that the ballast water meets acceptable levels of risk. In contrast, treating ballast water on board requires investment in equipment and crew training, as well as operational expenditures. However, the associated monitoring procedures would be simpler and could potentially be integrated with the treatment system to provide continuous feedback on treatment effectiveness.

It is probably inevitable that ships taking on ballast water in estuaries will take on sediment. Monitoring approaches need to address the combination of water and sediment. Monitoring the sediment phase is discussed later in this chapter, following the discussion of monitoring water.

Level I Monitoring

Level I monitoring consists of (1) an examination of the ship's logs and records of where and how much ballast water was initially loaded and where and how much of it was changed, accompanied by (2) continuous monitoring of basic physical-chemical water quality parameters, such as turbidity, salinity, temperature, concentration of dissolved oxygen, and pH (see Table 5-2). These parameters can be monitored by automatic, online equipment that provides continuous readouts for subsequent data storage or for direct transmission to shore. Alternatively, all of these parameters could be measured concurrently by handheld equipment at regular intervals.

TABLE 5-2 Basic Physical-Chemical Water Quality Parameters

Indicator

Definition

Potential significance for ballast water monitoring

Salinity

Amount of dissolved salts in water (reported as parts per thousand sodium chloride or as specific gravity).

Could indicate extent to which port water was changed with oceanic water.

Turbidity

Amount of light-reflecting material in suspension in water.

Could indicate concentrations of plankton and suspended sediment.

Temperature

Degree of heat.

The survival potential of ballasted organisms may be determined in part by (1) changes in temperature from voyage start to finish and (2) the temperature difference between ballast uptake and discharge ports.

Dissolved oxygen

Amount of oxygen dissolved in water.

May indicate general ability of ballast water to support living organisms.

pH

Level of acidity or alkalinity in water, as measured by the negative logarithm of hydrogen ion activity.

May indicate differences between port (estuarine) and oceanic water



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