The Application Research On Ballast Water Combined Treatment System

Ballast water maintains the stability of ships without cargos during the voyage. But its a lot of transport and discharge have caused great damage to the Marine ecological diversity. It has been pointed out that ballast water had negative influence on ecological environment by the Global Environmental Facility. International conventions of ballast water discharge standard adopted by the International maritime organization has been carried on the strict rules. It is in the urgent need of research and development the ballast water treatment technology, which is fast, safe and effective, for the global ocean shipping and marine ecological environment protection.We established UV/O3 treatment system in pilot scale and UV/electro-catalytic system in bench scale for ballast water microorganisms inactivated experiments, proving that the combined ballast water treatment systems have more advantages than individual unit processes. The combined processes have higher application value also because of the higher total residual oxidant(TRO) concentration and longer continuous deactivation they could provide.The bacteria sterilization and algae inactivation performance of O3, UV, UV/O3 pilot systems have been measured. The results indicate that under the UV/O3 treatment condition of UV intensity of 360μW/cm2, O3 dose of 2.12g/h, hydraulic retention time of 3.0s, the bacteria mortality is 3.02 lg and the algae morality is 1.08 lg, which are higher than that of the individual treatment processes. Under the same treatment parameters, but the hydraulic retention time is 1.0s, UV/O3 sterilized all the E. coli in 1h after sampling and inactivated all the D. salina in 1.5h after sampling. We affirm that UV/O3 system has advantages in microorganism inactivation than O3 and UV, and can satisfy the requirements of the IMO about discharge ballast water indicators.Under the condition of UV intensity of 45μW/cm2, current density of 60 m A/cm2, hydraulic retention time of 5.9s, the bacteria mortality rates of UV/Ti/Sn O2 and UV/Ti/Ru O2 systems are 5.67 lg and 4.82 lg. Under the same condition but changing the current density to 90 m A/cm2, the algae morality rates are 0.99 lg and 1.02 lg. These results are higher than those of individual electro-catalytic processes. By measuring samples’ TRO concentrations and decay rates of different electro-catalytic systems and also the continuous sterilization performance of different treatment systems, it is concluded that the UV/electro-catalytic systems have advantages in application of sterilization, and can meet the requirements of the IMO about discharge ballast water convention.