Abstract Summary
Greenery functions contribute to healthy living for citizens. Densely populated urban area's all over the World intend to prepare for future droughts periods by accessing new urban water sources for blue green infrastructure and greenery functions. An innovative opportunity of accessing fresh water in urban area's during periodical climate change enforced droughts is the so called Sewer Water Harvesting (SWH). Within the NWO program AquaConnect a demonstration case for the Amsterdam Metropolitan Region investigates the possibility and applicability of water harvesting from the urban sewage system. During droughts, the urban sewage systems are expected to act as a reliable and only available source of fresh water by quantity, not quality. Rain water buffers are empty and surface water becoming increasingly brackish. Therefore, new concepts need to be developed that allow water mining from urban sewage systems that can extract a suitable water quality for greenery functions and maybe also for urban agriculture functions. The paper describes the method and outcomes of a demonstration project at the Marineterrein Amsterdam and discusses sustainability and applicability The Water Harvesting Demonstrator consist of a mobile SWH installation containing of sewer water extraction pump, screening, fine drum sieving, direct nano filtration (400 Dalton removal) and optional UV disinfection with a capacity of 1 m3/h to produce irrigation water for Amsterdam's Park area's when and were needed. The paper elaborates on the technical conditions of the installations regarding recovery of water, energy demand and chemical use as well as on water quality analysis on feed water and product water to investigate the treatment performances and compliance to water reuse standards. The first results from the demonstrator indicate that SWH can provide a new and reliable water source during dry periods to support SWH. From an engineering perspective, challenges related to the water quality are unlikely to be insurmountable. With a water recovery percentage of 56% producing a bacteria and virus free irrigation containing less than 5 mg/L BOD, 0 mg/L TSS, 0.7 mg/L total-Phosphorous 12 mg/L NH4 and 14 mg/L total-Nitrogen the performance look very promising. Further water quality testing will be carried out in 2023. Additionally, three aspects still require further investigation: (1) currently there is a lack of regulatory framework, (2) responsibility for operation and ownership are unclear, and (3) extensive water quality testing and environmental impact assessment is needed. To accelerate innovation it is recommended to start as soon as possible with addressing these remaining issues. Commercial operation of SWH can provide an interesting opportunity, all the more so because SWH can also be used for household or industrial applications. The involvement of a wider variety of stakeholders can further help to overcome the remaining.
