taminant are evaluated based on viability and how solid the information basis is. If the information is based on adult exposure, the results are extrapolated to be protective of everyone, and a benchmark is set on a reference dose or cancer level. The value may be well below detection or treatability, but it will stand as the criterion for the contaminant.
Similarly, under the Safe Drinking Water Act, there is also a maximum contaminant level goal for oral ingestion set with respect to risk and conservativeness. There is no consideration of practicality. The goals are essentially zero risk, but zero risk is not achievable. There must be a consideration of what passes or what can be achieved.
From a risk assessment standpoint, this causes problems because the value cannot be detected epidemiologically. Some people have said that people are not getting sick from arsenic; therefore, there should not be a regulation, or the regulation should be set at a level where people do get sick. Epidemiology does not have that resolution. The bottom line is that these goals are below what can be detected in the real world.
As a result, it is not possible to backtrack to determine success. It is hoped that the risk assessments are legitimate.
Congress essentially said in the 1986 Safe Drinking Water Act Amendment that there would have to be more regulations. The EPA then had the task of trying to find additional chemicals to regulate that it had not already given Congress.
Now it is necessary to take a look from a systems standpoint. Hazard assessment via a critical control point process, such as that used in the food industry, could also be applied to drinking water. In that case, a system-wide examination from source to tap is done in order to identify problem areas and move forward.
There is a need for straightforward and reliable analytical methods that are relatively cheap. For many of the small utilities, the cost of monitoring is the major cost, particularly with small groundwater systems for which they really do not have surface infrastructure or big treatment plants. They basically have a well, a storage tank, and the lines that go out from them. Methods exist for nearly every contaminant, but sometimes they are expensive. Working toward cheaper methods that serve our purpose is necessary.
Another important need is low-maintenance treatment technologies. It is very hard to find operators that are well trained to run sophisticated treatment hardware. We need stand-alone equipment that will run automatically, a necessity if we are to move forward.
Point-of-use devices and point of entry devices have been suggested as a means to beat the problem of highly treated water being used to water lawns or wash cars while a small percentage is used for drinking. The idea would be good if every homeowner could be trusted to run a device reliably to remove all contaminants on the list, and this is a daunting task.
Contaminants removed from water have to be disposed. Clean Water Act activities focus primarily on contaminant control—point control through National Pollutant Discharge Elimination Systems (NPDES) permits, the permits on discharge from manufacturing or from point sources and nonpoint sources such as agricultural or water runoff. The parameters (e.g., pH, temperature) are very broad and are largely there to protect fish and other aquatic life from degradation.
There are controls on specific pollutants obviously, but in general, there are broad parameters. There is an increasing worry over the persistent organics or chemicals that have been created and are somehow getting into wastewater. There are some worries, but there is no way to know right now if they are dangerous, because too little is known.
With regard to drinking water source and resource issues, neither the Clean Water Act nor the Safe Drinking Water Act deals with resources directly. These acts were written that way specifically; Congress did not want to interfere with state’s rights in water resources. However, they have been used to deal with resources to some degree, and they certainly come to play in desalination, recycling, and reuse.
There are source water protection provisions in the Safe Drinking Water Act and the Clean Water Act that are aimed at prevention and control of contaminant releases. The Safe Drinking Water Act and the earlier versions really dealt with treatment plant operations.
One potential drinking water resource is obtained through desalination of salt water. In desalination, the main issue is brine disposal, particularly in inland areas. Desalination in coastal areas works well because the brines can be disposed by running them back into the ocean and, to a first approximation, they are relatively benign. To a certain extent this also works inland, as in the Los Angeles area where there are brine drains.
On the other hand, in agricultural areas in the Central Valley of Northern California, there are problems from agricultural drainage, which are essentially brines. The political and technical aspects of this prevent sending the brines down through the delta and into the ocean or creating a pipeline from the inland areas out to the ocean. In order to keep the lands in production there have to be better ways to dispose of the brines.