The Dan Region Wastewater Treatment Plant is among 30 projects from around the world chosen by the United Nations, to demonstrate the ability of local authorities to deal with environmental problems.

The plant, known to Israelis as Shafdan, was included on the list thanks to its unique method of using the natural filtration qualities of sand in order to improve the quality of sewage. After wastewater is purified in an ordinary facility, it is recharged into the ground, where it undergoes an additional, natural filtration in the sands of Rishon Letzion and Yavne. This improves the quality of the water such that it can ultimately be used safely for all forms of irrigation.

The list of projects was published in a special report of the UN Environment Programme and ICLEI, an international association of local governments that have made a commitment to sustainable development.

The report, which deals with the environmental challenges facing cities, was published last week, ahead of the UN Conference on Sustainable Development that was held in Rio de Janeiro.

Urban areas comprise only 1-2 percent of the area of the earth's surface, but they cause the emission of almost 80 percent of greenhouse gases. Today about half of the world's population lives in urban areas, and the forecast is that this figure will increase to over 60 percent within a decade.

According to the authors of the UN report, local authorities have the ability to get organized and to deal with a variety of environmental problems without being dependent on federal assistance. The 30 examples they provide are from from all over the world, including developing and poor countries.

The Shafdan plant that was named on the list belongs to the local authorities in the Dan region, but Mekorot, the national water company, is responsible for administering and carrying out the purification process.

Recently the company began to develop even more advanced methods of purifying the sewage before recharging it into the sand. This is necessary because despite the benefits of the current purification process, it was discovered that when the wastewater is recharged into the ground after undergoing only primary purification, it damages the soil that it reaches before it hits the sand.

As a result of that damage, experts have been forced to seek new areas where they can purify the wastewater, which are not easy to find in such a densely populated area.

The new method is designed to enable more efficient use of areas where the purified sewage is already being recharged into the soil. Today Mekorot pumps 130 million cubic meters of purified sewage water into the area of the sands. The water is almost equal in quality to drinking water, and is used for irrigation in the Negev.

The company points out that the new method of purification and filtration will also make it possible to remove polluters such as remnants of medicines, that until now were not removed in the purification process.

Among other notable projects in the report were: Water Smart Parks in the city of Stirling, Australia, where park planners used advanced irrigation methods to reduce water consumption by more 80 percent.

In Pangkal Pinang, Indonesia, the municipality and a private firm created a cooperative venture that turned an area that had been used as a zinc mine into a botanical garden.

An interesting innovation in the city of Portland, Oregon set an "urban growth boundary" beyond which building is forbidden. In order to meet this restriction the municipality developed more efficient methods for utilizing existing construction areas.