Thomas L. Maddox
T.L. Maddox Companies, Inc.
16149 Westwoods Business Park
Ellisville, MO 63021-4504 USA

It is estimated that as many as 3,000 alien species per day are transported throughout the world in the holds of ships. Most of these organisms do not survive the stress of the voyage and are not capable of competing in their new environments when they are discharged in a remote port. However, the records are replete with thousands of examples where alien species have thrived in their new environments and have evolved to wreak ecological and economic havoc in their new surroundings.

Ballast water presents unique challenges to conventional disinfection technologies owing to the large number density of organisms, the diversity of their composition, and the chemical and physical characteristics of ballast water. Thus, a combination of technologies is required to achieve the treatment goal of inactivating all organisms. Generally, most of the technology in use for conventional wastewater treatment is being evaluated as a possible solution to the ballast water treatment problem.

Filtration down to 100 micron particle size followed by intense, low-frequency sonic energy is being combined with ozone in an advanced, flow-through reactor to disinfect ballast water. The method uses a mechanically driven acoustic transducer operating at low-frequency to promote intimate mixing of gases, liquids, and solids to improve the contact between the organisms in ballast water and ozone bubbles, resulting in greater mortality at small dosing rates. The processes produce high-intensity acoustic compression and rarefaction waves which are propagated throughout the reactor. The intense pressure and turbulence induced shear caused by these waves will stress and traumatize the organisms, increasing their vulnerability to the ozone.

This proposal provides a progress report on the work, which is being funded by the National Oceanic and Atmospheric Administration Sea Grant Office. The work is proposed in three phases. Phase I demonstrated the effectiveness of combining the use of a low-frequency sonic contact reactor with ozone as an effective means to destroy the non-indigenous species and pathogens in ballast water. The Phase I work was primarily designed to generate sufficient data to assess the feasibility of the approach and to allow a preliminary design of a test module that would be deployed in subsequent phases of the project. Phase II activities consist of fabricating a test module and demonstrating the unit dockside at several locations. Phase III will incorporate the findings from early work into an operable, shipboard ballast water disinfection system.

Coupling of ozone disinfection with sonic energy and filtration down to 100 micron particle size could be a breakthrough combination of technologies which would allow the effective and economic use of ozone, a proven disinfection technology, for on board ballast water treatment.

The expected benefits of developing an ozone contactor as an onboard ballast water treatment technology are:

· Promotion of better contact of ozone with target organisms, thus reducing the physical Atime-space@ requirement and permitting its use aboard vessels.

· Traumatization of organisms through the imposition of a strong (215 dB re 1_Pa) acoustic field which may synergistically contribute to the inactivation of the organism.

· Reduction of the amount of ozone which must be used to effect inactivation, thus minimizing the negative influence of bromide in marine waters and improving the economics.

One mechanism which results in higher disinfectant dosage requirements is the association of viable particles with suspended matter in the water. Sonic disruption of these aggregates would enhance the contact of ozone with the target organisms. Also, organisms in a weakened physical state are more susceptible to inactivation. Administration of ultrasound, ozone, and filtration together produces an enhanced rate of Giardia cyst destruction, presumably through cyst damage and enhanced mass transport of ozone into solution.

There is mounting evidence that stressors such as abrasions or physical damage incurred during disinfection augment the disinfection process. The combination of technologies proposed here utilizes filtration and the disinfection power of ozone coupled with a low-frequency mechanically driven transducer. This device has been demonstrated to increase the mass transport rate of ozone into solution and promote energetic interparticle collisions which lead to particle size reduction. Since the device is mechanically driven, its scale-up potential is not limited by economics or technological barriers. The design relies on resonant vibrations of an elastic transducer, so the efficiency of energy transfer into a liquid medium is very high. The acoustic field created by the device is very intense, with displacements approaching one centimeter and 215 dB re1_Pa sound pressure level. The Phase I project was completed on September 30, 2000. Background on the process and results of the work completed are available upon request.