Good practice:

Sewer Mining for Urban Water Reuse

Sewer Mining is a concept that is gaining traction, end is considered an innovative way to address water scarcity. It extracts wastewater directly from the sewer network treats it on- site and produces water for on-site use. The technology is applied by the installation and testing of a sewer mining modular unit for urban green irrigation at the point of demand which is clearly of direct benefit for the sustainability of urban water management. To address resource efficiency issues in e circular economy context, compost-based eco-engineered growing media are also produced and reused as onsite fertilizers and thermal energy recovery schemes are investigated to minimize the pilot’s environmental footprint. These technologies are applied and tested for the first time in Greece in a real-world application, and the results aim to serve as a significant step towards transferable, modular, scalable and circular solutions. The main stakeholders and beneficiaries of the practice are water companies, industry, specialized SMEs, applied research institutes, city and regional authorities. Considering the main end-products of the system designed and implemented, new end-markets can be reached through the development of synergies. Public authorities can close the circle by providing new support services based on such energy-water-material management systems. Consequently, such services are not available at the time of the project implementation and refer to future actions.

The capital and operationa cost of the pilot unit for retrieving 15 m3 of wastewater per day is: MBR unit 100,0000€ and operational cost 0.5 €/m3. For the RO-involving scheme, 125,000€ and staff cost 25,000€/yr.

Sewer mining units enable recovery αnd utilization of water which otherwise would be disposed. Reduction of consumption of highly treated drinking water. Direct utilization of alternative water sources leveraging circular economy solutions to achieve environmental, social and financial benefits for the city. One unit currently in use, (https://dessin-project.eu/?p=2232) providing 10-12m2 of recycled water per day. Another installation in a park with 4ha of vegetation saves potable water.

The operation so far showed the most important problems that have occurred are concerning the small scale of the units due to the fact that the projects are related to pilot applications.

Water/wastewater companies, municipalities can benefit by saving drinking water and reducing the costs of transferring reclaimed water to the point of use. It is possible to implement innovative actions with simultaneous multiple benefits at environmental and economic level in the context of the circular economy. In addition, the implementation of such actions provides the opportunity to consider new practices that may lead the competent authorities to review and improve relevant legislation. By applying such methods initially on a small scale, the competent bodies can gain experience and decide on the optimal way of application on an even larger scale. Application in urban areas, parks etc can help develop green spaces while saving resources.