Scaling up water solutions II

Stricted legislation and a heightened emphasis on environmental stewardship are transforming conventional wastewater treatment plants (WWTPs) into greener and more efficient biorefineries, producing valuable bioproducts that are increasingly prevalent in society. Notably, the recent wastewater treatment Directive (UE) 2024/3019 introduces new objectives of energy neutrality and significant nutrient reduction in wastewater discharges. To achieve these goals, stricter limit values for nitrogen and phosphorus have been implemented. Furthermore, all WWTPs serving populations equivalent to more than 150,000 inhabitants will be required to implement nutrient removal processes. These legislative changes will inevitably increase operating costs for WWTPs, driven by the need for enhanced energy consumption to remove nitrogen and increased dosing of chemical reagents to precipitate phosphorus. This is necessary to comply with the stringent discharge parameters. The aim of this study is to produce high-quality treated water and biofertilizers from domestic wastewater through two distinct scenarios. The first scenario showcases the world's largest 100% solar anaerobic photobiofactory, which leverages purple phototrophic bacteria (PPB) (CBE JU project DEEP PURPLE). The technology's development has progressed from Technology Readiness Level (TRL) 5 during pilot-scale trials at the Estiviel WWTP in Toledo, Spain, to TRL 7 with the construction of a demonstration plant at the Linares WWTP. Employing a photobioreactor system with a treatment capacity of 350 m³/d (1500 population equivalents), the effluent consistently meets or exceeds European legislative standards (TP < 2 mg/L, TSS < 15 mg/L, BOD5 < 23 mg/L, and COD < 40 mg/L). Moreover, the process's flexibility allows for treated water to be adapted for agricultural applications, minimizing nitrogen and phosphorus uptake and serving as a valuable nutrient-rich irrigation resource. Additionally, phototrophic biomass has proven to be a low-cost feedstock for formulating biofertilizers with a C:N:P ratio of 100:15:13 and an N:P:K ratio of 100:98:25. The second scenario focuses on producing a valuable product, struvite (Aquavite®), recovered from nutrient-rich wastewater streams in WWTPs (BBI B-FERST project). The recovery efficiency of phosphorus(III) oxide (P2O5) in the Aquavite® production system exceeded 80%, while ammonium (NH4+) removal efficiency approached 40%. With a treated flow rate of up to 100 m³/d, the system produces an estimated 15 tons per year of P2O5-enriched struvite (28%), which can be used as a raw material for fertilizer formulation. Both the BBI DEEP PURPLE and BBI B-FERST projects provide full-scale solutions for nutrient recovery from urban wastewater, promoting the concept of a circular economy."

Facing changing conditions like climate change, water-stressed regions are exploring alternative water supply options, including agricultural and urban reuse. While required technologies are available, highly flexible and demand-driven management strategies for water reuse in urban and agricultural irrigation are still in the first stages of development, especially in Germany. In a research project, water reuse using treated municipal wastewater was tested and a cost-benefit analysis was carried out to derive the most efficient management strategies. This cost-benefit analysis combines the concepts of life-cycle costing and ecosystem services (ESS), which was used to develop a use-case-specific indicator-based evaluation matrix with decision-relevant economic indicators and ecological endpoints. The general and transferable ESS assessment matrix to assess the benefits was then applied in a case-specific context in Germany to quantify technology-induced changes in local ecosystem services. The transition from the theoretical matrix to the practical implementation revealed significant challenges in quantifying and monetising the identified ESS, mainly due to the scarcity of relevant data. To overcome this challenge, several approaches were evaluated. With this work, we want to show the conference participants a cost-benefit analysis using a German case study, which is now being transferred from concept to practice.

The treatment of high-concentration organic wastewater is currently a world problem, such as landfill leachate and digested sludge liquor, in which the concentration of organic matter and ammonia and nitrogen is dozens or even hundreds of times that of municipal wastewater. At present, the dual-membrane process is used to remove organic matter and add a large number of chemicals such as methanol as denitrification carbon source denitrification, which greatly increases the cost of treatment. Anaerobic ammonia oxidation (anammox) greatly saves aeration and carbon source and reduces the treatment cost compared with the traditional nitrogen removal process. Aiming at the bottlenecks of high concentration organic wastewater, such as the high cost of “dual-membrane process” and the production of “thick water” and the need to add a large amount of carbon source for biological nitrogen removal, we take the actual high concentration organic wastewater such as landfill leachate and digested sludge liquor as the research object. Using various types of anaerobic ammonia oxidation coupled with electro-oxidation and other technologies to achieve its depth of decarbonization and denitrogenation, improve the treatment efficiency, reduce the cost of treatment of tonnes of water by more than 95% and there is no secondary pollution, to achieve the dual objectives of environmental protection and economic benefits.