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1.
In marine recirculating aquaculture systems (RAS) ozone is often used in combination with biofiltration for the improvement of process water quality. Especially for disinfection purposes ozone residuals are required, that lead to a fast formation of secondary oxidants in seawater, summed up as ozone-produced oxidants (OPO). We studied the impact of OPO on nitrifying biofilter bacteria in a series of laboratory batch experiments by exposing (i) cell suspensions of the ammonia-oxidizing bacteria (AOB) Nitrosomonas marina strain 22 and the nitrite-oxidizing bacteria (NOB) Nitrospira strain Ecomares 2.1, (ii) a pure culture of the NOB Nitrospira strain immobilized on biocarriers, as well as (iii) a heterogeneous biofilm culture settled on biocarriers from a marine RAS for 1 h to different OPO concentrations up to 0.6 mg/l chlorine equivalent. Subsequent activity tests detected a negative linear correlation between OPO concentration and nitrifying activity of suspended pure cultures. Immobilization on biocarriers increased the tolerance of AOB and NOB dramatically, suggesting the biofilm matrix to be highly protective against OPO. Furthermore, we investigated the chronic effect of moderate ozonation at OPO concentrations of 0, 0.05, 0.10 and 0.15 mg/l chlorine equivalent on biofilter performance in a 21 d exposure experiment using 12 experimental RAS, stocked with tilapia (Oreochromis niloticus). Chronic exposure experiments could not reveal any harmful impact on biofilter performance for OPO concentrations up to 0.15 mg/l, even at continuous exposure. Surprisingly, nitrifying activity was enhanced at all OPO concentrations compared to the control without ozonation, suggesting moderate ozonation to promote biological nitrification. It can be concluded that rather health, welfare and performance of most cultivated fish species are the limiting factors for ozone dosage than nitrification performance of biofilters. The results may further have practical implications in relation to design and operational strategy of water treatment processes in RAS and might thus contribute to the optimization of an effective and safe treatment combination of biofiltration and ozonation. 相似文献
2.
本文通过在循环水养殖系统中添加不同浓度的臭氧,研究其对循环水养殖系统生物膜活性及其净化效能的影响.结果显示,当氧化还原电位(ORP)小于450 mV时,氨氮的去除率随着臭氧浓度升高而升高,最高去除率达39.9％,亚硝酸盐氮的平均去除率为28.2％,生物膜菌群的平均存活率为88.1％,生物膜对养殖水体氨氮和亚硝酸盐氮的处理效果良好;当氧化还原电位为500 mV时,经过臭氧24 h处理,氨氮和亚硝酸盐氮的去除率分别由36.5％、28.1％降到12.2％、8.4％,而臭氧4h处理后,生物膜对氨氮和亚硝酸盐氮的去除率分别由47.5％、32.1％降到5.0％、3.3％,水处理效果明显下降,生物膜菌群存活率由88.1％降到31.5％.由此可见臭氧添加浓度对生物膜及净化效能有重大影响.综合试验结果和分析评估,建议封闭循环水养殖系统的臭氧添加量以控制生物滤池内的氧化还原电位低于400 mV为宜,可保证循环水系统的安全性和经济性. 相似文献
3.
Recirculating aquaculture system (RAS) is an increasingly popular alternative to open aquaculture production systems. However, off‐flavours and odours can accumulate in the fish flesh from the circulating water and decrease the fish meat quality. Off‐flavours are typically caused by geosmin (GSM) and 2‐methylisoborneol (MIB) that are lipophilic compounds formed as secondary by‐products of bacterial metabolism. Even though GSM and MIB are not toxic, they often are disliked by consumers, and both have very low human sensory detection limits. Multiple methods have been suggested to remove or decrease GSM and MIB in fish, including ozonation, advanced oxidation processes (AOP)s and adsorption removal from water using activated carbon and/or zeolites. So far, purging with fresh water is the only efficient method available to remove the off‐flavours. There are multiple analytical methods available for the extraction and separation of GSM and MIB from fish flesh and water. This review discusses the current knowledge of GSM and MIB formation, the challenges faced by RAS farms due to these compounds and process solutions available for their removal. 相似文献
4.
一株高效脱氮菌株的分离鉴定及应用潜力分析 总被引：1，自引：1，他引：0
为了获得对虾养殖池塘中高效去除亚硝态氮和氨氮的菌株,采用富集培养分离的方法,从养殖水体中筛选得到1株去除亚硝态氮和氨氮的菌株,培养24 h后的去除率分别为96.17%和88.27%,编号为O-11。基于形态学、分子生物学及生理生化鉴定结果,明确了该菌株基本生物学特征以及可能的分类地位。分离菌株在20~30℃时有利于亚硝态氮的去除,而温度为20~35℃时对氨氮的去除效果较好;分离菌株在盐度小于30的环境中对亚硝态氮的去除能力受盐度变化的影响不大;在碱性环境中分离菌株对氨氮的去除能力较高。安全性检验可知,在菌浓度为10~5~10~8 cfu/mL的菌株O-11对凡纳滨对虾(Litopenaeus vannamei)是安全的,且在菌浓度为10~5 cfu/mL时能显著提高对虾的存活率,促进对虾生长。这说明,分离菌株O-11在水产养殖水体中有害氮脱除方面具有潜在的应用价值。 相似文献
5.
Turbot, Psetta maxima, represent a valuable and growing subsector of global finfish aquaculture, although bacterial infections such as edwardsiellosis have adversely affected the industry in recent years. During an experiment designed to investigate the effect of direct ozonation on fish performance in RAS, a bacterial disease outbreak (Edwardsiella tarda) occurred, presenting an opportunity to record additional effects of experimental ozonation regimes on performance of turbot grown in RAS. This short note thus collates phenomenological information on survival, growth and water quality parameters recorded during a 91 day experiment with juvenile fish. Alongside antibiotic therapy, a high ozone treatment (360 mV) improved survival of stock compared to those in a non-ozonated control (200 mV) and significantly so compared to low ozone treatment (320 mV). Both experimental treatments reduced total heterotrophic and Vibrio sp. bacterial loading and nitrite concentration in culture water compared to the control. Experimental ozone treatment also suggested a trend for improved growth and feed intake. Although no confirmed link or mechanism between ozonation and reduced impacts of bacterial infection are proven in this study, the observations add further evidence to the body of work demonstrating beneficial effects of ozonation on water quality, survival and growth of farmed fish. 相似文献
6.
Design and performance of recirculating aquaculture system for marine finfish broodstock development
Tropical and subtropical climatic conditions in India present an ideal and unique opportunity for being the leader in tropical marine finfish aquaculture. However, the problem persist due to non-availability of marine finfish seed for the culture. In response to this problem, broodstock development of different tropical marine finfishes for seed production was started. The present study was undertaken to design a recirculating aquaculture system (RAS) and studying their performance in managing the various water quality required for the marine finfish broodstock development and breeding. The design of RAS, developed in the present study, included a broodstock tank, egg collection chamber, electrical pump, rapid sand filter, venturi type protein skimmer and biological filter. Two RAS were designed, one was stocked with a demersal fish species, orange spotted grouper (Epinephelus coioides) and the other was stocked with a pelagic fish species, Indian pompano (Trachinotus mookalee) at the rate 1 and 0.5 kg/m3 with a sex ratio of 1:1 and 1:2 (female: male) respectively. Various physio-chemical parameters, viz, total ammonia nitrogen (TAN), nitrite, nitrate, pH, alkalinity, temperature, free carbon dioxide (CO2) and dissolved oxygen (DO) of both tank water were analyzed to assess the performance of recirculating aquaculture system in maintaining the water quality. Gonadal development of the fishes was assessed and the spawning performance was recorded and finally, economic performance of the system was also evaluated. During the entire experimental period, mean monthly total ammonia nitrogen was less than 0.07 and 0.06 mg L−1 and mean monthly nitrite was less than 0.02 and 0.01 mg L−1 in orange spotted grouper and Indian pompano RAS tanks respectively. The pH (7.8–8.2), DO (>4 mg/L) and alkalinity (100–120 mg/L) were found to be in optimum range in both recirculating aquaculture systems. Carbon dioxide was found to be nil during the entire experimental period in both the systems. In fact these levels were comparable or less than that is reported as the permissible limits for broodstock development. Indian pompano and Orange spotted grouper matured and spawning was obtained with production of fertilized eggs round the year. Economic evaluation showed the price of 10,000 fertilized eggs of orange spotted grouper to be US $ 1.33. The design of RAS devised in the present study is efficient in controlling and maintaining optimum water quality for broodstock development of both demersal and pelagic finfishes. The fishes stocked in RAS attained final maturation and round the year spawning was obtained. 相似文献
7.
自河口污泥中分离到两株有益菌,通过形态分析、革兰氏染色、生理生化测定、16S rRNA序列分析和系统发育树构建,其中一株鉴定为植物乳杆菌(Lactobacillus plantarum),另一株为枯草芽孢杆菌(Bacillus subtilis).建立了两株细菌的适宜生长条件,植物乳杆菌适宜生长pH为6.5、温度为30℃,枯草芽孢杆菌的适宜生长pH为6.0、温度为36℃.在实验室条件下,两株有益菌1∶1组合制剂对人工配制的海水中氨氮、亚硝酸盐、磷酸盐的降解率分别达到了73.2％、58.0％和52.4％;池塘养殖环境下,其对养殖水体中氨氮、亚硝酸盐、磷酸盐的降解率分别达到了86.3％、88.9％和68.3％,具有明显的水质净化效果.本研究结果可为建立两株有益菌的规模化发酵生产技术和生产应用奠定基础. 相似文献
8.
The nitrification process is a widely used biological approach responsible for ammonia and nitrite removal in recirculating aquaculture system (RAS) biofilters. Given this pivotal role, the influence of different water quality parameter on nitrification efficiency is important information for RAS operations. One influencing parameter is salinity, and salinity fluctuations in freshwater RAS biofilters are reported to affect the nitrifying bacteria. This study investigated the effects of abrupt increase in salinity in freshwater RAS on substrate-dependent (1’-order) as well as substrate independent (0’-order) nitrification rates. A 100% inhibition was found for surface specific removal (STR) of total ammonia nitrogen (TAN) and surface specific nitrite removal (SNR) when salinity was abruptly increased to 25‰ and above. A fast turnover (i.e. steep decline in [NH4-N+] and [NO2-N−]) were observed at lower salinities (≤10‰), while limited/no degradation of either ammonia or nitrite was seen at salinities above 25‰. At low substrate loading (1’-order process), removal rate constants (k1a) of 0.22 and 0.23 m d-1 were observed for ammonia and nitrite degradation, respectively, declining to 0.01 m d-1when adding marine RAS water increasing the salinity to 15‰. Similar observations followed at high nutrient loadings (0’-order process) with STR and SNR of 0.10 and 0.12 g N m-2 d-1, respectively, declining to 0.01 g N m-2 d-1 at 15‰. When salinities of 25‰ and 35‰ were applied, neither TAN nor nitrite degradation was seen. The results thus demonstrate a pronounced effect of salinity changes when freshwater RAS biofilters are subjected to fast/abrupt changes in salinity. RAS facility operators should be aware of such potential effects and take relevant precautions. 相似文献
9.
In recirculating aquaculture systems (RAS), the crucial step of eliminating toxic N compounds like ammonia and nitrite is mediated via nitrifying microorganisms and takes place in biofilters. In this study, analyses of microorganisms colonizing biocarriers of nine moving-bed biofilters of three different RAS operated with freshwater, brackish or marine process water uncovered site specific communities. Illumina-based amplicon sequencing of the V4-region of the 16S rRNA gene revealed a high microbial diversity with 1000–2500 species-level operational taxonomic units (OTUs) in all biofilters with the highest diversity in the brackish RAS. Proteobacteria, Bacteriodetes, Plantomycetes, Chloroflexi and Nitrospirae represented the most abundant phyla. 76 out of 674 known genera occurred in all nine biofilters and were defined as core-taxa, including nitrifying bacteria (Nitrosomonas and Nitrospira) as well as members of the (heterotrophic) genera Planctomyces, Blastopirellula, Nannocystis and Lewinella. Nitrifying communities composed of different, closely related and so far uncultured members of Nitrosomonas and Nitrospira were identified, strongly indicating that several potentially novel ammonia and nitrite oxidizing species are present in RAS biofilters. Relatives of known comammox Nitrospira were detected in the brackish biofilters, revealing 94–99 % identity of the 16S rRNA gene sequence to Ns. inopinata. Salinity tolerance tests with biocarriers derived from biofilters of the three distinct RAS showed an unexpected broad physiological flexibility with regard to salinity. Nitrification performance of freshwater nitrifiers was drastically reduced with increasing salinity and nearly completely inhibited at 15 PSU, while the brackish and marine nitrifiers showed a high resistance and maintained nitrification activity in a broad range of salt concentrations. This data can help to improve the nitrification process in RAS with changing salinity of the process water. 相似文献
10.
生物—电氧化法去除海水养殖循环水污染物 总被引：1，自引：0，他引：1
为提高海水养殖循环水处理效率,降低处理成本,本研究采用曝气生物滤器与电化学阳极氧化组合工艺,考察了不同阳极电势、进水氨氮和亚硝酸盐浓度下系统对氨氮及亚硝酸盐等污染物的去除效果,研究了微生物与工作电极之间的相互作用,并分析了电化学反应能耗。在水力停留时间为45 min、1.4 V阳极电压、进水氨氮和亚硝酸盐浓度分别为4.5和1.3 mg/L条件下,生物—电氧化法对氨氮去除率达88.8%,高出对照组7.6%,出水氨氮和亚硝酸盐浓度分别为0.5和0.9 mg/L,COD去除率为88.2%,高出对照组19.4%,平均能耗0.040 kWh/m~3,电极表面微生物生长对阳极电氧化过程有促进作用,微生物功能预测显示实验组硝化功能占比为0.03%,对照组为0.07%。研究表明,生物—电氧化法对海水养殖循环水的污染物有良好的去除效果,具有一定的发展应用潜力。 相似文献
11.
12.
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%. 相似文献
13.
14.
The effect of bioreactor design on nitrification efficiency has been well studied, but less is known about the overall impacts on water quality. Besides nitrification, submerged fixed bed bioreactors (FBBR) trap fine solid particles, whereas moving bed bioreactors (MBBR) grind solids, possibly increasing solids and particle accumulation in the system. In this experiment, the effects of different combinations of fixed bed and moving bed bioreactors on water quality, solids removal, particle size distribution, fish health based on histopathological changes and nitrification efficiency were studied in laboratory scale recirculating aquaculture systems (RAS) with rainbow trout (Oncorhynchus mykiss). Three set-ups with triplicate tanks were used: 1. two consecutive fixed bed bioreactors (FF); 2. a fixed bed bioreactor followed by a moving bed bioreactor (FM) and 3. two consecutive moving bed bioreactors (MM). Fish performance was not influenced by the design of the bioreactor, specific growth rate (SGR) being between 1.59 and 1.64% d−1 and feed conversion ratio (FCR) between 0.95 and 0.98. Water nitrite concentration was higher in the FF systems compared to FM and MM systems, whereas the average total ammonia nitrogen concentration (TAN) was not influenced by the treatments. Nitrification rate, which was measured in the laboratory, followed the water nitrite levels, indicating highest total ammonium oxidation rates in the MM systems. UV254 absorbance and total organic carbon (TOC) concentrations were higher in the groups with moving bed systems, indicating accumulation of organic substances in the circulating water. The total volume of particles was higher in the MM systems as compared to the FF systems. The total solids balance was similar in all the bioreactor groups, since the removal of solids by the FBBR backwash was compensated by the drum filter in the FM and MM systems. In general, no significant histopathological difference in gill, kidney, heart and liver tissue were observed between the RAS treatment groups and the flow-through treatment. 相似文献
15.
为解决淡水池塘集约化投饲养殖水体的营养物质富集问题,采用围隔试验方法,研究了蕹菜(Ipomoea aquatica)和水鳖(Hydrocharis dubia)两种植物对泥质和沙质两种底质养殖水体的净化效果。研究发现:泥质底水体的氨氮、亚硝酸盐氮和总磷(TP)自净去除率显著低于沙质底,而泥质底水体的高锰酸盐指数(CODMn)自净去除率显著高于沙质底(P<0.05);不同底质水体中,两种植物对水体氨氮、亚硝酸盐氮、总氮(TN)和CODMn的去除率显著高于相应对照组(P<0.05);12.5%与25.0%的水鳖处理对营养物质的去除率基本无显著差异(P>0.05),12.5%的蕹菜与水鳖处理组仅在泥质底水体中水鳖(MSBI)对氨氮的去除率显著小于蕹菜(MKC)以及MSBI对亚硝酸盐氮的去除率显著高于MKC(P<0.05);泥质底水体中植物处理对氨氮、亚硝酸盐氮、TN、TP和CODMn的最大去除率分别为60.07%、54.78%、52.68%、23.96%和47.32%,沙质底分别为72.43%、83.54%、57.20%、37.07%和40.75%;此外,试验末植物处理组水体的所测营养物质均存在一定程度的上升。沙质底水体中氨氮、亚硝酸盐氮和TP等营养物质波动较大且自净去除率高于泥质底;在泥质和沙质底水体中蕹菜和水鳖浮床均具有显著净化作用,本地种水鳖可作为生态浮床的潜力净水植物;浮床应用过程中应加强收割与收获等管理,以避免水体二次污染。 相似文献
16.
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. 相似文献
17.
Biological filters in aquaculture: Trends and research directions for freshwater and marine applications 总被引：1，自引：0，他引：1
Factors such as limitations in water quality and quantity, cost of land, limitations on water discharges, environmental impacts and diseases, are driving the aquaculture industry toward more intensive practices. This will force producers to adopt environmentally friendlier technologies. Recirculating systems, with a biofilter as the most prominent characteristic, treat internally the water contaminated with dissolved organics and ammonia and reduce the amount of water use and discharge from aquaculture operations. This paper reviews the implications of the changing use of recirculating aquaculture systems (RAS) on biofiltration research for freshwater and marine operations. Demand for cost effective biofilters will increase with the expansion of recirculating systems, both as a complement and replacement of traditional ponds. For freshwater aquaculture, emphasis should be placed in cost competitiveness, low head operations, intensification of ponds with RAS biofiltration and the evaluation of suspended growth systems. In the marine systems, an increase in demand of oligotrophic and ultraoligotrophic systems is expected, particularly in the nursery systems. Sizing and cost efficiency of biofilters for nursery operations should be addressed. Problems in marine biofilter acclimation appear to justify the development of new acclimation procedures. Biosecurity concerns, land cost and storm threats will drive nursery systems inland, where saltwater supply and disposal will force an increased water reuse. Denitrification strategies will need to be redefined and optimized for the marine nursery environment. 相似文献
18.
Steroid hormones have been shown to accumulate in recirculation aquaculture system (RAS) water over time; however, their influence on the reproductive physiology of fish within RAS remains unknown. Whether ozonation impacts waterborne hormone levels in RAS has likewise not been fully evaluated. To this end, a controlled 3-month study was conducted in 6 replicated RAS containing a mixture of sexually mature and immature Atlantic salmon Salmo salar to determine whether ozone, as typically applied in RAS to improve water quality, is associated with a reduction in waterborne hormones. Post-smolt Atlantic salmon (1253 ± 15 g) were stocked into each RAS; 109 of 264 fish placed in each system were sexually mature males, and 5 were mature females. Water ozonation, controlled using an ORP set-point of 290–300 mV, was applied with the pure oxygen feed gas within the low-head oxygenators of 3 randomly selected RAS, while the remaining 3 RAS did not receive ozone. The RAS hydraulic retention time was 6.9 ± 0.3 days. Study fish were raised under these conditions for 12 weeks; during weeks 10 and 12, triplicate water samples were collected from the following locations in each RAS: i) culture tank, ii) makeup water, iii) pre-biofilter, iv) post-biofilter, and v) post-gas conditioning. Concentrations of 3 waterborne hormones – testosterone, 11-ketotestosterone (11-KT), and estradiol (17β-estradiol) – were quantified using enzyme immunoassays (EIA). Estradiol was significantly reduced by ozonation; testosterone and 11-KT were also reduced by ozonation, although these reductions were not observed across all sampling locations and events. Testosterone and 11-KT concentrations, however, were significantly reduced following water passage through the biofilters of both ozonated and non-ozonated RAS. The results of this study demonstrate the potential for ozone to be used in RAS as a means of preventing the accumulation of steroid hormones. Further research is required to assess whether reducing hormones in this manner impacts precocious sexual maturation in RAS-produced Atlantic salmon. 相似文献
19.
Mafalda Figueiras Guilherme Kim Joo de Jesus Gregersen Lars‐Flemming Pedersen 《Aquaculture Research》2020,51(8):3274-3283
The recent development of recirculation aquaculture systems (RAS) potentially allows more sustainable and controlled rearing conditions. However, control of suspended microparticles and microalgae in RAS is challenging, as uncontrolled blooms of toxic algae or heterotrophic dinoflagellates can have catastrophic impacts on the production of fish. In this study, we tested the potential of protein skimmers to remove microalgae. In 100 L batch tests, protein skimmers were tested separately and in combination with ozone (O3), ultraviolet (UV) or hydrogen peroxide (H2O2). Three different and distinct microalgae cultures were tested with densities from 30,000 to 120,000 algae cells/ml in a triplicated experimental setup. Trial 1 included twelve 24‐hr replicated tests where protein skimmers with air or with two levels of ozone (low and high O3 exposure) were compared. The protein skimmer with air alone had a limited effect on the removal of microalgae compared to the untreated control algae tanks. When ozone and protein skimmers were combined, a clear additive effect was found, and all added microalgae were removed. Low O3 dosage and protein skimmers completely removed the algae cultures within 12 hr, while more than 95% of the algae were removed within 7 hr when a higher ozone dose was used. The second trial compared the removal capacity of protein skimmers in combination with UV, H2O2 and O3. These experiments showed no to limited additive effect of UV combined with protein skimming, but significantly increased removal efficiency (270% and 1,300%, respectively) was found when H2O2 and ozone were combined with a protein skimmer. The study showed an algae species‐specific response to a protein skimmer with ozonation and provided information on the transition from reactivity and consumption to accumulation of ozone‐produced oxidants. 相似文献
20.
The paper addresses two potential applications for electrochemical ammonia oxidation within the operation of recirculating aquaculture systems, in which nearly complete removal of N species is required. In one described application, a physical–chemical ammonia oxidation method is suggested to entirely replace conventional biological treatment methods (i.e. nitrification/denitrification). The second described method is suggested as a final polishing step for removing ammonia from effluents of denitrification reactors supplied with intrinsic organic matter, prior to the discharge of the water. Empirical results and cost assessment are reported for the second alternative, while the first, which was recently published, is discussed with respect to improvements, operational conditions and field tests required to induce its commercial application. The polishing alternative was shown capable of efficiently removing TAN in the effluents of RAS denitrification reactors fed with intrinsic organic solids. The cost for treating denitrification reactor effluents with TAN concentration of 10 mgN/L was estimated at 6.67 cent/m3 of discharged water. Since the chloride ion concentration in seawater and in most brackish waters is high, combining the intrinsic organic carbon denitrification process with subsequent ammonia polishing by electrochemically produced active chlorine may be a competitive approach for the removal of nitrogen species from seawater and brackish water RAS. 相似文献