Laboratory tests on heat treatment of ballast water using engine waste heat

Abstract

Waste heat recovery from shipboard machineries could be a potential source for heat treatment of ballast water. Similar to a shipboard schematic arrangement, a laboratory-scale engine-heat exchanger set-up harvesting waste heat from jacket water and exhaust gases was erected to test the level of species' mortalities. Mortalities were also assessed under experimental conditions for cultured and natural plankton communities at laboratory level. Effect of pump impellers on species' mortalities were also tested. Exposures between 60°C and 70°C for 60 sec resulted in 80-100% mortalities. Mortalities due to pump impeller effects were observed in the range of 70-100% for zooplankton. On the laboratory-scale arrangement, >95% mortalities of phytoplankton, zooplankton and bacteria were recorded. It was demonstrated that the temperature of tropical sea waters used as secondary coolant can be raised to cause species' mortalities, employing engine exhaust gases. The results also indicated that pump impeller effects will enhance species' mortalities. The limitations of the shipboard application of this method would be the large ballast volumes, flow rates and time for treatment.

Thermal desalination of ballast water using onboard waste heat in marine industry

“…Recent research efforts have focused on the effect of treatment temperature and time required for inactivation of certain organisms. Heat exposures between 60°C and 70°C for 60 seconds resulted in 80% to 100% mortalities of phytoplankton, zooplankton, and bacteria . Heat treatment technique under different operational conditions was also studied to treat the organisms smaller than 50 μm (phytoplankton and bacteria) in the ballast water .…”

“…A treatment time between 10 minutes and 16 hours is required for temperatures between 35°C and 40°C. About 20 hours of heating time was reported as effective at a temperature of 35°C . However, a higher temperature range such as 55°C to 75°C would require only 15 to 60 seconds, which is ideal in desalination process operations.…”

“…Heat exposures between 60°C and 70°C for 60 seconds resulted in 80% to 100% mortalities of phytoplankton, zooplankton, and bacteria. 15 Heat treatment technique under different operational conditions was also studied to treat the organisms smaller than 50 μm (phytoplankton and bacteria) in the ballast water. 4 Many studies have focused on developing thermal treatment systems for ballast water management.…”

“…About 20 hours of heating time was reported as effective at a temperature of 35°C. 15,21 However, a higher temperature range such as 55°C to 75°C would require only 15 to 60 seconds, which is ideal in desalination process operations. A recent study reported almost complete mortalities of phytoplankton, zooplankton, and bacteria at these temperatures.…”

“…A recent study reported almost complete mortalities of phytoplankton, zooplankton, and bacteria at these temperatures. 15 On the other hand, the use of process waste heat and renewable or nuclear energy sources has been widely advocated for desalination industry because of the large quantities of thermal energy required by desalination processes. [22][23][24][25][26][27][28][29][30][31][32] High-temperature desalination processes are usually constructed in cogeneration schemes to enable combined water-power production to improve overall economics and reduce environmental impacts.…”