The kind and quality of the water to be treated, as well as the softener model and its adjustment, have a significant impact on how frequently this backwashing process occurs and the corresponding amounts of brine and clean water. Not the soft water itself, but this backwash water, can interfere with on-site wastewater treatment equipment.
The resin regenerated by immersing it in a brine, which is a solution high in salt or potassium that removes calcium, magnesium, silt, and accumulated residues. The resin was then backwashed with a significant volume of brine and rinsed with clean water to eliminate this solution. This article will review the effects of water softener on septic system and its alternatives.
What Is a Water Softener and How Does It Work?
A water softener is a water conditioning equipment that purges a water supply of “hard” minerals like calcium and magnesium. Although hardness, or excessive levels of dissolved calcium and magnesium, is not harmful to the general population, it can lead to problems like scaling in pipes, water heaters, and other water fixtures like washing machines and dishwashers.
It can also make soaps and detergents less effective. The Ontario Drinking Water Objectives state that hardness is purely cosmetic and has no bearing on health. In Ontario, where groundwater is the main source of drinking water, water softeners are widely used in both residential and non-residential settings. But keep in mind that a water softener should only be used if the raw water supply has a hardness level more than 120 mg/L.
How Does It Work?
Ion exchange is the basis for how a water softener operates. Magnesium and calcium ions have a positive charge. The water softener will substitute negatively charged ions, typically sodium and/or potassium, for the positively charged calcium and magnesium ions.
Ion exchange occurs in the water softener’s conditioning tank or resin. The resin receives exchange ions in the form of potassium or sodium salts. The calcium and magnesium ions concentrate in the conditioning tank as ion exchange occurs in the resin. The ion exchange mechanism will slow down when the resin’s surface gets saturated with calcium and magnesium. As a result, periodic regeneration of the resin is required.
What happens when water softener drains into septic Systems?
Bacterial Impact
The chemical composition of water softener backwash may be influencing the bacterial population and, consequently, the efficacy of these organisms in onsite systems, especially in the septic tank, according to the onsite wastewater industry. Sodium and chloride, which will exist in solution in their ion forms, are the primary chemical pollutants of concern.
According to certain research, high sodium concentrations in salt might be harmful to vital septic tank microorganisms. Moreover, elevated manganese and calcium levels can slow down metabolism. Nonetheless, research has shown that the amounts of these components in a well-maintained water softener system are below the threshold levels needed to affect anaerobic digestion.
Impact on the Advanced Treatment Systems
- Based on the removal of organics and sediments, some research has shown that an aerobic treatment system receiving water softener backwash performs no differently than one that does not. But it’s crucial to keep in mind that elevated chloride levels have an effect on nitrification, which may affect how well an aerobic treatment unit that treats nitrogen performs. A system receiving water softener backwash may have operating difficulties as a result of many jurisdictions implementing stricter effluent targets.
- As previously mentioned in this article, the type of water softener, the amount of backwash, and the operation technique will all play a major role in determining whether or not the discharge will noticeably affect the treatment unit’s effectiveness. Because requirements and service implications can differ depending on the technology, it is advised to check with the manufacturer of a treatment unit to see if water softener backwash is compatible with their system.
Environmental Impacts
Aquatic plants and animals may suffer from direct discharge into surface waters because of the high levels of chloride present in the backwash. The suggested substitute for an on-site sewage system is subsurface disposal.
Concrete Corrosion impacts
Numerous anecdotal reports suggest that water softeners may exacerbate septic tank concrete corrosion. The main factor for concrete deterioration in septic tanks is sulfuric acid. Hydrogen sulfide, or H2S, is a waste product of the anaerobic bacterial breakdown of organic materials in the sludge layer of septic tanks that are typically in use.
When H2S reacts with oxygen at the water’s surface, it transforms into sulfuric acid (H2SO4), which corrodes the concrete in septic tanks. It is more likely that a raw water source with a high sulfur content—which is common in Ontario—is the cause of the corrosion seen in septic tanks and linked to the usage of water softeners. which could be increasing the production of sulphuric acid in the septic tank, leading to increased signs of visible corrosion.
Water softener backwash is not thought to be a contributing factor in septic tank corrosion because chlorine has not been demonstrated to hasten the corrosion brought on by sulfuric acid. Although it is unlikely to do so because rebar should not be exposed, the presence of chlorine ions from water softener backwash may contribute to the corrosion of reinforced concrete tanks, speeding up the process.
Alternatives for Water Softener Discharge Disposal
It is highly recommended that property owners, installers, and designers seek advice from the local permitting office regarding the best place to dump water softener backwash. Backwash must be disposed of in another way if it is not allowed to be dumped into the on-site sewage system.
The most popular subsurface backwash disposal technique uses pipe and stone that are buried in the native soil and positioned either vertically (dry well, soakaway pit, etc.) or horizontally (trench, French drain, etc.). When discharge to the on-site sewage system is prohibited by your local permitting authority.
- It is advised to have a minimum of 30 meters between your well and any wells on nearby properties and the backwash discharge site.
- The backwash discharge point should be as far away from surface water or wetlands as possible; at least 30 meters is advised.
- Increase the distance between bedrock and high ground water
- If at all possible, locate the backwash discharge of drinking water wells downgradient, or typically downward.
- To prevent system damage, be aware of where the other onsite wastewater system components are located when building the subsurface system.
- Suggest building a subsurface system using materials with a low clay content, particularly montmorillonite, to lessen the impact of sodium on the soil’s hydraulic conductivity. Perhaps imported sand fill is needed.
- To stop breakout to the ground’s surface, the drainage area’s (the stone volume beneath the pipe) volume should be roughly equal to the backwash volume.
Conclusion
The effect of a water softener on septic system is dependent on the efficiency of a water softener which is dependent on the level of hardness in the water, the volume of the volume of backwash, and the amount of excess sodium in the backwash .
A 2013 study conducted by the Water Quality Research Foundation found that in the case of efficiently operated water softeners, the performance of the septic tank was actually improved, but in cases where softeners were running inefficiently, they may have a negative effect on tank performance in terms of solids discharge into the leaching bed.
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References
Water Softener & Onsite Sewage Systems
https://www.oowa.org/wp-content/uploads/2020/07/FINAL-OOWA_Water_Softeners_InfoDoc_07162020.pdf
SOFTENER BRINE DISPOSAL TO SEPTIC SYSTEMS
https://wqa.org/wp-content/uploads/2023/05/2019_SoftenerBrineDisposalSepticSystems.pdf
