|其他题名: ||The Purification Performance of the Integrated Vertical Flow Constructed Wetland in Recirculating Aquaculture System|
|摘要: ||在我国水产养殖业迅猛发展的同时，传统的养殖模式带来了池塘水质恶化、养殖病害频发、水产品品质下降等一系列问题。这些问题如不能得到有效解决，将会严重影响到我国水产养殖业的可持续发展。针对这些问题，本研究将人工湿地应用到池塘养殖水质的净化和管理，通过三年来对人工湿地－池塘循环养殖系统中池塘以及湿地进出水水质的监测，以期了解人工湿地能否有助于解决池塘养殖过程中出现的水污染严重、病害暴发及品质下降等问题。本论文主要从以下几个方面开展了研究：1. 使用年限对人工湿地净化功能的影响；2. 不同水力负荷对人工湿地净化功能的影响；3. 人工湿地在循环养殖系统氮素循环中的作用；4. 池塘异味问题的来源以及人工湿地对养殖池塘异味问题的控制效果。主要研究内容与结果如下：
1) 通过监控2005－2007年人工湿地进出水水质发现，湿地进出水中TSS、CODcr、BOD5、TN、NH4+-N和NO3--N等指标均有显著性差异，湿地对这些指标有较高的去除效率，三年来人工湿地对池塘养殖水体均保持了较高的净化效率，对TSS、CODcr 和BOD5的平均去除率分别为57.3%、40.1%和52.0%，对TN、NH4+-N和NO3--N的平均去除率分别为52.6%、44.5%和34.0%，对TP的平均去除率为21.3%。三年来人工湿地对CODcr、BOD5、TN、NH4+-N和NO3--N的去除效率稳中有升，对Chl.a也有较高去除率，不过值得注意的是其对TSS和TP的去除效率有逐渐下降的趋势。湿地出水水质除溶氧外均能达到《国家渔业水质标准》规定，出水溶氧通过设在出口的曝气池和水道的复氧功能后也可以达到标准规定。
3) 关于人工湿地在循环养殖系统氮素循环中的作用研究表明，饲料投喂是人工湿地－池塘循环养殖系统中最大的氮素输入来源，占氮素输入总量的84.9%；鱼体收获是人工湿地－池塘循环养殖系统中氮素输出主要部分之一，占氮素输出的34.1%；人工湿地在养殖系统的氮素控制中发挥了较大作用，通过人工湿地输出的氮素占氮素输入总量的49.8%；据推算，其中有41.7 %的氮素通过湿地的反硝化作用输出，另外，湿地基质表面吸附和湿地植物吸收的氮素分别占输入总氮的4.0 %和4.1 %。
4) 2006－2007年关于人工湿地对池塘水体异味物质控制作用的相关研究表明，未循环塘中TN、TP、CODcr和TSS等指标均显著高于循环塘，高密度循环塘中TP、BOD5和CODcr等指标显著高于低密度循环塘，随着养殖密度的逐渐增加，池塘水体中TN、TP和TSS均呈现逐渐升高的趋势；通过湿地对养殖池塘水体进行循环有利于减轻蓝藻水华的爆发，循环塘中蓝藻种类数目、密度和在藻类总量中所占比率均低于未循环塘；2007年未循环塘中检测出了MIB、geosmin和β-cyclocitral三种异味物质，平均含量分别为63.3ng/L、152.6ng/L 和254.8ng/L，与未循环塘投放密度相同的循环塘中仅检出较低浓度的geosmin，2006年高密度循环塘中也出现了这三种异味物质，其中geosmin含量要高于未循环塘，而β-cyclocitral含量低于未循环塘；通过典型相关分析发现池塘水体中Oscillatoria sp.、Microcystis aeruginosa 和 O. kawamurae三种藻类的密度与水体中三种异味物质的含量相关，较高的富营养化水平是导致水体异味的重要原因。
5) 2006年当进水geosmin含量在5.6-255.3ng/L范围内波动时，人工湿地对其去除率保持在67％-81％之间；2007年当进水geosmin含量在3.5-88.0 ng/L范围内波动时，人工湿地对其平均去除率达到88％。在小试系统开展的研究还发现，在水力负荷为200mm/d和400mm/d时，小试系统对geosmin有较好去除效果，但当水力负荷提高到800mm/d直至1000mm/d时，小试系统对geosmin去除率出现了较大波动，有时甚至出现负值；在水力负荷为200mm/d至800mm/d时，小试系统对β-cyclocitral去除率均值达到94％，当水力负荷加大到1000mm/d时，小试系统去除率出现负值。
|英文摘要: ||With the development of aquaculture industry in China, the traditional culture mode has made serious impacts on the sustainable development of the aquaculture industry, including the deterioration of water quality, the occurrence of disease, the decline of aquaculture product quality, and so on. Aiming at these problems, the present research was carried out to apply the Integrated Vertical-Flow Constructed Wetland to the purification and management of the pond water. The water quality in the recirculating aquaculture system had been monitored for three years to find out whether these problems encountered in aquaculture industry could be solved by the constructed wetland. Researches were carried out from four aspects as follows: 1) the effect of the operation time on the purification performance of the constructed wetland; 2) the effect of the hydraulic loading rate on the purification performance of the constructed wetland; 3) the function of the constructed wetland in the nitrogen budget of the constructed wetland-pond recirculating aquaculture system; 4) what caused the off-flavor problems and the performance of the constructed wetland on the control of the off-flavor problems. The main research contents and the main results are summarized as follows:
1) Significant differences of several physicochemical parameters (TSS, CODcr, BOD5, TN, NH4+-N and NO3--N) were found between the influent and effluent of the constructed wetland through three years’ (2005-2007) monitoring. There was high treatment efficiency of the pond water by the constructed wetland, especially referring to the physicochemical parameters. The average removal rates of TSS, CODcr and BOD5 were 57.3%, 40.1% and 52.0%, respectively; those of TP, TN, NH4+-N and NO3--N were 21.3%, 52.6%、44.5% and 34.0%, respectively. The removal rates of Chl.a, CODcr, BOD5, TN, NH4+-N and NO3--N were stable all through three years. However, there was a decrease tendency of the removal rates of the TSS and TP from 2005 to 2007. All parameters except dissolved oxygen in the effluent of the constructed wetland could meet the standard of national fishery water quality. After all, dissolved oxygen could be recovered by the oxygen supplying equipment.
2) The effect of the hydraulic loading rate to the purification performance of the constructed wetland was studied on a small-scale constructed wetland with an area of 2 m2. There were high purification performances of CODcr, BOD5, Chla, TSS, TP, IP, TN and NO3--N at the hydraulic loading rates from 200mm/d to 800mm/d. At a lower hydraulic loading rate, the removal process was mainly found in the upper layer of the down-flow chamber. As the hydraulic loading rates increased from 200mm/d to 1000mm/d, the treatment efficiency of the wetland decreased accordingly. Negative removal rates of NO3--N, TP, Chla and TSS were found at 1000mm/d.
3) The nitrogen budget in the constructed wetland-pond recirculating aquaculture system showed that feed was the main source of the nitrogen gains, which accounted for 84.9% of the nitrogen gains, while catfish harvest was a main source of nitrogen losses, which accounted for 34.1% of the nitrogen losses. Constructed wetland was helpful for the control of nitrogen accumulation in the system. The nitrogen removed by the constructed wetland accounted for 49.8% of the total nitrogen gains; it was concluded that denitrification in wetland accounted for 41.7%, while substrate accumulation and plant assimilation accounted for 4.0% and 4.1%, respectively.
4) Relevant study on the management of off-flavor problems from 2006 to 2007 showed that the concentrations of physicochemical parameters such as TN, TP, CODcr and TSS in the static pond were significantly higher than the recirculating pond and the concentrations of TP, BOD5 and CODcr were significantly higher in the recirculating pond with a higher fish density, the increase of which accomplied with increases of the concentrations of TP, BOD5 and CODcr. Water recirculation by the constructed wetland was helpful for the control of dominance of cyanobacteria, and the species and density of cyanobacteria in recirculating pond were lower than those in the static pond. In 2007, MIB, geosmin and β-cyclocitral were detected in the static pond, with average concentrations of 63.3ng/L, 152.6ng/L and 254.8ng/L, respectively. However, only lower concentration of geosmin was detected in the recirculating pond. In 2006, these odorous compounds were also detected in the recirculating pond with higher fish density. Among them, the concentration of geosmin was higher than that in the static pond, while the concentration of β-cyclocitral was lower. It was found that the occurrence of Oscillatoria sp., Microcystis aeruginosa and O. kawamurae would be related with the three odorous compounds, and the trophic level was the main reason of the off-flavor problems.
5) As the concentration of geosmin in the influent varied from 5.6-255.3ng/L in 2006, the removal rate of the constructed wetland was from 67% to 81%. In 2007, the average removal rate was 88% when geosmin concentration varied from 3.5-88.0ng/L. In the small-scale constructed wetland, a high removal rate of geosmin was found at hydraulic loading rates from 200mm/d to 400mm/d, while there was a negative removal rate as the hydraulic loading rate increased to 1000mm/d. The average removal efficiency of β-cyclocitral was 94% as the hydraulic loading rate varied from 200mm/d to 800mm/d. However, a negative removal rate was also found as the hydraulic loading increased to 1000mm/d.
6) The concentrations of two odorous compounds (geosmin and MIB) detected in fish samples from the static pond were significantly higher than those from the recirculating pond in 2007. Geosmin concentration in fish samples from the static pond was above OTC from July to October and MIB concentration was above OTC on October, while the concentrations of both gesomin and MIB were below OTC in the recirculating pond. In sediment samples, both geosmin and MIB concentrations in the static pond were significantly higher compared with those in the recirculating pond. According to the correlation analysis of the odorous compounds in water, fish and sediment samples, significant correlation relationships were found between each two of them. In addition, significant correlation relationships of actinomycete numbers in sediment samples and geosmin concentration in fish and sediment samples were also observed.|
|Appears in Collections:||中科院水生所知识产出（2009年前）_学位论文|
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