Ice Pigging™ is an advanced and sustainable cleaning method for potable water distribution systems, raw water, processed water, and wastewater force mains. The method involves pumping a slurry of ice into a main through a hydrant or other existing fittings throughout the system and using pressure in the lines to push the ice pig downstream to an exit point through a similar fitting. Filling 20 to 30 percent of a pipe’s volume, the ice slurry cleans with a shear force between 100 and 1,000 times greater than water alone and provides more effective cleaning, and uses significantly less water than traditional flushing methods.

An ice pig works in a way like a glacier does. Rather than bulldozing sediment and biofilm through a line, it consumes the material into the ice. The ice pig enters and exits through a hydrant and or other existing fittings, therefore specialized launching and retrieval stations are not required as with mechanical pigging. Customer service isolation usually is not necessary with Ice Pigging™. Inorganic sediments and debris like iron and manganese can accumulate in or on water distribution system pipe walls causing pipeline restrictions and build-up. These restricted flows can cause increased discoloration, taste, and the quality of the water provided to the customer. Other technologies like water flushing and water-jetting are inefficient and sometimes ineffective.

Ice Pigging™ is an innovative, low-risk, award-winning advanced pipeline cleaning technology to clean drinking water pipes, sewer force mains, and siphons. The ice slurry can be inserted and removed through fire hydrants, (figure 1) line taps, and other existing fittings in a distribution system. Ice Pigging™ harnesses the characteristics of a semi-solid material that can be pumped like a liquid but behaves like a solid (figure 2) once the pig is formed in the pipe. Ice Pigging™ uses approximately 50 percent less water than standard water flushing and takes significantly less time. Typically, a section of pipeline being cleaned is out of service for no more than 60 minutes. A main feature of Ice Pigging™ is that it cannot get stuck permanently. If for some reason the pig were to get stuck, time would be allowed for the ice to melt and flush it from the pipeline. Ice Pigging™ is not affected by pipe bends, changes in diameter or butterfly valves which all pose problems for other pipeline cleaning technologies. Ice Pigging™ is far less intrusive to any system it’s used on.

The Benefits

Ice Pigging™ represents a sustainable best practice and unique approach to pipeline cleaning. The advantages include:

• Exceptionally low risk

• Produces quantifiable results

• Injects through existing fittings

• System pressure & flow pushes the ice

• Efficient, rapid, and environmentally friendly

• Uses up to 50% less water than standard flushing

• Effectively removes biofilm, iron, manganese, and sediments

• Suitable for pipes of all sizes up to 24 inches and materials

• Combines operational benefits of flushing with the impact of solid pigging

Methodology

To maintain the correct consistency of the ice pig a freezing-point depressant is used. The depressant being used is a food-grade fine table salt which is approved by the National Science Foundation (NSF). This is added to the water in the tank which is always sourced from a public potable water supply. The current maximum batch capacity is 2,700 gallons.

The brine is made in a 316-stainless steel delivery tanker and hose connections are made to the ice machines that are mounted on a separate trailer (Figure 3). The brine is fed into the ice machines which in turn freezes the liquid and returns it to the delivery tanker. This cycle continues until the ice slurry is at the correct thickness known as the “ice fraction”. Ice fraction measures the amount of ice crystals as a percentage of total volume.

Typically, thicker ice is used on plastic and sound concrete-lined pipes as well as asbestos cement, but when older unlined cast iron pipes are cleaned a thinner ice slurry is used that does not clean as aggressively. The thinner ice slurry will not disturb the tuberculation, which could damage the integrity of an old heavily corroded unlined cast iron pipe.

Ice Delivery

Setup for delivery varies slightly for each different application. A typical setup for a potable water main is shown (Figure 4). The delivery rig connects to the inlet hydrant or other suitable fitting (2 inches or greater tapping with valve control), and at the outlet, a flow analysis system is connected. This system measures and records the flow, pressure, conductivity, turbidity and water temperature as the water and ice are discharged. Once set up, the main is flushed briefly to note and record pre-flush readings. The main is then isolated by the owner’s operators and the required amount of ice is pumped into the main.

At the same time, the outlet hydrant is opened to create a flow and allow water to be displaced as the ice enters the main. With careful control between the inlet and outlet, the flows are balanced to allow slightly more ice into the main than the amount of water being displaced. This has the effect of the ice forming as a pig against a pressurized wall of water.

Once the required amount of ice is in the main, the delivery pump is turned off and the upstream valve is opened to allow the system flow and pressure to “push” the ice pig along the main toward the outlet hydrant. The flow rate is controlled by the outlet operator at this time. As the ice pig approaches the outlet, the conductivity reading will rise as the salty water of the melting pig arrives in front of the pig. The monitoring equipment will show the water temperature falling and conductivity rising as the ice arrives.

At this stage, the operator may collect samples of the ice at regular intervals for later analysis. (Figure 4) The temperature and conductivity will return to pre-flush levels when all the ice and salty water has flushed out of the system and the flushing shall continue briefly to allow the turbidity levels to return to pre-flush levels or lower according to instructions from the owner. The main is then returned to normal service. No disinfection is necessary.

Case History

In October of 2022, American Pipeline Solutions was contracted by a New York City area medical facility to ice pig the main distribution lines bringing potable water into the facility, as well as the eleven different pipelines transporting the water throughout multiple floors of the facility. Ice Pigging™ had not previously been used on interior pipelines, but with extensive knowledge and experience of our technicians, we were confident we would be successful.

The medical facility had sustained water discoloration and taste issues in eleven locations throughout the upper floors of the building. These locations included sinks, toilets, and showers. New sections of the facility had been completed just prior to the onset of the Covid pandemic. These areas were shut down for over a year resulting in water sitting, uncirculated, in the pipelines. Facility administrators believed this was the cause of the discoloration and taste issues. The maintenance team did its best to correct these problems by flushing the system using standard flushing procedures and UDF flushing practices. Nothing worked.

Customer Goals

The facility’s goal was to remove accumulated biofilm, iron, and sediment build up from the water distribution systems both inside and outside the facility.

Solution

APS technicians conducted a pre-project study to prepare a planned schedule of runs designed to clean the eleven compromised sections of the distribution system. The affected pipelines ranged in size from .5” to 8” in diameter. The plan called for use of the advanced Ice Pigging™ cleaning technology. The size of the exterior distribution system together with the interior pipelines required four 10-ton loads of ice slurry to be delivered one load per day. A post project report would identify the chemical, biological, and mechanical results.

Results

Ice Pigging™ accomplished nearly complete removal of accumulated biofilm, iron, and sediment. Thorough removal of these materials assured the facility there was limited risk of their release into the distribution system. Because no build up of these materials in the affected areas is now anticipated, future UDF requirements will be limited and more effective in preventive maintenance.

“This is incredible! We have tried cleaning this line by flushing multiple times and have never got results like this. The water has never come out this dark and brown. WOW!”