低频率运转下人工湿地对养虾水的去氮作用及其动力学

Performance and dynamics of nitrogen removal in constructed wetlands at low frequency for shrimp culture

联用虾塘设施、以低频率运转人工湿地生态系统循环处理养虾水,研究湿地去氮作用及其动力学。由表面流与水平潜流组成的复合型湿地生态系统(582.2 m^2)含斜坡区、挺水植物区与蓄水池,水力负荷1.65 m/d。养殖周期内(94 d)不换水,不用药,60 d后3次循环处理规模化养虾塘水,总氨氮(total ammonia nitrogen,TAN)、总氮(total nitrogen,TN)与亚硝基氮(nitrite nitrogen,NO_2-N)分别去除37.9%、26.7%(P≤0.01)与22.7%(P≤0.05)。湿地静止期间,挺水植物区NO_2-N、硝基氮(nitrate nitrogen,NO_3-N)与TN分别在废水停留6 h、18 h、24 h时去除17.5%、25.8%与25.9%(P≤0.01),去除速率常数为0.0362,0.0291与0.009 h^(-1)。试验期间,试验塘主要水化指标均控制在对虾生长安全范围,蓝绿藻被有效抑制,收获虾规格与产量优于对照塘(P≤0.01)。结果表明,复合型人工湿地生态系统联用塘内设施,以低频率运转循环处理虾塘水可有效去除TAN等有毒物及抑制蓝绿藻暴发,调控规模化养虾塘水质在对虾生长安全范围内,确保养殖成功。该文可为处理养殖废水人工湿地的构建和应用以及污染物去除动力学模型的建立提供参考。

A constructed wetlands ecosystem was developed with a low frequent operation combined with pond facilities to circularly treat culture wastewater for the purpose of studying the performance and dynamics of nitrogen removal in constructed wetlands. The FEW-SF wetlands ecosystem used in this study consisted of a free water surface flow （FWS） wetland and a subsurface flow （SF） wetland. The whole area of FEW-SF wetlands was 582.2 mE, including three units： the slope unit, the macrophyte unit, and the reservoir unit with an area ratio of 1：2.3：1.4. Two shrimp culture ponds with an equal size were set as experimental and control ponds respectively. Each culture pond was equipped with four microvesicle aerators and water purification nets （5.25 m×0.90 m） hung at 2 nets/mE. The experiment was conducted during a 94 day period with no water exchange and chemical use. Since the 60th day, the constructed wetlands ecosystem was operated for three times at a hydraulic loading rate （HLR） of 1.65 m/d and significantly removed TAN, TN, NOE-N by 37.9%, 26.7% （P≤〈0.01）, and 22.7% （P≤0.05） respectively. Removal efficiencies of various nitrogen when culture wastewater was retained in the macrophytes unit for 144h showed that NOE-N, NO3-N and TN were significantly （P≤0.01） decreased at 6 h （17.5%）, 18 h （25.8%）, and 24 h （25.9%）. The mean daily removal rate of each parameter declined with time and the removal rates of NOE-N, NO3-N and TN were 0.372-1.568 g/m^2·d, 0,880-2.600 g/m^2·d, 0.843-2.455 g/mE-d respectively and were higher than that of TAN. The concentrations of NOE-N, NOa-N, and TN declined with static time at an exponential function, in line with the first-order dynamics equation and the removal rate constants were 0.036 h-1, 0.029 h-1 and 0.009 h-1. The initial main component of TN in culture wastewater was TIN, and then the main component of TN was gradually converted to TON after about static 52 h.The main water quality in the experimental pond was within the acceptable range for shrimp growth or survival and blue-green algae bloom was strongly inhibited. At the end of the experiment, average adult shrimp size and yield were significantly larger or higher than that in the control pond （P〈~0.01）. This experiment shows that the constructed wetlands ecosystem can effectively remove nitrogen and inhibit blue-green algae growth at low frequency operation combined with pond facilities without water exchange and medicine usage during a culture period to maintain the good water quality and finally ensure a good harvest.