封闭循环水产养殖系统中三种生物滤池除氨氮效果的比较

分析了封闭循环水产养殖系统中生物滤池所采用的软性滤料、弹性滤料、半软性滤料3种生物滤料的特点,对填装这3种滤料的生物滤池处理养殖污水中氨氮的能力进行了比较和分析。实验结果表明,(1)在同样的水力停留时间下,加入同体积滤料的3个生物滤池对氨氮的去除能力不同,3个生物滤池的氨氮去除率均随着进水氨氮质量浓度的增加而降低;(2)在不同的水力停留时间条件下,每个生物滤池对氨氮的去除能力不同,水力停留时间为80 min时的氨氮去除率最高。在该系统中综合考虑水力停留时间及滤料的不同,弹性滤料滤池在水力停留时间为80 min时去除氨氮的效果最好,平均去除率达到53.2%。     

水力负荷对移动床生物滤器硝化功能的影响

为探索移动床生物滤器在封闭循环水养殖水体净化方面的作用,研究分析水力停留时间(HRT)和曝气量等水力负荷条件变化对移动床硝化效率、流化状态和养殖系统稳定性的影响规律。研究表明,低氨氮负荷条件下,HRT从6.7 min延长至10 min,移动床总氨氮(TAN)去除率随着HRT的延长而升高;而HRT在从10 min延长至20 min,TAN去除率并不会随着HRT的延长而升高;HRT在10 min时,TAN去除率较高且水流量较大,硝化效率最高,单位体积TAN去除率(VTR)平均达(63.11±26.77)g/(m3.d),最高达到110.19g/(m3.d);曝气流化状态的移动床TAN去除率和VTR均显著高于未曝气移动床。     

移动床生物膜反应器处理低浓度氨氮养殖废水试验

采用移动床生物膜反应器(MBBR)处理低浓度氨氮养殖废水,在不同水力停留时间(HRT)和不同曝气条件下,分析MBBR处理人工模拟的低浓度氨氮(2 mg/L左右)养殖废水的进出水氨氮、亚硝酸盐氮和硝酸盐氮的浓度变化,探讨HRT和曝气量对MBBR处理低浓度氨氮养殖废水的影响,并以实际鲟鱼养殖废水(氨氮浓度0.5～1.5 mg/L)和其他研究成果进行验证和比较.结果显示:MBBR的最优HRT为6～8 min,最优曝气量为180 L/h,相应的氨氮去除率为70％ ～ 75％,氨氮去除负荷为560～700 g/(m3.d),填料生物膜厚度为26～38 μm;膜表层结构多样,物种丰富,膜生长良好.该反应器对处理低浓度氨氮养殖废水具有的高效能力.     

水力停留时间对厌氧反应器脱氮效果的影响

本研究使用自主设计的厌氧反硝化器,以斜发沸石为填料,自然挂膜,与循环水养殖系统一级生物滤池串接,探索不同水力停留时间(HRT)下反应器的脱氮效果。结果显示,在实验过程中,反应器对无机氮(IN)、总氮(TN)均有较好的去除效果。在低水力停留时间(HRT7.43h)下,反应器主要去除的是氨氮(NH_4~+-N);高水力停留时间下(HRT≥7.43h),反应器主要去除的是硝酸盐氮(NO_3~–-N)。当HRT为17.52h时,反应器的脱氮效果最好,NO_3~–-N去除率为77.48%。此后,HRT延长,脱氮效果下降。脱氮效果越好,亚硝酸盐氮(NO_2~–-N)、NH_4~+-N积累越严重,NO_2~–-N最先开始积累。本研究可为厌氧反硝化装备的开发提供参考。     

水力停留时间、水温与氨氮浓度对浸没式生物滤池氨氮去除速率的效应

本文研究了采用浸没式生物滤池处理集约化养殖污水时 ,水力停留时间 (HRT/min)、水温(T/℃ )、总氨氮浓度 ([TAN] ,mgNH+4-N/L)对总氨氮去除速率 (R/gNH+4-N/m3 h)的效应。对实验数据的分析结果表明 ,它们之间的经验方程为 :当 [TAN]≥ 2 85mgNH+ 4-N/L ,R =0 2 6+ 0 2 9·HRT + 0 0 0 8·HRT·T -0 0 1·HRT2 ;当 [TAN]≤ 2 85mgNH+ 4-N /L ,R =(-0 78+ 0 2·HRT + 0 0 0 3·HRT·T -0 0 0 7·HRT2 )·[TAN ]+ 0 2 45。上述模型可说明在单因素作用时 ,氨氮去除速率与水温线性正相关 ,与总氨氮浓度为零级、一级反应关系 ,与水力停留时间呈双曲线相关。一定的水温、氨氮负荷条件下 ,存在使氨氮去除速率最大的水力停留时间 ,这对最优化设计与运行浸没式生物滤池有指导意义     

竹子填料海水曝气生物滤器除氮性能

生物滤器是循环水养殖系统的关键水处理单元,主要用于去除水体中水溶性的氮化物.采用人工模拟海水养殖废水,在系统运行的水力停留时间HRT为1h,水温为18～25 ℃,气水比为3∶1,初始C/N＝3∶1,pH为8.05～8.53条件下,对竹子填料浸没式生物滤器的挂膜过程和稳定运行阶段系统去除氨氮的运行特性,以及挂膜过程中的硝化细菌群落变化进行了实验研究.结果表明,在较低的NH+4-N浓度条件下,采用竹子填料的生物滤器有较快的挂膜速度,挂膜成功后滤料表面上生长的氨氧化细菌和亚硝酸氧化细菌的数量分别为4.5×105、1.5×105(光面)和1.1×106 CFU/ml(粗面).具有较高且稳定的氨氮去除效果,氨氮去除效率达到80%,出水浓度小于0.06 mg/L,满足海水循环养殖系统中的应用要求.     

生物—电氧化法去除海水养殖循环水污染物

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。     

水力停留时间对养殖污水固相反硝化处理效果的影响研究

为考察水力停留时间(HRT)对不同硝酸盐氮(NO3--N)浓度的养殖污水脱氮效果的影响,建立以聚己内酯(PCL)为碳源和生物膜载体的固相反硝化反应器,经历20 d培养,反应器成功启动。试验结果表明,当进水NO3--N浓度分别为100 mg/L以下、150 mg/L、200~300 mg/L时,反应器的最佳HRT分别为4、5.5和6 h,出水NO3--N浓度达到最低值,分别为17.9 mg/L、23.9 mg/L和34.1~47.4 mg/L,同时溶解性有机碳(DOC)没有大幅增加。反应器对氨氮(NH4+-N)亦有一定的去除效果,在反应器启动运行后,出水NH4+-N浓度明显下降,且在不同进水NO3--N及HRT下均稳定在5 mg/L左右,出水亚硝酸盐氮(NO2--N)一直维持在0.14 mg/L以下;同时,反应器对养殖污水中的溶氧(DO)和p H变化有一定抗性,缓冲能力较强。本研究对水产养殖脱氮的实验室研究和实际运行、管理具有参考意义。     

几种环境因子对循环水养殖系统中生物膜净化效率的研究

为研究环境因子对生物膜水质净化效果,对爆炸棉为滤料的生物滤器进行了试验。采用优势菌种挂膜后,在不同水温、溶氧(DO)、盐度、p H条件下,研究生物滤器对人工加富的海水养殖废水水质的净化效果。结果显示,水温28℃时,化学需氧量(CODMn)、氨氮(NH4+-N)、亚硝酸盐氮(NO2--N)、磷酸盐(PO43--P)去除率分别为69.3%、93.7%、93.7%、19.4%;DO 6.00 mg/L时,CODMn、NH4+-N、NO2--N、PO43--P去除率分别为72.8%、91.7%、97%、15.6%;盐度25时,CODMn、NH4+-N、NO2--N、硝酸盐氮(NO3--N)、PO43--P去除率分别为57.1%、98.4%、99.9%、100%、42%;p H 7.5时,CODMn、NH4+-N去除率分别为72.8%、93.3%。研究表明,水温28℃、DO 6.00mg/L、盐度25和p H 7.5为该生物滤器最适水质净化条件,此时生物膜净化效率较高,出水水质较好。     

水芹对富营养化水体的净化效果研究

利用聚乙烯板作为浮床栽植水芹(Oenanthe javanica),观测其对4组不同富营养化程度水体的净化效果。结果表明,水芹对总磷(TP)有较好的去除效果,初始浓度越高去除率越低,去除率范围53.3%～84.0%;水芹对低于5mg/L的总氮(TN)有较好的去除效果,去除率也随初始浓度升高而降低,去除率范围36.1%～85.7%,如果总氮浓度过高(达到20mg/L左右),去除效果不明显。试验组氨氮(NH3-N)的浓度虽然有明显的降低,但与对照组比没有明显优势,水芹对亚硝酸盐氮(NO2--N)的去除作用不明显,硝化细菌对氨氮和亚硝酸盐氮的去除起主要作用,水芹通过降低水中总氮水平对氨氮和亚硝酸盐氮有一定间接的去除作用。在整个试验过程中,各组高锰酸盐指数(CODMn)维持在较低水平(<3mg/L),未观察到栽植水芹对高锰酸盐指数的降低作用。     

三种因素对海水生物流化床启动期间营养盐去除及amoA基因表达的影响

在实验室规模下,以旋转式生物流化床(CB-FSB)为研究对象,研究了初始总氨氮(TAN)、水温及滤料膨胀率3种条件下,海水生物流化床生物过滤功能启动期间TAN和亚硝酸盐氮(NO-2-N)去除及amoA基因数量的变化。结果显示:生物流化床生物过滤功能启动所需时间随着水温的升高而缩短,在水温为15℃、20℃和25℃时,启动所需时间分别为27 d、25 d和23 d;初始TAN质量浓度的升高也会缩短生物流化床生物过滤功能启动所需要的时间,在初始TAN质量浓度为1 mg/L、2 mg/L、4 mg/L时,启动所需时间分别为24 d、22 d和21 d;在膨胀率为100%和150%时,启动所需时间无明显差别,分别为21 d和20 d,明显好于膨胀率为50%时启动所需时间27 d;amoA基因的数量变化与TAN去除率的变化有一定的相关性,并随着初始TAN浓度的升高而增多,在4 mg/L时数量最多,达到2.76×10~7copies/g。     

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.     

Treatment of hatchery wastewater by a sequencing batch reactor process

After settling pretreatment, the primary sludge wastewaters from a fish hatchery were treated in three five-litre bench-scale sequencing batch reactors. The sequencing batch reactors were operated concurrently under the same operating conditions. A cycle of 24 hours was adopted during the course of this study. Two different temperature regimes (22°C and 10°C) were employed, and a range of initial BOD₅ concentrations was treated. The results showed the occurrence of very high reductions in BOD₅ and COD concentrations, and very high removal of ammonia---nitrogen and suspended solids. The average five-day BOD₅ reduction was 98% for high influent concentrations, while the reduction for lower influent concentrations was 95%. The average five-day BOD₅ concentration for the effluents was less than 100 mg litre⁻¹. Nitrification was pronounced after 40 days of reactor operation. Denitrification occurred when the reactors were fed wastewaters with high BOD₅ concentrations, although it was not observed with low influent BOD₅ concentrations or at low temperatures (10°C). The overall treatment efficiency remained very high when the reactors were operated under a low temperature regime (10°C).     

Characterization of intake and effluent waters from intensive and semi-intensive shrimp farms in Texas

Two commercial shrimp farms in south Texas were evaluated for influent and effluent water quality from June to October 1994. The intensive farm, Taiwan Shrimp Village Association (TSV) had an average annual yield of 4630 kg ha^?1 while the semi‐intensive farm, Harlingen Shrimp Farm (HSF), had a yield of 1777 kg ha^?1. The study had three objectives: (1) to compare influent and effluent water from the intensive and semi‐intensive shrimp farms, (2) to show which effluent water‐quality indicators exceeded allowable limits, (3) to indicate inherent problems in farms operated with water exchange and summarize how findings from this study led to changes in farms' management that limited potential negative impact on receiving streams. Water samples were collected and analysed twice a week for the TSV farm and once a week for the HSF farm. Samples were analysed for dissolved oxygen (DO), salinity, pH, ammonia‐nitrogen (NH₃‐N), nitrite‐nitrogen (NO₂‐N), nitrate‐nitrogen (NO₃‐N), total phosphorus (TP), total reactive phosphorus (TRP), five‐day carbonaceous biochemical oxygen demand (cBOD₅), total suspended solids (TSS) and settleable solids (SettSols). Most of the effluent constituents showed fluctuations throughout the sampling period often related to harvest activity. Effluent pH at TSV was lower than influent values but within the regulatory requirements set by Texas Commission of Environmental Quality (TCEQ), formerly known as Texas Natural Resource Conservation Commission (TNRCC). HSF effluent pH values were higher than its influent, but still within TCEQ limits. Effluent DO mean levels were generally below the regulatory daily mean requirement, with values at TSV often below those for influent. Effluent nutrient concentrations and net loads were generally higher at the intensive shrimp farm, with NH₃‐N mean concentrations above the daily mean set by the TCEQ on several occasions. Effluent TSS concentrations were higher than influent for both farms, with daily mean values above the TCEQ limit. The two farms presented similar TSS concentrations despite their different stocking densities. However, TSS total net load and net load per hectare were higher at the intensive farm. The semi‐intensive farm presented higher cBOD₅ concentrations and net loads despite its lower stocking density, with daily mean values above the TCEQ limit. The cBOD₅ net load at TSV presented negative values indicating higher load at the influent than at the effluent. Analyses showed no evidence of self‐pollution between influent and effluent at the two farms. The high feed conversion ratio (FCR) values (2.3 and 2.7 for the intensive and the semi‐intensive farm respectively) suggest that better feed management is needed to reduce nutrient and solid net loads release from the two farms. The data obtained from this study resulted in several modifications in design and management of the two farms that reduced the potential negative impact on receiving streams. A brief summary of the improvement in selected effluent water‐quality indicators at the intensive shrimp farm is provided.     

A Survey of Water Quality Characteristics of Effluent from Hawaiian Aquaculture Facilities

Ten water quality parameters were measured in influent and effluent water at 11 aquaculture facilities in Hawaii. The data were grouped into four categories based on the types of organisms cultured: freshwater fish, freshwater prawn, marine fish, and marine shrimp. Within each category, concentrations of most parameters were lognormally distributed and spanned one to two orders of magnitude. Geometric mean concentrations of suspended materials, total nitrogen, total phosphorus, and pigments were highest in effluent from freshwater prawn ponds and lowest in marine fish pond effluent. Nitrate/Nitrite and total ammonia concentrations were higher in fish pond effluent than in crustacean pond effluent. Parameter concentrations were generally higher in effluent than in influent water, with freshwater fish and prawn ponds exhibiting the greatest increases in suspended materials and pigments. In contrast, nitrate/nitrite concentrations were lower in effluent than in influent waters. These data provide a basis for analyzing the environmental impacts of warm-water aquaculture effluent discharges.     

Chemistry of Sediment Pore Water in Aquaculture Ponds Built on Clayey Ultisols at Auburn, Alabama

The composition of sediment pore water was determined for ponds constructed on clayey Ultisols at Auburn, Alabama. Pore water was anaerobic and contained much higher concentrations of ferrous iron (Fe²⁺), soluble reactive phosphorus (SRP), total phosphorus (TP), total ammonia-nitrogen (TAN), and sulfide (S²⁻) than surface or bottom waters. Concentrations of SRP and TP in pore water were higher in ponds with high soil phosphorus concentrations than in a new pond with less soil phosphorus. Increased concentrations of organic matter in soil or larger inputs of feed to ponds favored greater microbial activity in soils and higher concentrations of TAN in pore water. The pH of pore water was 6.5–7.0, and pH was apparently controlled by the equilibrium:

Movement of Fe²⁺, SRP, and S²⁻ from pore water into pond water apparently was prevented by the oxidized layer of soil just below the soil-water interface. Pond managers should concentrate on maintaining this oxidized layer to reduce the tendency for toxic substances to diffuse into the pond water.     

Toxicity of Ammonia to Red Drum Sciaenops ocellatus Fingerlings with Information on Uptake and Depuration1

Median lethal concentrations of un-ionized ammonia-nitrogen to red drum (Sciuenops ocellarus) were 0.9 ± 0.14 mg/L (mean ± SE) after 24 h and 0.8 ± 0.16 mg/L after 48 h (salinity = 4.0%, temperature = 20 C, pH = 6.8–7.1). Ammonia moved quickly from the environment into the plasma with 90% of steady state concentrations being reached after 33 minutes. When ammonia-exposed fish were moved to ammonia-free water, 90% of the ammonia which had accumulated in the plasma was no longer present after 3.3 minutes. The sensitivity of red drum to environmental ammonia appears to be similar to that of most other fishes tested. Based on the median lethal concentrations for red drum observed in this study and the acute-chronic concentration ratios for other species of fish, it is suggested that red drum fingerlings be chronically exposed to no more than 0.05 mg/L un-ionized ammonia-nitrogen.     

The Effect of Biomass Density,Temperature, and Substrate on Transport Survival of Market-Size Freshwater Prawn,Macrobrachium rosenbergii

Abstract

After harvest, adult prawn are often transported for sales to live markets, such as ethnic Asian outlets, in major urban centers. Poor survival during transportation has hindered development and expansion of these markets. Methodologies to increase survival during transport could contribute to industry viability. Three independent trials were conducted. In the first trial, three biomass densities (25, 50 and 100 g/L) were evaluated in 100-L, open plastic containers aerated with pure oxygen and compressed air. Water quality analyses were performed prior to stocking. After 24 hours in the model transport containers, water quality analysis was conducted and all prawn were removed, determined to be alive or dead, and each group weighed and counted. There was no significant difference (P > 0.05) for prawn survival (overall mean 98%) among the three densities. Concentrations of dissolved oxygen and nitrite were not effected by hauling density (P < 0.05). Total ammonia-nitrogen and un-ionized ammonia-nitrogen concentrations increased (P < 0.05) as biomass densities increased, though values remained within what are considered tolerable ranges. In the second trial, the effect of added substrate and temperature on transport survival was evaluated with prawns stocked at the high density (100 g/L). Two water temperatures (21°C and 26°C) with and without substrate were evaluated in a 2 × 2 factorial with three replicate, 100-L model transport containers per treatment combination (12 containers total). Factorial analysis indicated no significant statistical interaction (P > 0.05) between the presence of substrate and water temperature on any measured variable. The main effects of substrate and temperature were then analyzed separately. The presence or absence of substrate had no significant impact (P > 0.05) on prawn survival. However, temperature had a highly significantly impact (P < 0.01) on survival; prawn survival at 21°C averaged 97% compared to 24% at 26°C. The third trial was a commercial verification trial in which 500 kg of live prawn were transported to New York from Kentucky. These data indicate prawn can be successfully transported at 100 g/L for 24 hours when temperatures are maintained near 21°C. Adding substrate to the transport tank appears to provide no benefit.     

An automated method of ammonia determination for use in mariculture

The precise and accurate determination of ammonia is important for both routine water management and research at a mariculture laboratory. An automated method was developed using a Technicon AA-II autoanalyser to measure total ammonia-nitrogen in seawater at both high (0–200 μmol l^?1) and low (0–10 μmol l^?1) ranges, using a single cartridge, with a precision of better than 2.2% (95% confidence). Phenol was used as the phenolic reagent, because sodium salicylate was found to be unsuitable for low level determinations of ammonia in seawater. The concentrations of nitrite usually found in mariculture tanks did not interfere significantly. Storage of filtered samples at 4°C in iodized bottles for 9 days or less gave an acceptable yield (± 5% of the initial value).     

循环水养殖系统生物滤池细菌群落的PCR-DGGE分析

通过模拟实验对循环水养殖系统中不同初始NH ₄N浓度的生物滤池中生物膜上和水中的细菌数量及群落种类组成进行了研究。对成熟生物膜及水体样品中的异养菌、氨氧化菌、亚硝酸盐氧化菌的培养计数结果表明,随着生物滤池初始氨氮浓度增大,除异养细菌数量逐渐下降外,生物膜上的氨氧化菌和亚硝酸盐氧化菌数量呈逐渐增加趋势,且均高出水样3~4个数量级;同时对上述样品的16S rRNA基因片段的PCR扩增产物进行变性梯度凝胶电泳(DGGE)分析及其序列同源性分析的结果表明,生物膜和水中都有较高的细菌多样性,同一初始氨氮浓度的滤池中生物膜上的细菌多样性高于水中的。生物滤池中的细菌主要由拟杆菌门的黄杆菌纲和变形菌门的α-、β-、γ-变形菌纲的15种细菌组成。生物膜上的优势菌包括奥雷氏菌属、湖饲养者菌属、泥滩杆菌属、沉积杆菌属、雷辛格氏菌属、冷蛇形菌属和亚硝化单胞菌属等;水体中的优势菌则有明显差异,主要有蛋黄色杆菌属、Nautella,玫瑰杆菌属和一种硫氧化菌等。初始氨氮越高的滤池中,亚硝化单胞菌属的细菌在生物膜上所占比例越高,逐渐成为优势菌之一。实验证实,挂膜初期,提高水体中初始氨氮浓度,有利于硝化细菌的富集和固着,提高生物滤池的除氮效率。