December 18, 2015
There are several methods that can be used to remove the buildup material from the pipe wall.
With Southern California’s population surge over the past few decades, the need for potable water has become one of the states highest priorities. Dwindling supplies from the Sierra Nevada ice pack and the Colorado River have forced agencies to find alternative water sources. The current drought, which has severely cut into the state’s water reserves, has only intensified the need for additional sources of water.
One of the solutions has been to tap into the existing groundwater. Unfortunately, the water tables contain high levels of dissolved solids, better known as salt.
Despite this challenge, agencies are currently extracting groundwater and converting it to potable water using desalters. This is done using a method known as reverse osmosis. The process removes dissolved solids from the feed water, creating a permeate for potable water purposes and concentrating the salts in the product water, or brine.
Manufacturers and water treatment facilities have traditionally found it difficult to dispose of their brine byproduct because of wastewater treatment plant restrictions on total dissolved solids. Trucking it outside of the region is cost-prohibitive. Brine lines allow businesses to set up shop further inland, where they are able to dispose of the salty wastewater inexpensively. The brine is then carried over a considerable distance to coastal plants where it is treated and disposed of into the ocean.
Maintaining brine lines is a considerable challenge because of the build up it creates inside of the trunk lines. Calcium carbonate (from hard water) and silica (sand) are a byproduct of the desalting process that bind together with the calcium chloride (salt) and attach to the pipe wall. This material hardens into a concrete like mass that surrounds the periphery of the pipe.
The fact is that if a brine line were to be neglected, it would eventually become completely consumed. The line would become blocked and wastewater would be unable to flow through it. Reinstating a line in this condition would be very difficult and extremely expensive.
The buildup in the pipe happens quite rapidly, so the material must be removed anywhere between six months to a year, depending on the conditions of the pipe.
Removing the material from the line requires a specialized process because of its hardness. Standard cleaning nozzles are ineffective in these conditions because they are unable to break up the brine in this a state.
There are various methods that can be used to remove the material from the pipe wall. However, each one of them carries a high level of risk. Whichever method is used, it must be performed by trained and experienced operators. The potential for pipe damage is very great and inexperience can have catastrophic results.
High-pressure jetters that operate in the 10,000-psi range provide a possible option. However, excessive pressure will not only cut through the material, but can penetrate the pipe wall itself.
Specialized pigging is also a method that is widely used. In this case, the pig is pulled hydraulically through the line, breaking up the material and dislodging it from the pipe wall.
Mechanical cleaning has been the preferred method for Innerline Engineering, a pipeline inspection and cleaning company located in Southern California. Initially, a milling nozzle was used. However, the cost of the nozzle was very high and the daily production rate was minimal.
One of the most effective cleaning tools has been the chain flail nozzle, which effectively breaks up the material around the periphery of the pipe. The carbide tipped chains break off the material as they spin through the line. Having plenty of spare carbide tips on hand is key, since they wear quickly and will need to be replaced regularly.
Recently, a crew attempted to clean a length of brine line. The operator had only used chain flails sparingly and didn’t know their limitations. Because of their inexperience, the mechanism completely shattered when they tried to force it through the line. Unfortunately, it wasn’t only the chain flail that was affected, but the pipeline was damaged, as well. It wound up being a very costly mistake.
On another occasion, a crew buried a chain flail under 20 ft of material when the brine collapsed behind it. In this case, the operator tried to work too fast, leaving loose material attached to the crown of the pipe behind the nozzle. Extracting the hose and chain flail wound up being time consuming and very costly, as well.
A chain flail must be moved through the line very slowly, otherwise they will experience mishaps like the ones listed above. Removing the brine is a very slow process. It cannot be hurried. The chain flail can only go as fast as it can break off the material. If it is forced to go faster, it will most likely break. The average speed of cutting is only 6 to 12 in. per hour.
An important part of cleaning brine lines is the introduction of a CCTV inspection camera. In most other conditions, a camera can be inserted at an upstream manhole and then brought down to observe the nozzle from a safe distance. However, because much of the pipe is consumed by the brine, it is not possible to do under these conditions. Periodically, the chain flail must be removed from the access point and a camera inserted in order to observe the progress being made and to determine the effectiveness of the cleaning. It is important that the operator enter the inspection van and see firsthand the condition of the pipe. At this point, changes can be made, if needed.
A CCTV camera can also alert the team of any damage that is being inflicted on the pipe itself. It may be necessary to shorten or lengthen the chains in order to adjust to changing conditions.
The brine is very abrasive and will tear up a hose quickly. In order to ensure that the primary hose is not affected, it may be necessary to add two or three lengths of leader hose; 25 ft of leader hose is much less expensive to replace that 600 ft of main hose.
Once the brine has been broken into pieces, it will fall to the base of the pipe. The best way to remove the material is to use a heavy nozzle that stays on the bottom of the pipe. This type of bottom dweller nozzle will sweep the chunks of brine effectively. It’s important to not get greedy and only take small bites. If the nozzle tries to pull more material out than it can handle, it may become stuck. Keep in mind that some of the broken pieces can weigh in excess of 100 lbs.
One of the most effective methods for cleaning brine lines has been chemical cleaning, when used in combination with mechanical cleaning. In this case, the chemicals are introduced into the line, which changes the composition of the material, making it much easier to remove with high pressure nozzles.
The brine line offers many benefits to the Watershed. Industries that produce salty wastewater that are high in total dissolved solids, are able to locate their operations inland, away from the coast, where real estate can be much less expensive. Agencies can tap into existing groundwater as they seek additional water resources.
With the growing need to dispose of salt resulting from the desalination process, experienced cleaning operators will be needed to keep the brine lines flowing.
Jim Aanderud is president of Innerline Engineering.