“Green” Chemicals Continue to Play a Critical Role in Water Quality

Background

As Water Quality Products reported on April 18th, EPA has just announced its “2014 to 2018 Strategic Plan” with goals that include protecting US waters, ensuring the safety of chemicals and protecting human health and the environment through enhanced compliance activities. The article notes that EPA “will continue its efforts to improve water quality, given the nation’s significant water infrastructure needs, focusing on common-sense, flexible approaches that rely on sustainable solutions, such as green infrastructure…” To accomplish these goals, they envision working more closely with other levels of government and industry to deliver environmental benefits in a pragmatic way.

While in the minds of some, chemicals have played a necessary but unappealing role in the past, they continue to be essential in supplying water of acceptable quality for a wide range of uses from drinking to industrial process water. Similarly, chemicals are necessary for wastewater treatment to ensure that these discharges meet all standards for environmental acceptability. Still, popular discussions of new options for water treatment usually focus on technologies that totally eliminate the need for the use of any chemicals. Sometimes the enthusiasm for adopting these chemical-free technologies leads to installations that are not adequately vetted to ensure their effectiveness and sustainability.

Looking forward, chemical water treatments continue to hold great promise as one of the tools that can most effectively meet EPA’s goals for “green” technology to promote human and environmental health. Many new chemicals are being offered in the markets and innovative applications of established chemicals now provide significant opportunities for immediate use to improve water quality.

Further, some chemical options do facilitate water reuse promising benefits for the efficient use of our water supply. As discussed in “Efficient and Effective Water Reuse” (WQP November 11, 2013), this practice is becoming a necessity for economic and regulatory reasons in some locales. With water supplies increasingly burdened with greater demand and heightened regulatory pressure for recycling, chemicals that permit these alternatives to be adopted are increasingly important.

“Green” Water Treatment

In developing better chemical alternatives that meet a specific application’s requirements it is important to recognize that the shortcomings associated with chemicals can come from the nature of each specific chemical employed, as well as the design of its dosing program. Additional risks can result from the interactive effects from using more than one chemical in the program, or the cumulative effects of the program over time. The safe handling of chemicals is also a key consideration to protect humans and the environment. New chemicals and treatment programs have been developed that address each of these situations.

Finding acceptable chemicals can be a challenge. For example, oxidizing biocides, have long played important roles in providing safe drinking water and to control biological contamination of non-potable water circuits including cooling tower and industrial process applications. The benefits and risks associated with these chemicals are well understood and can be responsibly delivered in well-designed programs. Still, concerns remain regarding some characteristics of their use including byproducts and cumulative effect of large scale use on the aquatic environment. While research into alternatives is underway, any call for an immediate ban on chlorine without demonstrated, reliable substitutes would be irresponsible.

The good news is that promising alternatives are emerging. For biological control, some non-oxidizing biocides that are less toxic or have fewer problem byproducts are now on the market. Multi-functional chemicals have been developed that minimize chemical load and potential chemical interactions. Some chemicals are now available in solid or concentrated form that allow for steady, slow release and/or safer handling. Some chemicals can now be generated on-site at small to medium scale reducing the potential for accidental chemical releases on-site and in transit. Chemicals that reduce fouling in water circuits can also improve heat transfer and lower energy requirements.

Many new chemicals can be combined effectively with other mechanical technologies such as filters, reverse osmosis, and continuous tube cleaning devices for greater efficiency and lower environmental impact. Similarly, modifications in operations and dosing patterns can significantly reduce the effects of chemicals. Sequential dosing of separate parts of the water circuit has been successfully used to dilute chemical concentrations. Timing of dosing and discharge can also be adjusted to minimize environmental impacts, without sacrificing the critical functions performed by the water system.

Chemicals and Water Supply

Chemicals can play a strategic role in water reclamation and reuse, especially for industry, power plants and heating and cooling facilities that are the largest consumers of water. Industry and power plants use large volumes of water in open and recirculating cooling systems. Cooling towers for HVAC also are very large consumers of water although they are spread out in hundreds of thousands of heating and cooling systems across the country. Other applications of reclaimed water include: agriculture, landscaping, public parks, golf course irrigation, dust control, construction activities, concrete mixing, and artificial lakes. Each of these applications will save fresh water supplies if the water quality requirements for the application can be met. Chemicals allow this to happen by effectively treating wastewater from municipal plants, process and cooling water from industrials, power plants to acceptable levels for these applications. Effective treatment that allows recycling and reuse will also lower the total level of discharges to the environment.

Green Chemical Strategies in Practice

Cooling Water Treatment

Water treatment programs for HVAC and industrial scale cooling water systems are universal across the country and provide an important service to maintain the efficiency and life expectancy of the equipment. Traditional treatment programs have addressed a wide range of fouling problems from biological to mineral scaling and corrosion using combinations of up to five or six chemical depending on the unique problems at each site. Some of these chemicals are receiving increasing scrutiny from regulatory authorities, in some cases limiting the dosing times and levels, as well as the discharge concentrations allowed into municipal wastewater systems or surface waters.

Among the potential chemicals available to address these problems is a single emulsion recently approved by the USEPA that prevents most types of fouling in cooling systems. The Mexel product is a blend of filming amines that addresses fouling by using a molecular coating mechanism to thwart microbiological and other fouling, rather than remediate it by treating the entire water column. The coating is renewed daily with brief injections, is biodegradable, and has lower toxicity and no dangerous byproducts compared to conventional treatment programs.

In use in other countries for more than 20 years, it has been proven effective in controlling potential health risks from macro- and micro-biofouling in applications of all sizes. The product has been effective in a wide range of water conditions including fresh and salt water, making it a viable choice for reclaimed water applications. The concentrated formula is easier to handle and safer for the public and environment because it cannot burn, explode, volatilize, or be weaponized as some other chemicals. Research has shown that it does not adversely affect municipal wastewater treatment systems and can be safely discharged into surface water under applicable permits. Field studies have documented improved heat transfer and energy efficiency resulting from fouling control as well.

Water reuse and reclamation

One of the most established uses of reclaimed water is reconditioned municipal wastewater employed for cooling and process water in industry and power plants. DOE has determined than over 60 plants are current users with more in development. Regulatory initiatives at the federal and state levels indicate the potential for significant expansion. To accomplish this, chemical treatment of the wastewater for each intended use will be necessary. For example, in power plant cooling uses, after removing suspended solids and other contaminants, the treated water usually requires antimicrobial treatment, as well as anti-corrosives, anti-scalants, surfactants, and/or neutralizers before reuse. If the cooling water or cooling tower blow-down is not recycled, the impacts of these additives must be taken into consideration when discharging. By using new chemicals in combination with innovative dosing programs and mechanical devices, this important “new” water resource can be fully realized and many locations in the US.

While it may seem paradoxical, adding new chemicals for water treatment can play an important, beneficial role in meeting EPA’s water quality and water supply goals. The challenge is to identify and implement the best available technologies that protect the human and natural environment most efficiently.

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