高锰酸钾氧化池塘藻毒素的研究

研究了高锰酸钾KMnO4对池塘微囊藻毒素(MC-LR)的去除效果,探讨反应影响因素(高锰酸钾质量浓度、温度、pH值、反应时间)对去除率的影响.结果表明,高锰酸钾能有效地去除水中的微囊藻毒素.高锰酸钾对MC-LR的去除率与高锰酸钾投加的质量浓度、温度、反应时间成正相关,其中高锰酸钾质量浓度对去除率的影响最大;其次为温度和pH,当温度为35℃时,去除率可达96.65%,当pH为3时,去除率也达到了95.1%;反应时间对去除率的影响不太显著.正交试验的结果也进一步证明了这一点.     

叶轮气浮装置设计及其在海水循环水养殖系统中的净化效果

为使气浮分离技术在工厂化循环水养殖水处理中的应用更加优化与规范化,改善气浮分离法的集成应用效果,通过优化设计适于循环水养殖水处理需求的各零部件,组装成叶轮气浮装置,集成应用于石斑鱼海水(盐度15)循环水养殖系统中。水质检测结果显示,进气量10 m3/h、水力停留时间(HRT)25 min是本实验叶轮气浮装置的最佳运行工况;最佳工况下,本叶轮气浮装置对总悬浮颗粒物(TSS)、总氮(TN)、化学需氧量(COD)、总氨氮(TAN)和亚硝酸盐氮(NO2--N)的平均去除率分别为42.13%、35%、32.69%、10.27%和7.64%,最高去除率分别为46.76%、40%、38.31%、14.04%和13.87%。研究表明,叶轮气浮装置能通过泡沫分离去除有机物,同时降低水体中的COD和TN水平,而对溶解性的TAN和NO2--N去除效果较差。     

高锰酸钾氧化池塘藻毒素的研究

研究了高锰酸钾KMnO4 对池塘微囊藻毒素(MC - LR) 的去除效果, 探讨反应影响因素(高锰酸钾质量浓度、温度、pH 值、反应时间)对去除率的影响。结果表明, 高锰酸钾能有效地去除水中的微囊藻毒素。高锰酸钾对MC- LR的去除率与高锰酸钾投加的质量浓度、温度、反应时间成正相关, 其中高锰酸钾质量浓度对去除率的影响最大; 其次为温度和pH, 当温度为35e 时, 去除率可达96. 65%, 当pH 为3时, 去除率也达到了95. 1%; 反应时间对去除率的影响不太显著。正交试验的结果也进一步证明了这一点。     

浅海养殖环境复合生态净化菌群的筛选及其净化功能

本研究由浅海网箱区富营养沉积物经多步富集和筛选获得高效复合生态净化菌群,对浅海养殖区的有机物、氨氮和亚硝酸氮有明显去除效果.研究了不同条件对复合菌液去除养殖水体中氨氮、亚硝酸氮和有机物能力的影响,并确定了最佳净化条件.结果表明,复合菌添加量、葡萄糖添加量,处理时间、温度、pH和盐度对复合菌的去除效果均有影响,实验条件确定为复合菌的添加量为3%、处理时间为4 d、温度为30±2 ℃、pH值为8.1±0.2、葡萄糖添加量为2 g/L和盐度为(30±10) g/L 时,去除效果达到最佳,此时氨氮、亚硝酸氮和溶解有机物的去除率可分别达到79.1%、85.2%和88.7%.     

养殖水体中二氧化碳去除技术试验研究

高密度循环水养殖水体中的二氧化碳积累是影响水处理效果和养殖效果的重要因素。研究通过对其影响因子的有效变控和再行检测＂水样＂中的游离CO2浓度等参数,获得对于CO2去除效果具有量化意义的试验结果。试验表明：CO2一次去除率最高接近80%,pH值显著升高,CO2浓度与pH值呈负相关对应关系。适当增加填料层厚度和密度、设计较大出水位置高度、选用优质填料及恰当气水体积比,都能起到提高CO2去除效果的作用。影响CO2去除率的主要因素有：起始CO2浓度、循环水流量、气水体积比、填料品种、CO2去除装置的结构型式、输入空气的流速等。养殖水体中的高浓度二氧化碳,可以通过特别设计的CO2去除装置加以高效去除。     

膜式氧合器不同解吸方式对水产养殖水体中氨氮去除效果的影响

研究了膜式氧合器3种不同解吸方式，即：O2对流法、真空抽取法和酸吸收法去除水产养殖水体中氨氮的影响因素，并比较对其氨氮的去除效果。结果表明，氨氮初始浓度和pH是氨氮去除率的主要影响因素；当pH＞9时，O2对流法和真空抽取法对氨氮去除效果比pH＜9时要高，而酸吸收法不论pH高低时比其它2种方法都能获得较高的氨氮去除率。     

养殖水电化学同步脱氮响应面优化与验证

本研究先通过单因子实验分析了电流密度、极板面积比、极板间距和初始pH对总氨氮(TAN)和硝态氮(NO3–-N)去除率的影响。采用Design-Expert软件中Box-Behnken的中心组合原则设计四因素三水平响应面实验，考察不同影响因子对脱氮效率的影响，并建立响应面模型优化反应条件，最后对优化的反应条件进行验证。结果显示，电流密度、极板面积比、极板间距和初始pH的变化对TAN去除影响不大，在所选反应条件下，TAN去除率均高于80%，但反应条件的改变显著影响硝酸盐(NO3?)的去除，NO3?去除率在29.8%~80.9%范围内变化。响应面模型的回归系数R2为0.9340，校正系数R2为0.8681，说明该模型具有较好的准确性。NO3?去除最优反应条件：电流密度为25.6 mA/cm2，阴阳极板面积比为1.6∶1，极板间距为2.5 cm，初始pH为6.6，对该反应条件下的脱氮效果展开实验验证发现，TAN去除率为87.3%，NO3?去除率为81.5%。研究表明，电化学处理可实现对TAN和NO3–-N的同步去除，同时，响应面模型的运用有助于优化电化学法在养殖水处理中的脱氮效率。     

不同曝气策略对SBBR处理模拟水产养殖废水净化效率的影响

为研究不同曝气策略对序批式生物膜反应器(SBBR)净化模拟的罗非鱼工厂化养殖废水的影响,实验设计构建了5个形态结构相同的SBBR反应器,探究在两个既定溶解氧(DO)水平下(即曝气段DO=2或3 mg/L)不同曝停比(1h/5h、2h/4h、3h/3h、4h/2h、5h/1h)对其净化效率的影响。研究结果显示:不同曝停比工况下氮素去除途径主要为同步硝化反硝化。总氨氮的去除率随曝停比的增大呈升高趋势。在曝气段DO=2 mg/L工况下,总无机磷氮的去除率随曝停比的增加呈升高趋势,硝化过程是影响氮素去除的主要因素。而在曝气段DO=3 mg/L工况下,总无机磷氮的去除率随曝停比的增加呈先升高后降低的趋势,在曝停比为4/2时达到最高。实验工况下不同溶解氧水平对COD的去除无显著影响,但是不同曝停比对COD的去除却有显著影响。在曝气段DO=2 mg/L工况下,出水磷浓度随曝停比的增加呈先积累后去除趋势,且磷素的去除率随曝停比的增加而增加。而在曝气段DO=3 mg/L工况下,磷素去除率均为正值,且随曝停比的增加先升高后降低,在曝停比为4/2时达到最高。     

高铁酸钾对微囊藻毒素的去除效果探讨

研究高铁酸钾对微囊藻毒素（MC—LR）的去除效果，探讨不同反应影响因素（反应时间、K2FeO4质量浓度、温度和pH）对去除率的影响。结果表明，K2FeO4能够有效地去除水中的MC—LR。K2FeO4对MC—LR的去除率与K2FeO4。投加质量浓度、反应时间成正相关，其中K2FeO4质量浓度对去除效果的影响较为明显；反应温度对去除率的影响不显著；pH对去除率也有重要影响，当pH分别为2和10时去除率分别为94．51％和87．96％。正交试验的结果也进一步证明了不同反应影响因素对去除效果的影响显著程度。     

2株氨氮去除菌的分离鉴定及去除率影响因素分析

为了获得养殖池塘中高效去除氨氮的菌株，本研究采用富集培养分离的方法从虾贝混养池中筛选得到2株氨氮去除能力较高的菌株，编号分别为9A-7和9A-19。分子生物学及生理生化鉴定结果一致表明，菌株9A-7为非典型弧菌（Vibrio atypicus），菌株9A-19为魔鬼弧菌（Vibrio diabolicus）。不同生长时期与氨氮去除率的关系结果显示，氨氮去除与菌株的生长是同步的。条件优化结果表明，培养液盐度、pH和培养温度对2菌株去除氨的效率均存在显著影响，其中盐度对2菌株氨氮去除率的影响相似，低pH和高温对菌株9A-7的去除率影响较小，而高pH对菌株9A-19去除率影响较小。当氨氮浓度为50mg/L，温度为25℃、盐度为30‰、pH为7.5时，培养至24h菌株9A-7和菌株9A-19除氨率分别高达74.67％和90.67％。这些结果为2株筛选菌的实际应用提供了依据。     

Foam fractionation efficiency of a vacuum airlift—Application to particulate matter removal in recirculating systems

The accumulation of particulate organic matter (POM) in recirculating aquaculture systems (RAS) has become an important issue with the intensification of finfish production. The objective of this study was to assess the foam fractionation efficiency of a vacuum airlift in different conditions (POM concentrations, airflow rates, bubble sizes, water renewal rates and feed addition). In sea water, the vacuum airlift allowed removing 20% of the initial POM concentration per hour (foam fractionation efficiency), corresponding to a 20.7-fold concentration factor between the tank and the foam. In rearing conditions, efficiency increased with decreasing water renewal rate or increasing POM concentration. An increase in airflow rate from 10 to 80 L min⁻¹ in the vacuum airlift significantly decreased foam fractionation efficiency when feed was added to the water. The impact of feeding was only observed with high airflow rates where bubble coalescence occurred. Calculated POM production by fish ranged between 15.9 and 23.5 g h⁻¹ and was equivalent to estimations based on feed conversion ratio (FCR). This indicated that all the POM produced was extracted by the vacuum airlift.     

Effect of different C/N ratios and hydraulic retention times on denitrification in saline,recirculating aquaculture system effluents

Data on operation and performance of cost-effective solutions for end-of-pipe removal of nitrate from land-based saltwater recirculating aquaculture systems (RAS) are scarce but increasingly requested by the aquaculture industry. This study investigated the performance of a (semi)commercial-scale fixed-bed denitrification unit using single sludge for treating effluent from a commercial, saltwater RAS used for production of Atlantic salmon (Salmo salar). A fixed-bed denitrification reactor was fed continuously with 3-days hydrolyzed sludge from the commercial RAS, and was operated at different hydraulic retention times (HRTs; 1.82, 3.64, 5.46, or 7.28 h) or influent C/N ratios (3, 5, 7, or 10). Twenty-four h pooled samples were collected from the inflowing RAS water and the hydrolyzed sludge as well as from the denitrification reactor outlet, and samples were analyzed for nutrients and organic matter content.Nitrate removal rates increased consistently with decreasing HRT (from 64.3 ± 5.2–162.7 ± 22.0 g NO₃-N/m³/d within the HRTs tested) at non-limiting C/N ratios, while nitrate removal efficiencies decreased (from 99.6 ± 0.3–58.2 ± 8.9 %). With increasing influent C/N ratios at constant HRT (3.64 h), nitrate removal rates increased until the removal efficiency was close to 100 % and nitrate concentration in the denitrification reactor became rate-limiting. A maximum nitrate removal rate of 162.7 ± 2.0 g NO₃-N/m³/d was achieved at a HRT of 1.82 h and an influent C/N of 6.6 ± 0.5, while the most efficient use of hydrolyzed sludge (0.19 ± 0.02 g NO₃-N removed/g sCOD supplied) was obtained with a HRT of 3.64 h and a C/N ratio of 2.9. Removal rates of organic matter significantly and consistently increased with decreasing HRT and increasing C/N ratio. In addition, reducing HRT and increasing C/N ratios significantly improved removal of total phosphorus (TP) and PO₄-P.In conclusion, optimal management of the operating parameters (HRT and C/N ratio) in a single-sludge denitrification process can significantly reduce the discharge of nitrogen, organic matter, and phosphorous from land-based saltwater RAS and thus contribute to increased sustainability.     

Foam fractionation and ozonation in freshwater recirculation aquaculture systems

Foam fractionation is often considered an ineffective way of removing organic matter from freshwater due to the low surface tension of the water. There is, however, a lack of studies testing foam fractionation efficiency in replicated freshwater recirculating aquaculture systems (RAS). Foam fractionation can be applied with or without ozone. Ozone is a strong oxidiser previously shown to improve water quality and protein skimmer efficiency. To test the efficiency of foam fractionation and ozonation (20 g O₃ kg^-1 feed) separately and in combination in freshwater RAS, a two-by-two factorial trial was conducted with each main factor at two levels (applied or not applied). Each treatment combination was carried out in triplicates using 12 replicated pilot scale RAS stocked with juvenile rainbow trout (Oncorhynchus mykiss) and operated at a feed loading of 1.66 kg feed m^-3 make-up water. The trial lasted 8 weeks and samples were obtained once a week. Ozone applied by itself significantly reduced the number of particles (83%), bacterial activity (48%) and particulate BOD₅ (5-days biochemical oxygen demand; 54%), and increased ultra violet transmittance (UVT; 43%) compared to the untreated control group. Foam fractionation by itself lead to significant reductions in particle numbers and volume (58% and 62%, respectively), turbidity (62%), bacterial activity (54%) and total BOD₅ (51%). A combination of both treatments resulted in a significant additional improvement of important water quality variables, including a 75% reduction in total BOD₅, 79% reduction in turbidity, 89% reduction in particle numbers and 90% reduction in bacterial activity compared to the control. The removal efficiencies were within the same range as those observed in previous studies conducted with foam fractionators in saltwater systems (with or without ozone), corroborating that foam fractionation may become a useful tool for controlling organic matter build-up and bacterial loads in freshwater RAS.     

Potential applications of indirect electrochemical ammonia oxidation within the operation of freshwater and saline-water recirculating aquaculture systems

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.     

Modeling the fate of dietary 17B-estradiol and its metabolites in an American eel (Anguilla rostrata) recirculating aquaculture system

Recirculating aquaculture system (RAS) is being applied in many aquaculture industries as it provides an opportunity to produce fish in a contained system with minimal use of water. In proposed RAS-based farming of the American eel, 17β-estradiol (E2) is being investigated as an in-feed drug to feminize and increase growth of farmed eels. This creates potential for release of E2 and its metabolites from the eel RAS and information is needed to monitor and manage eel farm effluents to reduce impact on the environment. In the current study, the concentrations of E2 and its metabolites (i.e., estrone (E1) and estriol (E3)) were monitored from different compartments in the RAS and analyzed by liquid chromatography tandem mass spectrometry (LC–MS/MS). E2 levels ranged from 8 to 25 ng/L in the water recirculating within the RAS and declined to 2–6 ng/L in the weeks post-treatment. E1 levels were within similar ranges as E2, whereas E3 levels were below 2 ng/L throughout the study. The results were used to develop a computational model to describe the fate of E2 and its metabolites in the RAS, and to delineate the influences of metabolism and hydrodynamics for the removal of E2 by RAS processes. The rapid removal of uneaten feed and feces downstream of inventory tanks was found to be the most significant mechanism for the removal of 2–6% of the E2 added in feed daily, producing a concentrated effluent stream suitable for strategic treatment strategies. Greater than 94% of E2 added to the system with feed was either metabolized by the eels and/or bacteria in the biofilters of the RAS or was sufficiently bound to solids fractions in the solid samples to resist organic extraction and detection. Additionally, reducing daily water exchange from 23 to 7% of the system water inventory resulted in an increase of only 1 ng/L in E1 concentrations within the RAS system while a negligible change in the concentration of E2 was observed.     

Coagulation of phosphorous and organic matter from marine,land-based recirculating aquaculture system effluents

Saline effluents from marine land-based aquaculture production can neither be disposed in common municipal wastewater treatment plants, nor disposed as landfill. Furthermore, stricter environmental regulations require the reduction of phosphorous and organic matter levels from marine environment discharges to minimize eutrophication. Chemical coagulation with FeCl₃ and AlSO₄ is commonly used for removing phosphorous and suspended solids in wastewater treatment. The capacity of these coagulants for creating particle aggregations depends on the characteristics and chemistry of the treated wastewater, such as the ionic strength or mixing conditions. Marine water has a higher ionic strength than fresh or brackish water, which may be beneficial when using chemical coagulants to treat the effluents from farms operated at high salinities. The following study compared the application of FeCl₃ and AlSO₄, to treat the two effluents discharged from a marine land-based recirculating aquaculture system (RAS) producing salmon (Salmo salar). The aim of the study was to determine; 1) in what effluent (sludge flow vs. exchange water overflow) at the end-of-pipe treatment the coagulant application is more efficient for the removal of PO₄³⁻-P, total suspended solids (TSS), total phosphorous (TP) and total chemical oxygen demand (TCOD); and 2) the optimal coagulant dose to apply and its associated chemical sludge production. The results show that more than 89 % removal of TCOD, TSS and TP is achieved when treating the sludge flow, arguably because the sludge flow contained the largest fraction of the target masses (P and organic matter) discharged from the system. Up to 80 % of TSS removal was achieved by simple sedimentation, and with the highest coagulant dose tested, up to 95 % of TSS could be removed from the effluent. To remove 90 % of PO₄³⁻-P, FeCl₃ and AlSO₄ need to be dosed at a molar ratio of 2.6:1 Fe:PO₄³⁻-P and 5.7:1 Al: PO₄³⁻-P, respectively. Dosing above 90 % removal efficiency did not significantly affect removal of PO₄³-P and TSS, but substantially increased the volume of chemical sludge produced. Finally, FeCl₃ is proposed as a better overall alternative for P removal at the end-of-pipe treatment in marine land-based RAS.     

An evaluation of solid waste capture from recirculating aquaculture systems using a geotextile bag system with a flocculant-aid

Two separate geotextile bag systems were evaluated as a means for capturing and dewatering bio-solids in the effluent stream from recirculating aquaculture systems (RAS). Each geotextile bag system used a high molecular weight cationic polyacrylamide (PAM) polymer as a flocculant-aid. The two systems were operated under freshwater and brackish water conditions. A complete analysis including water quality and agronomic sludge analysis was conducted at the North Carolina State University Fish Barn – a large-scale, freshwater RAS demonstration and growout facility. An evaluation of water quality and performance of a similar geotextile bag system was also conducted at the Marine Aquaculture Research Center near Marshallberg, North Carolina, USA, under brackish conditions (15 PPT). Results indicated that performance of each of the systems was similar with TSS, COD, TN, and TP removal greater than 95%, 65%, 50%, and 38%, respectively, for both systems. Analysis of the sludge collected in the freshwater system after 70 days in a dewatering, inactive mode, showed a moisture content (MC) of 86%, or 14% dry matter (DM), indicating the system was effective at passively dewatering the bio-solids. Nutrient removal efficiency may be system specific based on the geotextile bag size and influent flow rate.Geotextile bag systems using flocculant-aids are an efficient means for capturing and dewatering waste solids from RAS effluents. Optimized geotextile bag system designs depend on flow rate, feed rate, and solids dewatering time, and fate of the treated effluent. This evaluation will aid in predicting the expected performance and determining the appropriate size of a geotextile bag system. The type of treatment required downstream from the geotextile bag system used for solids capture in a RAS wastewater treatment system will depend on the intended fate of the treated effluent.     

加压溶气气浮技术用于净化养殖水体的研究

采用一套自主开发研制的加压溶气气浮装置,对养殖水体中的微颗粒进行净化。选取液位高度、液体流量、溶气压力进行单因子试验和正交试验,单因子试验结果表明,液位0.8 m具有浊度去除的最佳效果;液位1.0 m对浊度去除率和pH的增加率的影响较显著;液体流量为400~600 L/h时,浊度去除率最大;液体流量为200~400 L/h时,溶解氧和pH增加率最大;溶气压力为0.5 MPa时,浊度的去除率达到了最大值的72%,同时,pH的增加率也达到了最大值,溶气压力为0.4 MPa时,溶解氧的增加率达到了最大值;通过正交试验得到三因素的最优组合为:液位高度1.0 m、液体流量200~400 L/h、溶气压力0.4 MPa。     

Feasibility of using foam fractionation for the removal of dissolved and suspended solids from fish culture water

The results of an experimental study on the feasibility of foam fractionation to remove suspended and dissolved solids from fish culture water are presented. Foam fractionation was found to concentrate volatile solids (VS), total Kjeldahl nitrogen (TKN), and total suspended solids (TSS) in the foam condensate. Foam fractionation did not concentrate fixed solids (FS). Air flow rate and overflow height were found to be important operational factors in determining condensate concentration, condensate production and removal rates of VS. Predictive regression equations are presented to predict the performance of a typically configured foam fractionation device. Measurements of TKN and TSS in the foam condensate and fish culture water were well correlated with VS, indicating that VS measurements can be used to predict concentrations and removal rates of both TKN and TSS from fish culture waters that are similar to those analyzed.     

Proposal and assessment of an aquaculture recirculation system for trout fed with harvested rainwater

A sustainable aquaculture production involves alternatives, as recirculating aquaculture systems (RAS), in order to increase the water supply efficiency. This paper aims: a) to propose a method for dimensioning a RAS filled and additionally supplied with water from a rainwater harvesting systems (RHS) and; b) to evaluate the efficiency of the system based on the supply of rainwater from the RHS, the quality of water in the RAS, and the development of aquatic organisms. A pilot aquaculture farm for rainbow trout (Oncorhynchus mykiss) production was designed and dimensioned. On one hand, the RAS with a configuration based on a treatment tower provided acceptable values of pH, TAN, and alkalinity. The temperature was slightly above the recommended temperature but did not negatively impact trout development. On the other hand, the water use efficiency reached 178 L/kg of fish, instead of 210,000 L/kg in an open flow system for trout rearing. The RHS fulfilled the additional required water on the test period of the pilot farm and is expected to supply at least 92% on average during the useful life. Regarding the aquatic organisms’ development, the system allowed both a better Length/ weight ratio and a lesser mortality rate compared to previous studies of RAS. In contrast to other studies in the literature, the mathematical models for dimensioning the system were calculated as a function of the final biomass expected in the tank instead of the quantity of supplied feed. Therefore, this method confirmed the applicability of this alternative criterion for designing biofilters and aquaculture systems.