Koichi Ueda

Development of Ballast Water Treatment with Anthracite Filtering

To minimize the risk to the environment and to human health and arising from the transfer of harmful aquatic organisms and pathogens through the discharge of ships ballast water, an international treaty has been adopted, February 2004. The installation of a ballast water processing system, which complies with the standard of the treaty, is required for ships constructed after 2009. Via various methods; such as electrolytic, ozone and specialized pipes have been developed. However, the practical application has yet to be achieved. Mud precipitating in the ballast tank, and microorganisms in the mud were observed. The processing burden of the ballast water was examined. By developing a test plant to demonstrate of ballast water processing, and using anthracite filtrating, we have obtained basic data of characteristics of marine organism filtration. The unit showed an effective removal of the microorganisms, excepting pathogens, from the natural seawater. This was achieved with low operational costs and avoided impact to environment.

Washing of Tanks and Pipe Lines on Chemichal Tankers

This is to report on the results of the tank and pipe line washing experiment carried out on small chemical tanker of Japan in its actual operation.In the period from January to March 1994, after-discharge washing tests were carried out on a small chemical tanker which had carried Alpha-Methylstyrene and m-Disopropylbenzene. At this time, freshwater washing by using washing machine was conducted at the prescribed number of cycles. Wash water was accomodated in the slop tank through a discharge line and the amount of the wash water was mesured. Samples of this wash water were taken at the manifold in the couse of transfer to the slop tank and the times of sampling were recorded by a stop watch. Concentration of the residual substances in the wash water was mesured in the laboratory and the relation between the amount of the wash water and the residual concentration was graphically shown at every passage of time.In the tests, the required wash procedure was accomplished using a smalll amount of water that calculated by the formular in the International Maritime Organization P & A standard.Using these results, the required average amount of wash water is estimated in the case of the small chemical tankers.In order to decrease the required amount of washwater, it is necessary to decrease the dead spaces in the pipe lines during the washing.

Tank washing with detergent

On the tank washing of chemical tankers, it is desired to establish the tank washing standard for the prevention of sea pollution and to minimize the necessary wash water quantity. We investigate the cleanliness of the tank wall surfaces after washing and the concentration in the effluent. Red dyed alkylbenzene is used as the test liquid. After it is adhered to the tank wall, it is washed with jet water which contains detergent. Two sections are determined to examine the cleanlines after washing on the wall surfaces. One is the ceiling near the corner that is most difficult to wash and another is ther vertical wall that is easy to wash. The washing with the detergent is compared with that with fresh water.In the case of washing of alkylbenzene which is insoluble in water and low in viscosity, the necessary wash water quantity is decreased by using detergent. It is estimated by the coefficients obtained by the model tank test that if the ditergent is toxic, the necessary water quantity is decreased by about 13% and if it is not toxic, it is decreased by about 31%.

Removal of Residue from Cargo Tanks by Ventilation

For the chemical tanker, cargo residues of substances with a vapour pressure greater than 5×103 Pa at 20°C may be removed from a cargo tank by ventilation. But according to the prevention of marine pollution (MARPOL73/78), the ones with a vapour pressure less than 5×103 Pa at 20°C must not be removed by ventilation.Recently stripping systems are developed, and on some chemical tankers the stripping residues quantity is decreased less than one litre by using thin pipe.If chemical substances with the little vapour pressure are removed by ventilation, this procedure is very useful for the operation and the prevetion for sea pollution.Hence the posibility of the removal by ventilation was examined by the model tank test and on board test. The experimental results show that the residues in the tank well is removed by ventilation using the suction pipe or stripping pipe. And the liquid adhering to the wall can be also removed by the ventilation.

Oil/Water Interface Detector by means of Electromagnetic Induction

To prevent marine pollution by oil discharged from ships, the development of oil detecting devices of high performance and reliability has been internationally required. In the report, the performance of a detecting device of oil/water interface being newly developed at the Institute was investigated.In the tank cleaning procedure carried out on tankers during the navigation, the residual oily water is gathered to a slop tank on board. In spite of the fact that it is of great importance to detect the interface between oil and water in the tank in order to prevent oil from being discharged overboard, there is the fatal defect in the existing detection techniques that the residual oil of high viscosity adheres tightly to the detector head. Accordingly, the new detecting device of high reliability, which can effectively distinguish oil layer from water even when a little bit of oil of high viscosity may adhere to it, has been developed by applying electromagnetic induction method, and the performance of the device was experimentally investigated.