Foul Waters

A near by city engineer asked us to look into a mid-summer complaint from a citizen in an older neighborhood about tap water problems. The citizen and neighbors were complaining about a new car wash that they named as a source of contamination of their tap water. Since the new car wash had opened in the spring the residents were experiencing "noxious odors" "vile tastes" and a host of other complaints ranging from "skin rashes" to "shortness of breath" from the "chemicals" in their tap waters. It was generally agreed among the neighborhood that the problems were worst in the mornings or after the water had been static for a while in the pipes. The city had verified the presence of check valves on the tanks and pumping systems of the car wash, which eliminated this installation as a source of contamination.

The problem sounded very similar to that encountered in older homes and rural areas. Piping not flushed periodically with chlorinated waters became homes for colonies of the iron and sulphur reducing bacteria. The colonies obtained the oxygen needed for metabolism by reducing the sulphate in the water to sulphides. Sulphides are the odours of skunks, sewer gases and rotten eggs. Most people can smell sulphides at the low parts per billion range. Sulphides were created in the piped tap water as a result of microbial metabolism. In static water the sulphides accumulated in a localized "plug". When the "plug" of contaminated water in the pipe was discharged the sulphide odors were released and the offensive "rotten egg smells" were noted. The microbe colony however was not able to generate enough contamination to be noticed in the running water.

In most municipalities an attempt is made to adjust the chlorine levels in piped water to provide some residual at the extreme ends of the water distribution system but often this is not always successful and in hot weather the bacteria survive. The expense required to excavate buried services to flush with chlorine, when simply letting the water run cures the problem, is difficult to justify.


Forest For Trees

We received a call from an industry representative who had a problem pertaining to the accumulation of a fine, black, dust in the offices at one of their large city sites. The office staff was unionized and health and safety concerns were being raised because of this unknown black dust. The representative stated that a tire recycling operation and an incinerator were neighbors and suspected sources of the dust. Having done consulting work for their "in house" lab and being familiar with their resources we outlined a series of qualitative tests verbally for them to conduct on the dust to distinguish between possible sources. In this manner they could use their own resources and avoid our consulting fees.

Several weeks later we were informed that the suggested testing had been executed and the identity of the black dust was still unknown although the tire and incineration operations had been eliminated as the source of the problem. A meeting was scheduled and we were delighted to be informed that company technical personnel would be in attendance with the appropriate spending authority to allow us to conduct an identification through chemical analysis.

On the appointed day company representatives arrived bearing suitable samples and purchase order. Discussions began about the proposed course of investigation and the samples were passed around the table. Mid way through the discussions one of our scientists remarked that the samples of the black dust looked, felt and smelled remarkably like the "black" of "newsprint ink". In the absolute silence, which followed the representatives from the paper mill burst out laughing, the office in question was located above one of their used newsprint collection depots in a large city. An examination by microscopy and infra-red spectroscopy quickly and inexpensively confirmed the identity.