IRON REMOVAL

Water treatment specialists have struggled with submicron iron and IRB (iron reducing bacteria) issues in closed loop systems for years. This includes chill water systems, robotic welding systems, boilers, steam condensate recovery systems, etc.

In all cases, the combination of iron particulate and IRB’s can lead to serious corrosion and damage within these systems.

The IRB are nature’s recycling facility for iron particles. Within such closed loops, the bacteria establish colonies and exude a biofilm. This biofilm contains a low pH ingredient that helps to convert the iron particles to “bio-available” form that the bacteria can then ingest. Unfortunately, this low-pH environment is high corrosive and will eventually damage other components within the loop and to eventual replacement.

CHILLED WATER SYSTEM – TOYOTA MOTOR MANUFACTURING FACILITY

A major North American Toyota manufacturing plant has multiple 5-million gallon chilled water systems that had a history of mild corrosion. Iron levels in the recirculating water had peaked at 3.5 ppm, well over the 1.0 ppm target. Suspended iron in chilled water systems can settle and cause deposition, encouraging further corrosion and bacterial growth. Over time, this led to overly frequent chiller tube replacements and increased costs for operating these systems.

Particle analysis data showed that the bulk of the iron particles were submicron and in the 0.1 to 0.2 micron range. The existing 0.5 micron sand filter had been working well, but the particle sizes were just too small for its capabilities. In preliminary tests, NanoCeram water filters were able to remove iron to < 1.0 ppm with great success (Figure 1). Economic analysis, however, made the clean up of this massive system unfavorable with a one-use filter. Unless the filter could be regenerated, its cost/benefit ratio was not considered favorable enough to justify the program.

Argonide has since developed just such a regenerable process for reducing captured iron particulate from the filter. The data indicates that a NanoCeram filter can be cleaned up to 15 times with as much as 90% recovery per cleaning cycle. These results indicate a ten-fold increase in capacity for iron adsorption and capture with a given NanoCeram cartridge (see Figure 2).