A solution to the sludge problem
What is sludge?
Sludge is the solid phase produced during the wastewater treatment process.  Most sludge is the microbiological mass that is created as a result of the decomposition of organic material in wastewater, such that the quantity of dry sludge is dependent on the quantity of sewage that reaches the wastewater treatment facilities and the organic load in the wastewater.  

Sludge removal
The Shafdan system receives approximately 380,000 m³ of wastewater each day that produces about 15,000 m³ of sludge per day at the end of the treatment process (with a concentration of about 1% dry material).  The excess activated sludge (secondary biological sludge only) is currently disposed of at sea using alternating centrifugal pumps through an 11 km long 360 mm diameter pipe, of which 6 km is on land and 5 km is in the sea.  The sea outlet ends at a 38 m deep dispersal installation.   

The marine outlet is currently approved by the authorities as an excess sludge disposal solution, for which a sea sludge discharge permit has been issued, which is renewed periodically by the interministerial committee that grants such permits.  
Surveys have been made consistently during the last 10 years of the marine environment around the excess sludge disposal area and in a neutral area in order to monitor possible impacts on the environment.

These surveys began in 1977 before operation of the mechanical-biological facility and have continued uninterrupted since then.
The conclusion is that, other then a change in bio-diversity in the outlet environment, there is no substantial impact on the internal and external marine food chain.  

The disposal site environment is currently being tested methodically by the Israel Oceanographic and Limnological Research Institute.  The findings from these tests indicate a site that is not suffering from extensive pollutant impacts.
Since 1998, the marine outlet has also been serving as a disposal point for brines and for TBD (פאק"א ) industrial wastewater in the framework of an agreement between Igudan, the Manufacturers’ Association of Israel and the Ministry of Environmental Protection.  

According to Itai Pinkas, Chairman of Igudan Environmental Infrastructure: “After interim findings affirmed that there is a reduction of tens of percent in metal contaminants in the sludge, the Association will act to reach a permanent arrangement in legislation that will obligate the industrial plants to separate heavy metals and toxic waste from the general wastewater collection system.  We will act with all of our power to stop this ecological disaster that has continued for many decades.”
Through this pilot testing, the Association hopes to avoid instances that now occur whereby factories in the Dan Region discharge sewage containing heavy metals into the wastewater collection system and, in the end, to the Shafdan plant.

Waste treatment
Since the Shafdan treatment processes do not enable the removal of heavy metals from wastewater, these heavy metals find their way into the sludge and with it into the sea.  In the framework of a pilot test at industrial plants in the Dan Region, special tanks are stationed into which the wastewater, liquid wastes, solid sludge and single-use resins are collected that contain heavy metals.  After the tanks become full, the tanks are conveyed to the toxic waste disposal site at Ramat Hovav, where they are properly treated.  

Excess sludge at Shafdan
Approximately 14,000 m³ [of sludge] are discharged each day through an 11 km long carrier pipe.  
The association has chosen the agricultural option as the land-based solution for Shafdan sludge. This is being done in coordination with governmental ministries, the Municipality of Rishon Lezion and environmental organizations, led by the Israel Union for Environmental Defense.  
After investigating a range of solutions for land-based handling of Shafdan sludge, the Association has decided to also promote the agricultural solution for handling the sludge, which means processing of the sludge and spreading it on farmlands as a fertilizer, since it provides a suitable environmental, social and economic return.  

The agricultural alternative is based on the construction of eight anaerobic digesters and two pasteurization tanks that allow treatment of the sludge to a level defined in the regulations as Type A sludge.

 This allows the treated sludge to be spread without additional treatment in farmlands in the center and south of Israel.  Over the last few years, Igudan has already prepared the planning infrastructure for developing the digesters as a secondary backup alternative in the framework of its undertakings to the committee that grants discharge permits, when it becomes the preferred option.  Conveyance of the sludge and its spreading over farmlands will be performed by an outside concessionaire who will be selected in a public tender to be published by the Association.  The Association is acting to establish an anaerobic and pasteurization digestion system up to the primary settlement basins by April 2008, while the date for the completion of construction and start of operations of the system has been set for the end of 2011.  With final implementation of the land-based solution for the sludge, the Association will become a body that recycles 100% of its wastewater in a manner by which it will be a model for other treatment facilities in Israel while ensuring a clean marine environment and better environment for the residents of the Dan Region and all of the state’s citizens.