Case Study of Using the Strengite Process to Clean a Heavily Rusted Glycol System Without Creating Discharge
A System with Extreme Fouling
At Specsaver’s Headquarters in Whitely, England, the chilled water system contained four percent monoethylene glycol. It had become acidified and serious corrosion had occurred. The system volume was 2350 litres. Only the risers of the three story building were iron piping with the rest of the pipework largely plastic pipe. All of the 141 fan coil units were heavily fouled to the point that little cooling of the building was possible in spite of a new chiller being installed only a few months previously.
The system water carried a heavy load of rust with a total iron level of 4500 ppm. Filtering through 1 micron bag filters did little to reduce the iron load.
A New Way Forward: Cleaning the Impossible with No Discharge
The Strengite Process was used to clean this system without discharge. The antifreeze within the system was not lost. The cleaned up system water was pH adjusted to between 8.5 to 9.0 and had a iron level of below 1 ppm.
Approximately 38.7 kg of rusts were removed by the cleaning. This equates to an iron level of 11,914 ppm iron released during the clean. Traditional cleaning methods rarely go above 1000 ppm iron and would have required twelve cleanings to achieve this result. The Strengite Process achieved this in a single clean. 282,000 litres of water consumption and pollution were avoided.
X-ray analysis of the pipework indicated that approximately 65% of the rust was removed by the cleaning. Spalding from incomplely cleaned surfaces usually leads to problematic high dissolved iron levels. This did not occur because the Strengite chemistry surpresses iron solubility. Iron levels remained below 1 ppm even when sediment remained in the system water.
The entire cleaning and removal of contaminants took aproximately three weeks and included cleaning and flushing all the fan coil units and strainers which were very heavily fouled.
A by-pass filter was installed on the system to remove corrosion deposits as they erode from pipe walls over time. The iron level remained low months after the cleaning.
The Fate of the Collected Waste
The contaminants removed from the system were collected on filter bags. These bags could have been simply disposed of to the normal rubbish, but the decision was made to clean them up. The bags were washed and made available for reuse in future cleanings. This created a few hundred litres of water waste which contained all the removed system contaminants. The water waste was allowed to settle.
This produced a large layer of clear water that was drawn off and pH adjusted prior to discharge. The mucky bottom water was mixed with cement and allowed to further settle. The result was clear water on the top of the hard settled solids. The clear water was drawn off and pH adjusted prior to discharge. All the discharge water was tested for copper and found to have below 0.1 ppm total and soluble copper. The resulting dry solids were disposed of as cement waste at the local tip. Overall, compared to the volume of discharge water that standard chemical cleaning would have created, a reduction of greater than 99.99% in waste volume was achieved.
New Tools for Our Industry
The Whitely fouled glycol system was one of the most fouled closed loop systems that any of us had ever encountered. It represents an extreme example of closed loop cleaning. If current chemical cleaning methods had been used, the works would have failed. The level of fouling would have been too much to clean in any practical way. Iron transport and return to high levels of soluble iron would have fouled the newly installed chillers. There would have been little alternative but to re-pipe all or part of the system at considerable cost. Instead the Strengite Technology enabled the system clean-up in a straightforward manner while avoiding the creation of large amounts of costly to dispose of waste. All the original system glycol was preserved and able to be reused.
The Strengite technology has been used on other less difficult systems such as large buffer vessels and other building closed loop systems. Millions of litres of polluted water waste have already been avoided by use of the technology.
Strengite Process Equipment