By Emily Bolda, CWS-VI

In the March issue of WC&P, I discussed water analysis and how several analytical methods are performed. The taken from products in this type of testing is analyzed for a long list of inorganic and organic contaminants in order to determine real work begins after the results are obtained, when decisions and interpretations need to be made to determine the treatment options, assess the effectiveness of installed equipment, ensure drinking water or wastewater is in compliance, determine if an R&D project is on the right track or for product certification purposes. Water analyses can be powerful diagnostic tools for many applications.

Manufacturing and quality control uses

Water analysis can be used to monitor specific manufacturing processes. For example, pH and other testing can be performed on process waters to ensure certain media have been prepared correctly. Monomer and polymer monitoring can be employed during the manufacture and treatment of plastics. Drinking water treatment product manufacturers have quality control testing in place as part of their overall program. Products may be sampled and tested for performance and/or materials safety and to comply with internal or external specifications. Chemical manufacturers test their products to make sure they are of the right concentration and also to check for contamination by heavy metals, organic and other contaminants.

Research and development

In the water industry R&D processes, water analysis is extensively used. Experiments are designed incorporating water analysis as part of the process. Specific water samples can be incorporated into the experimental design in order to evaluate variables and measure product performance. Prototype or modified products such as filters, RO and water softeners can be challenged with known concentrations of contaminants to see how they perform. Some design problems can be diagnosed by analyzing product waters. For example, analysis of influent and product waters from a filter can indicate bypass in the system or other problems. Process media can be evaluated as part of internal research and development and for vendor qualification. Additionally, materials safety testing can be done internally, for informational purposes during the development phase and pre-testing for product certification.

Product certification

Laboratory testing for drinking water treatment unit and drinking water additive product certification involves extensive use of water analyses. Analyses are done to evaluate laboratory conditions during product testing. Performance testing, or contaminant reduction testing, involves analysis of several influent and effluent samples in order to calculate percent reduction for many products, as well as demonstrating compliance with standards for performance. Materials safety, or extraction testing, involves extensive water analysis; water compliance with standards as well as to identify any additional toxicological concerns for material safety.

Drinking water quality

Evaluation of public drinking water quality is another important venue for water analysis. Many tests are conducted by water treatment plants before and during treatment. This allows operators to gather data and make corrections to the treatment process, and to demonstrate compliance to applicable regulations.

Water analysis is especially important in treating and maintaining quality well water, which can become contaminated from rock substrate, agricultural and point-source pollution, since it is not subject to the same regulations as publicly supplied drinking water. Microorganisms, heavy metals and other inorganic contaminants (especially nitrates) and organic contaminants can all be found in groundwater; many can pose a risk to human health.

Privately supplied well water should be monitored periodically; continuing analysis can help determine if water quality has changed over time. If the supply is being treated by filtration or chemical addition, analysis will also help determine how well the equipment is functioning and whether maintenance or component replacement (such as filter cartridges) may be necessary, or if alternative/additional treatment technologies or modifications are needed.

General water characteristics

Knowing pH and alkalinity levels of water is important. Components of alkalinity can combine with both acids and bases, which act to buffer water and prevent sudden uncontrolled pH changes. pH can also affect the performance of some treatment methods.

Turbidity can result from clay, silt, organic or other suspended solids. Higher turbidity levels can be associated with disease-causing organisms. TDS, another basic indicator of water quality, describes the sum of dissolved materials present in water, which may include minerals, gases and organic constituents. Cations (positively charged ions) are ubiquitous in water and vary in type and concentration, depending on the water source. The main cations (calcium, sodium, potassium and magnesium) are not considered harmful, but in high amounts, can cause treatment issues, scale buildup and other problems.

Of particular concern is hardness caused by calcium and magnesium. Hard water decreases the effectiveness of detergents and soaps. Hardness can often result in scale, a solid material that coats the inside of pipes and water heaters, and can build up on water fixtures. Hard water may increase the energy spent on heating water because scale buildup can slow down heat transfer within water-heating equipment.

Soluble and insoluble silicates, which can protect distribution piping from water’s corrosive effects, can also contribute to scale buildup. Silica produces a glassy scale in high-temperature equipment. Copper and zinc can cause stains on porcelain and fittings, and can result from corrosion and deterioration of plumbing materials, and in high enough concentrations can have health effects. Iron and manganese are two other problem cations that may cause metallic taste, stains on laundry and porcelain fixtures and equipment fouling. Precipitated iron deposits and manganese can collect in pipelines, and tap water may contain reddish or dark sediment and also turbidity.

There are several metals that can also be dangerous. Arsenic occurs naturally in many forms in rocks and soil, water, air, and plants and animals. In water, it actually exists as arsenite/arsenate anions. Arsenic can be further released into the environment in the form of several different compounds through natural activities or through human actions. These include the manufacture and use of wood preservative, paints, dyes, semi-conductors and fertilizers, as well as copper smelting, mining and coal burning, and other manufacturing and industrial applications.

Lead is a naturally occurring metal that previously was used in a number of industrial capacities and commonly used in household plumbing materials and water service lines. Lead was used as a component of paint, piping, solder, brass and as a gasoline additive until the 1980s. Mercury, selenium, chromium and cadmium are other heavy metals with documented health effects. The presence of heavy metals in certain concentrations demands treatment with, for example, filters or RO systems with the ability to remove these contaminants. Heavy metals have established maximum contaminant levels (MCLs), which are concentrations at which public drinking water supplies cannot exceed.

Anions/nutrients

Some of the major anions are nutrients, but can contribute noticeable taste to water, corrosion and health effects in the case of nitrates and nitrites. Effects on humans can include cardiopulmonary problems, cancer, sterility, organ and central nervous system damage, changes in the blood, endocrine problems and acute injury to infants. Many groundwater sources contain small amounts of nitrate nitrogen. Nitrate results from seepage of water through soil containing nitrate-bearing minerals or from using certain fertilizers. Nitrates are also one of the products of decomposition of animal and human wastes, and their presence can indicate water pollution.

Almost all natural waters contain chloride and sulfate ions. Low-to-moderate concentrations of both chloride and sulfate ions add palatability to water. Sulfate water can indicate extreme hardness, large amounts of sodium salts or acidity. Alone or together, these can pose special problems in conditioning. Phosphates, in addition to those found in fertilizers, are also present in consumer products, such as detergents, baking powder, toothpaste, cured meats, evaporated milk, soft drinks, processed cheese, pharmaceuticals and water treatment chemicals. Chemical precipitation of phosphates can be accomplished by the addition of metal salts or lime, with polymers often used as flocculant aids. Surface water supplies are normally low in fluorides. Many municipalities add fluoride to drinking water supplies as a supplement to prevent dental caries.

Analysis of untreated water samples with high levels of one or more anion can help determine if a POU RO, deionization or distillation system will help, or if a more complex POE system is needed. Separately, concentrations of cations and anions determined in the laboratory are useful in themselves. They can also be used together. The concentrations of both can be used to determine the specific minerals present in the water.

Alternatively, a direct analysis of the prepared dissolved and suspended solids can be performed. Dried and prepared, samples can be subjected to a series of simple tests in order to identify particular minerals. This analysis can also be performed on a sample of scale deposits, the results of which can be used to diagnose certain water conditions.

Organic contaminants

There are literally millions of organic compounds present in our environment, both naturally occurring and synthetic. Organic compounds can be found in petroleum and coal, formed by natural processes acting on the organic chemicals of once living organisms. Numerous organic compounds are synthesized. They can include pesticides, materials used to make plastics, manufacturing byproducts, synthetic fabrics, dyes, gasoline additives, solvents, personal-care products, medications and disinfection byproducts. Some organic contaminants are known to be carcinogenic. Some have been identified as possible endocrine disruptors, which can cause harm to the reproductive, central nervous and immune systems of mice. For many, occurrence and concentration levels are so low that toxicity is yet to be determined and no risk to humans has been established. A combination of RO and carbon filtration is usually a good treatment recommendation for these contaminants.

Treatment options

The results of a water analysis should be compared against US EPA or state drinking water regulations to see if any contaminants exceed MCLs. Once problems have been identified, the prescription for the particular water problem can be evaluated. Some water quality problems (such as color and odor, or conditions such as hardness) are better handled through POE applications. Other contaminants can be mitigated through POU technology such as filters or RO. Still other problems require more than one technology. For example, RO systems designed for arsenic or nitrate reduction will last longer if hard water is softened prior to entering the unit, since hardness minerals can build up within the equipment and reduce effectiveness of the membrane elements. In addition, arsenic can be present in water in two chemical forms. If water contains trivalent arsenic, prechlorination is required prior to using RO. Chlorination oxidizes trivalent arsenic into its pentavalent form, which can then be removed with RO.

Iron is a contaminant that may require special considerations. Many treatment types are effective for the iron removal, but not all methods are equally effective under all conditions. Effectiveness depends on the concentration of the contaminant and other water conditions. Iron water with a neutral pH can be treated with softening, oxidation/filtration or sequestration. Larger amounts of iron and acidity may call for the use of a solution-feeding device and a filter, treatment with an alkali to raise pH and chlorine to precipitate iron. A simple filter can then be used to remove the precipitated insoluble iron.

Water softeners can remove limited amounts of iron. Ion exchange materials remove soluble ferrous ions, as well as calcium and magnesium ions. Most iron-bearing waters contain amounts of insoluble ferric iron along with soluble ferrous iron. The insoluble iron will precipitate out of the water and either clog the bed or coat the ion exchange beads, causing reduced capacity. This may require an iron pre-filter to prolong the life of the media. If organic contaminants are also present, a carbon filter should be part of the treatment design. High turbidity or presence of microorganisms may indicate inclusion of an additional component in the design, such as a pre-filter and treatment by ozone, UV or other technology.

Conclusion

Water analysis is an important piece of the water treatment puzzle and an effective tool for manufacturers, product dealers and other water treatment professionals. It will often reveal conditions that can be addressed in one of several possible ways. For water treatment, there may not be any one best answer; several solutions may be required to achieve satisfactory results. It is necessary to consider the particular contaminants present in the water and their concentrations. For R&D and quality control, it can provide revealing information about a product’s design and effectiveness, manufacturing problems or provide information for trending. To provide the best water for any demand, two important factors must be considered: what the water analysis indicates and to what end the results will be used.

About the author

Emily Bolda, CWS-VI, is Laboratory Supervisor for the Water Quality Association’s Gold Seal Certification Program at WQA’s International Headquarters and Laboratory. She has been with organization since 2006, and has worked in the water and drinking water industries since 1999. Bolda’s professional background is in analytical chemistry and product testing, and she holds a BS Degree from the University of Iowa. She can be reached by phone (630) 929-2534 or email ebolda@wqa.org to provide additional information concerning WQA’s Laboratory or Gold Seal Certification Program.

 

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