Monday, September 28, 2020

Hard Water Treatment Options

Water contains traces of minerals that are essential for human health. Water picks up tiny amounts of minerals and metals from rocks and soils. In elevated concentration these miners can be a nuisance, but in small enough quantities they improves the taste of water and provide essential elements. In many parts of the country water, especially groundwater contains high levels of dissolved calcium and magnesium ions. This is what is known as hard water. For generations water softeners have been sold to treat almost all well water ailments. They have been overused, and are bad for the environment and septic systems. There are other ways to treat water problems.

Water containing approximately 125 milligrams of calcium, and magnesium per liter of water or 7 grains per gallon can begin to have a noticeable impact and is considered hard. Concentration of magnesium and calcium above 180 milligrams per liter (10.5 grains per gallon) is considered very hard. As the mineral level climbs, there are observed impacts in our homes. Bath soap combines with the minerals and forms a pasty scum that accumulates on bathtubs and sinks. Hard water spots appear on everything that is washed in and around the home.

Many can live with the water spots and soap scum issues by adding vinegar to dishwashers and using hard water formulated shampoos, but it is the potential impacts on plumbing and appliances that induces them to get a water softener. When heated, calcium carbonate and magnesium carbonate are removed from the water and form a scale (lime scale) in cookware, metal hot water pipes, dishwashers and water heaters. As the scale builds up more energy is required to heat the water and hot water heater and appliances have work harder which will burn them out eventually. Thus, in hard water locations hot water heaters and other appliances have a shorter life.

The ubiquitous water softening system is an ion exchange system consisting of a mineral tank and a brine tank. The water coming into the house must pass through the mineral tank before it can be used. The mineral tank holds small beads of resin that have a negative electrical charge. The calcium and magnesium ions (along with small amounts of other minerals) are positively charged and are attracted to the negatively charged beads. This attraction makes the minerals stick to the beads as the hard water passes through the mineral tank. Sodium from salt is used to charge the resin beads. As the water is softened, the sodium ions are replaced and small quantities of sodium are released into the softened water making it taste salty. It is reported that the 10-year life-cycle costs for new, high-efficiency water softeners was $4,000 for water with 150 mg/L hardness. However, cost is not the only problem with the ion exchange water softeners. The brine tank is flushed out when the resin beads are recharged carrying the salty solution to the environment. The salinity of surface waters and groundwater is an emerging environmental concern. Research has shown that salinization has affected over a third of the drainage area of the contiguous United States even in areas without road salt.

Some regulators in California, Connecticut, Texas, Massachusetts, Michigan and Minnesota have identified the use of ion-exchange water softeners as a major source of sodium chloride to both surface waters and groundwater. Households that use ion exchange water softeners typically use sodium chloride; and the used brine is regularly discharged to either wastewater treatment plants or septic systems. Which in turn releases it into the environment since neither septic systems nor waste water treatment systems can remove salt.

The Bureau of Reclamation, California State Water Resources Control Board, Santa Clara Valley Water District, City of Phoenix, City of Scottsdale funded a study: “Evaluation of Alternatives to Domestic Ion Exchange Water Softeners.” The study took place in 2014 and was led by Peter Fox, Ph.D., a Professor at Arizona State University. They examined what in the industry is called water conditioner. Water conditioners often called “salt-free water softeners” do not remove calcium or magnesium, but rather render then less likely to deposit hard lime scale.

Using literature search to identify likely candidates, the researchers used DVGW – W512 the test physical water treatment techniques. DVGW-W512 is the test methodology used to determine effectiveness of water conditioning devices to prevent or reduce scaling in drinking water heating systems. The researchers measured scale reduction in water to see if physical water treatment techniques work. They looked at systems that did not require chemicals to be added to the water and the most promising techniques based on the literature review. These physical water treatment devices tend to work by forming subicron crystals of calcium carbonate that remain suspended in water and do not remove the calcium carbonate, so a water analysis would not have proven if these devices held the potential to be effective.

The researchers tested Template Assisted Crystallization, Electromagnetic treatment and electrically induced precipitation. They found that Template Assisted Crystallization worked best reducing lime scale by more than 95%. Both Electromagnetic treatment and electrically induced precipitation reduced scale formation by 40%-50%. The scale formed in the by the latter two was “soft” scale that easily brushed or washed off. The test does not determine long term accumulation

Water conditioners sold on the market today (six years later) work through a process called template assisted crystallization (TAC), have been certified by DVGW-W512 and are available in whole house units. In template assisted crystallization, water flows through a tank of TAC media. This media consists of tiny polymer beads covered in craters called “nucleation sites.” These nucleation sites act as templates to form the hardness micro-crystals. When the hard water comes into contact with the media, the magnesium and calcium ions are caught by the nucleation sites. As more calcium and magnesium ions build up within the sites, small micro-crystals form. and apparently retain their crystalline structure as they flow through your plumbing. They do not attach themselves to your water pipes as scale.

Electrically Induced Precipitation – An applied current induces the formation of “soft” scale on an electrode that must regularly cleaned off. I have seen this phenomena in my electric kettle which only requires a damp cloth to remove the soft scale while my old stove kettle needed to be replaced every few years. The scientists demonstrated why this was true in their tests.

Though magnetic devices have been sold for ages, there are none certified and no consistent standard. However, the researchers found that electromagnetic fields they created at the strength indicated in their study can reduce the formation of lime scale. There is no scientific consensus as to the effectiveness of magnetic water treatment and its removal mechanisms. No devises have been tested and certified. However, Dr. Fox’s team did test an electric current induced magnetic field around a pipe. That seemed to produce a soft precipitate.

These physical water treatment devices  do not remove the hardness minerals from the water, but to varying degrees reduce some of the problems associated with hard water. Today, water conditioners sold as “salt-free water softeners” are based on template assisted crystallization (TAC). Though these water conditioners do prevent the build up of lime scale, they do not produce soft water. Water softeners have been used for generations not only to prevent lime scale, but to remove low levels of iron, manganese and radionuclides from water. Iron can cause staining of sinks and fixtures, affect taste of drinking water, and contribute to pipe blockages. Iron and manganese can be removed with an iron filter or chlorination and filtration. Long-term exposure to high radionuclide levels can have many negative health effects. Reverse osmosis is effective in removing radionuclide levels, though some local health departments recommend replacing the well if possible. For generations the salt based water softener has been sold to remove other contaminants, but there are other options. Water conditioners can address lime scale.  Know your water chemistry and what contaminants you want to remove before buying any water treatment equipment.

1 comment:

  1. Amazing article about water treatment. thanks for sharing. you can get some great information about water softner from us.