AQUAPONIC SLUDGE DIGESTION FOR ORGANIC REDUCTION AND NUTRIENT REMINERALIZATION IN UASB REACTOR.

These first results on aquaponic sludge digestion are promising and highlight the interest to treat sludge directly onsite in order to reduce aquaponic system wastes and thus its impact on the environment and at the same time increase plant yield

Navigating towards decoupled aquaponic systems : a system dynamics design approach

The classical working principle of aquaponics is to provide nutrient-rich aquacultural water to a hydroponic plant culture unit, which in turn depurates the water that is returned to the aquaculture tanks. A known drawback is that a compromise away from optimal growing conditions for plants and fish must be achieved to produce both crops and fish in the same environmental conditions. The objective of this study was to develop a theoretical concept of a decoupled aquaponic system (DAPS), and predict water, nutrient (N and P), fish, sludge, and plant levels. This has been approached by developing a dynamic aquaponic system model, using inputs from data found in literature covering the fields of aquaculture, hydroponics, and sludge treatment. The outputs from the model showed the dependency of aquacultural water quality on the hydroponic evapotranspiration rate. This result can be explained by the fact that DAPS is based on one-way flows. These one-way flows results in accumulations of remineralized nutrients in the hydroponic component ensuring optimal conditions for the plants. The study also suggests to size the cultivation area based on P availability in the hydroponic component as P is an exhaustible resource and has been identified one of the main limiting factors for plant growth

Etude des éléments minéraux disponibles en aquaponie, de leur impact sur la productivité des laitues et de la potentielle amélioration de leur disponibilité.

Aquaponics is an integrated farming concept that combines fish and hydroponic plant production in a recirculating water system. This innovative technique has the potential to reduce the impact of fish and plant production on the environment by namely closing the nutrient loop. Indeed, the nutrients leaving the fish part are used to grow hydroponic plants. This thesis focused on the mineral elements available in aquaponics to grow plants. The thesis started by deepening the aquaponic concept. It was identified that the mineral elements available for plants growth in solution were lower concentrated than in hydroponics. It was assumed that an important parts of the nutrients input were unavailable and lost out of the aquaponic system via sludge spillage. This leaded to the necessity to determine the consistency of the plant growth and the proportion of mineral elements that were recycled in aquaponic systems. A solution to improve the recycling of these elements and increase their availability was also studied. Therefore, the performances of a one loop aquaponic system named the plant and fish farming box (PAFF Box), in terms of yields of fish and plant, energy and water consumption, and mineral elements mass balances were studied. The mineral nutritive elements were also characterised. For experimentation convenience, lettuce was taken as a model plant. To determine if aquaponics can assure consistent plant growth compared to conventional systems, lettuce growth has been compared between a one loop aquaponic solution, a hydroponic solution and a complemented aquaponic solution in deep water systems in controlled conditions. The latest allowed studying also the growth when nutrient concentrations are increased in the aquaponic solution. The potential of improvement of nutrient recycling for increasing their availability to plant by sludge digestion onsite was studied. Therefore, the mineralisation performance of sludge has been explored in simple aerobic and anaerobic reactors and in up-flow anaerobic sludge blanket reactors (UASB). In the term of this work, it appeared that aquaponics consumed and discharged less water to produce fish and plant but required more energy than conventional farming systems. The lettuce showed similar growth performance between aquaponic and hydroponic solution but significantly higher growth (i.e. 39% fresh mass increase) in complemented aquaponic solution. This indicated that lower mineral elements concentrations did not impact negatively plant growth and that an increase of concentrations improved growth compared to conventional hydroponics. Also the microorganisms and dissolved organic matter may play an important role for promoting plant roots and shoots growth in aquaponics. Mineral elements mass balances analysis showed that an important part of the elements were accumulating in sludge and lost by water and sludge spillage. However, the sludge digestion onsite showed promising results to recover these elements in available form for plants. It would allow reducing environmental footprints by limiting the nutrients loss and recycle even more water. Regarding these results an improvement of the one loop aquaponic system was suggested as a hybrid decoupled aquaponic system that would limit water and nutrients discharge and improve plant growth

Lettuce (Lactuca sativa L. var. Sucrine) Growth Performance in Complemented Aquaponic Solution Outperforms Hydroponics

Plant growth performance is optimized under hydroponic conditions. The comparison between aquaponics and hydroponics has attracted considerable attention recently, particularly regarding plant yield. However, previous research has not focused on the potential of using aquaponic solution complemented with mineral elements to commercial hydroponic levels in order to increase yield. For this purpose, lettuce plants were put into AeroFlo installations and exposed to hydroponic (HP), aquaponic (AP), or complemented aquaponic (CAP) solutions. The principal finding of this research was that AP and HP treatments exhibited similar (p > 0.05) plant growth, whereas the shoot weight of the CAP treatment showed a significant (p < 0.05) growth rate increase of 39% on average compared to the HP and AP treatments. Additionally, the root weight was similar (p > 0.05) in AP and CAP treatments, and both were significantly higher (p < 0.05) than that observed in the HP treatment. The results highlight the beneficial effect of recirculating aquaculture system (RAS) water on plant growth. The findings represent a further step toward developing decoupled aquaponic systems (i.e., two- or multi-loops) that have the potential to establish a more productive alternative to hydroponic systems. Microorganisms and dissolved organic matter are suspected to play an important role in RAS water for promoting plant roots and shoots growth

Plant production capacity in the PAFF box, an urban aquaponics module

Paff box production in 2014Aquapnics-urban agricultur

Biofilter in aquaponics

Aquaponics is a combination of aquaculture (fish farming) and hydroponics (horticulture). In this concept, the fish faeces and excreted ammonia are partially transformed into soluble nutrients which then are available for plants. Wastewater from aquaculture is filtrated by plants and return to the fish tank in a loop cycle. This strongly reduces the use of water and increases the economic efficiency with an additional production of plant, e.g. vegetables. From the hydroponics view, this combination allows important decreases in chemical nutrients use for plant grow. A central part of this system is the biofilter. The microorganisms that colonize it are essential to process the fish waste into soluble nutrients easily assimilated by plants. During this process, nitrifying bacteria convert free ammonia into nitrite and then nitrate. The first objective of this research will concern the identification and isolation of the main microorganism species involved by the dilution plating and metagenomics technics. The optimal conditions to process the fish waste will be determined for such microorganism. The efficiency of nitrite and nitrate production by these micro-organisms will be tested in different conditions (T°, pH, O2, water flow, support, etc..) in vitro at the lab scale and in aquaponics prototypes