Carbamazepine, a drug used to treat epilepsy, could become an important tool in finding pollutants in sources of drinking water, according to a study conducted by Hebrew University for Israel’s Water Authority. The study examined the contents of effluent that had undergone treatment and the treatment’s effectiveness.

The study, which was carried out by researchers at Hebrew University’s laboratory of environmental chemistry, was headed by Professor Ovadia Lev. Last week, representatives of the Water Authority's water quality department presented its main findings, together with those of other researchers in the field, to Environmental Protection Ministry officials.

The study found that effluent in Israel has hundreds of pollutants of various kinds that include pharmaceuticals, flame retardants, substances used in x-ray diagnoses, industrial substances and a wide variety of pesticides. After purification, the concentration of these substances in the reclaimed water, which is used to water crops, is very low.

But one substance — carbamazepine, which is used to treat epilepsy — withstands the purification process and remains in the reclaimed water. Its absence in tests of drinking water suggests that no effluent has penetrated the water source, making its presence an indication that reclaimed water is leaking into drinking water — a health hazard that could lead to discontinuing the use of the source in question. So far, the salinity of drinking water has been used to detect the presence of effluent, but it was found to be too imprecise.

A test at the Gush Dan Sewage Purification Plant, the largest in Israel, demonstrated the new indicator’s effectiveness. There, the reclaimed water is pumped to the sands of Rishon Lezion and Yavneh and into the ground, where it undergoes natural purification and is later used to irrigate farmland.

Four years ago, maintenance work was done on equipment pumping effluent from the ground, preventing it from spreading into the groundwater used for drinking and irrigation. After that work was done, the Water Authority tested nearby equipment used to pump drinking water and found a significant increase in the concentration of carbamazepine. This was proof that while the equipment was being maintained — and not being used — reclaimed water had penetrated into the drinking water pump.

The Water Authority also used its search for traces of the drug in the springs of the Galilee, a source of drinking water already known to be polluted, looking for signs when they will once again be fit for use.

The effort to detect carbamazepine is part of a larger process of increased water-quality testing in Israel. According to Water Authority data, 194 drinking-water sources were closed over the past decade thanks to improved detection of pollutants. The figure is twice that of the previous decade.

As far as finding traces of drugs and other substances in the reclaimed water, the concentrations are tiny, too small to have an effect on health, according to the Water Authority. But there is not enough information about the cumulative effect (in other words, exposure to several kinds of substances) or the effect of the mixture of several substances.

Now that the drug has been found to be an indicator of water pollution, the Water Authority intends to test regularly for it in drinking water. The test will also be used to detect and prevent the penetration of reclaimed water from the Gush Dan Sewage Purification Plant into nearby groundwater. Despite the danger, the plant’s method of using sand to purify the water is considered successful in comparative tests, where it was found to be more effective than other methods.