ISKI Expands Advanced Treatment for the Melen System: 2.4 Billion Lira Investment
A Drinking Water Security Investment for the Megacity
The Istanbul Water and Sewerage Authority (ISKI) has announced an expansion of advanced treatment investments to protect and improve the quality of the Melen water supply system on the Duzce-Sakarya line. Approved at the general assembly, the package allocates 2.4 billion lira to micropollutant removal and reuse capacity expansion.
Three Main Axes of the Investment
The plan is built around three main axes:
- Integration of a fourth stage (micropollutant removal) at three wastewater treatment plants in the Melen basin
- Rainwater harvesting and reduction of combined sewer overflows
- Installation of 28 new stations for real-time monitoring of industrial discharges
Drinking Water Quality at the Source
The Melen basin meets roughly 50 percent of Istanbul's drinking water demand. Routine monitoring in the basin over the past five years has detected micropollutant traces. While these stay below drinking water standards, they have raised the importance of source-level control for long-term health safety. The new investments aim to cut the micropollutant load from wastewater discharge by more than 80 percent.
Technology Choices
The technology set selected by ISKI's technical commission includes:
- Granular activated carbon (GAC) filters
- Ozonation units
- UV/H2O2 advanced oxidation
- Membrane bioreactor (MBR) modules
Plant-level technology selection is based on the characterization of incoming load.
Reuse Target
The high-quality effluent produced by the micropollutant removal stage will be used for landscape irrigation, street washing and industrial process water. Targeted reuse volume is 180,000 m³ per day. Reaching about 65 million m³ per year, this is expected to ease abstraction pressure on reservoir levels especially during summer.
Climate Adaptation Link
Drought conditions over the past three years have raised public awareness of drinking water security in the megacity. The investments are positioned not just as treatment performance upgrades but as an integral part of climate adaptation. ISKI aims to bring the share of recovered water in total water supply to 8 percent by 2030.
Implications for the Sector
The investment package creates a significant market opportunity for activated carbon, ozone generator, UV and membrane module importers and EPC firms handling installation and execution. Tenders are expected mid-year.