The global population continues to rise and is expected to reach 8.5 billion by 2030, according to predictions. Therefore, one of the significant challenges faced by modern agriculture is meeting the increasing food demands of the growing population while addressing water and soil scarcity, land degradation, and climate change. Given the current state of the fertilizer market, raw material and fertilizer prices are expected to remain high for agriculture. As a result, many countries are prioritizing the use of local alternative raw materials and methods to reduce dependency on imported sources and ensure food security.

On the other hand, managing nutrient-rich waste is a major issue both domestically and globally. One such waste is sewage sludge, which contains valuable organic matter and nutrients (P, N) beneficial for plants. There is no precise figure for the global amount of wastewater sludge in the literature. Although estimates can be made for the amount of sludge produced by municipalities, the total amount of industrial sludge is not well known, so the total real sludge quantity cannot be determined. For this reason, local governments, in cooperation with the private sector, need to create a database and develop a sustainable action plan. With such action plans, global sludge management can be made beneficial and sustainable for the environment.

REDCO has successfully completed solar sludge drying facilities in wastewater treatment plants, such as Iğdır, Bismil, Sorgun, Niksar, and Kastamonu in Turkey, which have also been supported by the European Union (EU). Furthermore, REDCO has become a reference facility provider for sludge drying in three continents (Europe, North Africa, and Asia), with several completed and ongoing projects. In addition, REDCO has commissioned solar sludge drying facilities in Morocco, including Had Soualem, Nador, and Dakhla.

**PRIVATE SECTOR – LOCAL GOVERNMENT COLLABORATION: AN IMPORTANT EXAMPLE OF SUSTAINABILITY FACILITY: NEW DELHI OKHLA WASTEWATER TREATMENT PLANT**

The Okhla wastewater treatment plant, built by the SUEZ company for Delhi Jal Board in New Delhi, India, is expected to become the largest wastewater treatment plant in Asia, with a capacity of 564,000 m³/day. Designed and built on new technologies, this plant will treat wastewater to international standards and includes advanced treatment, UV disinfection, and a solar sludge drying facility. It is planned that 60% of the energy (4.8 MW) required for the plant’s operation will be generated internally by producing biogas from the sludge.

**IMPORTANT COMPONENTS OF THE PLANT:**

* Chemical-free high-speed biological treatment

* Centralized type settlers

* Advanced treatment

* Two-phase anaerobic digestion system (Mesophilic and Thermophilic)

* Ultraviolet (UV) Disinfection

* Solar Sludge Drying Facility

With this project, SUEZ has taken a significant step in innovation and sustainability by reducing the plant’s area from 124 hectares to 47 hectares. Furthermore, they have advanced this step by not only focusing on water treatment but also on drying the resulting sludge and ensuring its final disposal. The plant will generate an average of 630 tons of sludge per day, which will be dried to the target dryness using REDCO’s designed and manufactured solar sludge drying facility. The facility spans an area of approximately 60,000 square meters with 35 solar sludge drying units. The dried sludge from the solar drying facility will be of Class A pathogen quality, suitable for use as fertilizer by farmers. The plant will operate in a fully automated manner with SCADA control for remote operation. REDCO has completed the installation of solar sludge drying equipment at the Okhla facility, the largest wastewater treatment plant in Asia for sustainability, and is now in the commissioning phase.

Once fully operational, instead of directly discharging millions of liters of sewage into the Yamuna River, the wastewater will be treated before discharge. Sewage from most parts of central and southern Delhi, including the NDMC area, will be directed to this facility. Wastewater will be treated using advanced technologies, including UV radiation. The facility will have the capacity to process 15 to 20% of Delhi’s sewage. Additionally, the biochemical oxygen demand (BOD) will be reduced to a level that can be used for various purposes.

Once the Okhla facility is fully operational, it will play a vital role in improving the water quality of the Yamuna River and, thus, the environmental health of Delhi.