[Geezer (OP)]

We are fortunate to have very good water except that it's a bit too hard. I'm thinking of installing a water softener. However, our waste water goes into our anaerobic septic system.

Will the brine discharge from the water softener kill the bacteria in the septic system and prevent it from working properly?

[RD]

I have no experience of this problem: I have soft water and I don't store my sh1t in a tank,
however I Googled this ...

Research Results

Researchers from NSF found that brine wastes had no negative effects on the bacterial population living in the aerobic treatment tank, even when the system was loaded with twice the normal amount of brine. The tests determined that water softener wastes actually help with treatment processes. WQA’s final report states that the wastewater has “a beneficial influence on a septic tank system by stimulating biological action in the septic tank and caused no operational problems in the typical anaerobic or the new aerobic septic tanks.”  In other words, the researchers in this study found that microorganisms living and working in a home aerobic treatment system are not harmed by water softener salts.

Researchers also found that the additional amount of water discharged to a treatment tank during the regeneration process had no negative impact. The question concerned whether the volume and flow rate of the regeneration brine might overload the system and cause carry over of solids into the drainfield. The study found that the volume of water discharged was comparable to or less than that from many automatic washing machines and other household appliances. Researchers also found that the wastewater flowed into the treatment tank slowly enough so that it caused minimal disturbance.

http://www.uwsp.edu/cnr/gndwater/privatewells/Water%20Softener%20Use%20Raises%20Questions%20for%20System%20Owners.htm


Sh1t experts disagree ... http://www.uwsp.edu/cnr/gndwater/privatewells/Water%20Softener%20Use%20Raises%20Questions%20for%20System%20Owners.htm#Disagreements

[Geezer (OP)]

Yes. It does seem to be a rather shιtty situation. The scientists in this (drain?) field don't seem to be able to get their shιt together at all, at all.

[CliffordK]

Many systems are configured so that the regeneration cycles dump the effluent untreated on top of the ground rather than into the septic system.  It would not be considered sanitary waste, and thus doesn't need septic treatment.

So, the bacteria and septic critters are being exposed to the same water that you are drinking.

In theory the system is basically doing ion exchange swapping Calcium and other heavier ions for Sodium.  And the Sodium is a nutrient for bacteria.

I don't know if my Grandmother ever had her system adjusted right.  I always thought her water tasted salty, and she had rust damage in her dishwasher and washing machine from the added salt.  She also had my Grandfather on a restricted salt diet for years and years and I always wondered about adding extra sodium into the water. 

Anyway,now that I have control of the system, I've turned it off and am happy without it.

If you have an iron problem, there are non-salt based systems that are effective at removing the iron.