'Circularity in the water cycle: reuse of iron sludge as flocculant' Iron sludge, a byproduct of drinking water production, is typically generated in large quantities. In both drinking water and wastewater treatment processes, iron salts are introduced as coagulants to facilitate the removal of particles and phosphate. Through acidic extraction of iron (hydr)oxides from the sludge, an aqueous iron salt solution can be derived and used as a coagulant. Consequently, iron sludge from a drinking water facility can be repurposed as a coagulant in a full-scale wastewater treatment plant. This circular coagulant has demonstrated superior effectiveness compared to commercial iron salts. Coagulation, flocculation, and sedimentation are widely adopted techniques for particle and phosphate removal in both drinking water and wastewater treatment. While iron salts are frequently employed as coagulants, their current availability is limited, and prices are prohibitively high. By repurposing iron from drinking water iron sludge, a more reliable supply is ensured, at significantly lower costs and with a reduced environmental impact. This approach has been successfully validated using sludge from a drinking water plant in a wastewater treatment facility, and in the future, it can also be directly integrated into drinking water production. This represents a fine example of efficient circularity in the water cycle.

'Closing the nutrient loop through nature-based treatment system in Devanahalli, Bengaluru, India' Devanahalli, a small town in Bengaluru, treats liquid waste through a nature-based treatment system. Greenhouse solar driers installed over the drying beds reduces drying time, reducing the land requirement. Pathogen elimination is an added advantage. The innovative monitoring mechanisms through IoT services helps real-time monitoring of sludge parameters. The treated sludge is co-composted through windrows with the organic waste to make an enriched compost which is then sold to the farmers. The treated water is used within the premises for gardening. Overall, it’s a comprehensive solution for economically viable, sustainable resource recovery model which can be replicated at larger scale. Current thermal treatment technologies can be energy intensive, with nutrient loss and greenhouse gas emissions. The nature-based treatment system with the cost-effective greenhouse solar driers requires no electricity, no chemicals or skilled labour. Innovative IoT services to monitor the operations of the system is first of its kind in liquid waste management. Co-composted sludge improves soil health, reduces chemical fertilizers and hence increases farmer’s income. Field experiments conducted to demonstrate the effect of sludge on crop yield is one of the novelties in the area. The end products (sludge and treated water) are reused safely by closing the nutrient loop.

'CellCap (Recovery and reuse of cellulose recovered from sewage' CellCap is a novel technology that enables the large scale commercial recovery and reuse of cellulose from the head of STWs. CellCap is a sieving device that consists of two parts (this is an important part of its the uniqueness); in step 1, the residuals (fats, hair, seeds, etc.) are removed from the sewage and in step 2, the IntenSieve® - an improved energy efficient sieve, the cellulose is captured. While recovering a valuable product, CellCap at the same time benefits associated with downstream operational, performance and cost improvements and increase the capacity using very limited space. Previous projects have been completed in which a cellulose-rich product was extracted from sewage. This stream turned out to be unsellable, due to the presence of contaminants. Since 2017, CirTec has been developing 2-stage technology to produce clean, marketable cellulose. IWA previously rewarded this development with a "high recommendation for further development". After various studies and installation of individual process steps at relatively small treatment plants, the technology will now be used on a large scale for the first time. The project includes the harvesting of cellulose (thus optimising the STW) to the high-quality use of cellulose as a raw material.