, that each vessel shall install some suitable form of water-purification apparatus. Some vessels have already made such at- tempts. Present Methods of Treating Water on Board Lake Vessels Filtration—The attempt at water purification most commonly found in use on vessels on the Great Lakes is filtration through small rapid sand filters, there being about 30 vessels using filters of this kind. These filters are used either as the sole means of treatment or as a prelimi- nary step in some other process of purification. The filters vary in size from 10 to 60 inches in diameter. Each filter is equipped with a shunt feed box for adding aluminum sul- phate to the water before filtration. On’ two vessels there are sand filters of a type somewhat different from that described above. In this apparatus the water first passes be- tween a series of iron plates so con- nected with an electric current as to form electrodes. The action of this electrode box is to cause a precipita- tion of iron hydrate, which is a good coagulant and one easy to remove by filtration. From the electrode box the water passes to a small coagulat- ing chamber, where some time is given for the coagulant to collect and partly settle. From this coagulating chamber the water passes through two small rapid sand pressure filters, connected in series. The apparatus is arranged to act automatically, so that the electric current is on only when water is being drawn through FIG. 2—TANK FILLED FROM SEACOCK BY GRAVITY OR BY SPECIAL DRINK- ING-WATER PUMP. WATER. DISTRIBUTED BY SPECIAL DRINKING- WATER PUMP pollution of boundary waters between the United States and Canada. Summary—As a result of the state- ments made above regarding the tak- ing of a ship’s drinking-water supply the system. It is so designed that the filters can be washed one at a time, the wash water being furnished by the filter in operation. Ultraviolet Ray Sterilization —Thirteen