Total Ammonia Nitrogen Removal Rate Research Articles

Growth, productivity and nutrient removal rates of sea lettuce (Ulva lactuca) in a land-based IMTA system with white seabass (Atractoscion nobilis) in Southern California

Three consecutive 3-week trials were conducted to assess the growth, productivity, and nutrient removal rates of sea lettuce (Ulva lactuca) cultured in effluents from white seabass (Atractoscion nobilis) raceways. All U. lactuca cultivation trials were conducted in 175 L tanks with a surface area of 0.89 m2 run in triplicate, with water quality and growth measurements taken weekly. For the shading trial, U. lactuca was stocked at 0.56 kg/m2 with either 0%, 30%, or 60% shade and seawater supplied at 63 tank volumes per day (vol./day) water exchange (7.6 L/min) for each tank. The removal rate of total ammonia nitrogen (TAN) decreased with increasing shade levels, and the peak exceeded 80% removal at 0% shading. Growth rate and productivity of U. lactuca under 0% shading was 12.09 ± 3.13%/d and 13.28 ± 4.66 g DW/m2/d, which were both significantly higher than other shading levels. For the stocking density and water exchange rate trial, the stocking density of U. lactuca was 0.56 or 1.12 kg/m2, and seawater exchange rates were 4, 12, or 63 vol./day in a 2-factor design. In this trial, TAN removal rates were 100% across all treatment combinations. Growth rate of U. lactuca was highest (20.36 ± 2.36%/d) at 0.56 kg/m2 under the exchange rate of 63 vol./day, and the productivity reached up to 30.89 ± 6.53 g DW/m2/d, which was not different than that of U. lactuca stocked with 1.12 kg/m2 at the same exchange rate (p = 0.47). In a trial comparing sand-filtered seawater (RAW seawater) with seawater effluent from a raceway containing A. nobilis (FISH seawater), TAN removal rate by U. lactuca was consistently nearly 100% when supplied with FISH seawater with a TAN concentration ranging from 0.11 to 0.18 mg/L. Growth rate and productivity of U. lactuca supplied with FISH seawater were 21.36 ± 2.25%/d and 33.83 ± 7.29 g DW/m2/d, respectively, which was not different than that for U. lactuca supplied with RAW seawater. However, the protein content of U. lactuca cultured with FISH seawater was significantly higher and C/N ratio significantly lower than those cultured with RAW seawater (p < 0.01), which indicated that U. lactuca was in a nitrogen-limited situation when cultured with RAW seawater. In light of the better understanding of U. lactuca performance achieved in our study, the optimum U. lactuca and A. nobilis density combinations will be confirmed in future studies based on nitrogen balance to maximize the nutrient removal rates and diversity of seafood production.

Total ammonia nitrogen removal and microbial community dynamics in an outdoor HDPE-lined shrimp pond with no water discharge

This study assessed the characteristics of a zero-discharge outdoor high-density polyethylene (HDPE)-lined demonstration aquaculture pond (400 m2) in terms of water quality variables, total ammonia nitrogen (TAN) removal and oxygen net primary production (NPP) indices, and photosynthetic microbiome over a 76-day crop cycle. The shrimp harvest yield was 4.1 t/ha/crop with an average daily gain (ADG) of 0.15 g/day and a feed conversion ratio (FCR) of 1.49. During shrimp cultivation with a semi-intensive stocking density (40 shrimp/m2), there were low levels of TAN (<1.01 mg-N/L), nitrite (<0.21 mg-N/L), and nitrate (<2.79 mg-N/L). Ammonia removal was mainly mediated by photoautotrophic uptake, as evidenced by the consistent estimated TAN uptake rate of 0.05 ± 0.02 g-N/m3 h, which was calculated based on photosynthesis. The overall TAN removal rate of 0.10 ± 0.08 g-N/m3 h was maintained by suspended microorganisms in water, which exceeded that of microorganisms attached to the HDPE liner surface. A positive oxygen NPP of 0.24–1.16 g-O2/m3 h during light availability indicated prevailing autotrophic conditions. The bacterial community in the water was dominated by Phyla Pseudomonadota (Proteobacteria; 16–32%), Bacteroidota (Bacteroidetes; 15–29%), Cyanobacteria (7–35%), and Actinomycetota (Actinobacteria; 3–39%). The chloroplast amplicon sequence variants (ASVs) indicated abundances of Bacillariophyta (27–97%) and Chlorophyta (0.4–67%). High centric diatom populations (Bacillariophyta) were detected throughout cultivation, while the proportion of green algae (Chlorophyta) was positively correlated with increased TAN availability when feeding was increased. The findings enabled estimations of TAN removal and oxygen NPP rates and provided an understanding of correlations between environmental variables and bacterial and phytoplankton populations in the outdoor lined shrimp pond.

Effects of dissolved organic carbon and total ammonia nitrogen concentrations with the same DOC/TAN on biofloc performance

The regulation of the carbon-to‑nitrogen ratio (C/N) is at the core of biofloc technology. This study compared the performance of bioflocs under different dissolved organic carbon (DOC) and total ammonia nitrogen (TAN) concentrations but the same DOC/TAN ratio. Dissolved organic carbon and total ammonium nitrogen were set at 200 mg/L and 10 mg/L (Group 200/10), 100 mg/L and 5 mg/L (Group 100/5), and 50 mg/L and 2.5 mg/L (Group 50/2.5), respectively. The TAN removal rates of groups A, B, and C were 1.89 ± 0.02 mg N/g TSS·h, 1.63 ± 0.03 mg N/g TSS·h, and 1.32 ± 0.02 mg N/g TSS·h, respectively, and the differences were significant (P < 0.05). At the phylum level, the microbial community structure was dominated by Proteobacteria, Bacteroidetes, Actinobacteria, Verrucomicrobia, and Planctomycetes. At the genus level, Gemmobacter, Hydrogenophaga, and Microbacterium were the dominant genera. Most of bacteria community differed significantly among the three groups. As the concentration of carbon and nitrogen sources increased, the Shannon index showed a decrease in bacterial diversity, and the number of heterotrophic bacteria significantly increased. The crude protein content of flocs in group A ((29.22 ± 0.20)%) was significantly lower than that in groups B ((30.56 ± 0.32)%) and C ((30.83 ± 0.20)%). In groups A and B with higher carbon and nitrogen concentrations, the copy numbers of genes related to nitrification were relatively low, but the copy numbers of genes related to denitrification were relatively high. Therefore, it can be concluded that with a ratio of 20 of DOC/TAN, increasing DOC and TAN concentrations led to a significant increase in TAN removal capacity, heterotrophic bacteria count, denitrification function gene copies, and crude protein content of bioflocs, and a decrease in bacterial diversity, nitrification function gene copies, and C/N of bioflocs (P < 0.05). These results suggest that the influence of DOC and TAN concentrations on bioflocs performance may be more significant than that of DOC/TAN, and should be fully considered in practical bioflocs technology systems.

Chlorine vs. Sodium Chloride Regeneration of Zeolite Column for Ammonium Removal from an Explosives Impacted Mining Wastewater

There has only been limited research on ammonium removal by zeolites followed by chlorine regeneration; these studies used batch tests and, in many cases, only dealt with single solute solutions as opposed to multi-component ones. To better simulate full-scale applications, this study used a continuous-flow ion exchange (IE) column system to assess the feasibility of chlorine regeneration of a zeolite IE column used for the removal of ammonium from synthetic explosives impacted mining wastewater (EIMWW). Multi-cycle column loading-regeneration tests were used to evaluate and compare the performance of a NaOCl (1000 ppm as free Cl2) solution with that of a standard salt regeneration solution (5% NaCl). In addition, the impact of two loading cycle durations was evaluated. After three operational cycles with 6 h loading phases, the TAN (total ammonia nitrogen) uptake after NaOCl regeneration was almost the same as that obtained with salt regeneration (0.21 meq/g vs. 0.21 meq/g). The zeolite with NaOCl regeneration showed a higher preference for TAN than with NaCl regeneration (Ca:TAN:K = 2.8:2.3:1 vs. 2.5:1.9:1 for the 6 h loading phase); however, the NaOCl regeneration took longer to complete. It was also found that effluent pH, total chlorine level, and free chlorine level during the chlorine regeneration were positively related, seemingly confirming that the ammonium is oxidized to nitrogen gas and producing hydrogen ions. Regardless of the regeneration solution, if one uses a two-column system, with one column online and the other offline, the shorter loading cycles (6 h) yield a substantially higher daily TAN removal rate.

An Eco-Friendly Conversion of Aquaculture Suspended Solid Wastes Into High-Quality Fish Food by Improving Poly-β-Hydroxybutyrate Production

The aquaculture industry is vital in providing a valuable protein food source for humans, but generates a huge amount of solid and dissolved wastes that pose great risks to the environment and aquaculture sustainability. Suspended solids (in short SS), one of the aquaculture wastes, are very difficult to be treated due to their high organic contents. The bioconversion from wastewater, food effluents, and activated sludge into poly-β-hydroxybutyrate (PHB) is a sustainable alternative to generate an additional income and could be highly attractive to the agricultural and environmental management firms. However, little is known about its potential application in aquaculture wastes. In the present study, we first determined that 7.2% of SS was PHB. Then, the production of PHB was increased two-fold by the optimal fermentation conditions of wheat bran and microbial cocktails at a C/N ratio of 12. Also, the PHB-enriched SS showed a higher total ammonia nitrogen removal rate. Importantly, we further demonstrated that the PHB-enriched SS as a feed could promote fish growth and up-regulate the expression of the immune-related genes. Our study developed an eco-friendly and simple approach to transforming problematic SS wastes into PHB-enriched high-quality food for omnivorous fish, which will increase the usage efficiency of SS and provide a cheaper diet for aquatic animals.

Model-based identification of biological and pH gradient driven removal pathways of total ammonia nitrogen in single-chamber microbial fuel cells

Experimental data that allow for a precise identification of the total ammonia nitrogen (TAN) elimination pathways in single-chamber microbial fuel cells (SC-MFCs) are still very rare. However, nitrification–denitrification and ammonia volatilization are commonly reported as the two main removal mechanisms. This work presents a mathematical model to quantify the contribution of volatilization to TAN removal in SC-MFCs. For model verification, three different experimental settings were performed with TAN concentrations of 57 to 111mgNL−1: (i) biotic tests using sealed cathode chambers with variable oxygen supply, (ii) biotic tests for determination of the pH gradient within the cathodic microenvironment and (iii) pH-induced abiotic gas release tests. In biotic tests, the TAN removal rate in closed-circuit was 29–37% higher compared to open-circuit mode, which indicated additional electrochemical conservation processes. A limitation of oxygen availability on the air-facing side of the cathode (0.1%) resulted in negligible TAN removal rates. In contrast, an atmospheric oxygen content of 21% increased the biological oxidation rate of TAN to 653–730mgNm−2Catd−1and the electrochemical ammonia stripping rate to 210–241mgNm−2Catd−1 at 22 °C. During electricity generation, a peak pH value of 9.6 was measured by microelectrode measurements, which might lead to free ammonia nitrogen concentrations of 39–40mgFANL−1 nearby the cathode surface. Based on the proposed model and assuming an inhibition of ammonium-oxidizing bacteria, a maximum TAN removal rate via ammonia volatilization of 785mgNm−2Catd−1 (T = 22 °C) at a current density of 322 mA m−2Cat is estimated.

Sarcocornia neei: A novel halophyte species for bioremediation of marine aquaculture wastewater and production diversification in integrated systems

The integration of bioremediation systems is one of the most promising techniques to mitigate the environmental impact of aquaculture effluents. Also, it allows nutrient recycling, production diversification, and the creation of high-value by-products. In marine aquaculture, where the implementation of salt-tolerant extractive species is essential, halophyte plants have demonstrated to be optimal candidates for bioremediation of saline aquaculture wastewater.This study aimed to evaluate for the first time the efficiency of Sarcocornia neei (Lag.), a halophyte plant with high adaptability, salinity tolerance and growth potential when irrigated with seawater, in removing nutrients from marine fish aquaculture wastewater and artificial effluents. Two experiments were carried out. In the first one, the growth rate, removal of inorganic nutrients, and accumulation of organic compounds in deep-water hydroponics and sand-substrate systems were evaluated in artificial effluents with different nitrogen and phosphate loads during 70 days. In the second, due to the better performance achieved by S. neei in deep-water systems, its nitrogen removal efficiency and productivity rates were evaluated in deep-water aquaponics with marine aquaculture wastewater and artificial effluents at higher nitrogen loads during 61 days.The highest productivity rates achieved by S. neei (14.41 ± 0.78 kg m−2) were obtained in deep-water culture units, reaching 100% plant survival, suggesting that this species is more suitable for its implementation in this type of system. Significant total ammonia nitrogen removal rates were obtained by the plants, achieving a maximum in sand-substrate systems (0.68 ± 0.41 g m−2 day−1). The results of nitrate removal rates obtained by S. neei (11.25 ± 31.38 g m−2 day−1) make this species an ideal potential candidate for the removal of this compound present in marine RAS effluents. Accumulation of organic compounds was corroborated by obtaining a significant increase (p < 0.05) in organic N (31.2 ± 0.1 mg g dry weight−1) and organic P (4.0 ± 0.6 mg g dry weight−1) content in plant biomass at the end of the trials.These results indicated that S. neei is a good candidate for its use as a biofilter for marine aquaculture wastewater. Further investigations should be done to analyze possible influences on growth rates and nutrient removal efficiency by adding essential micronutrients, adjusting effluent salinity, and implementing different plant densities. Also, further studies could be interesting to determine the feasibility of long-term integration of a bioremediation system with S. neei associated with marine aquaculture effluents, approaching its application to industrial-scale production systems.

Effect of water velocity on ammonium and nitrite removal in pilot scale fixed bed biofilters

The effect of water velocity on nitrification rates in fixed bed biofilters was investigated in three freshwater pilot scale RAS with rainbow trout. Removal of total ammonia nitrogen (TAN) and nitrite-nitrogen were assessed by NH4Cl spikes and tested at four different water velocities in the biofilters (1.4, 5.4, 10.8 and 16.2 m h−1) under identical conditions. Water velocities below 10.8 m h−1 significantly reduced TAN- and nitrite removal rates. The surface specific TAN removal rates correlated with the TAN concentrations at the water velocities 10.8 and 16.2 m h−1, and the first order surface removal rate constant was estimated at 0.45 m h−1. However, no correlations between TAN removal and TAN concentrations were found at the lowest velocities. Up to five-fold elevated nitrite levels were found in the RAS when biofilters were operated at 1.4 m h−1 compared to the trials at other water velocities, substantiating the significant effect of water velocity on both nitrification processes. The importance of biofilter hydraulics documented in this pilot scale RAS probably have implications for design and operation in larger scale RAS.

Characteristics of Ammonia Removal and Nitrifying Microbial Communities in a Hybrid Biofloc-RAS for Intensive Litopenaeus vannamei Culture: A Pilot-Scale Study

Ammonia is the main pollution factor of the aquatic environment in marine shrimp culture systems. In order to demonstrate the feasibility of the combination of biofloc technology and nitrifying biofilter for the ammonia removal, a 70-day production trial was conducted in a simplified pilot-scale hybrid biofloc-based recirculating aquaculture system (biofloc-RAS) with the intensive culture of Litopenaeus vannamei. Nitrogen dynamics and nitrifying microbial communities were investigated in three replicated systems simultaneously under the conditions of high feed loading and zero water exchange. Along with biofloc development in the culture tank and biofilm formation in the nitrifying biofilter during the trial, nitrification could be fastly and effectively established in the system, which was indicated by the dynamics of total ammonia nitrogen (TAN), NO2–-N, NO3–-N, and total nitrogen (TN) concentrations. Meanwhile, similar nitrifying microorganisms could be found between biofloc and biofilm, despite some differences in abundance, diversity, and composition of ammonia-oxidizing archaea and bacteria and nitrite-oxidizing bacteria. High TAN removal rate could be achieved and was significantly and positively correlated with abundances of these nitrifying microbial communities in both biofloc and biofilm, further indicating that both biofloc and biofilm could contribute highly to nitrification performance of the biofloc-RAS. The results of this study indicate a potential application of the biofloc-RAS in coastal intensive aquaculture.

Total ammonia nitrogen (TAN) removal performance of a recirculating down-hanging sponge (DHS) reactor operated at 10 to 20 °C with activated carbon

Removal of total ammonium nitrogen (TAN) is essential during transportation of live seafood due to its high toxicity to aquatic cultures. Recirculating TAN removal system has been proposed and installed for the transportation of live seafood, while TAN removal performance often deteriorates at low temperature range (10–20 °C) due to the decrease of nitrifying activity. The authors have previously developed down-hanging sponge (DHS) reactors as a recirculating TAN removal system, which is a trickling filter system that uses polyurethane-sponge media to retain nitrifying biomass. The present study aimed to examine TAN removal performance of DHS reactor operated at 10 and 20 °C, and the following 4 DHS reactors were operated for the purpose; the DHS reactor operated 1) at 20 °C, 2) at 20 °C with addition of powdered activated carbon (AC) as an additional biomass carrier, 3) at 10 °C, and 4) at 10 °C with AC (designated as 20 °C-DHS, 20 °C-DHS-AC, 10 °C-DHS, and 10 °C-DHS-AC reactors, respectively). The DHS reactors were operated for 472 d with feeding of artificial seawater media, and TAN loading rates increased stepwisely up to 200 mg-N L-sponge media−1 d−1. TAN removal performance was examined by determining the concentrations of TAN, nitrite and nitrate in influent and effluent. Additionally, amplicon sequencing of prokaryotic 16S rRNA gene sequence was performed at Day 34, 212 and 374 to identify the nitrifying bacteria involved in the TAN removal. Both the 20 °C-DHS and 20 °C-DHS-AC reactors showed 200 mg-N L-sponge media−1 d−1 of TAN removal rate, whereas the 10 °C-DHS reactor showed only 15 mg-N L-sponge media−1 d−1. Notably, the addition of AC enhanced TAN removal performance of the DHS reactor operated at 10 °C. The 10 °C-DHS-AC reactor showed 60 mg-N L-sponge media−1 d−1 of TAN removal rate, which was 4-folds higher than those found in the 10 °C-DHS reactor. The amplicon sequencing analysis revealed that ammonia-oxidizing (i.e., Nitrosomonas) and nitrite-oxidizing (Nitrospira and Nitrospina) bacteria (AOB and NOB, respectively) proliferated in the operated DHS reactors, and the relative abundance of those AOB and NOB were greater in the DHS reactors with AC addition (i.e., the 20 °C-DHS-AC and 10 °C-DHS-AC reactors). Intriguingly, temperature difference (20 °C and 10 °C) resulted in occurrence of different NOB communities, and Nitrospira and Nitrospina were prominent in the DHS reactors operated at 20 °C and 10 °C, respectively. DHS reactor is capable of removing TAN even at 10 °C, which is applicable as a recirculating TAN removal system for transportation of live seafood.

Energy-Efficient Ammonia Recovery in an Up-Scaled Hydrogen Gas Recycling Electrochemical System.

Nutrient and energy recovery is becoming more important for a sustainable future. Recently, we developed a hydrogen gas recycling electrochemical system (HRES) which combines a cation exchange membrane (CEM) and a gas-permeable hydrophobic membrane for ammonia recovery. This allowed for energy-efficient ammonia recovery, since hydrogen gas produced at the cathode was oxidized at the anode. Here, we successfully up-scaled and optimized this HRES for ammonia recovery. The electrode surface area was increased to 0.04 m2 to treat up to 11.5 L/day (∼46 gN/day) of synthetic urine. The system was operated stably for 108 days at current densities of 20, 50, and 100 A/m2. Compared to our previous prototype, this new cell design reduced the anode overpotential and ionic losses, while the use of an additional membrane reduced the ion transport losses. Overall, this reduced the required energy input from 56.3 kJ/gN (15.6 kW h/kgN) at 50 A/m2 (prototype) to 23.4 kJ/gN (6.5 kW h/kgN) at 100 A/m2 (this work). At 100 A/m2, an average recovery of 58% and a TAN (total ammonia nitrogen) removal rate of 598 gN/(m2 day) were obtained across the CEM. The TAN recovery was limited by TAN transport from the feed to concentrate compartment.

Mixing and scale affect moving bed biofilm reactor (MBBR) performance

Moving Bed Biofilm Reactors (MBBR) are used increasingly in closed systems for farming of fish. Scaling, i.e. design of units of increasing size, is an important issue in general bio-reactor design since mixing behaviour will differ between small and large scale. Research is mostly performed on small-scale biofilters and the question is to what extent this can be upscaled to a commercial level. Therefore, the objective of this research was to establish the effect of mixing and scale on MBBR performance. The research was done in two major parts; firstly effects of scale-sensitive factors were studied in small reactors. Secondly, performance of these small reactors was then compared to increasingly large reactor sizes, using the same inlet water quality and biofilm.Firstly, a 200L MBBR (medium scale) was operated continuously using a synthetic feed solution. Biofilm carriers from this reactor was used for short-term experiments in 0.8L reactors (small scale) and compared with the performance of the 200L medium scale reactor. Reactor geometry and superficial air velocity (mh−1) were identical in these experiments. Subsequently, the small reactors were incubated with biofilm carriers from three commercial farms and performance compared with these large scale reactors. In a number of additional experiments the effect of mixing and Total Ammonia Nitrogen (TAN) was tested at small and medium scale.The results showed that MBBR scale has a significant effect on TAN removal rate. In general, the larger the scale the better the performance. TAN removal (rTAN) at small scale (0.8L) is about 80% compared to that at medium scale (200L). The difference between small scale and large scale (>20m3) is even higher. These findings warrant further studies on whether a plateau is reached in rTAN at a certain scale; a study which will have considerable importance for optimal design and dimensioning of commercial scale RAS. It was further found that superficial air velocity is not a good scaling factor for MBBRs. Upscaling while maintaining geometry implies increasing air injection depth and therefore increased energy input will be required at a comparable superficial air velocity, which is not incorporated in the superficial air velocity term (mh−1). Superficial air velocity and media filling% were found to have a strong effect on mixing time at small scale. An air velocity below a threshold of 5mh−1 decreased TAN removal at both small and medium scale. Intense mixing at small scale increased TAN removal at low TAN concentration. However, at a high TAN concentration, the small scale MBBR always performed at not more than 80% of the capacity of the medium scale system, irrespective of the mixing conditions. Hence, the capacity of full scale systems will be under-estimated when based solely on small scale experiments.

Hydrogen Gas Recycling for Energy Efficient Ammonia Recovery in Electrochemical Systems.

Recycling of hydrogen gas (H2) produced at the cathode to the anode in an electrochemical system allows for energy efficient TAN (Total Ammonia Nitrogen) recovery. Using a H2 recycling electrochemical system (HRES) we achieved high TAN transport rates at low energy input. At a current density of 20 A m-2, TAN removal rate from the influent was 151 gN m-2 d-1 at an energy demand of 26.1 kJ gN-1. The maximum TAN transport rate of 335 gN m-2 d-1 was achieved at a current density of 50 A m-2 and an energy demand of 56.3 kJ gN-1. High TAN removal efficiency (73-82%) and recovery (60-73%) were reached in all experiments. Therefore, our HRES is a promising alternative for electrochemical and bioelectrochemical TAN recovery. Advantages are the lower energy input and lower risk of chloride oxidation compared to electrochemical technologies and high rates and independence of organic matter compared to bioelectrochemical systems.

Cultivation of Chlorella mutant in cellulosic ethanol wastewater using a static mixing airlift photo‐bioreactor for simultaneous wastewater treatment

Cellulosic ethanol wastewater (CEW) is a mixture of wastewater from different procedures of cellulosic ethanol production. It cannot be completely purified with a secondary treatment method, such as anaerobic digestion. Microalgae cultivation is an effective way that can achieve advanced wastewater remediation and biomass production simultaneously. In this study, a static mixing airlift photo‐bioreactor (PBR) was designed for the cultivation of a Chlorella vulgaris mutant (named as Chlorella vulgaris CEW‐1) that was induced by ultraviolet (UV) mutagenesis. The microalgae exhibited sufficient robustness to undiluted CEW and its growth process in CEW under different conditions was investigated. The maximum biomass productivity in the static mixing airlift PBR can reach up to 1.98 g/L. The chemical oxygen demands removal rate (CODrr), total ammonia nitrogen removal rate (TANrr) and total phosphorus removal rate (TPrr) of the CEW were 54.8%, 97.6%, and 84.2%, respectively. Moreover, the kinetics of cell growth and substrate consumption of CEW were developed with logistic and modified Luedeking–Piret models. The superior efficiency of the static mixing PBR in microalgae cultivation and CEW treatment was further validated and compared with the other two PBRs. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1274–1281, 2017

Structure optimization of CycloBio fluidized sand biofilters based on numerical simulation

To improve the removal efficiency for dissolved wastes within CycloBio (CB) fluidized sand biofilters (FSBs) in recirculating aquaculture systems, we investigated their structural design and optimization using computational fluid dynamics (CFD) modeling tools, an orthogonal test method, and experimental verification. Results showed that the effects of structural parameters on bed expansion from large to small were: cone height, cone diameter and slot width. The best combination was: cone height 60mm, cone diameter 165mm, and slot width 1.0mm. The solid phase was well distributed not only in the radial direction, but also in the axial direction in the optimized CB FSB. The bed expansion (40%–120%) was increased about 13%. Energy savings were 21%–28% at the same bed expansion. When the optimized CB FSB was used to treat synthetic aquaculture wastewater, with three bed expansions and four levels of C/N, total ammonia nitrogen removal rate expressed per unit of expanded bed volume was high, from 629 to 881gm−3day−1. All results indicated that the structure of the optimized CB FSB was more reasonable and that the combination of CFD simulation and the orthogonal test method could be successfully applied to structural optimization.

Treating Effect of Potassium Ferrate to Aquaculture Recirculating Water

Aquaculture waste water was a major sewage resource, and recirculating aquaculture is an important mode of aquaculture development. Potassium ferrate is a novel sewage treatment agent and the use of potassium ferrate as a aquaculture recirculating water purification agents had a very important significance in the theoretical and practical application. When the amount of potassium ferrate is 8mg / L, the removal rate of the total number of colonies is 98.8%, the removal rate of COD is 92.16%, 98.78%, and sulfide is 98.42%. For the total amount of ammonia and nitrite also has a certain effect, when the amount of potassium ferrate is 12mg / L, the nitrite removal rate was 44.61%, total ammonia nitrogen removal rate was 23.61%.

Removal of nitrogen by Algal Turf Scrubber Technology in recirculating aquaculture system

Ongoing research in recirculation aquaculture focuses on evaluating and improving the purification potential of different types of filters. Algal Turf Scrubber (ATS) are special as they combine sedimentation and biofiltration. An ATS was subjected to high nutrient loads of catfish effluent to examine the effect of total suspended solids (TSS), sludge accumulation and nutrient loading rate on total ammonia nitrogen (TAN), nitrite and nitrate removal. Nutrient removal rates were not affected at TSS concentration of up to 0.08 g L−1 (P > 0.05). TAN removal rate was higher (0.656 ± 0.088 g m−² day−1 TAN) in young biofilm than (0.302 ± 0.098 g m−² day−1 TAN) in mature biofilm at loading rates of 3.81 and 3.76 g m−² day−1 TAN (P < 0.05), respectively, which were considered close to maximum loading. TAN removal increased with TAN loading, which increased with hydraulic loading rate. There was no significant difference in removal rate for both nitrite and nitrate between young and mature biofilms (P > 0.05). The ATS ably removed nitrogen at high rates from catfish effluent at high loading rates. ATS-based nitrogen removal exhibits high potential for use with high feed loads in intensive aquaculture.

폐쇄시스템 내에서 죽은 산호골격이 수질과 고착성 연체동물에 미치는 영향

폐쇄 사육 시스템에서 고착성 무척추동물 특히 연체동물의 부착용 재료로서 이용되고 있는 dead rock과 live rock이 수질에 부가적으로 미치는 영향을 파악하고자 인도네시아로부터 수입된 dead rock과 live rock을 인공해수를 이용한 실험수조에 투입 한 후 수질변화를 관찰하였다. 두 종류의 rock들은 모두 pH 안정에 영향을 주었으며 질소화합물의 분해에도 일정한 영향을 주는 것으로 나타났다. dead rock의 경우 사용전 충분한 안정화 기간을 거침으로써 부착용 도구로서 뿐만 아니라 훌륭한 보조여과 기능을 담당할 수 있는 것으로 사료된다. live rock의 경우에는 이미 부착되어 서식하고 있는 조류나 박테리아에 의해 dead rock에 비해 더욱 높은 질소화합물 분해 능력을 나타냈으며 초기 투입 시 부착되어 있는 생물의 폐사나 해적생물의 유입에 따른 위험성을 제거 할 경우 사육시스템 내에서 단순한 부착용 재료로서 뿐만 아니라 다양한 목적에 이용가능 할 것으로 사료된다. Recently, for the purpose of constructing artificial ecosystem, the public aquarium and experimental mesocosm systems are receiving attention. To design and establish an aquarium and mesocosm system, there is need of several materials for simulating the environment, such as sediments, rocks, and plants. Expecially for sessile mollusks, there must be proper materials to which sessile invertebrates can adhere. Nowadays, many aquariums and mesocosm systems are using dead coral skeletons for sessile mollusks. This study was proceeded to have data on the effect of dead coral skeletons on water qualities with the experiment on the environmental factors. For this purpose, I made glass tank for experiment, chose two types of dead coral skeletons imported from the Indonesia and observed the change of water qualities and decomposition efficiency of TAN (total ammonia-nitrogen), nitrite (<TEX>$NO_2{^-}$</TEX>) and nitrate (<TEX>$NO_3{^-}$</TEX>). As a result, the lager the surface area was, the more TAN, nitrite and nitrate decomposition rate increased. In addition, coral skeletons covered with crustose algae and bacteria in the tank showed faster TAN, nitrite and nitrate removal rate and stabilization. Accordingly, this experiment suggested that dead coral skeletons could be used as a sub filter for the closed system as well as an adhering plate.

Comparison of the Nitrification Efficiencies of Three Biofilter Media in a Freshwater System

Total ammonia nitrogen (TAN) removal efficiencies of a sand filter (SF), polystyrene microbead filter (PF), and Kaldnes bead filter (KF) media were evaluated under ammonia loading rates of 5, 25, and 50 g <TEX>$m^{-3}day^{-1}$</TEX>. The volume of each filter media tested was 7 L, and the water flow rate for all filter media was 24 L/min. The specific surface areas of the SF, PF, and KF were 7,836, 3,287, and 500 <TEX>$m^2/m^3$</TEX>, respectively. Sand was fluidized and the other two media were trickle filtered. The volumetric TAN removal rate increased with increasing ammonia loading rate for all filter media. Mean volumetric TAN removal rates under the ammonia loading rates of 5, 25, and 50 g <TEX>$m^{-3}day^{-1}$</TEX> in SF (39.3, 168.6, and 322.7 g <TEX>$m^{-3}day^{-1}$</TEX>, respectively) were higher than those in PF (35.0, 157.4, and 310.5 g <TEX>$m^{-3}day^{-1}$</TEX>, respectively) and KF (32.1, 142.5, and 288.1 g <TEX>$m^{-3}day^{-1}$</TEX>, respectively). These results were related to differences in the specific surface areas of the filter media. PF was the most economic media for efficiently removing TAN.

Use of fluidized bed biofilter and immobilizedRhodopseudomonas palustrisfor ammonia removal and fish health maintenance in a recirculation aquaculture system

Intensive recirculating aquaculture relies on biofilters to sustain satisfactory water quality in the system. Fluidized bed and immobilized cell technologies were used to remove ammonia from the water and maintain fish health. A high-rate nitrifying fluidized bed biofilter combined with valveless filter was designed for use in a recirculation aquaculture system (RAS). The suspended solids produced during fish culture could automatically be removed using a valveless filter. Natural porosity with fitting proportion, steady fluidization and expanding rate was chosen as the fluidized carrier. The technology of bacterial separation and cultivation was used. The immobilized Rhodopseudomonas palustris (R. palustris) produced through a biotechnologically embedding medium is suitable for fish and could help prevent diseases. Nitrification was promoted through the selective rearing of nitrobacteria in a fluidized bed biofilter. Water quality was improved using fluidized bed biofilter and immobilized R. palustris in the RAS. In addition, the proposed system was able to reduce costs. Maximum fish load was 45 ± 3 kg m−3 in the closed recirculating water fish culture system, and water use was reduced by 80–90%. The total ammonia nitrogen removal rate of the technology was 80–95%, and nitrite N removal rate was above 80%.