TAN Removal Research Articles

Effect of Chelating Agent and Surfactant on TaN CMP in Weakly Alkaline Slurry

Co/TaN has been considered as one of the most promising candidates for barrier layers with the feature size of integrated circuit (IC) shrinking to 14 nm and below. The present work investigates the effect of chelating agent and non-ionic surfactant on Co/Cu/TaN CMP in weakly alkaline slurry without any oxidizer. The results show that TaN removal rate increases to the peak value 526 Å/min as the chelator concentration is 1ml/L. That is due to the formation of the water-soluble complex on the surface of TaN. What's more, the TaN removal rate reaches to 501 Å/min and the root mean square roughness (Sq) of TaN is 0.654 nm when non-ionic surfactant concentration is 10 ml/L under the system of 1 ml/L of the chelator. Meanwhile, by the cross-over experiment, it is when slurry is composed of 5 wt% abrasive content, 1 ml/L chelator and 10 ml/L non-ionic surfactant at pH 10 that removal selectivity of Co:Cu and TaN:Cu are comparatively higher and closer (Co:Cu∼2.74:1, TaN:Cu∼2.61:1) along with a good surface quality is obtained.

Microbial monitoring of ammonia removal in a UASB reactor treating pre-digested chicken manure with anaerobic granular inoculum

Performance and microbial community dynamics in an upflow anaerobic sludge bed (UASB) reactor coupled with anaerobic ammonium oxidizing (Anammox) treating diluted chicken manure digestate (Total ammonia nitrogen; TAN=123±10mg/L) were investigated for a 120-d operating period in the presence of anaerobic granular inoculum. Maximum TAN removal efficiency reached to above 80% with as low as 20mg/L TAN concentrations in the effluent. Moreover, total COD (tCOD) with 807±215mg/L in the influent was removed by 60–80%. High-throughput sequencing revealed that Proteobacteria, Actinobacteria, and Firmicutes were dominant phyla followed by Euryarchaeota and Bacteroidetes. The relative abundance of Planctomycetes significantly increased from 4% to 8–9% during the late days of the operation with decreased tCOD concentration, which indicated a more optimum condition to favor ammonia removal through anammox route. There was also significant association between the hzsA gene and ammonia removal in the UASB reactor.

Impact of temperature on ammonium and nitrite removal rates in RAS moving bed biofilters

The impact of temperature on bacterial processes is well known; however temperature related data on nitrification rates in aquaculture systems are fragmented and compiled from different studies. We sought to determine ammonium and nitrite removal kinetics over a temperature range from 6 to 36°C by using moving bed bio-elements from a freshwater RAS in steady state operated at 18°C. The impact of temperature on ammonium and nitrite oxidation rates was evaluated by transferring the colonized bio elements to six liter batch reactors (triplicated setup). Each reactor was acclimatized for 24h at each of the six temperatures (6, 12, 18, 24, 30 and 36°C) and then spiked with ammonium chloride or sodium nitrite under identical conditions. The average surface specific TAN removal (STR) increased a six-fold from 6 to 30°C (0.04–0.25g TAN m−2day−1) and dropped significantly at 36°C–0.14g TAN m−2day−1. The surface specific nitrite removal (SNR) increased linearly from 0.04gNm−2d−1 at 6°C–0.14gNm−2day−1 at 30°C, decreasing to 0.12gNm−2day−1 at 36°C. Throughout the temperature range tested, STR remained significantly larger than SNR. The temperature coefficient, Ɵ (6–30°C) for ammonium oxidation was 1.079; for nitrite oxidation the temperature coefficient was found to be 1.054. The data provided by this study can be applied dimensioning future RAS that utilizes temperature ranges below 10 and above 30°C.

Simultaneous ammonia and nitrate removal in an airlift reactor using poly(butylene succinate) as carbon source and biofilm carrier

In this study, an airlift inner-loop sequencing batch reactor using poly(butylene succinate) as the biofilm carrier and carbon source was operated under an alternant aerobic/anoxic strategy for nitrogen removal in recirculating aquaculture system. The average TAN and nitrate removal rates of 47.35±15.62gNH4–Nm−3d−1 and 0.64±0.14kgNO3–Nm−3d−1 were achieved with no obvious nitrite accumulation (0.70±0.76mg/L) and the dissolved organic carbon in effluents was maintained at 148.38±39.06mg/L. Besides, the activities of dissimilatory nitrate reduction to ammonium and sulfate reduction activities were successfully inhibited. The proteome KEGG analysis illustrated that ammonia might be removed through heterotrophic nitrification, while the activities of nitrate and nitrite reductases were enhanced through aeration treatment. The microbial community analysis revealed that denitrifiers of Azoarcus and Simplicispira occupied the dominate abundance which accounted for the high nitrate removal performance. Overall, this study broadened our understanding of simultaneous nitrification and denitrification using biodegradable material as biofilm carrier.

Electrooxidation for simultaneous ammonia control and disinfection in seawater recirculating aquaculture systems

A new operational approach for seawater recirculating aquaculture systems (RAS), which is based solely on physicochemical water treatment techniques, is described. Within this concept the fish are grown at very high TAN concentration and slightly acidic pH, the latter calculated to maintain the NH3 concentration lower than a predetermined threshold (typically <0.1mgN/l). The inherently high Cl− concentration in seawater enables efficient electro-generation of Cl2(aq) species and consequent electrooxidation of ammonia directly to N2(g). Fish pond water is constantly recycled between electrolysis tanks and the pond, supplying both disinfected water and most of the acidity required to maintain the necessary low pH in the fish pond. For establishing proof-of-concept gilthead seabream (Sparus aurata) was grown at the pilot scale for 133 consecutive days. Throughout this period the fish showed excellent growth rate and survival, along with excellent general health condition. 88% of the NH3 mass excreted by the fish was electro-oxidized in the pilot system, while at the same time the pond water was efficiently disinfected. The high TAN concentrations in the rearing water resulted in high current efficiency in the electrooxidation step, reduced water treatment units volume and generation of very low trihalomethane (THM) concentrations, attributed to the low pH allowed to develop during the electrolysis stage. The pilot system was operated in two stages differing in TAN concentration (30 and 65mgN/l) and pH (6.7 and 6.4, leading to NH3(aq) concentrations of 0.047 and 0.052, respectively). Average current efficiency in the TAN electrolysis step was 68%. Cost analysis showed that both capital and operational costs were highly competitive, as compared with conventional RAS operation. Specifically, the cost of the water treatment component within the pilot operation (TAN removal to N2(g) and water disinfection) was estimated at ∼$0.205per kg feed, out of which $0.079 was attributed to electricity costs.

HYDROPHOBIC MEMBRANE TECHNOLOGY FOR AMMONIA EXTRACTION FROM WASTEWATERS

ABSTRACT Total Ammoniacal Nitrogen - TAN (NH3 + NH4+) in wastewaters cause environmental degradation concerns due to their negative impacts on air, soil and water. Several technologies are available for TAN removal from the wastewaters. One emerging technology is the use of hydrophobic membrane as non-destructive NH3 extraction. In this paper the authors discuss the uses of gas permeable membrane (GPM) and its physicochemical characteristics that influence gas mass transfer rate, diffusion and recovery mechanisms of NH3 from liquid sources (e.g. animal wastewater). Several aspects of NH3 extraction from liquid manure and other TAN generation sources using GPM technology as well as its applicability for NH3 mitigation from liquid effluents and possible recovery as a nutrient for plant growth are also discussed in this review.

Ammonia removal from raw manure digestate by means of a turbulent mixing stripping process

In this study, ammonia stripping by means of a turbulent mixing process followed by pH neutralization was investigated as a simple and cost-effective ammonia removal technique to treat raw manure digestate. Batch tests conducted using CaO, NaOH and H2O2 to control pH and temperature and combinations thereof showed that sodium hydroxide was the most suitable chemical, as it is easy to handle, minimizes treatment time and costs, does not increase the solid content of the sludge and allows to easily control the stripping process. NaOH dosage mainly depended on buffering capacity rather than on total solid content. The analysis of the ammonia stripping process indicated that ammonia removal was strongly dependent on pH, and ammonia removal rate followed the pseudo-first-order kinetics. Total solid content slightly influenced TAN removal efficiency. When NaOH was applied to treat raw digestate at pH 10 and mean temperature of 23 ± 2 °C, TAN removal efficiency reached 88.7% after 24 h of turbulent mixing stripping, without reaching inhibitory salinity levels. Moreover, pH neutralization with sulfuric acid following the stripping process improved raw digestate dewaterability.

Influent COD/TAN ratio affects the carbon and nitrogen removal efficiency and stability of aerobic granules

Two identical sequencing batch reactors (SBRs) seeded with aerobic granules were operated with varying chemical oxygen demand/total ammonia nitrogen (COD/TAN) ratios (1–30). R1 was operated at increasing COD/TAN ratios (7.5, 10, 20, 30), while R2 was operated at decreasing COD/TAN ratios (7.5, 5, 3.5, 2, 1). The results indicated that high COD/TAN ratios (7.5–30) provided high COD removal efficiency (around 92%) and low TAN removal (33%), favoring heterotrophs that form white, fluffy flocs and large granules. Maintenance of high treatment efficiency and granular stability is hard due to high growth rate of heterotrophs. On the other hand, low COD/TAN ratios (2–5) provided high TAN removal efficiency up to 100%, while COD removal was relatively low (60%); leading to small, dense, orange granules enriched in nitrifiers with slow-growing but stable characteristics. The optimum COD/TAN ratio in terms of high COD and TAN removal and granular stability was found as 7.5. It was found out that bacterial population distribution among nitrifiers and heterotrophs can be adjusted by changing influent COD/TAN ratios. This study also proposed the polysaccharide to protein (PS/PN) ratio in the extracellular polymeric substance of the granules as indicators of their stability and value of 0.6 as threshold level for stable granulation.

Reagent use efficiency with removal of nitrogen from pig slurry via struvite: A study on magnesium oxide and related by-products

Controlled struvite formation has been attracting increasing attention as a near mature technology to recover nutrients from wastewater. However, struvite feasibility is generally limited by the high cost of chemical reagents. With the aim to understand and control reagent use efficiency, experiments and equilibrium model simulations examined inorganic nitrogen (TAN) removal from pig manure via struvite with added magnesium and phosphate reagents. Four industrial magnesium oxide (MgO), a commercial product and three by-products from magnesite calcination, were tested with phosphate added as a highly soluble potassium salt. TAN removal extents with the MgOs ranged from 47 to 72%, with the highest grade MgO providing the greatest extent of TAN removal. However, model analysis showed that all the MgO reagents were poorly soluble (only about 40% of added magnesium actually dissolved). The model results suggested that this poor dissolution was due to kinetic limitations, not solubility constraints. A further set of additional reagents (termed stabilization agents) were prepared by pre-treating the MgO reagents with phosphoric acid, and were tested separately as a source of both magnesium and phosphate. Results showed that acid pre-treatment of moderate to highly reactive MgOs (soft to medium-burnt) primarily formed bobierrite as the stabilizing agent, whereas the pre-treatment of very low reactivity MgOs (dead-burnt) mostly formed newberyite. The newberyite stabilizing agents achieved very high TAN removal extents of about 80%, which is significant, considering that these were formed from dead-burnt/low-grade MgOs. However, the bobierrite stabilizing agents achieved a substantially lower TAN removal extent than their medium-to-high reactivity precursor MgOs. Again, model analysis showed that the bobierrite stabilizing agents were poorly soluble, due to kinetic limitations, not solubility constraints. In contrast, the model suggested that the newberyite stabilizing agents almost completely dissolved to very effectively form struvite. A mechanism was proposed by which conditions near a dissolving reagent particle surface causes unwanted struvite nucleation onto and overgrowth of the reagent particle, inhibiting further dissolution and markedly reducing reagent efficiency. The findings of the study could have implications for reagent efficiency with struvite in general, even when using other solid reagents such as magnesium hydroxide or other MgOs.

Effects of alkalinity on ammonia removal, carbon dioxide stripping, and system pH in semi-commercial scale water recirculating aquaculture systems operated with moving bed bioreactors

When operating water recirculating systems (RAS) with high make-up water flushing rates in locations that have low alkalinity in the raw water, such as Norway, knowledge about the required RAS alkalinity concentration is important. Flushing RAS with make-up water containing low alkalinity washes out valuable base added to the RAS (as bicarbonate, hydroxide, or carbonate), which increases farm operating costs when high alkalinity concentrations are maintained; however, alkalinity must not be so low that it interferes with nitrification or pH stability. For these reasons, a study was designed to evaluate the effects of alkalinity on biofilter performance, and CO2 stripping during cascade aeration, within two replicate semi-commercial scale Atlantic salmon smolt RAS operated with moving bed biological filters. Alkalinity treatments of nominal 10, 70, and 200mg/L as CaCO3 were maintained using a pH controller and chemical dosing pumps supplying sodium bicarbonate (NaHCO3). Each of the three treatments was replicated three times in each RAS. Both RAS were operated at each treatment level for 2 weeks; water quality sampling was conducted at the end of the second week. A constant feeding of 23kg/day/RAS was provided every 1–2h, and continuous lighting, which minimized diurnal fluctuations in water quality. RAS hydraulic retention time and water temperature were 4.3 days and 12.5±0.5°C, respectively, typical of smolt production RAS in Norway.It was found that a low nominal alkalinity (10mg/L as CaCO3) led to a significantly higher steady-state TAN concentration, compared to when 70 or 200mg/L alkalinity was used. The mean areal nitrification rate was higher at the lowest alkalinity; however, the mean TAN removal efficiency across the MBBR was not significantly affected by alkalinity treatment. The CO2 stripping efficiency showed only a tendency towards higher efficiency at the lowest alkalinity. In contrast, the relative fraction of total inorganic carbon that was removed from the RAS during CO2 stripping was much higher at a low alkalinity (10mg/L) compared to the higher alkalinities (70 and 200mg/L as CaCO3). Despite this, when calculating the total loss of inorganic carbon from RAS, it was found that the daily loss was about equal at 10, and 70mg/L, whereas it was highest at 200mg/L alkalinity. pH recordings demonstrated that the 10mg/L alkalinity treatment resulted in the lowest system pH, the largest increase in [H+] across the fish culture tanks, as well as giving little response time in case of alkalinity dosing malfunction. Rapid pH changes under the relatively acidic conditions at 10mg/L alkalinity may ultimately create fish health issues due to e.g. CO2 or if aluminium or other metals are present. In conclusion, Atlantic salmon smolt producers using soft water make-up sources should aim for 70mg/L alkalinity considering the relatively low loss of inorganic carbon compared to 200mg/L alkalinity, and the increased pH stability as well as reduced TAN concentration, compared to lower alkalinity concentrations.

Nitrogenated compounds biofiltration under alternative bacterium fixation substrates

This study compares the behavior of nitrification (NH 4 + , NO 2 - and NO 3 - ), and performance, in terms of the surface TAN conversion rate (STR), volumetric TAN conversion rate (VTR) and removal percentage of TAN (PTR) among three fixation media of nitrifying bacteria (two alternatives (S 1 , S 2 ) and one commercial (C o )). The experiment was performed in two tests of 42 days each. Three isolated biofiltration systems were built for the experience, to which were added media colonized by bacteria as a “seed” to start the process of nitrification. Ammonium chloride (NH 4 Cl) was attached as source of ammonium in reconditioned freshwater, also gradually adding inorganic carbon (HCO 3 - ) to maintain moderate water hardness. The average results for both tests indicate that the substrates S 1 and S 2 show a statistically similar behavior to the substrate C o (P > 0.05) during the first 33 days (until steady state). For the second test in terms of performance, STR values were 0.40, 0.39, 0.39 g TAN m -2 d -1 recorded for S 1 , S 2 and C o , respectively; in terms of PRN, values were 92, 97 and 93% for S 1 , S 2 and C o , respectively. Regarding VTR, values of 72.31, 114.94, and 39.02 g TAN m -3 d -1 were recorded for S 1 , S 2 and C o , respectively. Statistical analysis provided that for STR and PRN, no significant differences, were found. But for VTR, statistically significant differences between means were evaluated, registering for the S 2 media the highest value of VTR.

Nitrification in a packed bed bioreactor integrated into a marine recirculating maturation system under different substrate concentrations and flow rates

AbstractBACKGROUND: A packed bed bioreactor (PBBR) activated with an indigenous nitrifying bacterial consortia was developed and commercialized for rapid establishment of nitrification in brackish water and marine hatchery systems in the tropics. The present study evaluated nitrification in PBBR integrated into a Penaeus monodon recirculating maturation system under different substrate concentrations and flow rates.RESULTS: Instant nitrification was observed after integration of PBBR into the maturation system. TAN and NO2‐N concentrations were always maintained below 0.5 mg L−1 during operation. The TAN and NO2‐N removal was significant (P &lt; 0.001) in all the six reactor compartments of the PBBR having the substrates at initial concentrations of 2, 5 and 10 mg L−1. The average volumetric TAN removal rates increased with flow rates from 43.51 (250 L h−1) to 130.44 (2500 L h−1) gTAN m−3 day−1 (P &lt; 0.05). FISH analysis of the biofilms after 70 days of operation gave positive results with probes NSO 190 ((β ammonia oxidizers), NsV 443 (Nitrosospira spp.) NEU (halophilic Nitrosomonas), Ntspa 712 (Phylum Nitrospira) indicating stability of the consortia.CONCLUSION: The PBBR integrated into the P. monodon maturation system exhibited significant nitrification upon operation for 70 days as well as at different substrate concentrations and flow rates. This system can easily be integrated into marine and brackish water aquaculture systems, to establish instantaneous nitrification. Copyright © 2011 Society of Chemical Industry

Ammonia Emissions from Surface Flow and Subsurface Flow Constructed Wetlands Treating Dairy Wastewater

Agricultural wastewater treatment is important for maintaining water quality, and constructed wetlands (CW) can be an effective treatment option. However, some of the N that is removed during treatment can be volatilized to the atmosphere as ammonia (NH(3)). This removal pathway is not preferred because it negatively impacts air quality. The objective of this study was to assess NH(3) volatilization from surface flow (SF) and subsurface flow (SSF) CWs. Six CWs (3 SF and 3 SSF; 6.6 m(2) each) were loaded with dairy wastewater ( approximately 300 mg L(-1) total ammoniacal nitrogen, TAN = NH(3)-N + NH(4)(+)-N) in Nova Scotia, Canada. From June through September 2006, volatilization of NH(3) during 12 or 24 h periods was measured using steady-state chambers. No differences (p > 0.1) between daytime and nighttime fluxes were observed, presumably due in part to the constant airflow inside the chambers. Changes in emission rates and variability within and between wetland types coincided with changes in the vegetative canopy (Typha latifolia L.) and temperature. In SSF wetlands, the headspace depth also appeared to affect emissions. Overall, NH(3) emissions from SF wetlands were significantly higher than from SSF wetlands. The maximum flux densities were 974 and 289 mg NH(3)-N m(-2) d(-1) for SF and SSF wetlands, respectively. Both wetland types had similar TAN mass removal. On average, volatilization contributed 9 to 44% of TAN removal in SF and 1 to 18% in SSF wetlands. Results suggest volatilization plays a larger role in N removal from SF wetlands.

Evaluation of submerged surface flow (SSF) constructed wetlands for recirculating tilapia production systems

A recirculating aquaculture system (RAS) treating tilapia production wastewaters used a two-step process combining a simple clarifier and a submerged surface flow (SSF) constructed wetlands for suspended solids removal and removal of nitrogenous compounds. This system successfully supported a commercial scale level of production (>35kg/m3) for over 36 months of operation. The innovative SSF wetland design incorporated a high hydraulic loading rate (3.03m/day), larger effective diameter media (380mm), and a deeper bed depth (0.90m) than previously suggested design guidelines. The SSF wetland flow pattern was characterized as plug flow with dispersion, but this analysis based on bed volume data indicated that media porosity was reduced from an assumed design value of 54–27% under operating conditions. The TSS, TAN, NO2-N, and NO3-N, percent mass removal for the SSF wetlands was 67.2, 46.0, 87.0, and 40.6, respectively. The TSS, TAN, NO2-N, and NO3-N mass removal for the SSF wetlands was 8.21, 0.58, 0.63, and 0.93g/(m2day), respectively. Optimal performance of the SSF wetlands with simultaneous removal of TAN and NO2-N, and NO3-N occurred at TAN loadings less than 6.0g/(m2day). Bed depth and hydraulic loading rates were major factors controlling this aerobic/anaerobic removal of nitrogen. The wetlands appeared to be oxygen limited at very high TAN loadings above 6.0g/(m2day). Site elevation (1189m) and warm culture temperatures (∼25°C) contributed, but supplemental aeration could provide better TAN removal. Summary of design parameters were presented. Mean KT values calculated for TSS, TAN, NO2-N, and NO3-N were 9.861, 0.614, 20.033, and 8.292days−1 compared favorably to other SSF systems.

Effluent Quality of a Conventional Activated Sludge and a Membrane Bioreactor System Treating Hospital Wastewater

Two lab scale wastewater treatment plants treating hospital wastewater in parallel were compared in terms of performance characteristics. One plant consisted of a conventional activated sludge system (CAS) and comprised an anoxic and aerobic compartment followed by a settling tank with recycle loop. The second pilot plant was a plate membrane bioreactor (MBR). The wastewater as obtained from the hospital had a variable COD (Chemical Oxygen Demand) ranging from 250 to 2300 mg l−1. Both systems were operated at a similar hydraulic residence time of 12 hours. The reference conventional activated sludge system did not meet the regulatory standard for effluent COD of 125 mg l−1 most of the time. Its COD removal efficiency was 88%. The plate MBR delivered an effluent with a COD value of 50 m g l−1 or less, and attained an efficiency of 93%. The effluent contained no suspended particles. In addition, the MBR resulted in consistent operational parameters with a flux remaining around 8 – 10 l m−2 h−1 and a trans membrane pressure <0.1 bar without the need for backwash or chemical cleaning. The CAS and the MBR system performed equally well in terms of TAN removal and EE2 removal. The CAS system typically decreased bacterial groups for about 1 log unit, whereas the MBR decreased these groups for about 3 log units. Enterococci were decreased below the detection limit in the MBR and indicator organisms such as fecal coliforms were decreased for 1.4 log units in the CAS system compared to a 3.6 log removal in the MBR.

Effect of particulate organic carbon on heterotrophic bacterial populations and nitrification efficiency in biological filters

Competition between heterotrophic and nitrifying bacteria is of major practical importance in aquaculture biofilter design and operation. This competition must be understood to minimize the negative impact of heterotrophic bacteria on an aquaculture system. On the other hand, the heterotrophic population is suspected of having a positive effect against pathogenic bacteria. Little information is available on the bacterial communities present within aquaculture systems, except for nitrifying bacteria, but a combination of traditional aquacultural engineering research methods and novel microbiological techniques offers new opportunities for the study of these communities.The heterotrophic bacterial population activity and the nitrification efficiency of a submerged biological filter were studied for an influent TAN concentration of 2mg/l and varying C/N ratios. The TAN removal rate was found to be 30% lower at a C/N ratio of 0.5 than at a C/N ratio of 0. For higher C/N ratios the reduction in nitrification efficiency was 50% while the attached bacterial abundance was doubled. Moreover, results confirm that abundance of sheared and attached bacteria are correlated. It is not known to what extent biofilter configuration might influence the relationship between heterotrophic and nitrifying bacteria, and further work will be carried out with moving bed and fluidized filters. A better understanding of the role of the heterotrophic bacteria in RAS will help to optimize any positive “biocontrol” effect and to minimize the microbial degradation of rearing water and the reduction of nitrification rates.

The tetrasporophyte of Asparagopsis armata as a novel seaweed biofilter

The red seaweed Asparagopsis armata (Harvey; Rhodophytae, Bonnemaisoniaceae) produces biologically active secondary metabolites that are valuable natural ingredients for cosmetics and medicine and its cultivation may therefore be a profitable venture. The tetrasporophyte of this species (“ Falkenbergia rufolanosa”) was successfully tank-cultivated as a continuous biofilter for the effluent of a commercial fish farm in southern Portugal. Optimal stocking density for highest biomass yield and a low level of other algal species in winter and late spring was 5× g centrifuged fresh weight l − 1 . The effect of total ammonia nitrogen supply (TAN flux) on biofiltration and biomass yield was investigated in winter and spring. Results revealed that A. armata is currently the seaweed-biofilter with the highest TAN removal of up to 90 μmol l − 1 h − 1 at a TAN flux of about 500 μmol l − 1 h − 1 . In the tanks used, this is equivalent to a removal of up to 14.5 g TAN m − 2 day − 1 . At a lower TAN flux of about 40 μmol l − 1 h − 1 , TAN removal by A. armata is more than double to what is reported at this flux for another successful seaweed biofilter, the genus Ulva. Monthly variation of A. armata biomass yield peaked in May and was lowest in January. At TAN fluxes between 300 and 400 μmol l − 1 h − 1 , an average water temperature of 21.7 °C and a total daily photon flux density of 47 Mol m − 2 , seaweed yield was over 100 g DW m − 2 day − 1 with a recorded maximum of 119 g. During spring, autumn and early summer, the biomass of A. armata within the experimental tanks doubled every week. A model for the up scaling of this finfish integrated aquaculture of A. armata varies the investment in biofilter surface area and estimates the return in biofiltration and biomass yield. Highest TAN removal efficiencies will only be possible at low TAN fluxes and a very large biofilter area, resulting in a low production of biomass per unit area. To remove 50% of TAN from the effluent (1 mt Sparus aurata; 21 °C), 28 m 2 of biofilter, designed to support a water turnover rate of 0.8 Vol h − 1 would be necessary. This system produces 6.1 kg FW (1.5 kg DW) of A. armata per day and has the potential to turn biofiltration into an economically sustained, beneficial side effect.

Nitrification performance of a propeller-washed bead clarifier supporting a fluidized sand biofilter in a recirculating warmwater fish system

A propeller-wash bead filter (PWBF) and a fluidized sand filter (FSF) on a 28m3 recirculating system stocked with tilapia maintained favorable water quality at five different feed rates, ranging from 0.9 to 4.5kg feed per day. TAN removal rates ranged up to about 200g TAN/m3 of media per day for each of the units. Peak rates of 244g TAN/m3 of media per day were observed when the recirculating flow was boosted by 20%. Roughly 75% of the removal was accomplished by the fluidized sand filter an observation that is consistent with the difference between the fluidized sand filter volume (0.92m3) and the bead filter media volume (0.28m3). The bead filter's primary function was clarification. At the highest daily feed load, over 570g dry weight of solids were removed during each daily bead filter backwashing event. A 20% increase in flow, at the same daily feed rate, improved solids removal to over 670g dry weight per bead filter backwash event. The PWBF and FSF combination provided suitable water quality for fish production; however, further increases in feed loading were limited by carbon dioxide buildup and oxygen limitations.

Impact of rapid impulse operating disturbances on ammonia removal by trickling and submerged-upflow biofilters for intensive recirculating aquaculture

Biofilters are regularly used in aquaculture production systems to remove ammonia and nitrite and are the only economically feasible ammonia removal devices in saltwater systems. Six identical 5.23L biofilters, three trickling and three submerged-upflow filters, were operated at predetermined water quality conditions (pH 7.5, temperature 25°C, salinity 5ppt, TAN 1mg/L), and then perturbed to simulate a number of possible operating disturbances, e.g. increased fish load, flushing of culture tanks, closing off of valves. Each disturbance was a controlled impulse change in ammonia concentration, temperature, pH or salinity. The maximum water quality ranges were pH 6–9, TAN 0.5–4.0mg/L, temperature 15–35°C, and salinity 0–10ppt. After each disturbance, the water quality was immediately returned to the predetermined (baseline) values. The ammonia removal across the filters was monitored during the disturbance and the recovery period for loss and subsequent restoration of biofilter removal efficiency. Baseline nitrification rates resumed within 1–2h after cessation of the shock. Some impulse shocks were temporarily detrimental to both filter types—especially low pH (−29% efficiency), low salinity (−13% to −18% efficiency), and low temperature (−11% to −13% efficiency). Raising the temperature (+9% to +12% efficiency) and TAN concentration (+0.30 to +0.36mg/L of filter additional TAN removal) appears to be beneficial to the biofilter.

Impact of positive ramp short-term operating disturbances on ammonia removal by trickling and submerged-upflow biofilters for intensive recirculating aquaculture

Biofilters are regularly used in freshwater aquaculture production systems to remove ammonia and nitrite and are the only economically feasible ammonia removal devices in saltwater systems. Six identical 5.23l biofilters, i.e., three trickling and three submerged-upflow filters, were operated at predetermined baseline water quality conditions (pH 7.5, temperature 25°C, salinity 5ppt, TAN 1mg/L), and then perturbed to simulate a number of possible operating disturbances, e.g. increased fish load, flushing of culture tanks, closing off of valves. Each disturbance was a controlled positive ramp short-term change in ammonia concentration (with other water quality parameters held constant) or temperature or pH or salinity. Ammonia removal across the biofilters was monitored during the disturbance and recovery period for loss and subsequent restoration of ammonia removal efficiency. Baseline water quality to the filters was resumed at the end of each disturbance and baseline ammonia removal occurred within 1 to 2h after end of disturbance. Ranges of variation in water quality were pH 7.5–9, TAN 1.0–4.0mg/L, temperature 25–35°C, and salinity 5–35ppt. Salinity increases over a 5–10h period reduced biofilter removal efficiency (−12 to −30% TAN removal); temperature increases, over a 1.6–10h period, offered about a 5% increase in TAN removal while gradual TAN increases, over a 3–12h period, although providing an approximately extra 1mg/L of removal did not significantly change removal efficiency; and gradual pH increases, over a 3–7.5h period, did not change biofilter removal efficiency significantly.