Introduction
Freshwater is becoming increasingly scarce and valuable, and agriculture and agro-processing sectors remain among the world’s largest users of this resource. This program has integrated various nature-based technologies and processes , e.g., algal ponding, constructed wetlands, hydroponics, aquaponics, vermiculture and permaculture to recover water and nutrients from effluent produced by agro -processing and to do so using a circular economy to generate agriculture and aquaculture products. The proof-of-concept was established within the first few years of the program. Algal ponding and wetland technologies were integrated with hydroponics and aquaponics with a focus on optimising the anaerobic digestion phase of the treatment process; effluent was successfully cleaned, crops were produced, and this was all done using an integrated effluent treatment/aquatic food production system. The next decade was designed to obtain societal support to scale up the project, while also further developing and optimising the process.
Recent research progress
The presentation will delve briefly into the progress that has been made in the following areas of research, all of which have supported the development of this alternative effluent treatment and food production system in an aquatic environment:
Culmination of this work
This alternative wetland-based system has been successfully integrated with hydroponics, vermiculture, permaculture and aquaponics, and has been tested on a commercial-pilot scale for the last three years. Approximately 350 m3 of brewery effluent is treated daily and about 250 m3 of cleaned water is returned to the brewery. Post anaerobically digested brewery effluent enters the system with a chemical oxygen demand (COD) of 400-600 mg/L and leaves at 60-80 mg/L. Total a mmonia enters at 40-50 mg/L and is discharged at < 1 mg/L. This integrated effluent treatment process produces over 2-tons of fresh vegetables per month, supporting seven farm workers, and this fresh-produce is used to support local feeding schemes and is sold to supermarkets.
Way forward
The next steps will be to develop partnerships so that we can demonstrate this approach using different effluent streams, in different geographical regions, using alternative crops and optimising the process for a more universal application. Future work will also look at including a finfish loop in the system to add nitrogen and additional, valuable protein-rich products because the primary effluent source can be nitrogen limited. The addition of aquaculture effluent might reduce the need for the addition of inorganic fertilizers needed to optimise plant production, but this remains to be tested.