Removing nitrogen and phosphorus from simulated wastewater using algal biofilm technique

Algal biofilmtechnology is a new and advanced wastewater treatment method. Experimental study on removing nitrogen and phosphorus from simulated wastewater using algal biofilm under the continuous light of 3500 Lux in the batch and continuous systems was carried out in this paper to assess the performance of algal biofilm in removing nutrients. The results showed that the effect of removing nitrogen and phosphorus by algal biofilm was remarkable in the batch system. The removal efficiencies of total phosphorus (TP), total nitrogen (TN), ammonia-nitrogen (NH₃-N), and chemical oxygen demand (COD) reached 98.17%, 86.58%, 91.88%, and 97.11%, respectively. In the continuous system, hydraulic retention time (HRT) of 4 days was adopted; the effects of removing TP, TN, NH₃-N, and COD by algal biofilm were very stable. During a run of 24 days, the removal efficiencies of TP, TN, NH₃-N, and COD reached 95.38%, 83.93%, 82.38%, and 92.31%, respectively. This study demonstrates the feasibility of removing nitrogen and phosphorus from simulated wastewater using algal biofilm.     

Pollutant removal by an integrated vertical-flow constructed wetland treating simulated river water by reoxygenation

The effects and mechanism of chemical oxygen demand (COD), nitrogen, and phosphorus concentration removal by an integrated vertical-flow constructed wetland were studied in the wetland system during one inlet–outlet operating period, in two typical stages (each stage is connective 24 h, sampled once every 4 h). The concentration of ammonia decreased along the flow direction in the system, while levels of nitrate (NO₃^?-N) increased. In one operating period, total nitrogen (TN) concentration fell with rising operation time due to evacuative reoxygenation. The TN and NH₃-N removal rates in the system were 26.6% and 97.5%, respectively. COD decreased rapidly in the early stages and more gradually in the direction of water flow of the wetland system. Average total phosphorus (TP) removal rate was 20.71%. TN and NO₃^?-N levels in water of the wetland had a tendency to decline gradually with increasing operation time. Ammonia concentrations displayed only a small variation with operation time. The results also indicated that the wetland was able to maintain its temperature. The oxygen content differed during the various operating stages and exerted a marked influence on COD, TP, and TN removal.     

人工湿地对有机污染物的去除效果与动态特征

通过对荣成人工湿地污水处理系统1999年1月至2004年12月间监测数据进行分析,确定系统的处理效果及有机污染物去除效果的动态特征。结果表明,人工湿地对SS、COD、BOD5均有很好的去除效果,出水质量浓度分别为27.6±6.6、90.0±12.5和22.7±4.3 mg.L-1,去除率分别为73.9%、63.8%和72.5%。大肠菌群、粪大肠菌群去除率分别为99.7%和99.6%。对NH4 -N和TP去除效果较差,出水质量浓度分别为11.2±2.7和2.03±0.29 mg.L-1,去除率分别为45.1%和30.2%。BOD5、COD的去除效果和季节变化有一定关系,每年的4—7月BOD5去除效果最佳,1月和12月去除效果最差。COD的去除效果每年6月和7月最高,1月和12月最低。分析BOD5、COD和SS去除效果的年际变化发现,BOD5和COD年平均去除率从1999年到2004年有增加的趋势。     

人工湿地处理富营养化水体的效果研究

通过在北京市野生动物救护中心构建表流湿地与潜流湿地相结合的复合人工湿地处理富营养化水体,研究该复合人工湿地对总氮（TN）、总磷（TP）及水体浊度的去除效果。结果表明：人工湿地对TP的去除效果好于对TN的去除效果,经过人工湿地处理的富营养化水体,表流湿地、潜流湿地和复合人工湿地对TP的平均去除率可分别达42%、55%、60%,对TN的平均去除率分别为27%、30%、34%,对水体浊度的平均去除率分别达43%、55%、75%。复合人工湿地对TP、TN以及浊度的去除效果受水体温度和溶解氧（DO）的影响,通过相关性分析发现,TP、TN和浊度的去除量与水体中的DO水平之间存在显著的负相关性,而与水体温度有正相关性,在显著性水平为0.05的条件下,相关系数分别为-0.829、-0.767、-0.765和0.674、0.757、0.774。复合人工湿地对TP、TN及浊度的去除率高于表流湿地和潜流湿地,表明复合人工湿地具有优于表流湿地和潜流湿地的整体性功能,能有效提高人工湿地对TN、TP以及浊度的去除率。     

生态沟渠净化稻田排水动力学分析和生物相特征

本研究以太湖流域常见的菱角、水葫芦、梭鱼草、圆币草等水生植物和人工水草、塑料立体弹性填料为生态强化载体,构建"水生植物-载体生物膜-菌藻"复合型生态系统,研究了稻田排水中的氮、磷等营养元素的去除特性,构建氮、磷污染物的降解动力学模型,并调查了沟渠内"微生物-藻类"生物相特征.结果表明,生态沟渠运行期间,随着水稻进入不同的生长阶段,系统内氮、磷等营养元素的去除率都呈普遍下降趋势,总磷、氨氮、总氮、硝态氮平均去除率分别达到87.1%、92.3%、77.5%、88.6%,其中氨氮的去除率最高,化学需氧量(CODMn)的去除效果并不显著,各实验周期的污染物降解趋势均符合一级动力学降解模型.经生物相分析揭示:随着复合生态系统运行延续,系统内微生物、藻类的种类及Shannon-Weiner index等多样性指数呈不断增长趋势,表明复合生态系统水质改善后更适于多种类细菌与藻类生存与繁殖;复合生态系统中的菌、藻、水生植物及其表面附着的生物膜对污染物的去除具有协同作用,强化了生态沟渠的自净能力.     

Algal purification of pretreated landfill Leachate

The efficiency of microalgae in removing various pollutants in landfill leachate after pretreatment by free stripping or air stripping was tested by a laboratory batch system. The results showed that Chlorella pyrenoidosa and Scenedesmus sp. had similar removal efficiencies with regard to ammoniacal‐nitrogen, oxidized‐nitrogen, orthophosphate and chemical oxygen demand (COD). The COD removal by algal treatment was better in Junk Bay (JB) leachate than in Gin Drinkers’ Bay (GDB) leachate (14–21% and 0.4–7% respectively). No significant difference (P > 0.05) was found in removing other nutrients including ammoniacal‐nitrogen, oxidized‐nitrogen and orthophosphate between leachate from the two landfills, regardless of the pretreatment used. The removal efficiencies of ammoniacal‐nitrogen and phosphorus were found to be higher in air‐stripped leachate than in free‐stripped one. Removal of ammoniacal‐nitrogen and phosphorus in air‐stripped leachate was 30% and 87% respectively. Poor removal of ammoniacal‐nitrogen was probably due to a deficiency in phosphorus (high N : P ratio) for algal growth in leachate. The two‐stage leachate treatment (ammonia stripping followed by algal purification) resulted in overall reduction of COD (38–51%), ammoniacal‐nitrogen (72–96%) and orthophosphate (79–96%).     

Field test of best management practice pollutant removal efficiencies in Shenzhen, China

This paper presents a study on the use of best management practices (BMPs) for controlling nonpoint pollution in the Xikeng Reservoir watershed located in Shenzhen, China. A BMP treatment train design, including a pond, a wetland, and a buffer strip placed in series was implemented at the reservoir location. A separate grass swale was also constructed at the site. Low impact development (LID) BMPs, namely a planter box and bioboxes, were used at the parking lot of the reservoir’s Administration Building. Samples were collected during storm events and were analyzed for total suspended solids (TSS), biochemical oxygen demand (BOD₅), ammonia nitrogen (NH₃—N), and total phosphorus (TP). The removal efficiencies of both BMP systems were evaluated using the Efficiency Ratio (ER) method based on the event mean concentration (EMC) data. In summary, the pond/wetland treatment train removed 70%―90% of TSS, 20%―50% of BOD₅, and 30%―70% of TP and NH₃—N. The swale removed 50%―90% of TSS, 30%―55% of BOD₅, −10%―35% of NH₃—N, and 25%―70% of TP. For the planter box and biobox, the ranges of removal rates were 70%―90%, 20%―50%, and 30%―70% for TSS, BOD₅, and ammonia and phosphorus, respectively.     

Effects of Al3+ on pollutant removal and extracellular polymeric substances (EPS) under anaerobic,anoxic and oxic conditions

The highest removal efficiencies of COD and TN were achieved under 10 mg/L of Al³⁺. The highest TP removal efficiency occurred under 30 mg/L of Al³⁺. EPS, PS and PN concentrations increased with the addition of Al³⁺. Sludge properties significantly changed with the addition of Al³⁺. Aluminum ions produced by aluminum mining, electrolytic industry and aluminum-based coagulants can enter wastewater treatment plants and interact with activated sludge. They can subsequently contribute to the removal of suspended solids and affect activated sludge flocculation, as well as nitrogen and phosphorus removal. In this study, the effects of Al³⁺ on pollutant removal, sludge flocculation and the composition and structure of extracellular polymeric substances (EPS) were investigated under anaerobic, anoxic and oxic conditions. Results demonstrated that the highest chemical oxygen demand (COD) and total nitrogen (TN) removal efficiencies were detected for an Al³⁺ concentration of 10 mg/L. In addition, the maximal dehydrogenase activity and sludge flocculation were also observed at this level of Al³⁺. The highest removal efficiency of total phosphorus (TP) was achieved at an Al³⁺ concentration of 30 mg/L. The flocculability of sludge in the anoxic zone was consistently higher than that in the anaerobic and oxic zones. The addition of Al³⁺ promoted the secretion of EPS. Tryptophan-like fluorescence peaks were detected in each EPS layer in the absence of Al³⁺. At the Al³⁺ concentration of 10 mg/L, fulvic acid and tryptophan fluorescence peaks began to appear, while the majority of protein species and the highest microbial activity were also detected. Low Al³⁺ concentrations (<10 mg/L) could promote the removal efficiencies of COD and TN, yet excessive Al³⁺ levels (>10 mg/L) weakened microbial activity. Higher Al³⁺ concentrations (>30 mg/L) also inhibited the release of phosphorus in the anaerobic zone by reacting with PO₄^3-.     

Performance of duckweed (Lemna minor L.) on different types of wastewater treatment

Duckweed (Lemna minor L.) has a wide application in Turkey having suitable climatic conditions. In this study, the growth of duckweed was assessed in laboratory scale experiments. They were fed with municipal and industrial wastewater at constant temprature. COD, total nitrogen (TN), total phosphorus (TP) and ortho-phosphate (OP) removal efficiencies of the reactors were monitored by sampling influent and effluent of the system. Removal efficiency in this study reflects optimal results: 73-84% COD removal, 83-87% TN removal, 70-85% TP removal and 83-95% OP removal. The results show that the duckweed-based wastewater treatment is capable of treating the laboratory wastewater.     

表面流人工湿地处理生活污水的研究

通过小试装置研究了表面流人工湿地对人工模拟生活污水的处理效果及相关运行参数。实验结果表明，表面流人工湿地系统对污水中的CODcr、TN、TP均有较好的综合净化能力，对各种污染物指标的去除率可分别达到CODcr 75％、TN75％、TP73％，其中CODcr和TN达到一级排放标准分别需3d和4d的表观停留时间，TP要达到二级排放标准则需6d的表观停留时间。而且，湿地植物对TN和TP的去除有比较明显的促进作用。     

Pilot-scale studies of domestic wastewater treatment by typical constructed wetlands and their greenhouse gas emissions

Three typical constructed wetlands (CWs) including Vertical Flow (VF), Free Water Surface (FWS), and Subsurface Flow (SF), and combined VF-SF-FWS constructed wetlands were investigated for the treatment of domestic wastewater with low C/N ratio. The performance of nutrient removal and the characteristics of greenhouse gas emissions, such as CH₄ and N₂O, from these CWs were compared. The results indicated that the four types of CWs had high removal efficiencies for organic matter and suspended solid (SS). The combined wetland also showed a comparatively good performance for nitrogen and phosphorus removal, and the removal efficiencies for total nitrogen (TN) and total phosphorus (TP) were 81.3% and 84.5%, respectively. The combined CWs had a comparative lower global warming potential. The FWS CW had the highest tendency to emit CH₄ and led to a higher global warming potential among the four types of CWs, which was about 586 mg CO₂/m²·h.     

Influence of varying nutrient and pesticide mixtures on abatement efficiency using a vegetated free water surface constructed wetland mesocosm

The nutrient and pesticide abatement efficiency of varying mixtures was examined in a vegetated free water surface constructed wetland. Three different agricultural chemical pollutant mixture conditions were assessed: nutrients only (N and P); pesticides only (atrazine, S-metolachlor and permethrin); and a mixture of nutrients and pesticides. With nutrients only, 672 h nutrient mitigation of 77–91% total phosphorous (TP) and 74–98% total nitrogen (TN) was associated with distance from the injection point and rainfall, whereas with nutrient and pesticide mixtures, 672 h nutrient mitigation of 11–71% TP and 84–98% TN were associated with distance and time. With pesticides only, 672 h pesticide mitigation of 50–99% was associated with distance and time, whereas with nutrients and pesticide mixtures, 672 h pesticide mitigation of 48–99% was associated primarily with distance. Dissipation half-lives were 2–10 times greater for P and 1.5–5 times greater for N when pesticides were present. Pesticide dissipation half-lives showed no clear differences with or without nutrients. While vegetated free water surface constructed wetlands can be effective best management practice tools to trap and abate agricultural run-off during rainfall events, efficiencies can be affected by different types of complex pollutant mixtures and wetland design and implementation should accommodate varying efficiencies.     

串联式垂直流生态滤池处理农村生活污水的试验研究

对串联式垂直流生态滤池处理农村生活污水进行了为期5个月的现场试验研究。结果表明：通过该工艺,污水中的COD、氨氮、总氮和总磷等污染物均得到了有效去除,在进水COD、氨氮、总氮和总磷平均质量浓度为73.19、25.08、48.55、0.55 mg·L-1时,平均去除率依次为65.6%、71.6%、58.7%、86.9%。COD、氨氮和总磷的去除主要发生在第一级生态滤池的进水0～40 cm阶段,而总氮浓度基本呈均匀下降趋势。串联式生态滤池对各污染指标较好的去除效果也证明了其是一种适合农村分散式污水处理、解决农村污水肆意排放的新途径。     

土壤渗滤系统中污染物去除效果分析

在土壤渗滤系统中,水力负荷、有机负荷和碳氮比等因素均对营养盐的处理效率具有显著影响.在实验室控温条件下,分析了不同水力负荷、有机负荷和环境条件对土壤渗滤系统污染物去除效果的影响.结果表明,在水力负荷小于0.15 m3·m^-2·d^-1的条件下,模拟生活污水中CODCr、总氮和总磷去除率分别达到84％、37％和93％以上,土壤（以干土计）亚硝酸盐细菌数量为4.50× 106 g^-1.装置上层产生的滞水对CODCr和磷酸盐的去除影响不大,但是由于处理系统内溶解氧浓度降低,使得氨氮硝化过程受到抑制,氨氮和总氮的处理效果均变差;在通气良好条件下,较高的碳氮比[m（碳）：m（氮）=5：1]对系统中总氮的去除更为有利.     

Circulating fluidized bed biological reactor for nutrients removal

A new biological nitrogen removal process, which is named herein “The circulating fluidized bed bioreactor (CFBBR)”, was developed for simultaneous removal of nitrogen and organic matter. This process was composed of an anaerobic bed (Riser), aerobic bed (Downer) and connecting device. Influent and nitrified liquid from the aerobic bed enters the anaerobic bed from the bottom of the anaerobic bed, completing the removal of nitrogen and organic matter. The system performance under the conditions of different inflow loadings and nitrified liquid recirculation rates ranging from 200% to 600% was examined. From a technical and economic point of view, the optimum nitrified liquid recirculation ratewas 400%. With a shortest total retention time of 2.5 h (0.8 h in the anaerobic bed and 1.5 h in the aerobic bed) and a nitrified liquid recirculation rate of 400% based on the influent flow rate, the average removal efficiencies of total nitrogen (TN) and soluble chemical oxygen demand (SCOD) were found to be 88% and 95%, respectively. The average effluent concentrations of TN and SCOD were 3.5 mg/L and 16 mg/L, respectively. The volatile suspended solid (VSS) concentration, nitrification rate and denitrification rate in the system were less than 1.0 g/L, 0.026-0.1 g NH₄ ⁺-N/g VSS·d, and 0.016–0.074 g NO_x ^?-N/g VSS·d, respectively.     

Removal of non-point pollutants from bridge runoff by a hydrocyclone using natural water head

A hydrocyclone using natural water head provided by bridge was operated for the treatment of stormwater runoff. The hydrocyclone was automatically controlled using electronic valve which is connected to a pressure meter. Normally the hydrocyclone was open during dry days, but it was closed after the capture of the first flush. The results indicated that the average pressure and the flow rate were directly affected by the rainfall intensity. The pressure head was more than 2 m when the rainfall intensity was above 5mm·h^-1. The percentage volume of underflow with high solids concentration decreased as the pressure and flow rate increased, but the percentage volume of overflow with almost no solids showed the opposite behavior. The total suspended solids （TSS） concentration ratio between the overflow and inflow （TSSover/TSSin） decreased as a function of the operational pressure, while the corresponding ratio of underflow to inflow （TSSunaer/TSSi,） increased. The TSS separation efficiency was evaluated based on a mass balance. It ranged from 25% to 99% with the pressure head ranging from 1.4 to 9.7 m, and it was proportional to pressure and flow rate. Normally, the efficiency was more than 50% when the pressure was higher than 2 m. The analysis of the water budget indicated that around 13% of the total runoff was captured by the hydrocyclone as a first flush, and this runoff was separated as underflow and overflow with the respective percentage volumes of 29% and 71%. The pollutants budget was also examined based on a mass balance. The results showed that the percentage of TSS, chemical oxygen demand （COD）, total nitrogen （TN）, and total phosphorus （TP） in underflow were 73%, 59%, 7.6%, and 49%, respectively. Thus, it can be concluded that the hydrocyclone worked well. It separated the first flush as solids-concentrated underflow and solids-absent overflow, and effectively reduced the runoff volume needing further treatment. Finally, four types of optional post treatment design are presented and compared.     

两级人工湿地用于村镇污水脱氮的长期运行特性研究

对沙田人工湿地稳定运行后的情况进行了长达6 a的监测,探讨了不同流态的两级潜流人工湿地长期运行的脱氮效能、不同形态氮的空间转化规律和几种主要影响因素。研究表明,在整个运行期间人工湿地的脱氮能力呈现低-高-低的变化趋势,这个过程的发生和湿地内部堵塞物的累积关联密切。在华南地区,季节变化对湿地脱氮的影响依然十分强烈：一方面,体现为季节温差对脱氮效果的明显影响,低温月份采用低负荷方式运行,TN去除率也仅有36.0%～47.6%,而高温期采用高负荷的运行方式,大多数月份TN去除率也能达到45.4%以上;另一方面,季节性雨量的不同会引起进水质量浓度的变化,导致湿地系统TN负荷率的改变,进而显著影响脱氮效果。有机氮、NH3-N、NO2--N、NO3--N在湿地内部存在明显的转化迹象,沿流程随着有机物的大量消耗,NO3--N去除能力逐渐下降并在湿地的末端出现了累积现象。通常情况下,由于采用了跌水曝气等措施,DO在湿地内的大部分区域都维持了较高水平,未对脱氮效果产生明显不利影响。     

呼伦湖冰封期污染特征分析及对水处理的意义

以内蒙古呼伦湖为研究对象,对其在冰封过程中总氮、总磷和有机物在冰体和水体中的浓度及分布特征及其在呼伦湖的空间变异性进行分析。结果表明,冰封条件下,呼伦湖水体中总氮、总磷和有机物的含量均大于其在对应冰体中的含量,其含量均值分别是其对应冰体中的3.144倍、2.200倍和3.042倍,即低温冷冻过程对水体中的污染物有一定的浓缩效应;水体中各营养盐和有机物的空间变异性明显小于其在冰体中的;从固-液相平衡理论、结晶学理论和热力学理论三个方面对冷冻浓缩效应做出了合理的解释。研究认为,可以将冷冻浓缩效应运用到给水处理和污水处理领域,这样既可以进行大规模的处理,也可以节约资源、保护环境。     

复合塘-湿地系统水生植物时空分布对氮磷去除的影响

利用复合生态塘-湿地处理系统水生植物时空格局异质性,研究了水生植物分布对氮、磷去除影响.结果表明,水生植物种类和数量的分布差异导致各单元氮、磷去除呈现不同的周期变化;水生植物主要通过改变硝化/反硝化进程、自身代谢和化学沉降速率影响NH3、NOx-、有机氮和总磷的去除.系统不同单元中氮、磷去除机制差异决定了NH3和总磷主要在曝气养鱼塘(去除率分别为29.5%、30.1%)、鱼塘(16.9%、17.8%)和水生植物塘(24.5%、19.4%)去除;NOx-主要在芦苇湿地(出水<0.4 mg/L)去除;而有机氮则主要在复合兼性塘(32.3%)和鱼塘(28.1%)去除.此外,生态塘出水中水生植物绝大部分被芦苇湿地所截滤,它们的腐败/释放导致湿地中NH3和总磷的表观去除率偏低(分别小于8.5%和11.5%).     

人工湿地系统对含沼液畜禽废水净化效果试验研究

为了考察人工湿地处理含沼液畜禽废水的可行性,采用水平潜流人工湿地对含沼液畜禽废水进行处理实验。试验结果表明：在进水流量1.5 m3.d-1,水平潜流人工湿地系统对含沼液畜禽废水具有较好的处理效果。废水中COD、TP、TN和NH4＋-N浊度平均去除率分别为59.21%、53.80%、55.09%和55.57%.另外,通过对人工湿地沿程的污染物变化试验分析表明,人工湿地系统对污染物的降解是沿人工湿地水流方向逐渐降低的。