Let It Rain!

Two hundred million cubic meters of rainwater go to waste in Israel every year. They flow through the city streets, pick up a variety of toxic substances and continue to the coast, where they pollute the beaches and the sea and harm marine life.

The innovative bio-filter technology developed in Australia and promoted in Israel by KKL-JNF is designed to allow this rainwater to be utilized in order to avoid pollution and maintain sustainable groundwater levels. It transforms a nuisance into a valuable resource.

Two new bio-filter facilities established by KKL-JNF in Ramla and Bat Yam demonstrated their efficiency during Israel’s recent rainstorms. They are designed to collect surface runoff water, purify it via environmentally friendly physical and biological methods, and then channel it into the aquifers as clean water. These new bio-filters join an older one that has been operating successfully in Kfar Sava for a number of years.

The monitoring systems installed in the three bio-filters show that the technology is operating extremely well: the polluted runoff water that enters the facility leaves it purified almost to the point of being fit for drinking. This treated water can then be injected into the groundwater or else used to irrigate gardens and crops of all types. The data show that 99.99% of the pollutants are removed from the water by the bio-filter treatment.

The bio-filter installation contains a number of layers of sand and vegetation. The top layer is covered with special plants that help to purify the water. The lower layers, which are not aerated, provide a habitat for a colony of bacteria that flourish in an oxygen-poor environment and have a large appetite for pollutants, including heavy metals, organic matter and oils. These bacteria encourage processes that purify the water.

Each bio-filter has a capacity of around 100 cubic meters. During the last rainfall episode, which continued for several days, each of the facilities filled up and emptied three times, purifying a total of around 300 cubic meters of water. Over the course of a single year, this could amount to thousands of cubic meters, depending on the quantity of precipitation.

In the dry season, when there is no rain, water can be pumped from contaminated wells, purified, and, once clean, either restored to the same well or added to the groundwater. This process has been described as dialysis of the aquifer.

There are a few fringe benefits provided by the bio-filter project.

Bio-filters significantly reduce flooding during heavy rainfalls and relieve the strain on the municipal drainage system.

It also creates attractive green neighborhood gardens that the local people can enjoy. Visitors to the bio-filter who expect to be confronted with a dismal-looking purification plant are in for a pleasant surprise, as the facility consists of attractive plant-filled pools surrounded by footpaths and bicycle trails.

This innovative project is defined as an experimental pilot, and researchers are still investigating various aspects of its functioning: bio-filters of different sizes, different types of vegetation and the quality of the water after purification. This work is being carried out under the auspices of a center for research into water-sensitive cities in Israel, which was established jointly by KKL-JNF Israel, JNF Australia and four academic institutions: Technion (Haifa), the Hebrew University of Jerusalem, Ben Gurion University of the Negev (Beersheba) and Monash University of Melbourne, Australia.

Source: Jewish National Fund