BEST PRACTICES

Even when not required by environmental regulations, the following best practices are recommended. In some instances, best practices presented here are actually required by regulations.

Mitigating the potential impact of a power plant’s blowdown water (or “boiler blowdown”) on the environment may be accomplished by reducing both the volume and hazardous make up of blowdown water through one or more of the practices described below.

• Minimize the volume of blowdown water by optimizing the frequency of cleaning boilers. One or a combination of the following practices are worth considering:
  - Conducting frequent chemical analyses to define normal cycle chemistry will facilitate identifying when the chemistry is abnormal and, therefore, when cleaning should take place.
  - Consider using such techniques as ultrasonic imaging, thermocouples, removable test strips and fiberscopic inspections to determine the location and/or type of deposits.
  - Consider sampling the boiler tubes annually to track scale build-up.
• Consider controlling the composition of the boiler feed water through an elevated oxygen treatment process (as opposed to using chemical additives such as hydrazine and morpholine) - which has been found to result in a more unified, finer-grained magnetite layer that requires less frequent cleaning.
• Consider inspecting for and replacing seals on the steam cycle appurtenances - which will potentially reduce the amount of oxygen that enters the system and, in turn, the frequency of boiler cleanings.
• Consider establishing a boiler cleaning frequency that is set according to the build-up of scale, rather than simply a predetermined schedule. This may reduce unnecessary cleanings.
• Consider using on-line cleaning, which entails cleaning the boiler with a sodium polyacrylate injection while it continues to operate. This practice takes less time, uses less hazardous chemicals and yields a waste stream that is easier to handle; however, the associated risk is potential contamination of the steam turbine. In addition, fewer deposits can be removed with this practice.