潮汐流湿地处理生活污水与温室气体释放试验研究

发布时间：2018-05-27 16:19

本文选题：人工湿地 + 分散处理　；参考：《北京建筑大学》2017年硕士论文

【摘要】：中国经济快速发展导致水环境问题日益严重。远离市政下水道的分散式污水难以集中处理,需适当分散处理之。其中,人工湿地技术非常适合处理分散式生活污水。然而,传统人工湿地具有处理能力低、占地面积大等缺陷。针对上述问题,本课题采用三级潮汐流人工湿地来实现高负荷的生活污水分散式处理。考察了系统整体运行效果和影响因素,并对温室气体排放进行相应研究。在运行周期为8 h、接触与空床时间均为4 h、水力负荷为1.26 m3/(m2·d)之试验条件下,三级潮汐流人工湿地对COD、NH_4~+-N、TN和TP去除率分别为85%、85%、39%和32%。系统对COD及NH_4~+-N去除率较高,但对TN与TP去除效果十分有限。污染物去除主要发生在第一级,其中COD、NH_4~+-N、TN和TP的去除率分别占到总去除率的83.8%、75.9%、79.9%和75.3%。在运行周期(8 h)固定条件下,接触与空床时间对潮汐流人工湿地处理效果影响显著。随接触期延长(2、4、6 h),第一级湿地的COD去除效率逐渐升高,从最低的65.9%升高至75.7%;但NH_4~+-N去除率却逐渐下降,从最高的68%下降到31.4%;而NO_3~--N累积率下降明显,从最高的38.8%下降到1.7%;TP去除率从11.5%提高到了29.8%。在接触与空床时间比(1:1)不变的条件下,运行周期长短影响潮汐流人工湿地的处理效果。第一级潮汐流人工湿地运行周期由6 h提升到8 h,污染物去除率明显提升。然而,周期继续延长后各污染物去除率增加放缓。当周期为16 h时,NH_4~+-N去除率甚至呈下降趋势。试验表明,在运行周期为12 h,接触与空床时间比为1:1的情况下,运行效果最好,出水NH_4~+-N与BOD5可分别维持在2~4 mg N/L和10 mg/L以下。潮汐流人工湿地去除效果也受液面变化的影响。其中,COD及TP受影响较小,NH_4~+-N及TN受影响较大。在运行周期为12 h(接触与空床时间均为6 h)条件下,第一级人工湿地各液面(高于基质层15 cm;与基质层持平;低于基质层20 cm)下COD、TP去除率分别维持在75%和30%左右。高液面限制了氧的传输,NH_4~+-N去除率从液面持平时的67.5%下降为58.5%;但形成的缺氧环境强化了反硝化,TN去除率从35.1%提高到42.5%。低液面强化了氧的传输,NH_4~+-N去除率提高到71.8%,但反硝化受到了限制,TN去除率下降为34.6%。本试验中较低的TN去除效果一是因进水C/N比值偏低,二是由于潮汐流人工湿地较强的复氧能力导致反硝化受限所致。分别考察分步进水、出水回流和增加进水无机碳源对强化TN去除的效果。前两种方式的目的在于优化进水有机碳源的利用,后一种方式旨在强化短程硝化/反硝化。在运行周期为12 h(接触与空床时间均为6 h)条件下,采用分步进水及出水回流方式使TN去除率升至59.8%和64.2%,比未强化前分别提高了15%和19%。在运行周期为8 h(接触与空床时间为均4 h)条件下,通过向进水中添加无机碳源,TN去除率可达到59.7%,比未强化前提高了21%。监测表明,潮汐流人工湿地温室气体释放呈一定规律,并受温度、液面变化的影响。潮汐流人工湿地复氧能力较强,导致CH_4释放较少(24.8 mg CO_2/(m2×h)),而N2O释放量较多(50.4 mg CO_2/(m2×h))。在接触期,各温室气体释放通量与水温成显著正相关(N2O:p0.001;CH4:p0.005)。在空床期,气温对N2O释放影响较大,呈显著正相关(p0.001),而对CH_4影响不明显。不同液面下,液面高于基质15 cm时,温室气体释放总通量最大为90.8 mg CO_2/(m2×h);液面与基质持平总释放通量最小,为61.1 mg CO_2/(m2×h)。总体上,潮汐流人工湿地温室气体释放总量(平均75 mg CO_2/m2×h))显著小于其他类型湿地(表面流:257 mg CO_2/(m2×h);水平潜流:358 mg CO_2/(m2×h);垂直流:162 mg/(m2×h))。
[Abstract]:The rapid development of China's economy has caused the problem of water environment increasingly serious. The dispersed sewage from the municipal sewer is difficult to concentrate and should be treated properly. Among them, the artificial wetland technology is very suitable for the treatment of dispersed domestic sewage. However, the traditional artificial wetland has the disadvantages of low processing capacity and large area. This project uses three stage tidal flow constructed wetland to realize high load domestic sewage dispersion treatment. The overall operation effect and influence factors of the system are investigated, and the greenhouse gas emission is studied. The operation period is 8 h, the contact and empty bed time are 4 h, the hydraulic load is 1.26 m3/ (M2. D), and the three stage tide The removal rates of COD, NH_4~+-N, TN and TP were 85%, 85%, 39% and 32%., respectively. The removal efficiency of COD and NH_4~+-N was higher, but the removal efficiency of TN and TP was very limited. The removal of pollutants was mainly in the first stage, and COD, NH_4~+-N, TN and removal rates accounted for 83.8%, 75.9%, 79.9% and 8 of the total removal rate (8). H) under fixed conditions, the effect of contact and empty bed time on the treatment effect of tidal flow constructed wetland was significant. With the extension of the contact period (2,4,6 h), the removal efficiency of COD increased gradually from the lowest 65.9% to 75.7%, but the NH_4~+-N removal rate decreased gradually from the highest to 31.4%, and the NO_3~--N accumulation rate decreased obviously. The maximum 38.8% decreased to 1.7%, and the removal rate of TP increased from 11.5% to 29.8%. in the condition that the contact and empty bed time ratio (1:1) remained constant. The operation cycle length affected the treatment effect of the tidal flow constructed wetland. The first stage tidal current constructed wetland was raised from 6 h to 8 h, and the removal rate of the pollutants was significantly increased. The removal rate of the pollutants increases slowly. When the cycle is 16 h, the removal rate of NH_4~+-N is even decreasing. The test shows that the operation effect is best when the operation period is 12 h and the contact and empty bed time ratio is 1:1, and the effluent NH_4~+-N and BOD5 can be maintained at 2~4 mg N/L and 10 mg/L respectively. The removal effect of tidal flow constructed wetland is also affected by liquid. The influence of surface change. Among them, COD and TP are less affected, and NH_4~+-N and TN are greatly affected. Under the operating period of 12 h (contact and empty bed time are 6 h), the liquid surface of first stage constructed wetland (higher than matrix layer 15 cm, with matrix layer is flat, lower than matrix layer 20 cm) COD, TP removal rate is maintained at 75% and 30% respectively. High liquid level restriction The removal rate of NH_4~+-N decreased from 67.5% to 58.5% at the liquid level, but the formation of anoxic environment strengthened denitrification, the removal rate of TN increased from 35.1% to the low level of 42.5%., and the removal rate of NH_4~+-N increased to 71.8%, but the denitrification was restricted and the TN removal rate decreased to the lower TN removal in the 34.6%. experiment. The result is that the C/N ratio is low and the two is due to the restriction of denitrification due to the strong reoxygenation ability of the tidal flow constructed wetland. The effect of the step influent, the effluent reflux and the increase of the inorganic carbon source for the enhancement of TN removal. The purpose of the first two ways is to optimize the utilization of the organic carbon source in the water intake. Short range nitrification / denitrification. Under the operating period of 12 h (both contact and empty bed time are 6 h), the removal rate of TN is increased to 59.8% and 64.2% by step influent and effluent reflux, and 15% and 19%. are increased by 15% and 19%., respectively, under the condition of 4 h between the contact and the empty bed, and the addition of inorganic carbon to the influent. The removal rate of TN could reach 59.7%, and 21%. monitoring showed that the release of greenhouse gas in the tidal flow constructed wetland showed a certain regularity and affected by the temperature and liquid level. The release of CH_4 was less (24.8 mg CO_2/ (M2 * h)), and the release of N2O was more (50.4 mg CO_2/ (M2 * h)). The release flux of greenhouse gases has a significant positive correlation with the water temperature (N2O:p0.001; CH4:p0.005). In the empty bed period, the temperature has a great influence on the release of N2O, which has significant positive correlation (p0.001), but the effect on CH_4 is not obvious. The maximum release flux of the greenhouse gas is 90.8 mg CO_2/ (M2 x H) when the liquid level is higher than the matrix 15 cm under different liquid levels. The minimum total release flux was 61.1 mg CO_2/ (M2 x H). In general, the total amount of greenhouse gas release from tidal flow constructed wetland (average 75 mg CO_2/m2 x H) was significantly less than other types of wetlands (surface flow: 257 mg CO_2/ (M2 x H), horizontal subsurface flow: 358 Mg (162)); vertical flow: 162
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

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