reverse osmosis

Arsenic and Water Treatment

Arsenic_1024x1024.png

Testing your water and detecting arsenic at any concentration is never good news, but rest assured there are reliable steps you can take to safely protect your health by treating your water.

Arsenic is a well known human carcinogen that occurs naturally in groundwater. Public water systems are regulated by the US EPA to never exceed 10 parts per billion of arsenic concentration, but health research demonstrates that no level of arsenic is safe to drink. In fact, EPA proposed 5 ppb as a standard in 1996. Levels this low have shown statistically significant impacts on IQ among children, but economic requirements for setting maximum contaminant levels have kept the official threshold higher than levels harmful to health.

If you want to remove arsenic from your tap water, there are a few important things you need to know. We’ve broken it down into a simple FAQ sheet.

What is “total arsenic”?

Your total arsenic concentration is generally comprised of two common oxidation states (or forms), arsenic III (aka arsenite) and arsenic V (aka arsenate). In drinking water, we are usually worried about Arsenic V. If you drink water with Arsenic V, however, it is quickly converted to Arsenic III–which is more toxic and bioreactive inside your body.

Does the source of my water make a difference?

The source of your water makes a difference to the amount of arsenic III versus arsenic V in your water. This matters for choosing appropriate treatment options. If your water is coming from a community or public water treatment system and that treatment system uses chlorine for disinfection, then you can generally assume that most arsenic (if found in your water) is in arsenic V form.

If your drinking water comes from a groundwater well and there is no chlorination (or other oxidative step) installed as existing treatment, then you can’t be sure what fraction of your total arsenic is comprised by arsenic III or arsenic V. A type of water quality test called Arsenic Speciation can help determine if your total arsenic is mostly arsenic III or arsenic V.

Does reverse osmosis remove arsenic?

Reverse osmosis water treatment technology can reliably remove arsenic V but does not reliable remove arsenic III. If your water’s arsenic is all or mostly arsenic V then you can reliably use reverse osmosis technology to remove arsenic from your drinking water.

If your water’s arsenic is mostly comprised of arsenic III then you will either need a special treatment technology OR you will need an additional treatment step to oxidize arsenic III to arsenic V before using reverse osmosis for treatment.

Reverse osmosis is not the ONLY method of arsenic removal, companies like AdEdge and others provide other ion exchange and filtration-based treatment options.

Do I need whole home water treatment to remove arsenic?

Whole home water treatment for arsenic removal is NOT necessary unless you regularly drink water from many of the taps in the house. You can safely choose to treat only the water you ingest or use for drinking by installing a Point of Use filter at your main water source in the home or building (like under your kitchen sink). This can save thousands of dollars, because according to public health research, arsenic does not show an appreciable impact on health via showers, tubs, or brushing teeth (unless concentrations are enormous, >1,000 parts per billion).

It is important to note that no treatment technology can ever truly remove a contaminant 100%. Water treatment with reverse osmosis can remove arsenic as much as 98% however. Most professionals and public health research suggests trying to reduce arsenic intake by drinking water to less than 3 parts per billion. 

Get in touch with the Tap Score team here if you have further question about your water quality or about treating arsenic in your water.

What is Reverse Osmosis (RO)?

Reverse Osmosis is an advanced water filtration technique, but is it for you?

RO-Title_1024x1024.png

Finally! A detailed explanation for the type of water filtration you’ve probably heard most about, and for a good reason–reverse osmosis (RO) treats more contaminants than almost any other filter.

RO can filter out contaminants like arsenic, bacteria, lead, and fluoride. This makes it a popular treatment technology in water systems, but also at home. RO systems range from under-the-sink to point of entry (POE) installations treating the whole home’s water.

If you already have an RO and are trying to diagnose a leak or a problem with your system, hop over to our handy problem-identification guide about RO system leaks. For newcomers or interested-RO owners, Tap Score created this guide to explain how reverse osmosis works, which contaminants it does and does not remove, and what some of the pros and cons of an RO system are.

How does Reverse Osmosis Work?

Osmosis occurs in the natural world and is essential to many plants and animals’ life processes (an example being when plants absorb water from soil). During osmosis, water moves across a semipermeable membrane from an area with a low concentration of dissolved particles to an area with a high concentration of dissolved particles. A semipermeable membrane is a material that lets some atoms or molecules through while stopping others–similar to a screen door letting in air but keeping bugs out. This flow leads to an equal concentration of particles in water on either side of the semipermeable membrane.

Reverse osmosis, on the other hand, does not occur in nature. It requires added energy in the form of pressure to force water to move from an area of high concentration of particles to an area of lowconcentration of particles.

RO_large.jpg

The effect is to concentrate contaminants on one side of the semipermeable membrane (the waste stream) and produce freshwater for drinking on the other side (fresh water product).

What does an RO System Include?

Reverse osmosis itself only includes the passage of water through a semipermeable membrane. However, RO systems always contain additional pre-treatment filters and often post-treatment filters. These extra filters are referred to as “stages”. For example, if you see an RO system advertised as a 5-stage system, that means water passes through 5 stages of filtration before arriving at your faucet.

RO_system_1024x1024.png

Pre-treatment

Semi-permeable membranes are very sensitive–this means they are easily damaged if water is not properly treated before reaching the membrane. There are multiple kinds of pretreatment filters that water must pass through to prevent foulingscaling, and premature RO membrane failure:

  • Multimedia filtration/microfiltration is used to filter out sediment particles such as sand, clay, and plant matter/microorganisms. If these particles are not filtered out, they can cause fouling–they accumulate on the RO membrane and plug it up. 
  • Granular activated carbon (GAC) removes organic contaminants and disinfectants in the water such as chlorine or chloramines. Chlorine and chloramines are oxidizers and can react with the RO membrane and “burn” holes in it. 
  • Antiscalants/scale inhibitors are chemicals added to water to prevent scaling on the RO membrane. Scaling happens when dissolved compound concentrations exceed their solubility limits and precipitate out of the water and onto the membrane. A common example is calcium carbonate, or CaCO3, which occurs frequently if you have hard water. 

If pre-treatment is not used or maintained properly, fouling and scaling can decrease water flow across the membrane and decrease water quality.

Post-treatment

Post treatment can include an additional GAC filter to remove any last organic contaminants that still remain, remineralization/alkaline treatment, or UV treatment for bacteria.

What Does Reverse Osmosis Remove from My Drinking Water?

RO can treat inorganic contaminants such as (but not limited to):Arsenic

  • Asbestos
  • Nitrates & sulfates
  • Lead, aluminum, copper, nickel
  • Dissolved solids/salts

However, because all RO systems also contain carbon and sediment pre-filters, they can also filter some pesticides, algae, some bacteria & viruses, and other organic contaminants. (For a full list of RO treated contaminants click here).

Reverse osmosis does not remove molecules smaller than 0.0001 micrometers or molecules that are nonpolar, such as dissolved gases. Specifically, it does not catch:

  • Some pesticides/herbicides (1,2,4-trichlorobenzene, 2,4-D and Atrazine)
  • Some ions & metals (chlorine, radon)
  • Organic chemicals that weigh less than water (Benzene, Carbon tetrachloride, Dichlorobenzene, Toluene and Trihalomethanes (THMs))

Though some of these small particles may be caught by the carbon pre-filters, it is not guaranteed.

Common Complications Using Reverse Osmosis

There are a number of downsides to using reverse osmosis, including:

  • Increased water usage: Only 20-30% of the source water is discharged as clean water while 70-80% is discharged as more concentrated wastewater, so your water usage and bill will most likely go up.
  • Lot of upkeep: You must be very diligent about changing all of the pre-treatment filters on time–if chlorine is in your water and breaks through, you may cause permanent damage. RO membranes must also be sent away and cleaned by a serving company 1-4 times per year.
  • Difficult installation: A hole must be drilled in your home’s main drain pipe for the wastewater line, and in the countertop/sink for the faucet.
  • Water pressure: RO systems can decrease water pressure throughout your house.
  • Limited under sink space: Storage tank for treated water can take up under sink storage.
  • Can remove too much: Reverse osmosis can filter out good minerals from water such as ion and manganese. 

The Ultimate Question: Is a Reverse Osmosis System Right for Me?

If you have a problem with inorganic contaminants such as arsenic, fluoride, or nitrates, or if you have a high total dissolved solid (TDS) count, RO is likely a great option for you. If you have multiple water quality issues that include both organic and inorganic contaminants, reverse osmosis is a good option that will cover all your bases.

It is important, however, for you to know your water’s full chemical profile before installing a reverse osmosis system. Why should you test before you treat with RO? RO is expensive and time consuming–so you’ll want to make sure this is the right choice. Further, membranes can be damaged by certain contaminants present in your water, so knowing what type of pretreatment you need is essential, just like Tap Score’s Essential Water Test.

Have more questions? Feel free to email us at contact@simplewater.us!

Why Is My RO Water Filter Leaking?

Do you have a reverse osmosis (RO) water treatment system? Is it not working properly? This is an article to help you determine why your drinking water filter is leaking and what you can do to fix your RO. 

Leaky_Filters_1024x1024.png

If you own and maintain a reverse osmosis water treatment system in your home, then you’re probably already aware that things sometimes go awry. The water quality engineers at SimpleWater have pulled together a helpful list of the most common problems people have with their Reverse Osmosis water filters at home along with the most common solutions.

Reverse Osmosis: Problems, Solutions – A Quick Guide

Scan the headlines below for common symptoms, causes, and solutions to water filter failures. If you have questions about your water quality or your water treatment system, please don’t hesitate to reach out to our professional water testing team.

Scale forming on the membrane?

Cause: Failure of the antiscalant, acid dosing device, or pH monitor

Fix: Check your dosing equipment is working properly and monitor all changes in water quality before and after the RO system. Ask our team for help by emailing: hello@simplewater.us or clicking on our help page.

Iron accumulation on the filters and membranes?

(Leading to a high pressure difference and low permeate flow)

Cause: High iron content in raw water, corroding pipes, failure of media filters

Fix: Check pipes and media filters. Ask our team for help by emailing: hello@simplewater.us or clicking on our help page.

Bacterial film on filters and membranes?

(Leading to high pressure difference and low permeate flow)

Cause: Ineffective sanitization or biocide

Fix:  Sanitize all filters, perform microbiological analysis, check chemical dosing tanks; heck for biocide adsorption on carbon filters, check contact times and dose rates, select broad-spectrum biocide for organic content. Ask our team for help by emailing: hello@simplewater.us or clicking on our help page.

Organic or humic content on filters and membranes?

Cause: High organic content

Fix: Test the feed water for TOC and color Ask our team for help by emailing: hello@simplewater.usor clicking on our help page.

Membrane damage leading to high salts passthrough and high flux?

Cause: Chlorine overdosing

Fix: Perform chlorine tests, check dosing equipment, redox meters, bisulfite levels and the general location of dosing equipment. Ask our team for help by emailing: hello@simplewater.us or clicking on our help page.

High Salt Passthrough?

Cause: Failure of the O-ring at the permeate tube

Fix: Check conductivity in each vessel and membrane. Ask our team for help by emailing: hello@simplewater.us or clicking on our help page.

Bacteria and colloid fouling of micron-pre filters and membranes

Cause: Breakthrough of your media pre-filter

Fix: Wash your media pre-filters and add some biocide. Ask our team for help by emailing: hello@simplewater.us or clicking on our help page.



| HOME | GET TAP SCORE | CONTACT US | FOR THE PRESS |