Author image: Roi Shifron Roi Shifron

Oct 9, 2019
Reading time 2 min Updated: Oct 15, 2019
What is the simple solution for sodium deviations in wastewater?

Unfortunately, there is no simple solution, but there are ways to manage it.

Look, many factories face the problem of high sodium levels in wastewater, which creates numerous issues. How do they cope?

The first thing worth doing is finding the source of the salt or sodium in the wastewater and trying to segregate it alone. Most of the wastewater arrives without salt, and often there is only one small stream that contains the salt. It is very easy to identify this stream. If you are familiar with the processes, you know where salt exists. If you aren't familiar with the processes, this stream can be identified using an electrode that measures conductivity. This electrode is cheap and simple. Once you manage to identify the salty stream, you can treat only that specific flow rather than implementing complex and comprehensive processes. This can be understood through the following example: it is much easier to treat raspberry concentrate than diluted raspberry juice.

Once we have found the salty stream, there are two options: a. Transferring the brine to the sea. b. Concentrating the sodium by transferring it to an evaporation pond or by using membranes or evaporators.

The salty stream usually also contains organic matter. If it is not removed, when you begin concentrating the salt, the organic matter causes odor issues and other problems, making it impossible to transfer the concentrated material to the sea. Organic matter can be separated using standard methods such as a clarifier or a DAF system. If the organic matter is dissolved, there is no choice but to perform biological treatment. Once the organics are removed, reverse osmosis (RO) can be used; however, it must be ensured that no other contaminants like fats or proteins remain. The presence of such contaminants prevents the use of RO as membranes will foul within minutes. Another option for treating salty wastewater is using an evaporator. The evaporator is more tolerant, and even if organics are present, it can be a good solution. If the wastewater contains volatile substances, additional treatment will be required for the evaporator's distillate.

Using an evaporator is an end-of-pipe solution for treating sodium-laden wastewater. The issue with this solution is the very high energy cost.

If the wastewater has deviations in sodium or salts, what is required to meet the standards?

As mentioned before: Step one is identifying the deviant stream within the various wastewater flows; step two is finding the appropriate treatment technology.

If you wish to discharge wastewater to the sea, you must obtain a permit for doing so.

In certain cases, wastewater can be sent to a third party for purification. This option is more expensive.

How can wastewater be discharged to the sea?

The wastewater undergoes laboratory testing and local inspections, and after receiving approval, it is discharged into a pipeline laid 4 km into the sea.

What are the regulations in Israel regarding sodium and chloride?

The Israeli standard is relatively stringent because municipal water is reused for irrigation. If the water is salty, it cannot be used for irrigation. There is a limit of 230 ppm for sodium and 430 ppm for chloride.

What happens in case of deviations?

Enforcement in Israel is not uniform. In the event of a deviation, fines are issued. If fines are imposed multiple times on the same entity, the Ministry of Environmental Protection begins legal proceedings for prosecution.

Are there situations where it is better not to treat the wastewater and just pay the fines?

Regulators are not supposed to allow this. Sometimes, if the deviation is small, a permit for the deviation can be obtained. If there is no permit, legal proceedings are initiated.

Is there an option to recycle the salt and even sell it?

In my estimation, recycling the salt is not feasible because it is "dirty," and generally, salt is very inexpensive.