12,000 m³/d (3.17 MGD)
In the heart of Israel, The Nisgav oxidation pond treated wastewater from various local and regional councils. The pond used surface aerators, was very inefficient and supplied only primary treatment. Not only was the effluent not in line with regulations, but the odor coming from the wastewater was a veritable nuisance to the surrounding communities.
The water flows come from a multitude of sources. The plant is surrounded by many communities and odor control had to be very strict. In addition, the effluent was destined to be used for unlimited irrigation and when rain is abundant, to be discharged into the nearby Timna stream. Discharge into streams calls for the highest standard of effluent under the new “Inbar Committee” regulations.
The answer was a state-of-the-art plant, which includes a combined pre-treatment system with fine filtration and removal of sand, grit and oil; a raw sewage flow equalization pond; a biological treatment system based on conventional activated sludge technology with aerobic, anoxic and anaerobic areas for the biological removal of BOD, nitrates and phosphorous; secondary clarifiers; a tertiary sand filtration system by gravity and contact cell for disinfection with hypochlorite; a sludge treatment system (including thickening, aerobic stabilization and centrifuges); a drain water collection system; an additional reservoir and administrative buildings. Odor control systems were installed both at the pre-treatment stage and at the sludge treatment stage.
The existing pond receives 7,500 m3/d. The modern WwTP was designed to receive 9,000 m3/d at a first stage and 12,000 m3/d at a second stage. Phosphorus removal is obtained via a biological system. However, the addition of alum to remove excess phosphorous was also prepared.