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.     

Effects of C/N ratio on nitrogen removal with denitrification phase after a nitrification-based biofloc aquaculture cycle

In the current study, we set up a denitrification process to remove the nitrogen pollutants, especially nitrate (NO₃^–-N), from the wastewater after a nitrification-based biofloc technology (BFT) aquaculture cycle. Five different treatments (CN0, CN1, CN2, CN4 and CN6, respectively) were used, which involved addition of extra carbohydrate with variable ratios of elementary organic carbon to NO₃^–-N by weight (C/NO₃^–-N ratio equal to 0, 1, 2, 4, and 6, respectively). With CN2, CN4, and CN6 treatments, NO₃^–-N was decreased (with increasing alkalinity) to ≤ 6.42 ± 0.30 mg·L⁻¹ and low amounts (close to zero) of nitrite (NO₂^–-N) were achieved. However, there were high concentrations of residual NO₃^–-N and/or NO₂^–-N in CN0 and CN1. CN2 achieved the best denitrification, wherein 81.00 ± 0.95% of the initial input nitrogen was removed. By fitting the equations, the highest nitrogen recycling rate (23.08 mg-N·g-C⁻¹) was achieved with a C/NO₃^–-N ratio of 4.16. Denitrifying bacteria were the dominant bacteria in all extra carbohydrate added treatment groups. Although denitrifying polyphosphate accumulating organisms contributed to the removal of phosphorus, high concentrations of residual soluble reactive phosphate (SRP) were observed in all treatment groups. Overall, extra addition of carbohydrate with C/NO₃^–-N ratio ≥ 2 is advisable for nitrogen removal, while the highest nitrogen recycling rate will be achieved with a ratio of 4.16.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.     

不同水力停留时间和进水硝酸盐浓度下香蕉杆为碳源的固相反硝化性能研究

固相反硝化去除水产养殖尾水中硝酸盐氮(NO₃^–-N)具有广阔的应用前景,水力停留时间(hydraulic retention time,HRT)和进水硝酸盐浓度(influent nitrate concentration,INC)是影响反硝化系统反硝化性能的主要因素之一,需要对HRT进行优化,掌握其最大NO₃^–-N处理能力。本研究首次以香蕉杆为反硝化反应器的外加碳源,在流场环境下,测定不同HRT和INC下反硝化系统对NO₃^–-N、亚硝酸盐氮(NO₂^–-N)、氨氮(NH₄⁺-N)、总氮(TN)、总磷(TP)和化学需氧量(COD)的去除效果。并采用基于Illumina Miseq测序平台的高通量测序技术,对反硝化系统运行初期及末期的细菌群落进行16S rDNA V3和V4区测序分析。结果显示,香蕉杆反应器的最佳HRT为20 h,对应NO₃^–...     

Formaldehyde degradation in denitrifying woodchip bioreactors: Effects of temperature,concentration and hydraulic retention time

Formalin is applied in certain aquaculture systems to control parasites infestations as well as bacterial and fungal diseases. This study investigated the capacity of end-of-pipe denitrifying woodchip bioreactors to remove potentially harmful amounts of residual formaldehyde (FA) from aquaculture effluents. Formaldehyde was readily removed by experimental- and field-scale denitrifying woodchip bioreactors and the removal of FA was found to be a combination of an initial adsorption of FA to woodchip surfaces (52 ± 2.8 g FA/m³ woodchips) and microbial degradation. Volumetric FA removal rates reaching 261 ± 27 g FA/m³/d were found at FA inlet concentrations of 90 mg FA/L and hydraulic retention times (HRT) of 5 h. High FA removal efficiencies ranged from 88.3 ± 4.6–99.8 ± 0.2% found for FA inlet concentrations –up to 105 mg FA/L and HRTs between 3.4 and 15 h. Microbial FA degradation rates in woodchip bioreactors were positively correlated to temperature with a Q₁₀ value of 2.27 and a corresponding Arrhenius temperature coefficient of 1.086 for the investigated temperature range of 7–23 °C. At a commercial, outdoor recirculating aquaculture system (RAS) three full-scale woodchip compartments, achieved an average volumetric FA removal rate of 29.4 ± 0.2 g FA/m³/d and a removal efficiency of 82.5 ± 0.8% during the first 24 h following addition of FA. The results demonstrated that woodchip bioreactors are efficient in removing residual FA from RAS effluents and that nitrate removal was transiently enhanced during FA removal.     

循环水养殖系统管式射流集污特性试验研究

工厂化养殖池内的污物聚集效果是养殖池设计建造和运行管理的重要指标,对提升养殖技术和管理水平具有重要意义。针对一种典型的工厂化鱼类养殖池,对边侧管式射流系统驱动下的流场特性和污物聚集效果进行研究,探讨了射流角度、射流流速和循环抽吸方式等因素对养殖池内水体流场特性及污物聚集分布规律的影响。利用手持式ADV流速仪在养殖池内进行布点测量,获得各点流速数值,然后利用MATLAB软件进行流场插值构图,研究养殖池的流场分布特性;污物聚集特性采用图像法进行处理分析。研究表明:管式射流驱动作用下,流速从池心向外呈"V"型变化。在射流角度固定为40°条件下,射流速度越大,池心低流速区域范围越小,污物聚集效果越好。当射流速度达到0.3 m/s时,污物基本聚集于池心;在流速固定的情况下,对污物聚集效果存在一个最佳的射流角度,约为40°。池内循环抽吸模式对流场和污物聚集效果同样有着显著的影响。研究表明,采用底部抽吸时,排污孔附近的径向流速与切向流速均高于边侧抽吸模式,且污物聚集效果明显优于边侧抽吸模式。该研究成果可用于工厂化鱼类养殖池管式射流水力驱动系统的优化设计,在不影响养殖对象生长的前提下,可尽量提高射流流速,最佳射流角度一般为40°左右,并尽量采用底部抽吸模式。     

End-of-pipe denitrification using RAS effluent waste streams: Effect of C/N-ratio and hydraulic retention time

Environmentally sustainable aquaculture development requires increased nitrogen removal from recirculating aquaculture systems (RAS). In this study, removed solids from a large commercial outdoor recirculated trout farm (1000 MT year⁻¹) were explored as an endogenous carbon source for denitrification. This was done by (1) a controlled laboratory experiment on anaerobic hydrolysis of the organic matter (from sludge cones, drumfilter, and biofilter back-wash) and (2) an on-site denitrification factorial experiment varying the soluble COD (COD_S)/NO₃-N ratio from 4 to 12 at hydraulic retention times (HRT) from 50 to 170 min in simple 5.5 m³ denitrification reactors installed at the trout farm.The lab-experiments showed that the major part of the readily biodegradable organic matter was hydrolyzed within 14 days, and the hydrolysis rate was fastest the first 24 h. Organic matter from the sludge cones generated 0.21 ± 0.01 g volatile fatty acids (VFA) g⁻¹ total volatile solids (TVS), and the VFAs constituted 75% of COD_S. Analogously, 1 g TVS from the drum filter generated 0.15 ± 0.01 g VFA, constituting 68% of the COD_S. Comparison of the laboratory hydrolysis experiments and results from the on-farm study revealed as a rough estimate that potentially 17–24% of the generated VFA was lost due to the current sludge management.Inlet water to the denitrification reactors ranged in NO₃-N concentration from 8.3 to 11.7 g m⁻³ and COD_S from 52.9 to 113.4 g m⁻³ (10.0 ± 1.2 °C). The highest NO₃-N removal rate obtained was at the intermediate treatments; 91.5–124.8 g N m⁻³_reactor d⁻¹. The effect of the C/N ratio depended on the HRT. At low HRT, the variation in C/N ratio had no significant effect on NO₃-N removal rate, contrary to the effect at the high HRT. The stoichiometric ratio of COD_S/NO₃-N was 6.0 ± 2.4, ranging from 4.4 (at the high HRT) to 9.3 (at the low HRT). A simple model of the denitrification reactor developed in AQUASIM showed congruence between modeled and measured data with minor exceptions. Furthermore, this study pointed to the versatility of the NO₃-N removal pathways expressed by the bacterial population in response to changes in the environmental conditions; from autotrophic anammox activity presumably present at low C/N to dissimilatory nitrate reduction to ammonia (DNRA) at high C/N, besides the predominate “normal” heterotrophic dissimilatory nitrate reduction (denitrification).     

碳源及C/N对反硝化细菌净化循环养殖废水的影响

针对目前循环养殖废水水质处理过程中存在脱氮碳源不足的问题,本文以高NO3--N降解能力和低NO2--N积累量为碳源优化指标,研究了乙醇、丙三醇、葡萄糖、蔗糖、乙酸钠和酒石酸钾钠6种碳源及不同碳氮比（C/N）对复合菌群净化循环养殖废水效果的影响。试验结果显示,不同碳源及C/N对养殖废水的NH4 -N去除率并无显著差异,且各处理组的NH4 -N去除率高达98%左右,显著地高于对照组（p<0.05）;当以葡萄糖、蔗糖等糖类物质为外加碳源时,试验过程中有明显的NO2--N积累现象;当以醇类物质为外加碳源时,NO2--N积累量几乎为零,且NO3--N去除率高达90%左右,显著地高于对照组（58.96%）;特别是以乙醇为外加碳源且C/N为3.0时,复合菌群对养殖废水的TN、NH4 -N和NO3--N去除率分别高达93.28%、98.90%和91.82%。虽然外加碳源短期内会引起水体CODMn含量大幅升高,但可被反硝化细菌迅速降解;此外,外加碳源还能改善水体pH值,经处理组净化后的水体pH值维持在7.5左右。试验结果表明,循环养殖废水水质净化过程中添加相应的碳源及并适当控制C/N比能显著改善池水水质,提高生物脱氮效率。     

Activated sludge denitrification in marine recirculating aquaculture system effluent using external and internal carbon sources

Stringent environmental legislation in Europe, especially in the Baltic Sea area, limits the discharge of nutrients to natural water bodies, limiting the aquaculture production in the region. Therefore, cost-efficient end-of-pipe treatment technologies to reduce nitrogen (N) discharge are required for the sustainable growth of marine land-based RAS. The following study examined the potential of fed batch reactors (FBR) in treating saline RAS effluents, aiming to define optimal operational conditions and evaluate the activated sludge denitrification capacity using external (acetate, propionate and ethanol) and internal carbon sources (RAS fish organic waste (FOW) and RAS fermented fish organic waste (FFOW)). The results show that between the evaluated operation cycle times (2, 4, and 6 h), the highest nitrate/nitrite removal rate was achieved at an operation cycle time of 2 h (corresponding to a hydraulic retention time of 2.5 h) when acetate was used as a carbon source. The specific denitrification rates were 98.7 ± 3.4 mg NO₃⁻-N/(h g biomass) and 93.2 ± 13.6 mg NO_x⁻-N/(h g biomass), with a resulting volumetric denitrification capacity of 1.20 kg NO₃⁻-N/(m³ reactor d). The usage of external and internal carbon sources at an operation cycle time of 4 h demonstrated that acetate had the highest nitrate removal rate (57.6 ± 6.6 mg N/(h g biomass)), followed by propionate (37.5 ± 6.3 mg NO₃⁻-N/(h g biomass)), ethanol (25.5 ± 6.0 mg NO₃⁻-N/(h g biomass)) and internal carbon sources (7.7 ± 1.6–14.1 ± 2.2 mg NO₃⁻-N/(h g biomass)). No TAN (Total Ammonia Nitrogen) or PO₄^3- accumulation was observed in the effluent when using the external carbon sources, while 0.9 ± 0.5 mg TAN/L and 3.9 ± 1.5 mg PO₄^3--P/L was found in the effluent when using the FOW, and 8.1±0.7 mg TAN/L and 7.3 ± 0.9 mg PO₄^3--P/L when using FFOW. Average sulfide concentrations varied between 0.002 and 0.008 mg S^2-/L when using the acetate, propionate and FOW, while using ethanol resulted in the accumulation of sulfide (0.26 ± 0.17 mg S^2-/L). Altogether, it was demonstrated that FBR has a great potential for end-of-pipe denitrification in marine land-based RAS, with a reliable operation and a reduced reactor volume as compared to the other available technologies. Using acetate, the required reactor volume is less than half of what is needed for other evaluated carbon sources, due to the higher denitrification rate achieved. Additionally, combined use of both internal and external carbon sources would further reduce the operational carbon cost.     

陆基圆池循环水条件下养殖密度对大口黑鲈生长及养殖效能的影响

为研究陆基圆池循环水养殖条件下大口黑鲈(Micropterus salmoides)适宜的养殖密度,设置55、65、75、85、95尾/m²等5种养殖密度(分别标记为A1、A2、A3、A4、A5组),进行了63 d的大口黑鲈养殖试验,通过测定和分析试验鱼的体质量日增长率、体长日增长率、饲料系数、体质量均匀度和单位面积产量等指标,评价不同养殖密度对大口黑鲈生长和主要养殖效能的影响。结果显示:(1)从次低密度的A2组(65尾/m²)至密度最高的A5组(95尾/m²),试验鱼的体长日增长率基本上随着养殖密度的提高而下降,最高的A2组比A3、A4和A5组分别高了31.6%、82.9%和92.3%,并且差异显著(P<0.05);(2)从A2组至A5组,试验鱼的体质量日增长率和特定生长率均随着养殖密度的提高而下降;(3)A2组的饲料系数比A1、A3、A4和A5组分别降低了16.7%、28.6%、55.4%和56.9%;(4)单位面积产量和产品均匀度均在A2组达到最高。基于生长性能及养殖效能的综合评价,陆基圆池循环水养殖条件下大口黑鲈成鱼养殖阶段较适宜的养殖密度为65尾/m²。     

室内循环养殖系统中曝气流量对尼罗罗非鱼生长的影响

曝气流量是曝气推流循环养殖系统的重要控制性因素,为综合研究不同曝气流量对鱼类生长和鱼肉品质的影响,参照野外养殖基地,利用自行设计的室内循环流水养殖模型,在0、30和50 L/min三组曝气条件下,以尼罗罗非鱼[初始体质量为(23.61±3.50)g]为对象,进行为期56 d的研究。结果显示:①30 L/min组中尼罗罗非鱼的最终体质量和特定生长率分别为(79.56±3.82) g和(2.81±0.54)%/d,其中特定生长率比0和50 L/min组分别高出11.07%和8.49%,同时该曝气流量下血清中的总蛋白和甘油三酯浓度较高,而尿素氮浓度较低,比如第56天时总蛋白浓度比0和50 L/min组分别高出57.43%和10.43%,甘油三酯浓度则分别高出22.19%和12.32%,但尿素氮浓度降低了39.02%和37.50%。葡萄糖浓度受曝气流量影响不显著。50 L/min组谷丙转氨酶和谷草转氨酶活性高于0和30 L/min组;②第56天时30 L/min组中鱼肉的硬度、弹性和咀嚼性高于0和50 L/min组,硬度分别比0和50 L/min组高出27.10%和15.85%,弹性高出9.1...     

封闭循环水系统生物滤池气水比对水质净化效能的影响

通过在全封闭循环水系统中养殖半滑舌鳎(Cynoglossus semilaevis Gunthe), 研究了不同气水比对曝气生物滤池净化效能, 以及对DO、pH值的影响。结果表明: 本试验系统在温度为(19±1)℃, 系统循环次数为15次, 养殖池DO保持在12 mg/L以上的运行条件下, 随着气水比由0.75 : 1~1.50 : 1的增加, 生物滤池氨氮的去除率由35.0%增加至52.0%, NO₂-N的去除率由8.2%增加至44.6%, 气水比对硝化反应影响显著, 但对化学需氧量COD的去除率影响并不显著, 其平均去除率为10.14%; pH值有增加的趋势, 生物滤池进水口到出水口的pH值由7.97增加至 8.08; 气水比最佳运行参数为1.25:1。同时还发现1级生物滤池进水口DO接近饱和, 1级到末级滤池间DO仅降低了10%左右, 系统pH值在7.9~8.1。本研究所获参数, 可供生物膜法处理养殖循环水的条件优化作参考。

     

循环海水养殖中生物滤器生物膜研究现状与分析

综述了循环海水养殖中生物滤器生物膜的研究进展,包括生物膜的形成、结构、原理、生物多样性以及功能,重点阐述生物膜的微生物学特征,介绍微生物生态学方法,特别是分子生态学方法在生物膜研究中的应用及其在生物膜微生物群落结构与功能研究的最新成果.     

Effects of bioflocs with different C/N ratios on growth,immunological parameters,antioxidants and culture water quality in Opsariichthys kaopingensis Dybowski

Biofloc technology (BFT) is a new ecological aquaculture technology that is intended not only to eradicate pollutants and elevate feed utilization but also to enhance immunity and antioxidant activity in aquatic animals. A 28‐day feeding trial was implemented to evaluate the effects of promoted bioflocs on the water quality, growth performance, immunological parameters and antioxidant status of Opsariichthys kaopingensis Dybowski juveniles in low exchange culture tanks. Three hundred sixty healthy O. kaopingensis juveniles (7.1 ± 0.02 g) were irregularly distributed among 12 tanks. Four C:N ratios in triplicate tanks were tried: C/N = 10.8:1 with a commercial diet (control), C/N = 15:1, C/N = 20:1 and C/N = 25:1. Anhydrous glucose (99.97%) was added to the commercial diet to maintain elevated carbon ratio in the three treatments. Uninterrupted 24‐hr aeration was supplied during the test by using an air‐stone connected to an air pump to develop the bioflocs in the water column. The results indicated that BFT significantly reduced total ammonia nitrogen (TAN), nitrite (NO2^?‐N), total phosphorus (TP) concentrations and water transparency (Secchi depth) in C/N 15, C/N 20 and C/N 25 (p < .05), whereas the chemical oxygen demand (COD) and nitrate nitrogen (NO3^?‐N) concentrations gradually increased over time. In addition, weight gain, specific growth rate (SGR), survival and protein efficiency ratio (PER) were significantly elevated in C/N 20, while food conversion rate (FCR) was considerably decreased (p < .05) in C/N 20, compared with the control. Significant increases in lysozyme (LSZ), glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) and alkaline phosphatase (AKP) activities of O. kaopingensis were found in the C/N 20 group after a 28‐day feeding trial (p < .05). Comparing the antioxidant capacity of O. kaopingensis in gills, brains, kidneys, hepatopancreas, intestines and serum of juveniles from the four experimental groups, the activity of superoxide dismutase (SOD), total antioxidant capacity (T‐AOC), catalase (CAT) activity and glutathione peroxidase (GSH‐PX) activity of juveniles in the C/N 20 group were significant higher (p < .05), and the content of malondialdehyde (MDA) was considerably lower, than in the control. Overall, these findings suggest that BFT not only can enhance O. kaopingensis growth performance and strengthen antioxidant status but also can upgrade immune response, ensuring the sustainable development of aquaculture.     

凡纳滨对虾工厂化养殖水体中微小辐环藻HY01的分离鉴定及对不同氮源的响应

凡纳滨对虾(Litopenaeus vannamei)工厂化养殖池中,一株硅藻在养殖中后期长期占优势,因其个体较小且细胞外壳覆盖一层硅质膜,难以用光学显微镜直接准确鉴定其分类地位。通过对该藻株进行分离纯化,利用光学显微镜和电子显微镜,结合分子生物学技术,鉴定该分离藻株为微小辐环藻HY01 (Actinocyclus exiguous HY01)。藻细胞直径约为(11.4±1.0) μm,壳面上有很多小孔,光学显微镜下不可见,且壳中央的孔密度较壳边缘稀疏,壳边缘具有眼斑结构,有3~5个唇形突。以不同浓度氨氮和硝态氮为氮源培养微小辐环藻HY01,结果显示,微小辐环藻HY01均能利用氨氮和硝态氮进行生长,最适宜生长的氨氮和硝态氮浓度分别为600和882 μmol/L,但以氨氮为氮源时微小辐环藻HY01的最大细胞密度、最高比生长速率以及蛋白含量均低于以硝态氮为氮源,表明微小辐环藻HY01可能更喜欢利用硝态氮,但对较高浓度的氨氮有一定的耐受性。     

循环水养殖系统中养殖密度对松江鲈生长的影响

为研究配合饲料条件下循环水养殖系统(RAS)中养殖密度对松江鲈生长的影响,选取体长为(2.97±0.12)cm、体质量为(0.26±0.03)g的松江鲈,分别按40尾/m²(A组)、80尾/m²(B组)和120尾/m²(C组)共3个养殖密度,在RAS中进行了为期240 d的养殖试验。试验结果显示：A组鱼的终末体质量、终末体长、体质量日增长量、存活率等均显著高于其他两组,A组鱼的体长日增长量显著高于C组(P<0.05);不同密度组间鱼体肥满度无显著性差异(P>0.05)。试验组单位面积产量由高到低依次为：C组(2.83 kg/m²)、B组(2.51 kg/m²)、A组(1.72 kg/m²)。试验组鱼体质量与体长均呈幂函数相关(m=aL^b,a=0.007 6～0.008 9,b=3.123 6～3.209 4),体长、体质量生长均以三次函数拟合较好。各组间的鱼体长、体质量变异系数均差异显著(P<0.05),其中B组最小...     

双层浮球生物滤器设计及其水产养殖水处理性能试验

工厂化水产养殖水体的处钾主要包括增氧、分离（分离固体物和悬浮物）、生物过滤（降低BOD、氨氮和亚硝酸盐）、曝气（去除二氧化碳等）和杀菌消毒等处理过程。其中,悬浮物和氨氮去除是主要技术难点。自20世纪80年代,各国学者深入研究了固定滤床和流化滤床、喷淋滤床和浮球生物滤器（bead filter）等悬浮物和氨氮综合处理装置的性能。     

工厂化对虾养殖池管式射流集污水力特性

工厂化养殖池内水体的流场分布特性直接决定了其对残饵、粪便等的排污性能。本实验研究了管式射流驱动模式下,射流角度与射流流速对养殖池内水体流场与污物聚集特性的影响。养殖池流场特性采用点式流速仪进行布点测量,利用MATLAB软件对流场特性进行分析。采用相机采集的养殖池集污效果图像,并利用Photoshop软件与自行开发的不规则图形面积分析软件对图像进行分析。研究表明,流速从池心向外呈"V"型变化,在射流角度固定的情况下,射流速度越大,池心低流速区域越小,污物向池心的聚集效果越好;在流速固定的情况下,存在一个最佳的射流角度,本实验在24 cm/s流速条件下,射流角度为40°时,池内污物聚集效果最优。结论认为在保证养殖对象生长的前提下,可尽量提高射流流速;在24 cm/s流速条件下,最佳射流角度在40°左右。本研究成果可为工厂化养鱼池、养虾池等管式射流水力驱动系统的优化设计提供参考依据。     

The growth of disk abalone, Haliotis discus hannai at different culture densities in a pilot-scale recirculating aquaculture system with a baffled culture tank

The growth rate of disk abalone, Haliotis discus hannai, energy consumption and changes in water quality were monitored in a pilot-scale recirculating aquaculture system (RAS) for 155 days. Baffles were installed in the RAS culture tanks to enlarge the attachment area and clean out solid waste materials automatically by hydraulic force only. The experimental disk abalones, of shell length 24.5 ± 0.5 mm, were cultured at three stocking densities, 700, 1300 and 1910 individuals/m² bottom area, in triplicate. The abalones were fed with sea mustard, Undaria pinnatifida, once a week. The abalone feed conversion rates and daily growth rates ranged from 24.5 to 25.9 and 0.32 to 0.36%, respectively. Their daily shell increments and survival rates ranged from 67.7 to 78.6 μm/day and 87.6–92.2%, respectively. The growth in weight tended to decrease at a culture density of 1300 individuals/m² bottom area, while shell increments and survival rates were acceptable at this density. The total power consumption for heating was 1185.4 kW, comprising 30.2% of the total power consumption, while the average water exchange rate was only 2.9% per day. The total ammonia nitrogen stabilized below 0.07 mg/L, after conditioning of the biofilter. The NO₂⁻–N, NO₃⁻–N and total suspended solid concentrations were also maintained within acceptable ranges for the normal growth of disk abalone. The use of the RAS with these newly designed culture tanks for disk abalone culture produced 1300 individuals/m² bottom area with a water exchange rate of only 2.9% per day and used about one-tenth of the heat energy of a conventional flow-through system.     

循环水养鳗系统生物过滤器中微生物群落的代谢特性

为了研究鳗鱼循环水养殖系统不同水处理单元的微生物群落碳代谢特征,实验采用Biolog Eco技术,分析了流化床两个槽和滴流式生物过滤器上、中、下三层的生物膜微生物群落功能多样性。结果显示,流化床两个槽和滴流式生物过滤器中、下层微生物多样性指数（Shannon-Wiener指数、Simpson指数和Pielou指数）无显著差异（P>0.05）,但均显著高于滴流式生物过滤器上层（P<0.05）。平均色度变化（AWCD）与主成分分析（PCA）均证明滴流式生物过滤器上层与其它采样点微生物代谢差异较大。各采样点微生物未对ECO板某一大类碳源表现出偏好,但对衣康酸、D-半乳糖醛酸、L-精氨酸、L-天门冬酰胺、L-丝氨酸、D-甘露醇、D-木糖、N-乙酰-D-葡萄糖氨、吐温40、吐温80、苯乙胺等单一碳源利用较好;而对γ-羟丁酸和α-丁酮酸以及D,L-α-磷酸甘油和1-磷酸葡萄糖利用较差。某些碳源种类如D-葡糖胺酸、α-D-乳糖、2-羟基苯甲酸仅能被部分采样点的微生物利用。本实验利用Biolog EcoPlateTM技术研究中试规模循环水处理单元微生物群落代谢特征,研究结果为生物过滤器的调控提供了一种新的思路即可以通过碳源调节,来促进生物膜微生物群落结构的改变以此提高水处理效率。