RECLAIMED WASTEWATER AQUAPONICS IN EUROPE: FIRST EVIDENCE OF INTEGRATED FISH PRODUCTION FROM THE “AWARE” PRODUCTION SYSTEM
Introduction
Reclaimed water aquaculture for food production has been explored in water-scarce regions outside Europe as a strategy to enhance water efficiency and food security, although the literature remains limited and partly outdated (Kumar and Sierp, 2003; Edwards, 2000; Blumenthal et al., 2000). In Europe, wastewater reuse has traditionally focused on agricultural and environmental applications, supported by recent regulatory developments such as EU Regulation 2020/741 and circular economy strategies (European Commission, 2023; Ramm and Smol, 2024). However, integration of reclaimed water into aquaculture remains virtually absent. Historically, aquaculture operating with depurated wastewater was tested in Europe since the late 19th century, particularly in Germany, but never achieved large-scale adoption due to high operational costs, seasonal constraints, and low public acceptance.
This study presents the first fish production cycle of the first recirculating aquaponic system in Europe using reclaimed municipal wastewater. The system integrates advanced quaternary wastewater treatment with aquaponic production, demonstrating technical feasibility and addressing key barriers related to water quality, regulation, and system integration. The results contribute to the development of circular water-food systems in Europe.
Materials and Methods
The experimental activity was conducted at the "AWARE" production system (Castellana Grotte, Bari, Italy), a recirculating aquaponic system (RAS) fully supplied with treated municipal wastewater. The system (Green in Blue, Barcelona, Spain) operates as a closed-loop unit integrating fish and plant production, consisting of two fish tanks (2.7 m3 each; 5.4 m3 total) and three deep water culture (DWC) hydroponic units, each with a cultivation area of 7.5 m2 (22.5 m2 total). The overall system water volume is 12 m3. Water circulation is driven by a digitally controlled pump (Peraqua E.Pro) that draws water from the sump tank and passes it through a biofiltration unit, where suspended solids are retained and nitrogen is biologically converted from ammonia to nitrite and subsequently to nitrate.
A total of 150 Nile tilapia (Oreochromis niloticus) were reared over a nine-month production cycle in one of the two fish tanks using treated wastewater. Initial mean fish weight and length were 106.6 ± 25.5 g and 16.4 ± 1.4 cm, respectively. Fish were maintained under controlled conditions (pH 6-7; dissolved oxygen ≈ 6.5 mg L-1) and fed a commercial floating diet (Dibaq Tilapia Feed, 2 mm, 35% crude protein) using automated feeding systems adjusted monthly.
Simultaneously, the three DWC units supported continuous cultivation of leafy and herbaceous crops, including lettuce (Lactuca sativa var. capitata), basil (Ocimum basilicum), broccoli (Brassica rapa subsp. sylvestris), and parsley (Petroselinum crispum), maintained throughout the production cycle at a density of 25 plants m-2 under greenhouse natural lighting conditions. Plants were harvested progressively upon reaching commercial maturity and replaced to ensure continuous production.
Water quality parameters, including dissolved oxygen, pH, nitrogen species, oxidation-reduction potential (ORP), and temperature, were continuously monitored using an automated sensor-based system (Senect Control). Fish growth performance and somatic indices were assessed through monthly biometric sampling.
Results
During the nine-month experimental production cycle, the "AWARE" system demonstrated the technical feasibility of aquaponic production fully supplied with reclaimed municipal wastewater. Water quality parameters remained stable throughout the trial ensuring suitable conditions for both fish rearing and plant cultivation. The biofiltration unit effectively supported nitrification processes, allowing the biological conversion of ammonia into nitrite and nitrate while maintaining nitrogen compounds within acceptable thresholds for aquaponic production. No mortality or water quality deterioration was observed during the experimental period.
Nile tilapia exhibited regular growth throughout the production cycle, with progressive increases in body weight and total length and condition factor (K) values indicative of good physiological status (final mean fish weight and length were 418 ± 106 g and 27 ± 3 cm with a K-factor = 2) (Figure 1) (FCR = 1.9 and SGR = 0.48). Fish adapted successfully to the reclaimed-water environment, showing normal behaviour and no evidence of stress-related conditions during rearing. The overall growth performance confirmed the suitability of the treated wastewater for sustaining fish production under recirculating aquaponic conditions.
Figure 1 - Growth parameters in tilapia reared in the new AWARE aquaponic system.
At the end of the production cycle, a total of 55.6 kg of Nile tilapia biomass was harvested. Fish processing generated 20 kg of ready-to-use fillets, corresponding to a fillet yield of approximately 36% of total biomass. The remaining 35.6 kg (64%) consisted of processing by-products, including 7.8 kg of bones, 15.3 kg of heads, and 12.5 kg of viscera. Additional studies are currently ongoing to further evaluate food safety, nutritional composition, and consumer acceptability of the fish products obtained from reclaimed-water aquaponic production.
Simultaneously, the DWC hydroponic units supported continuous cultivation of lettuce, basil, broccoli, and parsley throughout the entire experimental cycle. All crops reached commercial maturity regularly, enabling sequential harvesting and replacement without interruption of production. Plant development was homogeneous among the cultivation units, and no significant nutritional deficiencies or phytotoxic effects were detected, indicating that nutrient availability derived from fish metabolism and microbial mineralization was sufficient to sustain plant growth.
Overall, the results provide the first experimental evidence in Europe that reclaimed municipal wastewater can be successfully integrated into aquaponic food production systems. The "AWARE" system demonstrated stable operation, effective integration between wastewater treatment and biological production, and the capacity to simultaneously support fish and vegetable cultivation within a circular water-food framework. These findings highlight the potential of reclaimed-water aquaponics as an innovative strategy for improving water reuse efficiency and advancing circular economy approaches in European food production systems.
References
Blumenthal U.J., Peasey A., Ruiz-Palacios G. & Duncan D.M. (2000). Guidelines for wastewater reuse in agriculture and aquaculture: recommended revisions based on new research evidence. WELL Study Report, London School of Hygiene and Tropical Medicine, UK.
Edwards P. (2000). Wastewater-fed aquaculture: state of the art. In: Jana B.B., Banerjee R.D. & Heeb J. (Eds.), Waste Recycling and Resource Management in the Developing World. University of Kalyani, India and International Ecological Engineering Society, pp. 37-49.
Kumar M.S. & Sierp M. (2003). Integrated wastewater treatment and aquaculture production. Rural Industries Research and Development Corporation (RIRDC) Publication, Canberra, Australia.
European Commission (2023). Regulation (EU) 2020/741 of the European Parliament and of the Council of 25 May 2020 on minimum requirements for water reuse. OJ L 177, 5.6.2020, p. 32-55.
Ramm K. & Smol M. (2024). The potential for water recovery from urban waste water - The perspective of urban waste water treatment plant operators in Poland. Journal of Environmental Management, 358, 120890.