Borgmann Aquaponics Hydroponics
Figure 19. Graphical comparison between sludge production, sludge reduction, and sludge outtake
assuming a TSS reduction of 90%, a HRT of 10 days, and an SRT of 80 days (y‐axis). The days are
displayed on the x‐axis.
assuming a TSS reduction of 90%, a HRT of 10 days, and an SRT of 80 days (y‐axis). The days are
displayed on the x‐axis.
5.2. Nitrate Flow Estimates
As can be seen schematically in Figure 6, the flow rate from RAS to the plants is determined by the
plant evapotranspiration rate derived from the FAO Penman-Monteith Equation. Unlike in the case of
other macronutrients, the remineralization potential for N is marginal, as almost all of it is denitrified
to atmospheric dinitrogen gas due to anaerobic activity in the system. The graphs in Figures 12–14
show the hydrological flow under natural light conditions, and the associated RAS nitrate balance and
the N-NO3 concentration in the RAS depending on different cultivation area sizes in non-illuminated
greenhouse environments in Central Europe. For robust fish at rearing densities of approx. 50 kg¨ m´3,
100 m2 of growth area would be sufficient to maintain acceptable water quality for the fish in a DAPS.
The situation is different for more sensitive fish species, for whom these densities are suboptimal such
as sturgeon or if bio labels are targeted that usually require lower densities (10–25 kg/m3). However,
using artificial light in industrial DAPS production systems result in a different scenario (Figure 13).
In this case, a much smaller cultivation area is needed to achieve a sufficient evapotranspiration rate to
maintain low and stable N-NO3 values in the RAS system for both robust and sensitive fish species.
As can be seen schematically in Figure 6, the flow rate from RAS to the plants is determined by the
plant evapotranspiration rate derived from the FAO Penman-Monteith Equation. Unlike in the case of
other macronutrients, the remineralization potential for N is marginal, as almost all of it is denitrified
to atmospheric dinitrogen gas due to anaerobic activity in the system. The graphs in Figures 12–14
show the hydrological flow under natural light conditions, and the associated RAS nitrate balance and
the N-NO3 concentration in the RAS depending on different cultivation area sizes in non-illuminated
greenhouse environments in Central Europe. For robust fish at rearing densities of approx. 50 kg¨ m´3,
100 m2 of growth area would be sufficient to maintain acceptable water quality for the fish in a DAPS.
The situation is different for more sensitive fish species, for whom these densities are suboptimal such
as sturgeon or if bio labels are targeted that usually require lower densities (10–25 kg/m3). However,
using artificial light in industrial DAPS production systems result in a different scenario (Figure 13).
In this case, a much smaller cultivation area is needed to achieve a sufficient evapotranspiration rate to
maintain low and stable N-NO3 values in the RAS system for both robust and sensitive fish species.
5.3. Hydroponics Sizing Based on P Availability
Figure 16 shows the P dynamics in the hydroponic component with a cultivation area of 600 m2,
when running the model for 1000 days under natural light conditions (growing lettuce as it requires
low light intensities allowing for an extended production period). This optimization step determines
a sufficient cultivation area based on the P inflow from both RAS and ANRC to the hydroponic
component. The nutrient remineralization results in the fact that a much higher amount of plants can
be supplied with P; i.e., in this case 600 m2. At fish biomass saturation (Figure 17) the P availability is
expected to correct its deficit. Consequently, when starting the system, P would have to be added until
day 150. Alternatively, one could cultivate an area that is proportional to the amount of fish tanks that
are in use, and adapt it accordingly.
when running the model for 1000 days under natural light conditions (growing lettuce as it requires
low light intensities allowing for an extended production period). This optimization step determines
a sufficient cultivation area based on the P inflow from both RAS and ANRC to the hydroponic
component. The nutrient remineralization results in the fact that a much higher amount of plants can
be supplied with P; i.e., in this case 600 m2. At fish biomass saturation (Figure 17) the P availability is
expected to correct its deficit. Consequently, when starting the system, P would have to be added until
day 150. Alternatively, one could cultivate an area that is proportional to the amount of fish tanks that
are in use, and adapt it accordingly.
5.4. UASB Sizing Determination
Figure 18 shows the maximum load of the UASB in liters of sludge, whereas Figure 19 displays the
sludge flow within the UASB. To achieve an upflow of 0.5 m¨ h ´1 a circulation pump with a sufficient
capacity is needed. Sizing a UASB should be treated with caution, as the sludge concentration has a
high impact on the volume requirement. For this analysis, a TSS proportion of 3% was considered.
Sludge that is not pre-treated (i.e., pre-concentrated) most likely has a lower TSS proportion and thus
requires a higher UASB reactor volume.
Figure 18 shows the maximum load of the UASB in liters of sludge, whereas Figure 19 displays the
sludge flow within the UASB. To achieve an upflow of 0.5 m¨ h ´1 a circulation pump with a sufficient
capacity is needed. Sizing a UASB should be treated with caution, as the sludge concentration has a
high impact on the volume requirement. For this analysis, a TSS proportion of 3% was considered.
Sludge that is not pre-treated (i.e., pre-concentrated) most likely has a lower TSS proportion and thus
requires a higher UASB reactor volume.
6. Discussion
The main purpose of this study was to elaborate an integrated design approach for DAPS
and to spot possible drawbacks based on a system dynamics model that has been developed here.
The findings of this theoretical study indicate that the evapotranspiration rate will have a high impact
on the RAS water quality in DAPS. This is because the water use in the hydroponic component is
the main factor for RAS water replacement (and thus refill with clean water) that regulates water
quality (Figures 14–16). As a consequence of this dependency, determining the evapotranspiration
rate of a specific plant species appears to be a crucial step when designing a DAPS. A comparison
between natural lighting (Figure 12) and artificial greenhouse lighting (Figure 13) underpins these
findings and additionally shows a considerably greater potential for cultivating sensitive fish species.
To what degree artificial lighting pays out needs to be explored in a crop and fish dependent economic
assessment. Another option—mainly for RAS focused systems—to regulate the nitrate levels in
the RAS is the implementation of a denitrification tank. This conflicts with the general objective
of aquaponics that aims at using all available nutrients and, dependent on the carbon source used
(e.g., formalin, methanol), raises concerns about the consumer safety. DAPS that follow an even
more goal-oriented approach by recycling generated sludge, however, should not waste resources
unnecessarily. On that score, a hybrid system as illustrated in Figure 20 could be a viable alternative
for regulating nitrate levels in the RAS. To size the N-regulating hybrid part, Licamele [9] provides the
sizing parameter of 2.5 kg fish feed for the production of 16 lettuce plants.
for regulating nitrate levels in the RAS. To size the N‐regulating hybrid part, Licamele [9] provides
the sizing parameter of 2.5 kg fish feed for the production of 16 lettuce plants.
unnecessarily. On that score, a hybrid system as illustrated in Figure 20 could be a viable alternative
for regulating nitrate levels in the RAS. To size the N-regulating hybrid part, Licamele [9] provides the
sizing parameter of 2.5 kg fish feed for the production of 16 lettuce plants.
for regulating nitrate levels in the RAS. To size the N‐regulating hybrid part, Licamele [9] provides
the sizing parameter of 2.5 kg fish feed for the production of 16 lettuce plants.
Figure 20. The hybrid decoupled system is a combination of the one-loop and the decoupled approach.
Whereas the one-loop aquaponic system is regulating the nitrate of the RAS system, the decoupled
hydroponic part utilizes the recycled nutrients from the ANRC. Especially for systems that focus on
fish production, their advantage is that no denitrification, and thus no waste of nitrate is required.
Whereas the one-loop aquaponic system is regulating the nitrate of the RAS system, the decoupled
hydroponic part utilizes the recycled nutrients from the ANRC. Especially for systems that focus on
fish production, their advantage is that no denitrification, and thus no waste of nitrate is required.
Sizing the hydroponics cultivation area of a DAPS requires another approach than in a balanced
one‐loop system. Whereas it is custom to take feed as a sizing factor, in DAPS, it might be more
reasonable to size the hydroponic component based on the evapotranspiration potential and other
macronutrient availabilities. There are two main reasons: (1) the remineralization capacity of N is
low, whereas it is expected to be high for other macro nutrients; (2) Since nutrient supplementation
in DAPS is managed anyway to achieve highly concentrated nutrient solutions, it is more favorable
to add N as it is largely available and cheap. In contrast, P being a declining and limited resource on
earth [83], should be recycled to a high degree and not added from an external source. The result
showed that enough P for lettuce was available to cultivate at least 600 m2 of lettuce with a density of
16 lettuce plants per m2. Taking this as a reference parameter, the graphs of the variation experiments
(Figures 12 and 13) display good water qualities for this cultivation area. With respect to the hybrid
approach, only the ANRC effluents can be used in order to size the decoupled hydroponic component.
In DAPS, the nutrient and water use efficiency is quite remarkable, as an agricultural irrigation
efficiency of 10% would free up more water than is evaporated off by all other users [84]. The results
showed that also in terms of P‐recycling this approach is progressive as P for agricultural purposes
is a limited fossil resource [4] (i.e., this refers to soil‐based agriculture as well as fertilization in
hydroponic systems) and P‐recycling is crucial to avoid world hunger [19,85]. Nevertheless, the sludge
remineralization has to be applied with caution. Zekki et al. [86] reported that nutrient solution
recycling could lead to declining harvests in NFT systems. It is suspected that this is most likely due to
sulfate ion accumulation in the nutrient solution. However, since it dilutes in the DAPS hydroponic
component, it can be expected to be high enough to avoid negative impact on plant growth.
one‐loop system. Whereas it is custom to take feed as a sizing factor, in DAPS, it might be more
reasonable to size the hydroponic component based on the evapotranspiration potential and other
macronutrient availabilities. There are two main reasons: (1) the remineralization capacity of N is
low, whereas it is expected to be high for other macro nutrients; (2) Since nutrient supplementation
in DAPS is managed anyway to achieve highly concentrated nutrient solutions, it is more favorable
to add N as it is largely available and cheap. In contrast, P being a declining and limited resource on
earth [83], should be recycled to a high degree and not added from an external source. The result
showed that enough P for lettuce was available to cultivate at least 600 m2 of lettuce with a density of
16 lettuce plants per m2. Taking this as a reference parameter, the graphs of the variation experiments
(Figures 12 and 13) display good water qualities for this cultivation area. With respect to the hybrid
approach, only the ANRC effluents can be used in order to size the decoupled hydroponic component.
In DAPS, the nutrient and water use efficiency is quite remarkable, as an agricultural irrigation
efficiency of 10% would free up more water than is evaporated off by all other users [84]. The results
showed that also in terms of P‐recycling this approach is progressive as P for agricultural purposes
is a limited fossil resource [4] (i.e., this refers to soil‐based agriculture as well as fertilization in
hydroponic systems) and P‐recycling is crucial to avoid world hunger [19,85]. Nevertheless, the sludge
remineralization has to be applied with caution. Zekki et al. [86] reported that nutrient solution
recycling could lead to declining harvests in NFT systems. It is suspected that this is most likely due to
sulfate ion accumulation in the nutrient solution. However, since it dilutes in the DAPS hydroponic
component, it can be expected to be high enough to avoid negative impact on plant growth.
For commercial aquaponic systems, DAPS might provide the best solution on the long run, as
running the sub‐systems semi‐autonomously allows the supplementation of nutrients that are only
required by the plant crop separately, in a smaller volume, and without any consequences for the
water quality in the RAS. In addition, compared to intensive aquaculture, coupled as well as
decoupled approaches can improve the water quality in the fish rearing tanks as accumulation of
nitrate is reduced.
As reported from commercial scale aquaponic production systems, sublethal effects on growth
performance, feed conversion, health, but also reproductive functions may substantially impede
harvest yield and profitability when nitrate levels in water exceed species-specific thresholds [22,23,87].
We must, however, remark that this study is of a theoretical kind and needs to be verified.
Even though there is sufficient knowledge about the impact of several parameters on RAS, the effect
of (long term) accumulation of nutrients on plant growth (and nutrient uptake rates) still remains to
be determined. The same applies to the impact of different HRTs on the nutrient remineralization
performance. More information about it is needed under different environmental conditions in order
to determine the optimal settings for DAPS. Moreover, upscaling effects need to be integrated in the
future to add robustness to the model. It is also not clear yet, whether the use of DAPS is economically
feasible. Still, we believe that restrictions on nutrient emissions and associated cost of wastewater
disposal in the future will most probably be a major driver for aquaponic development. To figure this
out, further investigations integrating the economic side are required.
performance, feed conversion, health, but also reproductive functions may substantially impede
harvest yield and profitability when nitrate levels in water exceed species-specific thresholds [22,23,87].
We must, however, remark that this study is of a theoretical kind and needs to be verified.
Even though there is sufficient knowledge about the impact of several parameters on RAS, the effect
of (long term) accumulation of nutrients on plant growth (and nutrient uptake rates) still remains to
be determined. The same applies to the impact of different HRTs on the nutrient remineralization
performance. More information about it is needed under different environmental conditions in order
to determine the optimal settings for DAPS. Moreover, upscaling effects need to be integrated in the
future to add robustness to the model. It is also not clear yet, whether the use of DAPS is economically
feasible. Still, we believe that restrictions on nutrient emissions and associated cost of wastewater
disposal in the future will most probably be a major driver for aquaponic development. To figure this
out, further investigations integrating the economic side are required.
7. Conclusions
AnyLogic software and system dynamics analysis constituted a valuable tool to understand the
dynamics and design boundaries of DAPS. During the last decades, scientific aquaponics literature
was mainly based on one-loop aquaponic systems. However, this approach results from a trade-off
between RAS and hydroponics instead of meeting the optimal conditions for the respective sub-systems.
Even though there is no empirical data on the productivity of the system’s hydroponic component,
we conclude that in terms of nutrient and water recycling the system contributes to closing the cycle.
The results showed that sizing the system is contingent on the evapotranspiration rate. The higher the
evapotranspiration rate, the smaller the required hydroponic cultivation area. The AnyLogic outcome
showed that this is particularly relevant when focusing on sensitive fish species. In the long term, this
is of great relevance as fertilizer costs are rising with the increasing world population as well as the
demand for no-emission systems minimizing environmental impact. Regarding the ANRC, further
research is needed with respect to its remineralization performance depending on different HRT and
SRT. This and the specific nutrient uptake of plants in a DAPS hydroponic environment are required to
substantiate the current DAPS model. In conclusion, it can be said that while technical research in this
area is important, additional geographically dependent follow-up studies are needed, dealing with the
economically viable size of DAPS as well as the comparison with equivalent hydroponic systems.
AnyLogic software and system dynamics analysis constituted a valuable tool to understand the
dynamics and design boundaries of DAPS. During the last decades, scientific aquaponics literature
was mainly based on one-loop aquaponic systems. However, this approach results from a trade-off
between RAS and hydroponics instead of meeting the optimal conditions for the respective sub-systems.
Even though there is no empirical data on the productivity of the system’s hydroponic component,
we conclude that in terms of nutrient and water recycling the system contributes to closing the cycle.
The results showed that sizing the system is contingent on the evapotranspiration rate. The higher the
evapotranspiration rate, the smaller the required hydroponic cultivation area. The AnyLogic outcome
showed that this is particularly relevant when focusing on sensitive fish species. In the long term, this
is of great relevance as fertilizer costs are rising with the increasing world population as well as the
demand for no-emission systems minimizing environmental impact. Regarding the ANRC, further
research is needed with respect to its remineralization performance depending on different HRT and
SRT. This and the specific nutrient uptake of plants in a DAPS hydroponic environment are required to
substantiate the current DAPS model. In conclusion, it can be said that while technical research in this
area is important, additional geographically dependent follow-up studies are needed, dealing with the
economically viable size of DAPS as well as the comparison with equivalent hydroponic systems.
Acknowledgments: The work was partly supported by Aquaponik Manufaktur GmbH and the COST Action
FA1305: The EU Aquaponics Hub-Realizing Sustainable Integrated Fish and Vegetable Production for the EU.
In addition, big “tack” goes to Stefan Bengtsson for providing constructive feedback.
Author Contributions: Simon Goddek is the main author of this manuscript. He was assisted by the other
co-authors in form and content.
Conflicts of Interest: The authors declare no conflict of interest.
FA1305: The EU Aquaponics Hub-Realizing Sustainable Integrated Fish and Vegetable Production for the EU.
In addition, big “tack” goes to Stefan Bengtsson for providing constructive feedback.
Author Contributions: Simon Goddek is the main author of this manuscript. He was assisted by the other
co-authors in form and content.
Conflicts of Interest: The authors declare no conflict of interest.
Appendix A
The software diagram is split up in multiple parts for overview reasons (see Figures A1–A4).
The whole software diagram can be accessed via the main author and/or supplementary material.
Figure A1. Software diagram of one fish tank of the RAS part of the AnyLogic model. The feed rate is
linked to the total feed rate in Figure A2.
linked to the total feed rate in Figure A2.
Figure A2. Software diagram of the nitrogen and phosphorus balance in the whole RAS system.
The inflow is linked to Figure 13, whereas the outflow is linked to Figure A3 (ANRC) and A4 (hydroponics).
Figure A3.
(a Software diagram covering sludge balance as well as the remineralization rate of P in the ) Anaerobic remineralization performance; (b) P flow of the ANRC.
ANRC. ( Watera) Anaerobic remineralization performance; ( 2016, 8, 303 b) P flow of the ANRC.
(a Software diagram covering sludge balance as well as the remineralization rate of P in the ) Anaerobic remineralization performance; (b) P flow of the ANRC.
ANRC. ( Watera) Anaerobic remineralization performance; ( 2016, 8, 303 b) P flow of the ANRC.
Figure A4. Software diagram of the hydroponic system consists of water, nitrogen, and phosphorus
balances. The water balance is affected by the evapotranspiration rate under the given conditions, the
nutrient and phosphorus balance is linked to the lettuce nutrient uptake and the inflow from RAS and
ANRC. A negative nutrient stock means that additional nutrient supplementation is required.
balances. The water balance is affected by the evapotranspiration rate under the given conditions, the
nutrient and phosphorus balance is linked to the lettuce nutrient uptake and the inflow from RAS and
ANRC. A negative nutrient stock means that additional nutrient supplementation is required.
Appendix B
The CLDs provide a good overview of the causal loop relationships of the three autonomous
system components: RAS, hydroponics, and ANRC. They have served as a basis for the AnyLogic
software diagrams.
The CLDs provide a good overview of the causal loop relationships of the three autonomous
system components: RAS, hydroponics, and ANRC. They have served as a basis for the AnyLogic
software diagrams.
Figure B1. Causal loop diagram of the RAS. Together with the flow charts in Figures 5 and 7–9, this
CLD was used to create the RAS AnyLogic model shown in the Appendix Figures A1 and A2. The
CLD shows the impact of different water quality parameters on fish growth as well as the impact of
the feed rate on the RAS‐derived TAN and nitrate concentrations. The CLD comprises of several
inputs of which the design inputs (e.g., amount of fish per m2) that are fixed and the control inputs
(such as pH, temperature, and feed
CLD was used to create the RAS AnyLogic model shown in the Appendix Figures A1 and A2. The
CLD shows the impact of different water quality parameters on fish growth as well as the impact of
the feed rate on the RAS‐derived TAN and nitrate concentrations. The CLD comprises of several
inputs of which the design inputs (e.g., amount of fish per m2) that are fixed and the control inputs
(such as pH, temperature, and feed
Figure B2. Causal loop diagram (CLD) of nitrogen in hydroponics. This CLD shows the dependencies
for plant N uptake and illustrates complex N processes in a hydroponic system. Remarkable is the fact
that the nitrate concentration has an impact on the root:shoot ratio. In one-loop aquaponic systems the
nitrate concentration is known to be quite low as a result of trade-offs between the RAS and hydroponic
sub-systems. Consequently, higher concentrated DAPS hydroponic nutrient solutions are expected to
generate more shoot and less root biomass. Together with the flow charts shown in Figures 5, 8 and 9
and the FAO Penman-Monteith equation this lead to a simplified hydroponic AnyLogic model as can
be seen in the Figur A4.
for plant N uptake and illustrates complex N processes in a hydroponic system. Remarkable is the fact
that the nitrate concentration has an impact on the root:shoot ratio. In one-loop aquaponic systems the
nitrate concentration is known to be quite low as a result of trade-offs between the RAS and hydroponic
sub-systems. Consequently, higher concentrated DAPS hydroponic nutrient solutions are expected to
generate more shoot and less root biomass. Together with the flow charts shown in Figures 5, 8 and 9
and the FAO Penman-Monteith equation this lead to a simplified hydroponic AnyLogic model as can
be seen in the Figur A4.
Figure B3. Causal loop diagram of the UASB. The remineralization mechanisms of the UASB show the
impact of SRT and HRT on the remineralization rate, and reactor size determination. The corresponding
impact of SRT and HRT on the remineralization rate, and reactor size determination. The corresponding
AnyLogic model is illustrated in the Figure A3.
References
1. Rakocy, J.E. Aquaponics-Integrating Fish and Plant Culture; Wiley-Blackwell: Hoboken, NJ, USA, 2012;
pp. 344–386.
2. Graber, A.; Junge, R. Aquaponic systems: Nutrient recycling from fish wastewater by vegetable production.
Desalination 2009, 246, 147–156. [CrossRef]
3. Vermeulen, T.; Kamstra, A. The need for systems design for robust aquaponic systems in the urban
environment. Int. Symp. Soil. Cultiv. 2013, 1004, 71–78. [CrossRef]
4. Goddek, S.; Delaide, B.; Mankasingh, U.; Ragnarsdottir, K.; Jijakli, H.; Thorarinsdottir, R. Challenges of
Sustainable and commercial aquaponics. Sustainability 2015, 7, 4199–4224. [CrossRef]
5. Kloas, W.; Groß, R.; Baganz, D.; Graupner, J.; Monsees, H.; Schmidt, U.; Staaks, G.; Suhl, J.; Tschirner, M.;
Wittstock, B.; et al. A new concept for aquaponic systems to improve sustainability, increase productivity,
and reduce environmental impacts. Aquac. Environ. Interact. 2015, 7, 179–192. [CrossRef]
6. Jijakli, M.H.; Delaide, B.; Gott, J. Plant Production Capacity and Nutrient Mass Balance in the PAFF Box, an
Urban Aquaponics Module: Preliminary Findings; Geography and Environment University of Southampton:
Southampton, UK, 2016.
7. Goddek, S. Three-loop Aquaponics Systems: Chances and challenges. In Proceedings of the International
Conference on Aquaponics Research Matters, Ljubljana, Slovenia, 22 March 2016.
8. Seawright, D.E.; Stickney, R.R.; Walker, R.B. Nutrient dynamics in integrated aquaculture-hydroponics
systems. Aquaculture 1998, 160, 215–237. [CrossRef]
9. Licamele, J.D. Biomass Production and Nutrient Dynamics in an Aquaponics System. Ph.D. Thesis,
University of Arizona, Tucson, AZ, USA, 2009.
10. Neto, R.M.; Ostrensky, A. Nutrient load estimation in the waste of Nile tilapia Oreochromis niloticus (L.)
reared in cages in tropical climate conditions. Aquac. Res. 2013, 46, 1309–1322. [CrossRef]
11. Adler, P.R.; Summerfelt, S.T.; Glenn, D.M.; Takeda, F. Evaluation of the effect of a conveyor production
strategy on lettuce and basil productivity and phosphorus removal from aquaculture wastewater.
In Proceedings of the Second International Conference on Recycling the Resource Ecological Engineering
for Wastewater Treatment, Waedenswil-Zurich, Switzerland, 18–22 September 1995; Staudenmann, J.,
Schönborn, A., Etnier, C., Eds.; Trans Tech Publications: Waedenswil-Zurich, Switzerland, 1996; pp. 131–136.
12. Roosta, H.R.; Hamidpour, M. Effects of foliar application of some macro- and micro-nutrients on tomato
plants in aquaponic and hydroponic systems. Sci. Hortic. (Amst.) 2011, 129, 396–402. [CrossRef]
13. Savidov, N.A.; Hutchings, E.; Rakocy, J.E. Fish and plant production in a recirculating aquaponic system:
A new approach to sustainable agriculture in Canada. Acta Hortic. 2007, 742, 209–222. [CrossRef]
14. Rakocy, J.E.; Bailey, D.S.; Shultz, K.A.; Cole, W.M. Evaluation of a commercial-scale aquaponic unit for
the production of tilapia and lettuce. In Proceedings of the 4th International Symposium on Tilapia in
Aquaculture, Orlando, FL, USA, 9–12 November 1997; pp. 357–372.
15. Mirzoyan, N.; Tal, Y.; Gross, A. Anaerobic digestion of sludge from intensive recirculating aquaculture
systems: Review. Aquaculture 2010, 306, 1–6. [CrossRef]
16. Mirzoyan, N.; McDonald, R.C.; Gross, A. anaerobic treatment of brackishwater aquaculture sludge:
An alternative to waste stabilization ponds. J. World Aquac. Soc. 2012, 43, 238–248. [CrossRef]
17. Mirzoyan, N.; Gross, A. Use of UASB reactors for brackish aquaculture sludge digestion under different
conditions. Water Res. 2013, 47, 2843–2850. [CrossRef] [PubMed]
18. Sterman, J. Business Dynamics: Systems Thinking and Modeling for a Complex World; McGraw Hill: New York,
NY, USA, 2000.
19. Sverdrup, H.U.; Ragnarsdottir, K.V. Challenging the planetary boundaries II: Assessing the sustainable
global population and phosphate supply, using a systems dynamics assessment model. Appl. Geochem. 2011,
26, S307–S310. [CrossRef]
20. Borshchev, A. The Big Book of Simulation Modeling; AnyLogic North America: Chicago, IL, USA, 2013.
21. Schrader, K.K.; Davidson, J.W.; Summerfelt, S.T. Evaluation of the impact of nitrate-nitrogen levels
in recirculating aquaculture systems on concentrations of the off-flavor compounds geosmin and
2-methylisoborneol in water and rainbow trout (Oncorhynchus mykiss). Aquac. Eng. 2013, 57, 126–130.
[CrossRef]
Water 2016, 8, 303 27 of 29
22. Davidson, J.; Good, C.; Welsh, C.; Summerfelt, S.T. Abnormal swimming behavior and increased deformities
in rainbow trout Oncorhynchus mykiss cultured in low exchange water recirculating aquaculture systems.
Aquac. Eng. 2011, 45, 109–117. [CrossRef]
23. Davidson, J.; Good, C.; Welsh, C.; Summerfelt, S.T. Comparing the effects of high vs. low nitrate on the
health, performance, and welfare of juvenile rainbow trout Oncorhynchus mykiss within water recirculating
aquaculture systems. Aquac. Eng. 2014, 59, 30–40. [CrossRef]
24. Bonachela, S.; González, A.M.; Fernández, M.D. Irrigation scheduling of plastic greenhouse vegetable crops
based on historical weather data. Irrig. Sci. 2006, 25, 53–62. [CrossRef]
25. FAO. FAO Irrigation and Drainage Paper: Crop Evapotranspiration; Allen, R.G., Pereira, L.S., Raes, D., Smith, M.,
Eds.; FAO: Rome, Italy, 1998.
26. Zolnier, S.; Lyra, G.B.; Gates, R.S. Evapotranspiration estimates for greenhouse lettuce using an intermittent
nutrient film technique. Am. Soc. Agric. Biol. Eng. 2004, 47, 271–282. [CrossRef]
27. Boulard, T. Evapotranspiration in greenhouses. Encycl. Water Sci. 2003. [CrossRef]
28. Jolliet, O.; Bailey, B. The effect of climate on tomato transpiration in greenhouses: Measurements and models
comparison. Agric. For. Meteorol. 1992, 58, 43–62. [CrossRef]
29. Fernández, M.D.; Bonachela, S.; Orgaz, F.; Thompson, R.; López, J.C.; Granados, M.R.; Gallardo, M.; Fereres, E.
Measurement and estimation of plastic greenhouse reference evapotranspiration in a Mediterranean climate.
Irrig. Sci. 2010, 28, 497–509. [CrossRef]
30. Möller, M.; Assouline, S. Effects of a shading screen on microclimate and crop water requirements. Irrig. Sci.
2006, 25, 171–181. [CrossRef]
31. Deutscher Wetterdienst WESTE-XL. Available online: https://kunden.dwd.de/weste (accessed on
13 September 2015).
32. Timmons, M.B.; Ebeling, J.M. Recirculating Aquaculture, 3rd ed.; Ithaca Publishing Company LLC: Ithaca, NY,
USA, 2013.
33. Rakocy, J.E.; Masser, M.P.; Losordo, T.M. Recirculating Aquaculture Tank Production Systems:
Aquaponics—Integrating Fish and Plant Culture; Southern Regional Aquaculture Centre: Stoneville, MS,
USA, 2006; pp. 1–16.
34. Gullian-Klanian, M.; Arámburu-Adame, C. Rendimiento de juveniles de tilapia del Nilo Oreochromis
niloticus en un sistema híperintensivo de recirculación acuícola con mínimo recambio de agua. Lat. Am. J.
Aquat. Res. 2013, 41, 150–162.
35. El-Shafai, S.A.; El-Gohary, F.A.; Nasr, F.A.; van der Steen, N.P.; Gijzen, H.J. Chronic ammonia toxicity to
duckweed-fed tilapia (Oreochromis niloticus). Aquaculture 2004, 232, 117–127. [CrossRef]
36. Al-Hafedh, Y.S.; Alam, A.; Alam, M.A. Performance of plastic biofilter media with different configuration
in a water recirculation system for the culture of Nile tilapia (Oreochromis niloticus). Aquac. Eng. 2003, 29,
139–154. [CrossRef]
37. Dalsgaard, J.; Lund, I.; Thorarinsdottir, R.; Drengstig, A.; Arvonen, K.; Pedersen, P.B. Farming different
species in RAS in Nordic countries: Current status and future perspectives. Aquac. Eng. 2013, 53, 2–13.
[CrossRef]
38. DeLong, D.P.; Losordo, T.M.; Rakocy, J.E. Tank Culture of Tilapia; Southern Regional Aquaculture Centre:
Stoneville, MS, USA, 2009; No. 282.
39. Eding, E.H.; Verdegem, M.; Martins, C.; Schlaman, G.; Heinsbroek, L.; Laarhoven, B.; Ende, S.; Verreth, J.;
Aartsen, F.; Bierbooms, V. Tilapia farming using Recirculating Aquaculture Systems (RAS)—Case study in
the Netherlands. In Handbook for Sustainable Aquaculture; Eurofish International Organisation: Copenhagen,
Denmark, 2009.
40. Veras, G.C.; Murgas, L.D.S.; Rosa, P.V.; Zangeronimo, M.G.; da Ferreira, M.S.S.; Leon, J.A.S.-D. Effect
of photoperiod on locomotor activity, growth, feed efficiency and gonadal development of Nile tilapia.
Rev. Bras. Zootec. 2013, 42, 844–849. [CrossRef]
41. Resh, H.M. Hydroponic Food Production: A Definitive Guidebook for the Advanced Home Gardener and the
Commercial Hydroponic Grower; CRC Press: Boca Raton, FL, USA, 2012.
42. Appels, L.; Baeyens, J.; Degrève, J.; Dewil, R. Principles and potential of the anaerobic digestion of
waste-activated sludge. Prog. Energy Combust. Sci. 2008, 34, 755–781. [CrossRef]
Water 2016, 8, 303 28 of 29
43. Zhao, L.; Guo, J.; Lian, J.; Guo, Y.; Yue, L.; Gou, C.; Zhang, C.; Liu, X. Study of the dynamics and material
transformation characteristics of nitrite denitrification in UASB. Biotechnol. Biotechnol. Equip. 2015, 29,
907–914. [CrossRef]
44. Cuervolopez, F.; Martinez, F.; Gutierrezrojas, M.; Noyola, R.; Gomez, J. Effect of nitrogen loading rate and
carbon source on denitrification and sludge settleability in upflow anaerobic sludge blanket (UASB) reactors.
Water Sci. Technol. 1999, 40, 123–130. [CrossRef]
45. Lettinga, G.; Pol, L.W.H. UASB-process design for various types of wastewaters. Water Sci. Technol. 1991, 24,
87–107.
46. Ross, L.G. Environmental physiology and energetics. In Tilapias: Biology and Exploitation; McAndrew, B.J.,
Ed.; Springer Netherlands: Dordrecht, The Netherlands, 2000; pp. 89–128.
47. Alfredo, M.H.; Hector, S.L. Blood gasometric trends in hybrid red tilapia Oreochromis niloticus (Linnaeus)
ˆ O. mossambicus (Peters) while adapting to increasing salinity. J. Aquac. Trop. 2002, 17, 101–112.
48. El-Sayed, A.-F.M. Tilapia Culture; CABI Publishing: Oxfordshire, UK, 2006.
49. FAO. Cultured Aquatic Species Information Programme. Oncorhynchus Mykiss. Available online: http:
//www.fao.org/fishery/culturedspecies/Oncorhynchus_mykiss/en (accessed on 21 August 2015).
50. Finstad, B.; Staurnes, M.; Reite, O.B. Effect of low temperature on sea-water tolerance in rainbow trout,
Salmo gairdneri. Aquaculture 1988, 72, 319–328. [CrossRef]
51. Coghlan, S.M.; Ringler, N.H. Temperature-dependent effects of rainbow trout on growth of atlantic salmon
parr. J. Great Lakes Res. 2005, 31, 386–396. [CrossRef]
52. Azevedo, P.A.; Podemski, C.L.; Hesslein, R.H.; Kasian, S.E.M.; Findlay, D.L.; Bureau, D.P. Estimation of
waste outputs by a rainbow trout cage farm using a nutritional approach and monitoring of lake water
quality. Aquaculture 2011, 311, 175–186. [CrossRef]
53. Westin, D.T. Nitrate and nitrite toxicity to salmonid fishes. Progress Fish-Cult. 1974, 36, 86–89. [CrossRef]
54. Barton, B.A. Principles of Salmonid Culture; Developments in Aquaculture and Fisheries Science; Elsevier:
Amsterdam, The Netherlands, 1996; Volume 29.
55. Wedemeyer, G. Physiology of Fish in Intensive Culture Systems; Springer: Berlin, Germany, 1996.
56. FAO. Cultured Aquatic Species Information Programme. Clarias Gariepinus. Available online: http:
//www.fao.org/fishery/culturedspecies/Clarias_gariepinus/en (accessed on 21 August 2015).
57. Wellborn, T.L. Channel Catfish: Life History and Biology; Southern Regional Aquaculture Centre: Stoneville,
MS, USA, 1988.
58. Tucker, C.S.; Hargreaves, J.A. Biology and Culture of Channel Catfish; Elsevier Science Ltd.: Amsterdam,
The Netherlands, 2004.
59. Horváth, L.; Tamás, G.; Seagrave, C. Carp and Pond Fish Culture, 2nd ed.; Blackwell Science Ltd.: Oxford,
UK, 2002.
60. FAO. Cultured Aquatic Species Information Programme. Sander Lucioperca. Available online: http:
//www.fao.org/fishery/culturedspecies/Sander_lucioperca/en (accessed on 21 August 2015).
61. Keen, G.A.; Prosser, J.I. Interrelationship between pH and surface growth of Nitrobacter. Soil Biol. Biochem.
1987, 19, 665–672. [CrossRef]
62. Tyson, R.V.; Simonne, E.H.; Davis, M.; Lamb, E.M.; White, J.M.; Treadwell, D.D. Effect of nutrient solution,
nitrate-nitrogen concentration, and pH on nitrification rate in Perlite medium. J. Plant Nutr. 2007, 30, 901–913.
[CrossRef]
63. Parker, R. Aquaculture Science, 2nd ed.; Delmar Publications: Clifton Park, NY, USA, 2002.
64. Huang, Z.; Gedalanga, P.B.; Asvapathanagul, P.; Olson, B.H. Influence of physicochemical and operational
parameters on Nitrobacter and Nitrospira communities in an aerobic activated sludge bioreactor. Water Res.
2010, 44, 4351–4358. [CrossRef] [PubMed]
65. Blackburne, R.; Vadivelu, V.M.; Yuan, Z.; Keller, J. Kinetic characterisation of an enriched Nitrospira culture
with comparison to Nitrobacter. Water Res. 2007, 41, 3033–3042. [CrossRef] [PubMed]
66. Sonneveld, C.; Voogt, W. Plant Nutrition of Greenhouse Crops; Springer Netherlands: Dordrecht,
The Netherlands, 2009.
67. Resh, H.M. Hydroponic Tomatoes; Taylor and Francis: Abingdon, UK, 2002.
68. Kafkafi, U.; Tarchitzky, J. Fertigation: A Tool for Efficient Water and Nutrient Management; IFA and IPI: Paris,
France, 2011.
Water 2016, 8, 303 29 of 29
69. Chen, Y.; He, J.; Mu, Y.; Huo, Y.-C.; Zhang, Z.; Kotsopoulos, T.A.; Zeng, R.J. Mathematical modeling of upflow
anaerobic sludge blanket (UASB) reactors: Simultaneous accounting for hydrodynamics and bio-dynamics.
Chem. Eng. Sci. 2015, 137, 677–684. [CrossRef]
70. Lu, X.; Zhen, G.; Estrada, A.L.; Chen, M.; Ni, J.; Hojo, T.; Kubota, K.; Li, Y.-Y. Operation performance and
granule characterization of upflow anaerobic sludge blanket (UASB) reactor treating wastewater with starch
as the sole carbon source. Bioresour. Technol. 2015, 180, 264–273. [CrossRef] [PubMed]
71. Alvarez, R.; Lidén, G. The effect of temperature variation on biomethanation at high altitude.
Bioresour. Technol. 2008, 99, 7278–7284. [CrossRef] [PubMed]
72. Rakocy, J.E.; Shultz, R.C.; Bailey, D.S.; Thoman, E.S. Aquaponic Production of Tilapia and Basil: Comparing a
Batch and Staggered Cropping System; Nichols, M.A., Ed.; University of the Virgin Islands: St. Croix, VI, USA,
2004; Volume 648, pp. 63–69.
73. Davidson, J.; Summerfelt, S.T. Solids removal from a coldwater recirculating system—Comparison of a swirl
separator and a radial-flow settler. Aquac. Eng. 2005, 33, 47–61. [CrossRef]
74. Rafiee, G.; Saad, C.R. Nutrient cycle and sludge production during different stages of red tilapia
(Oreochromis sp.) growth in a recirculating aquaculture system. Aquaculture 2005, 244, 109–118. [CrossRef]
75. Suhr, K.I.; Letelier-Gordo, C.O.; Lund, I. Anaerobic digestion of solid waste in RAS: Effect of reactor type on
the biochemical acidogenic potential (BAP) and assessment of the biochemical methane potential (BMP) by
a batch assay. Aquac. Eng. 2015, 65, 65–71. [CrossRef]
76. Lambers, H.; Chapin, F.S.; Pons, T.L. Plant Physiological Ecology, 2nd ed.; Springer: Berlin, Germany, 2008.
77. Steingrobe, B.; Schenk, M.K. A model relating the maximum nitrate inflow of lettuce (Lactuca satvia L.) to the
growth of roots and shoots. Plant Soil 1994, 162, 249–257. [CrossRef]
78. Letey, J.; Jarrell, W.M.; Valoras, N. Nitrogen and water uptake patterns and growth of plants at various
minimum solution nitrate concentrations. J. Plant Nutr. 1982, 5, 73–89. [CrossRef]
79. Mathieu, J.; Linker, R.; Levine, L.; Albright, L.; Both, A.J.; Spanswick, R.; Wheeler, R.; Wheeler, E.;
de Villiers, D.; Langhans, R. Evaluation of the nicolet model for simulation of short-term hydroponic lettuce
growth and nitrate uptake. Biosyst. Eng. 2006, 95, 323–337. [CrossRef]
80. Klas, S.; Mozes, N.; Lahav, O. Development of a single-sludge denitrification method for nitrate removal
from RAS effluents: Lab-scale results vs. model prediction. Aquaculture 2006, 259, 342–353. [CrossRef]
81. González-González, A.; Cuadros, F. Effect of aerobic pretreatment on anaerobic digestion of olive mill
wastewater (OMWW): An ecoefficient treatment. Food Bioprod. Process. 2015, 95, 339–345. [CrossRef]
82. Van Rijn, J. Waste treatment in recirculating aquaculture systems. Aquac. Eng. 2013, 53, 49–56. [CrossRef]
83. Dawson, C.J.; Hilton, J. Fertiliser availability in a resource-limited world: Production and recycling of
nitrogen and phosphorus. Food Policy 2011, 36, S14–S22. [CrossRef]
84. Rogers, P. Facing the freshwater crisis. Sci. Am. 2008, 299, 46–53. [CrossRef] [PubMed]
85. Ragnarsdottir, K.V.; Sverdrup, H.U.; Koca, D. Challenging the planetary boundaries I: Basic principles of an
integrated model for phosphorous supply dynamics and global population size. Appl. Geochem. 2011, 26,
S303–S306. [CrossRef]
86. Zekki, H.; Gauthier, L.; Gosselin, A. Growth, productivity, and mineral composition of hydroponically
cultivated greenhouse tomatoes, with or without nutrient solution recycling. J. Am. Soc. Hortic. Sci. 1996,
121, 1082–1088.
87. Van Bussel, C.G.J.; Schroeder, J.P.; Wuertz, S.; Schulz, C. The chronic effect of nitrate on production
performance and health status of juvenile turbot (Psetta maxima). Aquaculture 2012, 326–329, 163–167.
[CrossRef]
© 2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC-BY) license (http://creativecommons.org/licenses/by/4.0/).
1. Rakocy, J.E. Aquaponics-Integrating Fish and Plant Culture; Wiley-Blackwell: Hoboken, NJ, USA, 2012;
pp. 344–386.
2. Graber, A.; Junge, R. Aquaponic systems: Nutrient recycling from fish wastewater by vegetable production.
Desalination 2009, 246, 147–156. [CrossRef]
3. Vermeulen, T.; Kamstra, A. The need for systems design for robust aquaponic systems in the urban
environment. Int. Symp. Soil. Cultiv. 2013, 1004, 71–78. [CrossRef]
4. Goddek, S.; Delaide, B.; Mankasingh, U.; Ragnarsdottir, K.; Jijakli, H.; Thorarinsdottir, R. Challenges of
Sustainable and commercial aquaponics. Sustainability 2015, 7, 4199–4224. [CrossRef]
5. Kloas, W.; Groß, R.; Baganz, D.; Graupner, J.; Monsees, H.; Schmidt, U.; Staaks, G.; Suhl, J.; Tschirner, M.;
Wittstock, B.; et al. A new concept for aquaponic systems to improve sustainability, increase productivity,
and reduce environmental impacts. Aquac. Environ. Interact. 2015, 7, 179–192. [CrossRef]
6. Jijakli, M.H.; Delaide, B.; Gott, J. Plant Production Capacity and Nutrient Mass Balance in the PAFF Box, an
Urban Aquaponics Module: Preliminary Findings; Geography and Environment University of Southampton:
Southampton, UK, 2016.
7. Goddek, S. Three-loop Aquaponics Systems: Chances and challenges. In Proceedings of the International
Conference on Aquaponics Research Matters, Ljubljana, Slovenia, 22 March 2016.
8. Seawright, D.E.; Stickney, R.R.; Walker, R.B. Nutrient dynamics in integrated aquaculture-hydroponics
systems. Aquaculture 1998, 160, 215–237. [CrossRef]
9. Licamele, J.D. Biomass Production and Nutrient Dynamics in an Aquaponics System. Ph.D. Thesis,
University of Arizona, Tucson, AZ, USA, 2009.
10. Neto, R.M.; Ostrensky, A. Nutrient load estimation in the waste of Nile tilapia Oreochromis niloticus (L.)
reared in cages in tropical climate conditions. Aquac. Res. 2013, 46, 1309–1322. [CrossRef]
11. Adler, P.R.; Summerfelt, S.T.; Glenn, D.M.; Takeda, F. Evaluation of the effect of a conveyor production
strategy on lettuce and basil productivity and phosphorus removal from aquaculture wastewater.
In Proceedings of the Second International Conference on Recycling the Resource Ecological Engineering
for Wastewater Treatment, Waedenswil-Zurich, Switzerland, 18–22 September 1995; Staudenmann, J.,
Schönborn, A., Etnier, C., Eds.; Trans Tech Publications: Waedenswil-Zurich, Switzerland, 1996; pp. 131–136.
12. Roosta, H.R.; Hamidpour, M. Effects of foliar application of some macro- and micro-nutrients on tomato
plants in aquaponic and hydroponic systems. Sci. Hortic. (Amst.) 2011, 129, 396–402. [CrossRef]
13. Savidov, N.A.; Hutchings, E.; Rakocy, J.E. Fish and plant production in a recirculating aquaponic system:
A new approach to sustainable agriculture in Canada. Acta Hortic. 2007, 742, 209–222. [CrossRef]
14. Rakocy, J.E.; Bailey, D.S.; Shultz, K.A.; Cole, W.M. Evaluation of a commercial-scale aquaponic unit for
the production of tilapia and lettuce. In Proceedings of the 4th International Symposium on Tilapia in
Aquaculture, Orlando, FL, USA, 9–12 November 1997; pp. 357–372.
15. Mirzoyan, N.; Tal, Y.; Gross, A. Anaerobic digestion of sludge from intensive recirculating aquaculture
systems: Review. Aquaculture 2010, 306, 1–6. [CrossRef]
16. Mirzoyan, N.; McDonald, R.C.; Gross, A. anaerobic treatment of brackishwater aquaculture sludge:
An alternative to waste stabilization ponds. J. World Aquac. Soc. 2012, 43, 238–248. [CrossRef]
17. Mirzoyan, N.; Gross, A. Use of UASB reactors for brackish aquaculture sludge digestion under different
conditions. Water Res. 2013, 47, 2843–2850. [CrossRef] [PubMed]
18. Sterman, J. Business Dynamics: Systems Thinking and Modeling for a Complex World; McGraw Hill: New York,
NY, USA, 2000.
19. Sverdrup, H.U.; Ragnarsdottir, K.V. Challenging the planetary boundaries II: Assessing the sustainable
global population and phosphate supply, using a systems dynamics assessment model. Appl. Geochem. 2011,
26, S307–S310. [CrossRef]
20. Borshchev, A. The Big Book of Simulation Modeling; AnyLogic North America: Chicago, IL, USA, 2013.
21. Schrader, K.K.; Davidson, J.W.; Summerfelt, S.T. Evaluation of the impact of nitrate-nitrogen levels
in recirculating aquaculture systems on concentrations of the off-flavor compounds geosmin and
2-methylisoborneol in water and rainbow trout (Oncorhynchus mykiss). Aquac. Eng. 2013, 57, 126–130.
[CrossRef]
Water 2016, 8, 303 27 of 29
22. Davidson, J.; Good, C.; Welsh, C.; Summerfelt, S.T. Abnormal swimming behavior and increased deformities
in rainbow trout Oncorhynchus mykiss cultured in low exchange water recirculating aquaculture systems.
Aquac. Eng. 2011, 45, 109–117. [CrossRef]
23. Davidson, J.; Good, C.; Welsh, C.; Summerfelt, S.T. Comparing the effects of high vs. low nitrate on the
health, performance, and welfare of juvenile rainbow trout Oncorhynchus mykiss within water recirculating
aquaculture systems. Aquac. Eng. 2014, 59, 30–40. [CrossRef]
24. Bonachela, S.; González, A.M.; Fernández, M.D. Irrigation scheduling of plastic greenhouse vegetable crops
based on historical weather data. Irrig. Sci. 2006, 25, 53–62. [CrossRef]
25. FAO. FAO Irrigation and Drainage Paper: Crop Evapotranspiration; Allen, R.G., Pereira, L.S., Raes, D., Smith, M.,
Eds.; FAO: Rome, Italy, 1998.
26. Zolnier, S.; Lyra, G.B.; Gates, R.S. Evapotranspiration estimates for greenhouse lettuce using an intermittent
nutrient film technique. Am. Soc. Agric. Biol. Eng. 2004, 47, 271–282. [CrossRef]
27. Boulard, T. Evapotranspiration in greenhouses. Encycl. Water Sci. 2003. [CrossRef]
28. Jolliet, O.; Bailey, B. The effect of climate on tomato transpiration in greenhouses: Measurements and models
comparison. Agric. For. Meteorol. 1992, 58, 43–62. [CrossRef]
29. Fernández, M.D.; Bonachela, S.; Orgaz, F.; Thompson, R.; López, J.C.; Granados, M.R.; Gallardo, M.; Fereres, E.
Measurement and estimation of plastic greenhouse reference evapotranspiration in a Mediterranean climate.
Irrig. Sci. 2010, 28, 497–509. [CrossRef]
30. Möller, M.; Assouline, S. Effects of a shading screen on microclimate and crop water requirements. Irrig. Sci.
2006, 25, 171–181. [CrossRef]
31. Deutscher Wetterdienst WESTE-XL. Available online: https://kunden.dwd.de/weste (accessed on
13 September 2015).
32. Timmons, M.B.; Ebeling, J.M. Recirculating Aquaculture, 3rd ed.; Ithaca Publishing Company LLC: Ithaca, NY,
USA, 2013.
33. Rakocy, J.E.; Masser, M.P.; Losordo, T.M. Recirculating Aquaculture Tank Production Systems:
Aquaponics—Integrating Fish and Plant Culture; Southern Regional Aquaculture Centre: Stoneville, MS,
USA, 2006; pp. 1–16.
34. Gullian-Klanian, M.; Arámburu-Adame, C. Rendimiento de juveniles de tilapia del Nilo Oreochromis
niloticus en un sistema híperintensivo de recirculación acuícola con mínimo recambio de agua. Lat. Am. J.
Aquat. Res. 2013, 41, 150–162.
35. El-Shafai, S.A.; El-Gohary, F.A.; Nasr, F.A.; van der Steen, N.P.; Gijzen, H.J. Chronic ammonia toxicity to
duckweed-fed tilapia (Oreochromis niloticus). Aquaculture 2004, 232, 117–127. [CrossRef]
36. Al-Hafedh, Y.S.; Alam, A.; Alam, M.A. Performance of plastic biofilter media with different configuration
in a water recirculation system for the culture of Nile tilapia (Oreochromis niloticus). Aquac. Eng. 2003, 29,
139–154. [CrossRef]
37. Dalsgaard, J.; Lund, I.; Thorarinsdottir, R.; Drengstig, A.; Arvonen, K.; Pedersen, P.B. Farming different
species in RAS in Nordic countries: Current status and future perspectives. Aquac. Eng. 2013, 53, 2–13.
[CrossRef]
38. DeLong, D.P.; Losordo, T.M.; Rakocy, J.E. Tank Culture of Tilapia; Southern Regional Aquaculture Centre:
Stoneville, MS, USA, 2009; No. 282.
39. Eding, E.H.; Verdegem, M.; Martins, C.; Schlaman, G.; Heinsbroek, L.; Laarhoven, B.; Ende, S.; Verreth, J.;
Aartsen, F.; Bierbooms, V. Tilapia farming using Recirculating Aquaculture Systems (RAS)—Case study in
the Netherlands. In Handbook for Sustainable Aquaculture; Eurofish International Organisation: Copenhagen,
Denmark, 2009.
40. Veras, G.C.; Murgas, L.D.S.; Rosa, P.V.; Zangeronimo, M.G.; da Ferreira, M.S.S.; Leon, J.A.S.-D. Effect
of photoperiod on locomotor activity, growth, feed efficiency and gonadal development of Nile tilapia.
Rev. Bras. Zootec. 2013, 42, 844–849. [CrossRef]
41. Resh, H.M. Hydroponic Food Production: A Definitive Guidebook for the Advanced Home Gardener and the
Commercial Hydroponic Grower; CRC Press: Boca Raton, FL, USA, 2012.
42. Appels, L.; Baeyens, J.; Degrève, J.; Dewil, R. Principles and potential of the anaerobic digestion of
waste-activated sludge. Prog. Energy Combust. Sci. 2008, 34, 755–781. [CrossRef]
Water 2016, 8, 303 28 of 29
43. Zhao, L.; Guo, J.; Lian, J.; Guo, Y.; Yue, L.; Gou, C.; Zhang, C.; Liu, X. Study of the dynamics and material
transformation characteristics of nitrite denitrification in UASB. Biotechnol. Biotechnol. Equip. 2015, 29,
907–914. [CrossRef]
44. Cuervolopez, F.; Martinez, F.; Gutierrezrojas, M.; Noyola, R.; Gomez, J. Effect of nitrogen loading rate and
carbon source on denitrification and sludge settleability in upflow anaerobic sludge blanket (UASB) reactors.
Water Sci. Technol. 1999, 40, 123–130. [CrossRef]
45. Lettinga, G.; Pol, L.W.H. UASB-process design for various types of wastewaters. Water Sci. Technol. 1991, 24,
87–107.
46. Ross, L.G. Environmental physiology and energetics. In Tilapias: Biology and Exploitation; McAndrew, B.J.,
Ed.; Springer Netherlands: Dordrecht, The Netherlands, 2000; pp. 89–128.
47. Alfredo, M.H.; Hector, S.L. Blood gasometric trends in hybrid red tilapia Oreochromis niloticus (Linnaeus)
ˆ O. mossambicus (Peters) while adapting to increasing salinity. J. Aquac. Trop. 2002, 17, 101–112.
48. El-Sayed, A.-F.M. Tilapia Culture; CABI Publishing: Oxfordshire, UK, 2006.
49. FAO. Cultured Aquatic Species Information Programme. Oncorhynchus Mykiss. Available online: http:
//www.fao.org/fishery/culturedspecies/Oncorhynchus_mykiss/en (accessed on 21 August 2015).
50. Finstad, B.; Staurnes, M.; Reite, O.B. Effect of low temperature on sea-water tolerance in rainbow trout,
Salmo gairdneri. Aquaculture 1988, 72, 319–328. [CrossRef]
51. Coghlan, S.M.; Ringler, N.H. Temperature-dependent effects of rainbow trout on growth of atlantic salmon
parr. J. Great Lakes Res. 2005, 31, 386–396. [CrossRef]
52. Azevedo, P.A.; Podemski, C.L.; Hesslein, R.H.; Kasian, S.E.M.; Findlay, D.L.; Bureau, D.P. Estimation of
waste outputs by a rainbow trout cage farm using a nutritional approach and monitoring of lake water
quality. Aquaculture 2011, 311, 175–186. [CrossRef]
53. Westin, D.T. Nitrate and nitrite toxicity to salmonid fishes. Progress Fish-Cult. 1974, 36, 86–89. [CrossRef]
54. Barton, B.A. Principles of Salmonid Culture; Developments in Aquaculture and Fisheries Science; Elsevier:
Amsterdam, The Netherlands, 1996; Volume 29.
55. Wedemeyer, G. Physiology of Fish in Intensive Culture Systems; Springer: Berlin, Germany, 1996.
56. FAO. Cultured Aquatic Species Information Programme. Clarias Gariepinus. Available online: http:
//www.fao.org/fishery/culturedspecies/Clarias_gariepinus/en (accessed on 21 August 2015).
57. Wellborn, T.L. Channel Catfish: Life History and Biology; Southern Regional Aquaculture Centre: Stoneville,
MS, USA, 1988.
58. Tucker, C.S.; Hargreaves, J.A. Biology and Culture of Channel Catfish; Elsevier Science Ltd.: Amsterdam,
The Netherlands, 2004.
59. Horváth, L.; Tamás, G.; Seagrave, C. Carp and Pond Fish Culture, 2nd ed.; Blackwell Science Ltd.: Oxford,
UK, 2002.
60. FAO. Cultured Aquatic Species Information Programme. Sander Lucioperca. Available online: http:
//www.fao.org/fishery/culturedspecies/Sander_lucioperca/en (accessed on 21 August 2015).
61. Keen, G.A.; Prosser, J.I. Interrelationship between pH and surface growth of Nitrobacter. Soil Biol. Biochem.
1987, 19, 665–672. [CrossRef]
62. Tyson, R.V.; Simonne, E.H.; Davis, M.; Lamb, E.M.; White, J.M.; Treadwell, D.D. Effect of nutrient solution,
nitrate-nitrogen concentration, and pH on nitrification rate in Perlite medium. J. Plant Nutr. 2007, 30, 901–913.
[CrossRef]
63. Parker, R. Aquaculture Science, 2nd ed.; Delmar Publications: Clifton Park, NY, USA, 2002.
64. Huang, Z.; Gedalanga, P.B.; Asvapathanagul, P.; Olson, B.H. Influence of physicochemical and operational
parameters on Nitrobacter and Nitrospira communities in an aerobic activated sludge bioreactor. Water Res.
2010, 44, 4351–4358. [CrossRef] [PubMed]
65. Blackburne, R.; Vadivelu, V.M.; Yuan, Z.; Keller, J. Kinetic characterisation of an enriched Nitrospira culture
with comparison to Nitrobacter. Water Res. 2007, 41, 3033–3042. [CrossRef] [PubMed]
66. Sonneveld, C.; Voogt, W. Plant Nutrition of Greenhouse Crops; Springer Netherlands: Dordrecht,
The Netherlands, 2009.
67. Resh, H.M. Hydroponic Tomatoes; Taylor and Francis: Abingdon, UK, 2002.
68. Kafkafi, U.; Tarchitzky, J. Fertigation: A Tool for Efficient Water and Nutrient Management; IFA and IPI: Paris,
France, 2011.
Water 2016, 8, 303 29 of 29
69. Chen, Y.; He, J.; Mu, Y.; Huo, Y.-C.; Zhang, Z.; Kotsopoulos, T.A.; Zeng, R.J. Mathematical modeling of upflow
anaerobic sludge blanket (UASB) reactors: Simultaneous accounting for hydrodynamics and bio-dynamics.
Chem. Eng. Sci. 2015, 137, 677–684. [CrossRef]
70. Lu, X.; Zhen, G.; Estrada, A.L.; Chen, M.; Ni, J.; Hojo, T.; Kubota, K.; Li, Y.-Y. Operation performance and
granule characterization of upflow anaerobic sludge blanket (UASB) reactor treating wastewater with starch
as the sole carbon source. Bioresour. Technol. 2015, 180, 264–273. [CrossRef] [PubMed]
71. Alvarez, R.; Lidén, G. The effect of temperature variation on biomethanation at high altitude.
Bioresour. Technol. 2008, 99, 7278–7284. [CrossRef] [PubMed]
72. Rakocy, J.E.; Shultz, R.C.; Bailey, D.S.; Thoman, E.S. Aquaponic Production of Tilapia and Basil: Comparing a
Batch and Staggered Cropping System; Nichols, M.A., Ed.; University of the Virgin Islands: St. Croix, VI, USA,
2004; Volume 648, pp. 63–69.
73. Davidson, J.; Summerfelt, S.T. Solids removal from a coldwater recirculating system—Comparison of a swirl
separator and a radial-flow settler. Aquac. Eng. 2005, 33, 47–61. [CrossRef]
74. Rafiee, G.; Saad, C.R. Nutrient cycle and sludge production during different stages of red tilapia
(Oreochromis sp.) growth in a recirculating aquaculture system. Aquaculture 2005, 244, 109–118. [CrossRef]
75. Suhr, K.I.; Letelier-Gordo, C.O.; Lund, I. Anaerobic digestion of solid waste in RAS: Effect of reactor type on
the biochemical acidogenic potential (BAP) and assessment of the biochemical methane potential (BMP) by
a batch assay. Aquac. Eng. 2015, 65, 65–71. [CrossRef]
76. Lambers, H.; Chapin, F.S.; Pons, T.L. Plant Physiological Ecology, 2nd ed.; Springer: Berlin, Germany, 2008.
77. Steingrobe, B.; Schenk, M.K. A model relating the maximum nitrate inflow of lettuce (Lactuca satvia L.) to the
growth of roots and shoots. Plant Soil 1994, 162, 249–257. [CrossRef]
78. Letey, J.; Jarrell, W.M.; Valoras, N. Nitrogen and water uptake patterns and growth of plants at various
minimum solution nitrate concentrations. J. Plant Nutr. 1982, 5, 73–89. [CrossRef]
79. Mathieu, J.; Linker, R.; Levine, L.; Albright, L.; Both, A.J.; Spanswick, R.; Wheeler, R.; Wheeler, E.;
de Villiers, D.; Langhans, R. Evaluation of the nicolet model for simulation of short-term hydroponic lettuce
growth and nitrate uptake. Biosyst. Eng. 2006, 95, 323–337. [CrossRef]
80. Klas, S.; Mozes, N.; Lahav, O. Development of a single-sludge denitrification method for nitrate removal
from RAS effluents: Lab-scale results vs. model prediction. Aquaculture 2006, 259, 342–353. [CrossRef]
81. González-González, A.; Cuadros, F. Effect of aerobic pretreatment on anaerobic digestion of olive mill
wastewater (OMWW): An ecoefficient treatment. Food Bioprod. Process. 2015, 95, 339–345. [CrossRef]
82. Van Rijn, J. Waste treatment in recirculating aquaculture systems. Aquac. Eng. 2013, 53, 49–56. [CrossRef]
83. Dawson, C.J.; Hilton, J. Fertiliser availability in a resource-limited world: Production and recycling of
nitrogen and phosphorus. Food Policy 2011, 36, S14–S22. [CrossRef]
84. Rogers, P. Facing the freshwater crisis. Sci. Am. 2008, 299, 46–53. [CrossRef] [PubMed]
85. Ragnarsdottir, K.V.; Sverdrup, H.U.; Koca, D. Challenging the planetary boundaries I: Basic principles of an
integrated model for phosphorous supply dynamics and global population size. Appl. Geochem. 2011, 26,
S303–S306. [CrossRef]
86. Zekki, H.; Gauthier, L.; Gosselin, A. Growth, productivity, and mineral composition of hydroponically
cultivated greenhouse tomatoes, with or without nutrient solution recycling. J. Am. Soc. Hortic. Sci. 1996,
121, 1082–1088.
87. Van Bussel, C.G.J.; Schroeder, J.P.; Wuertz, S.; Schulz, C. The chronic effect of nitrate on production
performance and health status of juvenile turbot (Psetta maxima). Aquaculture 2012, 326–329, 163–167.
[CrossRef]
© 2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC-BY) license (http://creativecommons.org/licenses/by/4.0/).
Add Comment