Water Treatment

Washington Water Treatment, Testing, and Sampling

“A little learning is a dangerous thing;
drink deep, or taste not the Pierian spring:
there shallow draughts intoxicate the brain,
and drinking largely sobers us again.”      –Alexander Pope

Our experience managing water systems has provided us with the opportunity to see a wide range of treatment systems, which operate with varying degrees of success.  Most components in water requiring removal can be treated with one of three entirely different methods.  Our goal is to work with you to help you choose the treatment method that will best serve your needs.

What is the Approval Process?

The first step is to determine the treatment goals and level of service.  Next, enough water samples need to be collected to have an adequate understanding of the water chemistry.  Nearly every treatment process depends on impurities or characteristics in the water that are not directly a problem; however, they cause an indirect interference with the treatment process.  Alkalinity, tannins, and pH are common examples.

Once the water quality sample results have been assembled, the most reasonable treatment strategy can be determined.  Once a treatment technology has been selected, whether or not to run a pilot project needs to be determined.  In some cases, such as with surface water treatment, larger treatment plants, or treatment plants with a large number of unique parameters, a small-scale pilot study is absolutely required before the design is started.

In other cases, with well established technologies, smaller flow rates, and where public health is not at risk, a formal pilot study often costs more than the treatment plant itself.  Therefore, if the treatment plant is small and/or we have a high degree of confidence in the success of the approach, we may recommend installing a “full-scale” pilot treatment plant, which when successful, becomes the final installation.

In either case, it is wise to work with the WSDOH to establish the appropriate type of pilot study and the parameters that need to be considered.

The pilot study (either a true pilot, or full-scale pilot) is designed, submitted and approved.  Then the equipment can be installed.  Once finished and samples have been taken, the full scale treatment plant can either be certified as complete (full scale approach), or the main treatment plant designed (small pilot approach).

Sometimes, the installed treatement plant requires additions or adjustments to optimize performance.

One unique analysis we perform with every treatment plant is to consider the cost of treating the water at full-flow vs. treating at a lower rate with the utilization of storage.  Often times it is less expensive to add storage than to maximize the rate of water treatment.

Arsenic Testing and Treatment

Arsenic is a primary contaminant that can cause problems in the digestive system, skin, and is a known carcinogen.  It is regulated in water with a concentration above 0.0104 mg/L.  Arsenic can be difficult to treat, depending on the other constituents in the water.  We work with you to determine your water quality goals, and then develop a treatment strategy to meet your needs.  For more information see our Arsenic Treatment Technical Article.

Chlorination

Chlorination is usually installed for disinfection.  However, it can also be used for improving Taste and Odors, or as an oxidant for iron removal.

There are several different methods of chlorinating drinking water (chlorine gas, Calcium Hypochlorite, on-site generation from a salt brine, or bleach).  For small systems, injecting bleach (sodium hypochlorite) is the most simple, reliable, and cost-effective method.

We design chlorine injection systems that are easy to install, operate, and maintain.  While we will specify diaphragm pump injectors, if that is your preference, we believe that the cost, flexibility and ease of maintenance for the peristaltic pumps is hard to beat.

Our primary advantage in the chlorination designs we develop is that we make every effort to minimize the cost of providing effective contact time.  While it is easy to design long serpentines or large reservoirs, these solutions are often very costly.  We customize the contact time solution for each and every situation to minimize the construction cost.

Color

There are two primary causes of color in water: “Red water” (oxidized) iron, and tannins.  As suggested by the name, red water iron is red.  Tannins can be yellow, brown, or green.  Other contaminants can cause staining, but color refers to the color of the water itself.

Red water iron is typically removed by coagulation and then filtration.  Depending on the pH and other water chemistry parameters this process can either be very simple, or very complex.

Tannins are a class of large, complex organic molecules that come from the decay of vegetation.  They can be removed by either ion-exchange or oxidation.  Tannins are usually very difficult to remove.  While we can be 100% successful in treating tannins, they require a “guess and check” methodology.  Sometimes we are successful with our first, educated guess, but sometimes they require two or three tries.

Corrosion Control

Lead and Copper in your water is a result of corrosive water dissolving copper plumbing, brass fittings, or lead solder from the inside out.  In severe cases, it can cause blue or green staining on plumbing fixtures.  Lead is a well-known health concern.  Some people are sensitive to copper.  In some cases, corrosive water can lead to a catastrophic premature failure of a house’s plumbing.

Lead and copper are only rarely found in the drinking water source.  Therefore, the presence of these contaminants at the tap is almost always a result of corrosive, not contaminated, source water.

The most important step in corrosion control is to determine the cause of the corrosivity and the most effective method of treatment.  We have developed some very simple and inexpensive field tests to help determine the best treatment methods.  We have found that “by the book” treatment does not always work and that it is important to combine both the theoretical treatment methods with findings on-site.  This results in a little extra expense up-front, but results in huge savings during the construction and follow-up phases.

Corrosion Control Approval Process

Corrosion control begins with sampling.  If lead and copper is detected above the action limits, then additional samples for conductivity, hardness and alkalinity need to be sent to a lab.  pH must also be measured on-site as it can change with time.  Ideally, two sets of these samples should be taken three to six months apart.

Once the samples are collected, then a corrosion control strategy recommendation must be made.  This can either be done by DOH (for a fee) or by a consulting engineer (likely also for a fee).  Once the approach has been selected by the waterr system and approved by DOH, then the design of the treatment plant can be developed and submitted.  Usually, the design is either presented as a small or full-scale pilot.  From there the design is reviewed, approved, and constructed.

Disinfection

Chlorination is the most common method of disinfection.  Other methods that can be used independantly, or in concert with each other include UV light, ozone, and hydrogen peroxide.  UV light is especially popular with private homes or businesses requiring disinfection treatment for interrnal processes.

Filtration

Filtration is a physical process whereby particles are removed from water.  These particals may be sand, silt, clay, bacteria, or organics.  The size of the particle determines the most appropriate filter.  At times, multi-step filters are appropriate to prevent filters designed to remove the smallest particles from being clogged with the larger ones.  Filtration methods include: multi-media beds, centrifuges, woven filters (bags or cartridges), and membranes.  The most important aspect of a filtration design is to thoroghly undsterstand the characteristics of the particles to be filtered.  Not surprisingly, the smaller particles tend ot be the most difficult.  Indeed, extremely small particles (colloidal iron, clay, etc) are sometimes most successfully treated by understanding and taking advantage of their chemical rather than physical properties.


Hardness

While hardness is more common in the Midwest and South, there are pockets of hard water in the west as well.  For small water systems, ion exchange (water softener) is the most effective treatment technology.  This is one technology that is very well established and is almost always a simple and straightforward project.  While hardness is not a regulated contaminant, some systems choose to treat for hardness to protect their pipes and the plumbing systems of each home.  If the community members conduct a significant amount of outdoor watering, it may be better for individuals to treat water at their homes, so irrigation water does not need to be treated.

Iron

Groundwater containing iron also commonly has manganese.  Iron causes red-orange staining.  The presence of manganese results in brown to even black stains.

Iron is usually treated by one of two methods: ion exchange or oxidation filtration.  We match the best technology with your water use patterns, operational preferences, water chemistry, and budget.  Iron and Manganese are usually easy to treat; although, the presence of tannins, or an extreme pH can require a multi-step approach.

Iron Bacteria

Iron Bacteria are easy to remove from a water system with a shock chlorination; however, they are very, very difficult to remove from a well and/or aquifer.  If a well has become fouled with iron bacteria, we are able to assist you with developing a plan for eliminating, or controlling the problem.

Beware of anyone who simply proposes shock chlorination of a well to control iron bacteria.  While this may cause an initial kill of bacteria with an impressive flushing of gooey sludge, it more often than not makes the long term condition of the well worse rather than better.  An understanding of microbiology, hydrogeology, and well construction is essential to successfully controlling iron reducing bacteria.

Manganese

Manganese is a naturally occurring mineral in some groundwater.  It is not health concern, but causes dark brown to black staining.  It is often found in association with iron.  Manganese is treated by the same oxidation-filtration or ion exchange processes.  Manganese can be a little more difficult to remove because it oxidizes very slowly without the presence of a catalyst such as Manganese dioxide.

Nitrates

Nitrates can be found naturally in groundwater, but are usually the result of contamination.  Manure piles, drainfields, and heavy fertilizer application are common sources of nitrate contamination.  When possible, the source of contamination should be identified and eliminated, if possible.

Nitrate is a primary contaminant and can cause methemoglobinemia (blue baby syndrome) at concentrations above 10 ppm.  The only practical method of removal for a small public water system is through ion exchange.  Private homeowners can also consider reverse osmosis as a viable alternative.

Ion exchange for nitrate removal requires very careful operation and maintenance of the treatment plant.  If the plant is not properly regenerated on the required schedule, nitrate dumping can occur, resulting in higher nitrate levels after the treatment plant than in the natural source water.  We recognize these factors and work carefully with the communities requiring treatment to take their responsibility for maintaining the treatment plant very seriously.

Odor

The most common odor in public water systems is the “rotten egg gas”, hydrogen sulfide.  This gas is often found in parallel with iron and manganese.  Hydrogen sulfide comes out of water very easily as a gas.  Therefore, in systems with a reservoir, simply spraying the water across the top of the reservoir with adequate venting is often enough to remove all smell.  If a reservoir is not available or practical, injection of an oxidant (chlorine, ozone, hydrogen peroxide) is often the best solution.

While tannins are more commonly associated with color, they can also cause “fishy” odors.  See the section on Tannins for more information.

Strong chlorine or chemically odors are sometimes presence on chlorinated systems.  Ironically, sometimes the solution to these taste and odor problems is to increase the concentration of chlorine in the water.  Flushing or other operational controls are the answers in other situations.  Rarely does the strong chlorine odor require expensive treatment techniques.  Private homes often desire to install activated carbon filters to remove all chlorine before it enters the house.

In every odor situation we believe that the first and most important step is to identify where the odor is coming from and then resolve the odor problem based upon the water chemistry.

Sand/Sediment

As with other water quality issues, the first and most important step is to identify what the contaminant is and why it is a problem.  Sand and sediment are generally easy to resolve; however, it is extremely important to understand the nature of the problem.

If you have sand because your well is failing or was improperly constructed, then installing a simple sand filter might fix the problem of sand in your lines, but it will mask the root of the problem: a well that needs attention.  Beware of cheap solutions today that cause tens of thousands of dollars in expense a few years down the road.

Taste

Taste and Odor are inseparably linked.  See Odor.

Tannins

Tannins are a class of large organic molecules.  Each water source has a different “blend” of tannins.  Some water has undetectable levels of tannins.  Other water has relatively high concentrations of tannins, but they have no color/taste/odor properties and don’t interfere with other treatment processes.  Other tannin blends are very difficult to remove and require a complicated multi-step treatment process and regular maintenance and on-going expenses.

The two primary methods of removing tannins are ion exchange and oxidation-filtration.  Since tannins have an overall negative charge, specialized anion exchange resins are required.  There are two primary classes of these resins, each with two sub-catagories.  Each water has a different soup that may require different media, or a combination thereof.

Oxidation-filtration requires the use of a strong oxidant such as hypochlorite (chlorine), potassium permanganate, or ozone.  A coagulant is often times also required.  Once oxidized and coagulated into a filterable floc, the actual filtration media is often less important.  In this situation, the filtration process is strictly physical.

Other . . .

Everything found in water can be treated; however, each source of water is different.  What works on one water system may fail miserably on another.  We have a strong background in chemistry.  We believe that the only way to successfully treat water is to understand why we choose various processes, media, and approaches.  Rather than simply rely on cut sheets and manufacturer’s claims, we insist on understanding our treatment designs from the fundamental principals of chemistry and physics.

We believe in being up front and honest when it comes to water treatment.  There are never any guarantees.  We can run pilot plants and do extensive water quality testing, but we cannot and will not guarantee that a treatment plant will work perfectly.

We believe that any engineering firm or contractor that makes the claim that their treatment is guaranteed to work, is not being realistic.  All treatment designs must be based upon the best information available and understanding of chemistry, but in the end, there is no way to be certain of absolutely everything that is in the water that could effect the treatmen outcome.