Reuse of wastewater is another potential source of drinking water. The current problem with reuse is that there is not much information about the health effects of persistent organics. There are enough persistent organics in the water for some concern, which may or may not be legitimate. It will be some time before there is adequate health information to go forward. Unfortunately, there may well be pressure to regulate before there is a good handle on the associated risks.

In terms of needs, wastewater and reuse treatment technologies are certainly needed to control these persistent organics. The Orange County Water District and others are doing some very interesting work on this. Ideally it would be good to get away from a chemical and biochemical approach to this problem and instead try to remove all organics regardless of their potential for harm.

Another problem with wastewater reuse is contamination by disinfection by-products. Water disinfection technologies are needed to minimize these by-products, especially with the growing concern about nitroso-containing chemicals. The work on membranes is impressive but could improve. The reliability of membranes is great, but lowering the energy costs will make a difference, particularly for applications to smaller systems.

The main issue with drinking water treatment has always been dealing with microbial pathogens in a multiple-barrier approach. The laws from the Safe Drinking Water Act, the Surface Water Treatment Rule and its variations, prescribe a physical removal basis and a disinfection basis. Source water protection now presents an additional barrier, and physical removal has many steps: coagulation, flocculation, precipitation, and filtration.

Waste minimization of sludge is still an issue. Dealing with and minimizing sludge and finding other types of coagulants that do not produce as many tons of sludge would be great. Removal of the problematic chemical contaminants is also important; if they cannot be kept out of the sources, then they must be removed through treatment.

All surface water systems and any groundwater system will have multiple contaminants. Until regulating contaminants one by one stops, utilities are going to have to work with multiple contaminants that may be quite distinct chemically.

The immediate needs for water treatment include improvement in the membrane technology, such as pretreatment, resistance to fouling, durability, ease of use, and breadth of contaminant removal.

There are some oxidized metals and metalloids and other chemicals on the horizon. Of the chemicals dealt with in drinking water on a national basis, from a public health side, arsenic is the biggest issue and is worse than most contaminants except for the microbials and disinfection by-products. Treatment needs lie in the area of “-ate” control: arsenate, chromate, nitrate, perchlorate, phosphate, silicate, and others.

Utilities are looking at their distribution systems, many of which have been in the ground for a hundred years and are finding that the systems are starting to fall apart. The systems have to be replaced at a rate of more than a million dollars per mile. Many larger systems are thousands of miles in length.

Most utilities deal with physical failure on a when-it-happens basis. If a main blows causing a sinkhole in the middle of the street, they go out and fix it. Most utilities have a replacement rate of around 1 percent a year.

Options are needed that would minimize corrosion and damage. Infiltration and intrusion of contaminants, particularly microbials, have to be prevented. In the urban setting, drinking water transmission lines run in the same areas as sewer lines. Sewer lines leak and the area in soil around sewer lines has a lot of contaminants that are not wanted in drinking water. The problem is particularly bad in cities that use wells; as wells are kicked on and off, there are pressure fluxes through the distribution. There can be zones of zero or negative pressure moving through. Siphoning also occurs.

There is a cross-connection from different types of intrusions to worry about. About a third of waterborne disease outbreaks are associated with distribution system failures. There are going to be regulations on distribution system protection in the next four to six years.

There may be ways of lining the distribution system pipes with polymers or membranes that would help harden the system. Methods exist but more are needed. Furthermore, in-place pipeline rehabilitation materials and the methods for putting them in without digging up streets would be beneficial.

Systems must maintain disinfection and the disinfectant residual in distribution because of potential intrusions and to some extent because of the potential for bioterrorism. However, increased disinfection boosts disinfection by-products, but these are currently regulated. Additionally, there is a need to have residual and to control biofilms that can sequester materials.

What are the needs for distribution systems? A broad-spectrum disinfection agent that can persist in the distribution system and does not create problematic by-products is critical. Chlorine works well but its use has downsides. It creates halogenated by-products and a taste that people do not like.

Water systems are incredibly vulnerable to bioterrorism, from both the chemical side and the biological side. It is pretty remarkable that to date there is no evidence of attacks

Front Matter (R1-R12)

Executive Summary (1-4)

Context and Overview 1 Meeting the Global Water Challenge (5-10)

2 Green Chemistry: The Impact on Water Quality and Supplies (11-18)

3 Methylmercury Contamination of Aquatic Ecosystems: A Widespread Problem with Many Challenges for the Chemical Sciences (19-26)

Water Quality and Supply: Analysis and Treatment4 Desalination: Limitations and Challenges (27-39)

5 Organic Contaminants in the Environment: Challenges for the Water/Environmental Engineering Commmunity (40-46)

6 AquasentinelSM: Biosensors for Rapid Monitoring of Primary-Source Drinking Water (47-52)

Business Opportunities and Responsibilities7 Some New Approaches at the Orange County Water District (53-59)

8 A Perspective from a Water Company (60-65)

9 Sustainable Development: Role of Industrial Water Management (66-74)

10 Water Solutions and Strategies in the Chemical Industry (75-80)

11 Classifying Drinking Water Contamination for Regulatory Consideration (81-86)

Appendix A: Workshop Participants (87-88)

Appendix B: Biographical Sketches of Workshop Speakers (89-91)

Appendix C: Origin of and Information on the Chemical Sciences Roundtable (92-92)

Appendix D: For Further Reading (93-94)