The Impacts of Water Softener on Onsite Wastewater ......The Impacts of Water Softener on Onsite Wastewater Systems - A different approach - Presented by: DOMINIC MERCIER, P.ENG. M.A.SC

The Impacts of Water Softener on Onsite Wastewater Systems - A different approach -

Presented by:

DOMINIC MERCIER, P.ENG. M.A.SC.

Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

Table of content Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

1. Context

2. The Clash of Clans

3. Scientific background about water softener discharge impacts

4. Proper design is possible

5. Design Tools

6. Questions

Context Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

According to Stats Canada, 38% of Alberta households using non-municipal water supply had a water treatment device on the main supply pipe. An increase of 65% since 2007.

Context Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

Is it fair to say that people have the right to have access to both good drinking water as well as an efficient septic system ?

Coexistence of drinking water treatment devices and septic systems is inevitable and has been there for more than half a century. As long as

people will live in places not hooked to the big pipe and municipal supply, this will remains;

Billions of $ have been spent on product development in both water and wastewater industries. We are able to transform sewage into drinking

water, but somehow, water softener brine discharge is still an unsolved mystery;

HOW IN THE WORLD IS IT STILL POSSIBLE THAT IN 2017

THESE 2 INDUSTRIES CANNOT HAPPILY COEXIST ?

Clash of Clans Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

For decades, this topic have raised debates. Each group of interest have their beliefs, policies and point of view. The positions are often light years apart depending on which end of the pipe they are. Let’s review the principal aspects claimed by each group:

Wastewater Equipment Manufacturers;

Drinking Water Equipment Manufacturers;

Regulators;

Home owners;

Scientists and Researchers;

Clash of Clans – What they say Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

Wastewater Equipment Manufacturers:

The volume of Water Softener Backwash (WSBW) overloads the Septic System;

Salt eats concrete (corrosion);

Brine destratifies the septic tank layers, increases solids discharge and plug effluent filters;

Brine inhibits bacteria development and decreases treatment quality;

Brine plugs the septic field;

We void our warranty if WSBW is discharged to our treatment units;


Drinking Water Equipment Manufacturers :

WSBW has no effect on Septic System (bacteria development or performances)

WSBW can even improve performance of ATU (metabolism of bacteria higher at a higher electrical conductivity)

No proven relationship between effluent filter clogging or increase of solids content with WSBW

Volume of WSBW no different then other common household appliances such as washing machines (26 to 130 L vs. 57 to 170 L);

WSBW can improve solid settling in the septic tank (Ca and Mg act as coagulants);


Regulators:

Several Canadian Onsite Regulations consider WSBW to be part of domestic wastewater and therefore must be sent to the septic system;

Plumbing Codes requires that all types of water generated by a water appliance must be discharged in the domestic sewage pipe;

Diverting WSBW to another type of disposal system may cause permitting issues since most regulation requires that a building shall be equipped with only one Septic System;


Home Owners:

Diverting WSBW generate more expenses, especially for existing properties;

Seeing the warranty of an wastewater treatment system worth thousands of dollars is unacceptable;

Should we have to choose between good drinking water and a septic system covered by a warranty ?

Having the septic system constructed before the well is drilled (common in new home construction), puts them in a catch 22 situation where they face the problem of hard water once the septic is done;


Scientists and Researchers:

Corrosion of septic tank is by greater proportions, the work of hydrogen sulfide gas then the action of salt;

Sodium causes soil aggregates to swell and disperse. This reduces hydraulic conductivity especially in higher clay content soils;

Calcium and magnesium overcome the bad effects of sodium on soils particles and increase permeability;

Sodium is linked to poorer settling as calcium and magnesium are linked to improvement in settling (calcium is extensively used in wastewater treatment plants) ;


Scientists and Researchers:

No correlation has been established between WSBW and septic system performances,

Some water softener regenerates too frequently, uses too much salt and discharges high volume of water during backwash;

High sodium content may increase effluent filter clogging or higher solid content. This maybe be overcome by higher calcium and magnesium balance (lower M/D). More research needed;

Potassium WS will reduce corrosion but the bad effect on soils will remain;

The ratio of monovalent (Na+) to divalent cations (Mg2+ and Ca2+) appears to be a good indicator to predict impact on septic systems. This is referred to as the M/D ratio. A ratio below 5 assuring low to no risk on septic systems (Novak study);

Clash of Clans Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

Can this be more confusing ?

Scientific background Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

If we acknowledge that answers to this mind boggling mystery shall be provided by the scientific community or in other word rigorous and non-

bias third parties, then we can state the following:

Potential negative impacts of WSBW on septic tanks, treatment units and soil dispersal systems are real and mostly related to the sodium discharge;

Calcium and magnesium discharge can overcome the effects of sodium;

Types and efficiency of the water softener plays a great deal in the risk of negative impacts;

Diverting the WSBW away from the septic system deprives it from the beneficial divalent cations (Ca + Mg) and leave only the bad sodium (Na);

Tools such as the M/D ratio verification and good equipment selection can prove to be simple yet useful tools to avoid negative impacts from WSBW;

Proper Design Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

What the Drinking Water Specialist should do:

Use only NSF-44 efficiency rated equipment. That assures minimal efficiency of 3350 grains/lb of salt and minimum 1000 grains per 5 gallons of regeneration water;

Choose Demand Initiated Regeneration (DRI) softener over time-clock.

Proper Design Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

What the Septic System Designer should do:

Get the information about the water softener and obtain its characteristics (easy on the internet or through vendors). Look for the certifications, efficiency ratings (grains per lb of salt), backwash volume, regeneration frequency;

Obtain from the owner (or from sampling), analysis of the raw underground water (total hardness, iron, manganese, sodium, potassium);

Calculate the M/D ratio and formulate recommendations, especially if the ratio is 5 or higher (in some case diverting might be an option in high M/D ratio);

Design the septic system considering the extra water from the regeneration cycles. If the well is not drilled yet, notify the owner about the impacts and consider a safety factor on the design flow;

Look for treatment septic systems honoring warranty even with brine discharge;

Design tools Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

Design tools: Groundwater analysis


Design tools: Water Softener spec sheets


Design tools: M/D ratio calculator


Design tools: M/D ratio calculator


Google: monovalent divalent ratio Excel

Innovative Eco-Efficient Solutions for Onsite Wastewater Treatment

QUESTIONS

Documents

The Impacts of Water Softener on Onsite Wastewater ......The Impacts of Water Softener on Onsite Wastewater Systems - A different approach - Presented by: DOMINIC MERCIER, P.ENG. M.A.SC