Chemistry for Water

Water, one of the most abundant compounds on Earth, is special because all life-forms on Earth are totally water dependent, observes Leiv K. Sydnes, a chemistry professor at the University of Bergen, in Norway. "Water amounts to up to 80% of our bodies and plays diverse chemical roles in humans as well as in flora, fauna, soil, and air."

Yet a huge portion of the world's population does not have access to a reliable supply of drinking water. And pollution of water resources is a global problem. These issues and related technology questions were the focus of CHEMRAWN XV, the latest in the Chemical Research Applied to World Needs series of international conferences.

Sydnes, who is president of the International Union of Pure & Applied Chemistry (IUPAC), was one of the speakers at the opening session of CHEMRAWN XV. The meeting, which took place at Maison de la Chimie in Paris last month, was opened by Pierre Potier, president of the Maison de la Chimie Foundation and a member of the French Academy of Sciences. It was held under the auspices of IUPAC; the United Nations Educational, Scientific & Cultural Organization; and the Organization for Economic Cooperation & Development.

The major objective of CHEMRAWN XV was to discuss how chemistry and chemical engineering could help tackle problems relating to the distribution of water, its purification and analysis, waste treatment, and water pollution. A second objective was to provide leaders and decisionmakers in governments, industries, universities, and other concerned organizations with proposals and recommendations on how chemistry can help solve water-related problems.

"The total global supply of water is astronomical," Sydnes noted. "But from the consumer's point of view, it is a pity that more than 97% of this is found in the oceans and can, therefore, not be directly used for drinking. Of the remaining amount, approximately one-eighth is suitable for drinking.

"Unlike other natural resources, such as coal and oil, water is infinitely renewable," he continued. "But in spite of efficient natural recycling, we are facing a global water problem, mainly because the world's population has been growing at an exponential rate for decades. In 1920, there were 1 billion people; in 1960, some 3 billion; and today, there are over 6 billion of us. As a result, the average amount of drinking water available per person has been and is still decreasing."

According to the World Health Organization (WHO), about 2.4 billion people do not have access to basic sanitation facilities, and more than 1 billion people do not have access to safe drinking water. The organization points out that 86% of all urban wastewater in Latin America and the Caribbean, and 65% of all wastewater in Asia, is discharged, untreated, into rivers, lakes, and oceans. In India, for example, 1.1 million L of raw sewage is dumped into the Ganges River every minute. This fact is startling, WHO observes, considering that 1 g of feces in untreated water may contain 10 million viruses, 1 million bacteria, 1,000 parasite cysts, and 100 worm eggs.

UNCLEAN WATER, WHO notes, causes diarrhea, which kills about 1.8 million people worldwide each year, 1.6 million of whom are children under the age of five. And every year, diarrhea strikes about 4 billion people, causing about 4.5% of the global burden of disease, according to Alan Smith, former director of research at the British specialties firm Laporte (now part of Germany's Degussa) and chair of the CHEMRAWN XV Future Actions Committee. Unclean water also causes cholera, dysentery, guinea worm infection, typhoid, intestinal worm infection, and trachoma.

WHO statistics relating to water supplies are alarming, Smith observed. "One-sixth of humanity currently lacks access to any form of improved water supply within 1 km of their homes." An improved drinking water source, according to WHO, is any type of water supply facility--ranging from a protected well to indoor-piped water--that is likely to provide sufficient quantities of safe water to a community or individual.

The United Nations' Millennium Development Goal No. 7 sets a target of halving the proportion of people without access to an improved source of drinking water by 2015. The goal was agreed to at the UN Millennium Summit in New York City in September 2000 as part of its Millennium Declaration. The target also has been adopted by the World Summit on Sustainable Development, organized by the UN Commission on Sustainable Development and held in 2002 in Johannesburg, South Africa. Achieving this goal "would require at least 125,000 unserved people to be connected to safe water supplies each day before 2015," Smith remarked.

Municipal and industrial demands for water, and its quality, vary from country to country, he pointed out. The electronics industry, for example, requires ultrapure water with only a few parts per trillion impurities for computer chip manufacture. Meanwhile, people in poor countries drink untreated water from sources also used for bathing and the care of their animals, he observed.

Chemistry lies at the heart of water-quality issues, both positively and negatively, observed Dennis L. Hjeresen, manager of the pollution prevention and sustainability program at Los Alamos National Laboratory and former director of the American Chemical Society's Green Chemistry Institute.

On the negative side, water pollution from industrial, agricultural, and other land-based sources is one of the most pressing environmental issues facing the world today, Hjeresen said. One source of water pollution is the chlorine used in both water treatment and pulp and paper bleaching, metal processing, pharmaceutical manufacturing, textile dyeing and cleaning, corrosion control, and processes such as photography. Persistent, bioaccumulating compounds used in agricultural chemistry cause a significant biological impact. And nitrate residues from agricultural and other sources accelerate eutrophication, the nutrient enrichment of bodies of water that eventually leads to oxygen depletion.

On the positive side, green chemistry can provide the tools to protect water quality in the face of increasing global pressures on water quantity, Hjeresen pointed out. In combining environmental improvement, economic performance, and social responsibility in addressing global problems, green chemistry focuses on improving industrial processes so that they preserve water quality, he explained. "The use of green chemistry to reduce water contamination at the source has proven more cost-effective than either abatement or remediation approaches."

Chemistry also has a key role in distributing, storing, and protecting water, according to Jean-Bernard Lartigue, president of petrochemicals at Atofina, the chemical arm of the French oil group Total. He emphasized the key infrastructural role that plastics play in water distribution and use.

Plastics are cost-effective, durable, flexible, and easy to transport and assemble, he said. Applications include pipes for water distribution, water sanitation, and crop irrigation; water storage containers; and sheeting to protect water from pollution and evaporation. Polyethylene is the material of choice for drinking water receptacles, whereas polyvinyl chloride is preferred for infrastructure applications.

"Long lengths of plastic pipes can be readily produced in one go," he said. "They exhibit longevity of service, do not corrode or leak even under high pressure and high stress, and are safe and environmentally friendly."

CHEMRAWN XV highlighted several other areas where developments in chemistry and chemical technology could help improve water supply and quality.

SEPARATION SCIENCE is an important area where chemists and chemical engineers have a key role to play; for example, in developing better water treatment chemicals--coagulants, flocculants, and dispersants--to enable reuse of wastewaters, Smith noted. New membranes for separation and cheaper desalination processes can also help to improve the supply and quality of water, he added. "The emphasis nowadays is that all new water treatment chemicals should be biodegradable and should not add to the environmental burden," he said. "Twenty years ago, a new treatment chemical was judged simply on performance, but now, in addition to performance, toxicity, environmental impact, and water conservation are also crucial. Focus clearly needs to be placed on companies to use less water, and they should also be encouraged to recycle wastewater."

Industrial water management, which relies heavily on separation science, is one of the key elements of a sustainable water supply, remarked Manian Ramesh, vice president for research and development at Nalco Chemical Co., a company based in Naperville, Ill., that provides water treatment programs and services.

A sustainable water supply requires various components, including conservation, water reclamation, waste minimization, recycling, evaporation control, and desalination, he said. "The main challenges for water resource management in industry are the precise control of corrosion, scale, and microbial fouling. However, residual water management chemicals, excess biocides, and organic and other materials found in water are barriers to water recycling."

Ramesh noted that polymers are used extensively as flocculants, coagulants, and dispersants for treating water in the papermaking, petroleum refining, oil production, mining, steel production, and automotive industries. Coagulation and flocculation, he explained, are used to separate suspended solids from water whenever their natural settling rates are too slow to provide effective clarification.

Many conventional polymers used in water treatment require so-called carrier hydrocarbon-based oils as solvents and surfactants, Ramesh pointed out. "Every year, approximately 100 million lb of carrier hydrocarbon solvent and over 5 million lb of surfactants are released into the environment," he said.

IN ANOTHER EXAMPLE of the importance of separation science in water treatment, Satinder Ahuja, president of Ahuja Consulting, Calabash, N.C., outlined techniques for removing arsenic from water. The methods include adsorption, membrane separation, ion exchange, chemical precipitation, and coagulation. Naturally occurring arsenic in groundwater contaminates drinking water in Bangladesh and also endangers water supplies in Argentina, Chile, France, India, the U.S., and other countries. "In Bangladesh, it is seriously affecting the health of more than 60 million people, and for many, it ultimately leads to a slow and painful death from a variety of cancers," Ahuja explained at a CHEMRAWN XV workshop. "Out of 64 districts in Bangladesh, 61 are affected by the problem. In these districts, arsenic concentrations range from 10 ppb to 14,000 ppb, whereas the proposed safe level is 10 ppb."

Last year, Ahuja wrote a letter to C&EN inviting chemists and chemical engineers to help solve the problem (C&EN, June 9, 2003, page 4). "The appeal brought a large number of responses," Ahuja told workshop participants.

In a related development, Ahuja and John M. Malin, senior adviser for European and Middle Eastern Affairs at ACS, traveled to Bangladesh last April to meet with authorities at Dhaka University and officials of the Bangladesh Chemical Society to organize a regional workshop on the problem of arsenic contamination. The aim of the workshop, which is planned for later this year or next year, is to enable scientists from various disciplines in Bangladesh to meet scientists from other countries to address the arsenic problem and evaluate how best to involve local government agencies to assist in implementing the proposed solutions. IUPAC and the ACS Office of International Activities are supporting the project.

At the CHEMRAWN XV workshop, Ahuja noted that the Bangladesh government is approaching the problem of arsenic contamination by initially targeting single-family units. "To this end, the government temporarily approved, on Feb. 25 this year, four commercially useful technologies that small family units can use for removing arsenic from contaminated water," he said. "The four technologies rely on activated alumina, ion exchange with cerium, synthetic iron oxide, and a composite iron matrix. The iron matrix technology is the only one based on Bangladesh resources and is also the most economical."

Disinfection is another area discussed at the Paris meeting where the chemical sciences play a critical role in improving the quality of water. "Disinfection products have made a fantastic contribution to public health," observed Yves Levi, professor of public health and environment at the University of Paris-South.

Chlorine-based compounds in particular remain the materials that have brought some of the largest sanitary benefits to humanity, Levi said. Thousands of lives would be saved every day if each community had access to a bleach supply. However, because of the reactivity of chlorine, it generates unwanted by-products by its interactions with dissolved organic matter. The world still seeks a compound with the same disinfecting efficiency as chlorine at the same price and without any by-product.

Because of the pros and cons of using chlorine derivatives as disinfectants, Levi noted, they are used to different extents from one continent to another. For example, monochloramine is widely used in the U.S., whereas it is not used or is forbidden in some European countries. The opposite can be said for chlorine dioxide.

The use of chlorine for domestic water treatment has unquestionably been effective as a mainstay in reducing waterborne diseases worldwide, Hjeresen concurred. "However, chlorine from manufacturing almost inevitably makes its way to aquatic ecosystems and impacts organisms that are integral to food chains," he said. "Once present in the environment, chlorine compounds interact with other compounds, leading to the formation of carcinogenic chloramines, which bioaccumulate within the food chain." Oxidation technologies, based on the catalytic activation of hydrogen peroxide, for example, provide effective yet green alternatives to the use of chlorine for water disinfection, he suggested.

DISINFECTION of drinking water, especially when coupled with improved sanitation and hygiene practices, is one of the world's greatest public health opportunities, according to Ellen M. Meyer, a senior associate development chemist at Arch Chemicals, Charleston, Tenn. At one of the CHEMRAWN XV workshops, Meyer presented case studies on the use of low-cost, low-technology water treatment systems for providing safe drinking water in impoverished regions of Malawi, Guatemala, and Honduras. The methods rely on the use of bleach solution prepared locally from calcium hypochlorite granules or tablets produced by Arch. In Honduras, where 54% of the population lives in rural areas, the need for water treatment "is particularly acute," Meyer said. "Between 1990 and 1995, diarrheal diseases were the cause of 55% of all deaths among young people in Honduras. By comparison, the estimated mortality rate in the same period in countries with more advanced water treatment was much lower, with Puerto Rico at 0% and Chile at less than 3%." In a project cosponsored by Johns Hopkins School of Public Health, Arch has conducted field research on the use of calcium hypochlorite feeders in the water distribution system that the Honduran government has installed in many villages.

Called Sanna, the locally produced and inexpensive system is composed of a small dilution tank that drips into the community water storage tank. Water flows into and out of both tanks continuously. Granular calcium hypochlorite is added to the dilution tank through a feeder typically once a week.

The system suffers from the disadvantage that the chlorine dosage varies significantly. In addition, the calcium hypochlorite slurry is not stirred. As a result, the granules settle at the bottom of the dilution tank and block the drainage tube. The Johns Hopkins team is currently evaluating an alternative feeder that uses calcium hypochlorite tablets. The feeder allows the calcium hypochlorite to dissolve more slowly and provides a more consistent chlorine dosage.

CHEMRAWN XV also highlighted the role of analytical sciences for maintaining and improving water quality.

"All improvements in water treatment processes and quality management come from analytical evolutions," Levi observed. Improvements in sensors; microbiological analysis, including measurement of microbial viability; and tools for predicting global biological effects are still in big demand, he said. The coupling of chromatography with mass spectrometry has advanced considerably in recent years, he added. However, there is still a need to develop analytical tools that can be employed closer to the sampling point.

Philippe Garrigues, a professor of environmental and toxicological chemistry at the University of Bordeaux, France, remarked that the family of organic contaminants "is becoming larger and larger in the aquatic environment, and this is a big challenge for the analytical environmental chemist."

Sensitive analytical techniques such as gas or liquid chromatography coupled to mass spectrometry enable determination of very low concentrations of numerous organic compounds suspected of being detrimental to human health, such as plasticizers, detergents, surfactants, human and veterinary drugs, soaps, musks, natural and synthetic estrogens, flame retardants, and pesticides. These compounds are suspected of various adverse effects, including carcinogenicity, mutagenicity, endocrine disruption, neurotoxicity, and immunosuppression, he said.

An emerging issue in water quality is the occurrence of trace pharmaceuticals in wastewater and their behavior during wastewater treatment, according to Damia Barcelo, a professor of environmental chemistry at Barcelona University, Spain. Although these compounds can be degraded in the environment, they could act as if they were persistent simply because they are continually introduced into water systems through effluents from sewage treatment plants. Modern mass spectrometric techniques, he pointed out, have substantially increased the selectivity and sensitivity of the determination of pharmaceutical compounds in wastewater samples. Detection limits range from 10 ng per L to 10 µg per L.

Using liquid chromatography coupled to electrospray tandem mass spectrometery, Barcelo's group has determined concentrations of beta-blockers, lipid-regulating agents, and anti-inflammatory drugs in local wastewater samples. They find concentrations ranging from 26 ng per L to 3.6 µg per L, indicating the low efficiency of conventional sewage treatment plants in degrading these compounds, Barcelo said. "Consequently, these compounds can easily enter the aquatic environment via sewage effluents and therefore pose a risk to the production of drinking water," he reported. However, recent experiments with a membrane bioreactor as an additional treatment step suggest that some of these drugs can be efficiently removed, he added.

Marina Coquery, director of research at the Agricultural & Environmental Engineering Research Institute in Lyon, France, spoke about the analytical challenges for monitoring water quality in relation to the European Water Framework Directive (WFD). This directive is probably the most significant legislative instrument to be introduced in recent years, she said. "The overriding objective of the policy is the achievement of 'good status' for all water bodies," meaning that they comply with all quality standards.

WFD was established by the European Parliament and Council on Oct. 23, 2000, as a framework for action for the European Community in the field of water policy. The key goals are the general protection of the aquatic ecology in Europe and the protection of specific unique and valuable habitats, drinking water resources, and bathing water. The framework sets out clear deadlines for implementing key milestones. It includes establishment of a monitoring network by 2006 and achievement of the environmental objectives by 2015.

Meanwhile, in January 2001, the European Commission adopted a proposal establishing a list of 32 priority hazardous substances and groups of substances of major concern in European waters to be monitored under WFD. The list includes volatile compounds such as benzene and chlorobenzenes; biocides; lead, mercury, cadmium, and nickel; polyaromatic hydrocarbons; and polybrominated diphenyl ethers (PBDEs).

IMPLEMENTATION of WFD should intensify monitoring of aquatic ecosystems and improve control of contaminants, Coquery said. Good chemical status is achieved when concentrations of priority pollutants are below the environmental quality standards that will be specified in a supplementary directive. To achieve good status for water bodies, member states will have to implement river basin management plans, including water-monitoring programs, and take measures when results do not comply with the standards, Coquery explained. She noted, however, that although European harmonized methods for sampling and analysis are already available for a large number of the priority substances, some of the methods would have to be revised to meet WFD requirements. Water analysis poses many challenges, Coquery pointed out. Better methods than already exist will be needed for some priority substances, such as cadmium, chlorpyrifos, and tributyl compounds in water. For some others, such as alkylphenols, PBDEs, C₁₀–C₁₃ chloroalkanes, and organotin compounds, routine methods have yet to be developed. Some standard methods are not applicable to specific matrices--for example, the determination of metals in transitional and coastal waters. On the other hand, practical standard methods do not exist for suspended matter, sediments, and biota samples.

Furthermore, four priority substances, namely nonylphenols, octylphenols, PBDEs, and C₁₀–C₁₃ chloroalkanes, "comprise rather poorly defined groups of chemicals consisting of a large number of congeners and isomers," Coquery explained. For this reason, monitoring data that are available for these groups often relate to specific individual compounds or have been obtained by quantitative methods that are not comparable.

CHEMRAWN XV was a considerable success, said William F. Carroll Jr., vice president of chlorovinyl issues at Occidental Chemical Corp., Dallas; president-elect of ACS; and chair of the CHEMRAWN XV Scientific Committee. "The meeting attracted many leaders from the chemical and water industries," he pointed out. "It not only emphasized the differences in world needs and desires for water but also showed how chemists and chemical engineers can provide solutions to the problems of supplying water for world needs.

"Some humans have only water that is dangerously contaminated," he said, while "others worry about parts per trillion in basically safe water that could be better." Appropriate technology, whether for mass treatment or point-of-use application, will improve things for all. The types of technology will undoubtedly be different, but each one must be sustainable economically, he added.

Carroll was one of the members of the CHEMRAWN XV Future Actions Committee that met several times during the Paris meeting. One of its jobs is to produce a set of perspectives and recommendations. "The first action of the Future Actions Committee for the conference will be to encourage smaller conferences to work on specific problems in certain countries," he said.

"In the end, the challenge is water for all," Carroll concluded. "That challenge is economic, technological, and rooted in policy. We have a long way to go."