(photo credit: Gil Zohar)
‘Phew, stinky-pooh,” said a recent young visitor to the Shafdan sewage treatment center, located in the sand dunes south of Bat Yam and north of Palmahim.
But the truth is more prosaic and less smelly, explains Nelly Icekson-Tal, the manager of the state-of-the art Dan Region Wastewater Treatment and Reclamation Project.
“Most of the 100 or so complaints lodged annually by Rishon Lezion residents about the foul smell in fact originate with gardeners who have put down odoriferous fertilizer – which neighbors mistake for Shafdan,” she explains. The treatment plant in fact rarely smells like the fecal matter it treats.
Owned and operated by the Dan Region Associations of Cities, Shafdan today collects and treats the raw sewage from 2.5 million people in 23 municipalities in central Israel. In cooperation with the Mekorot national water company, Shafdan sends the purified wastewater south to irrigate the Negev.
Today one of the largest and most advanced treatment plants of its kind in the world, the seaside facility was established in 1955 by Tel Aviv and six neighboring cities. Back then the sewage was simply poured into reeking oxidation ponds which sprawled over 200 dunams. In a low-tech solution, bacteria aided by photosynthesis and evaporation would slowly reduce the sewage bio-mass. The ponds not only smelled putrid but were a mosquito-breeding hazard and ecological nightmare.
In 2000 the oxidation ponds were finally closed and replaced by a hi-tech process. Half of the vacated area was turned over to Rishon Lezion; the other half serves as overflow pools for especially rainy days. At present Shafdan treats 350,000 cubic meters of wastewater per day, down 20,000 m3 from a year ago thanks to public water saving initiatives.
That wastewater is brought to Shafdan by a skein of pipes across the Dan region. The first phase of the mechanical-biological sludge treatment system is to pour the water through a screening system that filters out the grease, grit and scum. Next it is run through a sand and clay separator and the effluent placed in aeration tanks, where it simultaneously undergoes a biological denitrification and nitrification process.
Powered by electricity rather than the sun, the aerator today finishes in 15 hours what used to take two to three months of natural oxidation.
As a fascinating demonstration in the visitors’ center shows, the ever-clearer mixed liquor – now cleaned of phosphorus and nitrogen – is then sent to clarifying ponds, where huge screw pumps make another separation for sludge recovery.
Prior to 1988 – when Israel became a signatory to the Barcelona Convention for the Protection of the Mediterranean Sea Against Pollution (known since 1995 as the Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean) – the sludge from Shafdan was routinely dumped in the sea. In fact, the Environment Ministry canceled Shafdan’s marine-discharge permit only in 2004, following a protest campaign by Greenpeace and Adam, Teva v’Din (Israel Union for Environmental Defense).
Today a new sludge extraction system of centrifuges is being tested whereby all the pathogens and toxic heavy metals like mercury and zinc will be removed, allowing the treated, odorless organic material to be used as fertilizer rather than being sent to landfills as is currently being done. The new system is slated to begin operating in 2012.
With the sludge removed, the reclaimed water is then passed through 30
meters of sand before ultimately percolating down to the coastal
aquifer. Two hundred observation wells monitor that process to ensure
no pollution is inadvertently allowed to contaminate the aquifer. After
400 days of this final filtering, the treated water is pumped up and
sent south via the National Water Carrier to irrigate the Negev. The
recycled water has its own pipe network, colored purple for easy
identification. Though potable, treated sewage water is not used for
drinking in Israel.
Highly mechanized, Shafdan operates with only 45 staff – including
those working in its PR department. Tours, which last for one and a
half hours, must be booked in advance.
For more info call (03) 963 5111, or see http://www.mekorot.co.il/Eng/Mekorot/VisitorsCenters/Pages/ShafdanCenter.aspx