Mike-O-Pedia FAQs for Water Treatment Professionals

The purpose of the “Mike-O-Pedia” is to share knowledge with our peers.  We will be posting on a regular basis and look forward to answering questions or discussing comments and applications with our dealer customer base.

Topic: Water Softeners

Which Salt to Do We Use?

Scale Removal

Removing Iron with a Water Softener

Water Hardness & Low pH

Should I use an upper screen?

What type of resin do I use in a softener?

How long does softener resin last?

Should I install a water softener to remove lead?


Topic: Activated Carbon

GAC Specifications – What do they measure?

Iodine Number

How closely in size is the contaminant to a molecule of iodine?   The higher the iodine number the better the removal of molecules which closely resemble iodine.  Iodine is a small molecule therefore it measures ability to adsorb lower molecular weight smaller substances.

Molasses Number

Molasses number Is a measurement of the degree of decolorization of a standard molasses solution.  It is a relative guideline for measuring the capacity of the carbon to remove color molecules.

Abrasion Number

Demonstrates the carbons ability to withstand degradation during handling – before and after it is placed into service.  Lower abrasion numbers result in more dust and fines.

Density, Backwashed & Drained (BWD)

This is the number of pounds required to fill a cubic foot of volume capacity.  Caution– The density of activated carbon types varies.

TCN – Trace Capacity Number

The Trace Capacity Number measures the number of high energy pores in an activated carbon product. These high energy pores are required to remove difficult to adsorb contaminants, such as MTBE. The theory behind the test is similar to the Iodine number, where the iodine number reports the mg Iodine per gram of carbon in a standard iodine solution. Since iodine is so strongly adsorbed, it is essentially fills all of the adsorption pores (high energy and low energy). The TCN number uses a more difficult to adsorb species and reports the mg loaded per gram of carbon. A higher TCN number on a carbon would indicate a higher number of high energy pores, which would suggest better loading in an application with difficult to remove contaminants.

Ash

The ash content of a carbon can be defined as the noncombustible mineral matter that is contained in activated carbon. It is the residue that remains after the combustion of a carbonaceous material and is normally defined on a weight basis. The ash content is dictated by the raw material used to manufacture an activated carbon product and is why a high purity raw material is necessary to produce a high purity activated carbon product. There are also additional post-processing steps, such as acid washing, to reduce the amount of ash content in an activated carbon product.

Water Soluble Ash

Ash measures the level of purity.  It is the inorganic residue left after the heating process.  It consists of silica, calcium, alumina, iron, magnesium with a potential for arsenic.  Carbon may be acid washed or water rinsed to reduce ash content. Water extractable ash has the highest impact on the product quality as it affects the effluent.

Can Activated Carbon be regenerated?

Activated carbon cannot be regenerated like ion exchange resin.  Activated carbon can be reactivated by carbon manufacturers.  The reactivation process is similar to the original activation process. The resulting product is distributed for waste water applications.  Municipalities contract to reactivate segregated lots for re-use.

It is possible to reactivate activated carbon with steam.  Beverage manufacturers have large carbon filters which have steam injection.  The heat from the steam will push off the more weakly held contaminants freeing up pores for continued use.  The steam also sanitizes the carbon bed.  Steam reactivation will restore the life of the carbon bed but eventually the cost outweighs the benefit and a new carbon bed must be installed.

Which type of carbon do I use?

What is Enhanced Coconut Carbon?


Topic: Arsenic Removal

Arsenic is a grey, semi-metal element.  Arsenic enters ground water from both natural sources and human activity. Contamination can sometimes be traced to deep-water brines produced from gas and oil well drilling. It is also be found in wood preservatives and may be a byproduct of herbicide production.

Health Effects

Arsenic has a primary drinking standard because it is known to have health effects when present in drinking water.  Skin lesions, circulatory problems and nervous disorders can occur.  Prolonged exposure may result in skin, bladder, lung and prostate cancer.  For this reason, the EPA has set the MCL to 0.01 mg/L (micrograms per liter).   Arsenic removal from wells

Arsenic Reduction/Removal from Water

Arsenic is one of the hardest ions to remove from water.  It usually occurs in water as either arsenate (AsV) or arsenite (AsIII).  Test results report the total arsenic concentration including arsenic as arsenate and arsenic as arsenite. Aresenite is a greater health concern and more difficult to remove.  For this reason, most treatment solutions start by adding an oxidant to the water to convert all arsenic to the arsenate form.  Oxidation can be accomplished through the addition of chlorine, ozone or greensand.  Note: Chloraminated water utilizing only monochloramine (NH2Cl) will not completely oxidize AsIII to AsV).

Heating or boiling water will not remove arsenic from water, it may increase the concentration as the water is evaporated off.

To determine the best removal treatment the water must first be tested by a certified lab.

Removal methods include Activated Alumina, Manganese Greensand Filtration, Distillation, and Reverse Osmosis.  Urbans Aqua offers specialty products – Purolite’s FerrIX™ A33E and Graver’s Metsorb®.  All products used for arsenic removal should be NSF or WQA Gold Seal Certified.

Before embarking on a treatment regiment, a full water analysis is necessary.  Since Arsenic is anionic, you must test for competing anions.  Both Purolite and Graver have a water profile work sheet that must be filled out, so they can better estimate bed life.  Contact Urbans Aqua for equipment system design.

Download Documents:

Product Pros Cons
Activated Alumina Potential for non-hazardous disposal as solid waste.

Easy maintenance

Highly selective for AsV; AsIII must be oxidized

pH < 6.5 or lower if silica is present

Distillation Reduces to < 2 ppb Only practical for small quantities of water treatment
Ion Exchange Anion SBA I & II Effective for AsV

Optimum pH >7

AsIII must be oxidized and removed prior to resin bed.

Nitrate, fluoride, selenium & sulfate will compete with AsV for exchange sites resulting in earlier exhaustion.

 

Manganese Greensand Effective for AsV AsIII must be oxidized and removed prior to greensand filter. Iron must be present in raw water equal to or greater than the arsenic. 

 

Reverse Osmosis (RO) Effective for AsV AsIII must be oxidized and removed prior to RO.  Care must be taken to prevent damage to membrane.

 

FeriX™A33E Selective removal of arsenic.

pH for treatment 7

Operates similarly to ion exchange resin.

EBCT 2.5-5 Minutes (typically 3 minutes).

No Regeneration

Low pressure differential

Potential for nitrate dumping.

Offsite regeneration available for large installations.

Metsorb® Removes AsV & AsIII.

EBCT 1.5-3 Minutes.

Also removes lead, cadmium, copper, zinc, chromium+6 & selenium.

Potential for non-hazardous deposal as solid waste.

No regeneration

Potential for high pressure differential.