If you’re new to handling brine waste and are looking for more information about properly treating it for recycling or discharging, you might be wondering “what is brine waste, and how can it be treated or disposed of?”
This article provides a general overview of what brine waste is, how it occurs or is made, and how it should be treated prior to use in production and/or discharge so you can better understand the proper way to handle these often-problematic streams.
What is brine waste?
In general, “brine” is any solution with an extremely high concentration of salts such as sodium chloride, which can occur either naturally (as with seawater, deep-water ocean pools, salt lakes, etc.) or as a byproduct of industry. These byproducts, or “brine waste” streams, are typically highly concentrated salt solutions that, in some cases, contain more than twice the amount of concentrated salts than natural brine solutions. Brine waste can also carry various contaminants, which differ depending on which process the brine waste is a byproduct of.
Brine waste streams can be some of the most challenging to treat or discharge because their composition and purification requirements can be rather dynamic and complex.
Some examples of brine waste created as a byproduct of industry include:
- cooling tower and boiler effluent
- reverse osmosis (RO) and ion exchange waste/reject streams
- produced water from extracting oil and natural gas
- chlor-alkali and chemical plant waste
- acid rock and mine drainage
- food preservation and manufacturing waste streams
- desalination waste from potable water creation
- irrigation runoff
Brine waste is typically either recycled for use in the facility’s process or treated for disposal. For example, solutions with a high concentration of salt are known to reduce thermal conductivity, so brine waste is often recycled and reused as a cooling agent for steel heat exchangers in many power plants. This type of brine is often treated to remove dissolved oxygen and other harmful contaminants since brine waste can be highly corrosive to plant machinery and piping if untreated, and the presence of dissolved oxygen and other contaminants can increase that risk.
Varying salt concentrations in the brine stream will also determine how the temperature, pressure, and other threshold limitations will need to be adjusted during production, so facilities that use brine as part of their process often run frequent tests to ensure the relevant purification requirements are consistently met. It’s an arduous process that often requires round-the-clock monitoring. For this reason, it’s extremely important to have your water treatment specialist evaluate what the brine is being used for in addition to where and how it is being recycled and/or discharged to ensure its composition remains appropriate for the process or disposal at hand.
How do you treat brine waste?
Below, we break down a general overview of the various brine waste treatment and disposal options available and what they mean for your facility:
Recycling brine waste for reuse
As mentioned earlier in the article, many industrial processes require brine in part of their process, such as hydrometallurgy, sodium hypochlorite, lithium carbonate, and chlor-alkali manufacturing plants, to name a few. Some facilities even use leftover brine for irrigation or deicing.
Regardless what your facility is using the recycled brine waste for, keep in mind that brine leftover from production often accumulates contaminants along the way, such as:
- heavy metals
- organic compounds
- sulfates, nitrates, and phosphates
- suspended solids
The brine waste can be pretreated with coagulants, polymers, additives, and pH adjustment to settle out many of the larger contaminants, including metals, sulfates, and other suspended solids that can foul membranes and cells down the production line. Other contaminants, such as calcium, can scale equipment, so depending on the manufacturing process and brine requirements, there are several membrane and ion exchange technologies that can prevent these issues and produce a useful brine stream adequate for your process.
For example, if a chlor-alkali plant is looking to reuse brine waste that is contaminated with metals like iron, vanadium, or manganese, they will often have trouble with the fouling of downstream equipment, which can often lead to unscheduled plant downtime and other delays. The brine stream might be treated with specialty chelating resins that target specific metals for removal without being exhausted by sodium, thereby removing the unwanted contaminants while preserving the salt concentration in the brine solution.
When it comes to facilities that produce lithium carbonate or lithium hydroxide, specialty ion exchange resins can be used to remove unwanted metals and other contaminants, and the brine stream can then be further treated with high-pressure membranes that can separate out and concentrate the lithium carbonate and lithium hydroxide, so the technologies and methods of purification and/or separation vary greatly depending on the quality of the brine waste and the brine composition required for production.
Treating brine waste for discharge
Most brines are technically considered nontoxic, but industrial brine waste released in heavy concentrations to the environment or to local publicly owned treatment works (POTW) can cause an assortment of issues if untreated. For example, if the waste contains more than just sodium, it can possibly harm aquatic life in local waterways. In some cases, simply diluting the brine waste prior to discharging might be a practical solution. It can also be against discharge regulations, which can cause your facility to pay a heavy fine.
Most discharge regulations will require a reduction in the amount of sodium, total suspended solids, and contaminants in general, which can often be treated with membrane technology such as ultrafiltration followed by reverse osmosis. Because of the high concentration of salt in brine, pretreatment is often used to help protect downstream filtration units and equipment.
Another option for treating brine waste is evaporation. This can be done in an outdoor evaporation pond or with a technique called vacuum evaporation. By evaporating the effluent under vacuum, the boiling point is reduced (thereby saving energy) and what’s left is a crystalized mass of salt and, separately, a purified water stream. This method can be useful for drying brine filtrates thoroughly, and it can be implemented in tandem with other treatments to boost effectiveness.
Whichever method your facility uses to treat its brine waste for discharge, make sure it is done so in compliance with the facility’s POTW or National Pollutant Discharge Elimination System permits.
Can SAMCO help?
SAMCO has over 40 years’ experience custom-designing and manufacturing brine waste treatment systems, so please reach out to us with your questions. We have strong expertise in this area and can evaluate your brine waste and selectively apply the right combination of custom technologies to treat the stream, no matter how unique and complex it may be.
You can contact us here to set up a consultation with an engineer or request a quote. We can walk you through the steps for developing the proper solution and realistic cost for your brine waste treatment system needs.