New Bio-filters Purify Surface Runoff Water for Reuse

Wednesday, March 04, 2015 11:48 AM

“When rainwater flows through the city streets it picks up a variety of toxic substances. This water goes to waste and actually causes damage...This innovative initiative allows us to transform 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 enable surface runoff water to be collected, purified via environmentally friendly physical and biological methods, and then channeled 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.

Biofilter along a street promenade in Bat Yam under construction. Water is harvested and purified in the vegetation pit (in the far background). Photo: Yoav Devir

Two hundred million cubic meters of rainwater go to waste in Israel every year. They are washed down to the coast, where they pollute the beaches, the sea and marine life. The innovative bio-filter project is designed to allow this rainwater to be utilized in order to avoid pollution and prevent groundwater levels from dropping further. 

Part of the runoff purification process. Photo: Yoav DevirThe technology was developed in Australia, and KKL-JNF promotes its use in Israel with the support of Friends of KKL Mexico and  JNF Australia. The new facilities in Ramla and Bat Yam were installed with the help of Blue Box donors and members of the JNF Australia Gold Patrons Club.

“When rainwater flows through the city streets it picks up a variety of toxic substances,” explained KKL-JNF Central Region Director Haim Messing. “This water goes to waste and actually causes damage by polluting the rivers, the groundwater and the sea. This innovative initiative allows us to transform a nuisance into a valuable resource.”

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.

Polluted rainwater (left), before being purified by the biofilter (right). Photo: Courtesy Dr. Yaron ZingerThe data show that 99.99% of the pollutants are removed from the water by the bio-filter treatment.  Even a non-scientist can tell the difference; a glance at the jars of water collected in Ramla and Bat Yam during the rainstorm a few days ago is enough: the water collected prior to its entering the system was cloudy and yellowish, while the treated water was clean and clear.

Haim Messing explained how the technology works. 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. These bacteria encourage processes that purify the water. 

This integrated system efficiently removes a variety of pollutants, including heavy metal particles, organic matter and oils. The treated water is injected into the groundwater by means of wells dug nearby.

Part of the Bat Yam biofilter. Photo: Yoav DevirEach 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.

But what happens in the summer, when no rain falls? In the dry season 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.

The water and plants in the bio-filter help to reduce temperatures in summer, and in our hot dry country this is a great advantage.

Biofilter in Ramle. Photo: Yoav Devir“Apart from utilizing the rainwater and protecting water sources and beaches from contamination, the bio-filters in Ramla and Bat Yam have another important contribution to make,” said Messing. “In the past, when rainfall was heavy, roads and even apartments in some of the older neighborhoods would become flooded. But during this last episode of rainfall things were much better, because a large proportion of the surface runoff water flowed into the bio-filters and so there was less of a strain on the municipal drainage system.”

The bio-filter in Kfar Sava was installed in close proximity to a new residential neighborhood and formed an integral part of the plan for the area. The projects in Ramla and Bat Yam, however, show that long-established neighborhoods, too, can benefit greatly from this initiative.

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 is a fringe benefit of the bio-filter project: it creates attractive green neighborhood gardens that the local people can enjoy,” added Messing.

Ramle biofilter ingegrated as part of the street. Photo: Yoav DevirAnd, indeed, a visit to the installations reveals pleasant green oases within the city and along its main roads. In Bat Yam an attractive promenade built along the length of the bio-filter offers a strip of grass between footpaths and cycle trails.

The Ramla bio-filter is situated right at the entrance to the city, adjacent to the intercity highway. The promenade, the seats and the well cared for garden around the facility all help to beautify the approach to the city.

The new bio-filters were built with the cooperation of the community, and they have been warmly received by local residents, who were quick to realize the many advantages the project would bring. “We’re already being approached by people from other neighborhoods who want to have a bio-filter installed in their part of the city, too,” said Messing.

Donor recognition sign honoring the efforts of the JNF Australia Blue Box Donors and Gold Patrons. Photo: Yoav DevirThis 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 – all these are being monitored and examined. 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: The Technion (Haifa) The Hebrew University of Jerusalem, Ben Gurion University of the Negev (Beersheba) and Monash University of Melbourne, Australia.

Planning for water-sensitive cities is based upon optimum use of limited water resources in a world beset by uncertainty in the wake of climate change and mankind’s changing needs. Water-sensitive cities are characterized by their use of sustainable solutions, appropriate technologies and activities designed to raise public awareness.

The research underway today is expected to continue for a number of years yet, but the initial data collected from the three bio-filters are very encouraging. “The first bio-filters show how the principle works, and we want them to be very much more than just a successful experiment: in the future we would like to see them become the norm throughout Israel,” said Messing. “Many other cities could benefit from similar facilities and help to bring about a significant change in the country’s water economy.”