Public health officials are becoming concerned about chlorine, a chemi

Public health officials are becoming concerned about chlorine, a chemical that is added to many municipal water supplies to reduce bacterial growth. New evidence shows that the rate of first-trimester miscarriages is increased significantly when pregnant women drink five or more glasses of chlorinated water per day. When the chlorine in the water reacts with plant material acids the chemical trihalomethane is formed. Trihalomethane is believed to be the cause of the miscarriages, and it is also linked to increased cancer risk in animals. Lead, which has been shown to cause brain damage in small children, is another main contaminant of urban water systems, as it seeps from old pipes into the water flowing through them. Many water supplies are also contaminated with toxic bacteria, cysts, or algae. Increasing concerns about the effects of harmful contaminants have caused an increase in the number of alternate methods of water filtration that are available to the general public.

There are six major systems, each with its advantages and considerable drawbacks. Steam distillation, in which water is boiled and the steam is collected and cooled, produces water without contaminants. However, energy must be used to heat the water, the resulting water tastes flat, and some organic compounds may boil with the steam and contaminate the water. Carbon filtration removes chlorine from water and leaves it with a better taste, but it cannot remove minerals or heavy metals. In addition, the filter is no longer effective if it becomes clogged, and the carbon can trap and breed harmful bacteria. The ion exchange method uses charged particles in a filter which are exchanged with charged particles in the water to remove minerals and toxic metals. This method has a corrosive effect on pipes, and it does not remove organic molecules. It also increases the level of sodium, iron, and lead in the water. Ultraviolet light is simple and can kill microorganisms, but it has no effect on chemicals or minerals in the water. Reverse osmosis removes minerals, toxic heavy metals, and bacteria by forcing the water through a semipermeable membrane. This method is extremely slow, wastes large amounts of water, and corrodes the most durable of pipes.

Of the many different types of water filtration systems available, a combination KDF/carbon block system may be the most effective. The KDF system, which stands for kinetic degradation fluxion, forces water through a chamber containing a mixture of copper and zinc. In the chamber, electrochemical reaction that takes place removes
chlorine, chloramine, iron, hydrogen sulfide, and many other harmful substances from the water. The water is then forced through a solid carbon block filter, which removes more impurities, such as bacteria and algae, from the water. Many KDF/carbon block filtration systems also contain a ceramic pre-filter, which removes other bacteria such as Escherichia coli, Streptococcus sp. fecal coliform, as well as cysts such as Cryptosporidium sp. and Giardia sp. As a by-product of filtration, the KDF/carbon block system puts small amounts of copper and zinc into the water that are not harmful to humans.

1. Which of the following best describes the organization of the passage?

A. Several methods are described and ranked in terms of desirability.
B. A general theory is offered and refuted by several counterexamples.
C. A current process is assailed, and several alternatives are presented as possible replacements.
D. An old solution is revived as a possible remedy to a new problem.
E. A paradox is presented, and several examples are used to reconcile it.

2. Each of the following is a disadvantage of the ion exchange method of water filtration EXCEPT:

A. higher sodium levels in the water
B. damaged pipes
C. unaffected contaminants of an organic nature
D. dangerous copper and zinc contamination
E. an increase of lead

3. According to the passage, which of the following can be inferred about the KDF system?

A. It prevents the formation of trihalomethane in the water supply.
B. It would work much better if used in concert with a semipermeable membrane.
C. The electrochemical reaction causes most of the copper and zinc that are originally introduced into the water to dissolve.
D. Without the additional ceramic pre-filter, it is no more effective than the combined effect of ion exchange and ultraviolet light.
E. Its ability to remove iron from water is superior to that of ion exchange.

4. According to the passage, the author’s opinion of the best water filtration system would probably change if which of the following were true?

A. If the KDF system is used indefinitely, the levels of copper and zinc that it introduces into the water supply will eventually become toxic.
B. All new residential dwellings are fitted with pipes made of durable plastic that lead cannot seep through.
C. Ultraviolet light is one-tenth as expensive as each of the other techniques mentioned.
D. Subsequent studies have revealed that there is no relation between trihalomethane and cancer.
E. KDF is available only in urban areas with tax bases that withstand the cost of installing such a system.