Contamination: Different Types and MTBE

Types

Water can become contaminated in many ways. The different forms of contamination come from different sources and are dealt with in different ways.

The two main forms:

1. bacterial
2. chemical

1. Bacterial contamination is usually measured by the fecal coliform levels in the water. Fecal coliform is an indicator organism; it is easily measured and can signal the presence of other harmful bacteria in water. This sort of bacterial contamination can occur as a result of improper water treatment (for example, not chlorinating water from a wastewater treatment plant properly), as a result of rotten or corroded piping allowing bacterial growth in pipes, or as a result of poor water storage. There are many examples of large-scale bacterial water contaminations across the United States, though this sort of contamination also happens on smaller scales, in small water supplies and private wells.

Often, bacterial contaminations can be dealt with either by chlorinating or increasing the amount of chlorine added to water, or by boiling water before use to kill the bacteria. While chlorination is a task that must be done at the level of the water supplier, individual water users or homeowners can boil their water before use to make it safe in this type of contamination. Bacterial contaminations usually make water unsafe for drinking, or cooking where the water is not boiled, and do not usually affect water use in terms of bathing, washing clothes or dishes, or recreational water use.

2. Chemical contamination is measured by a test specific to a particular chemical. Water suppliers are required to test periodically for the presence of certain chemicals in water supplies. Most chemicals can only be detected by this specific testing; there is no test for general “chemical contamination,” and there are many different chemicals that could contaminate water supplies. MTBE, which this work focuses on, is a specific chemical that has contaminated many water supplies. Chemicals can enter water from either point sources (such as a specific leak from a pipe or a dumping site) or from non-point sources (such as oil or other gasoline products from large-scale runoff from a highway or parking lot.) Often, chemical contamination occurs when chemicals in the ground from these sources leach into groundwater. This has happened on a large scale to water suppliers as wells as to individual private wells.

Chemical contamination events are often more difficult to respond to than bacterial contaminations. Most chemicals cannot be boiled away, and must be removed through technical processes such as adding other substances to render chemicals harmless or through filtering water. These technical processes can be time-consuming and expensive.

Bacterial

• the crypto-sporidium parasite contaminated public water supply in Milwaukee, WI in 1993, causing over 400,000 people to become ill
• bacteria entering aging pipes of the Pawtucket, RI public water system in August 1992 forced over 100,000 people to boil their water for weeks

Chemical

• TCE, a chemical solvent, was discovered in the ground-water of Woburn, MA in 1979; this event sparked the legal proceedings chronicled in the book and movie "A Civil Action" (24)
• dioxin, a man-made, highly toxic waste chemical, was dumped in the ground in Love Canal, an area of Niagra, NY, leading to the eventual evacuation of the area