Performance of constructed wetland treating wastewater from seafood industry.

Wastewater from seafood industry contains high concentrations of organic matter, nitrogen compounds, and solid matter. Constructed wetland can be used as tertiary treatment and for nutrient recycling. This research studied the performance of nitrogen and suspended solids removal efficiency of a constructed wetland treating wastewater from a seafood-processing factory located at Songkhla, southern Thailand. The existing constructed wetland has dimensions of 85 m, 352 m and 1.5 m in width, length and depth respectively, with an area of about 29,920 m2. The water depth of 0.30 m is maintained in operation with plantation of cattails (Typha augustifolia). Flow rate of influent ranged between 500-4,660 m3/d. Average hydraulic retention time in the constructed wetland was about 4.8 days. Influent and effluent from the constructed wetland were collected once a week and analyzed for pH, temperature, dissolved oxygen (DO), biochemical oxygen demand (BOD5), Suspended solid (SS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), organic nitrogen (Org-N), nitrate (NO3-N), and nitrite (NO2-N). The average removal efficiencies of BOD5, SS, TKN, NH3-N, and Org-N were 84%, 94%, 49%, 52% and 82%, respectively. It was found that the constructed wetland acting as a tertiary treatment process provided additional removal of BOD5, SS and TKN from wastewater from the seafood industry.     

人工湿地植物水质净化作用的数值模拟研究

研究区域永年洼湿地面临生态退化、水污染严重等问题,已通过人工种植湿地植物进行生态修复及水质改善。永年洼连续2年的水质监测结果表明,随着湿地植物的种植和生长,洼内水体的氨氮(NH3-N)、总氮(TN)、总磷(TP)等都有不同程度的下降。本文根据湿地植物对水质的作用机理,通过MIKE模型的EcoLab中水质过程自定义及编辑功能,基于湿地植物的泌氧、细菌活性增加和植物吸收作用下水化学反应过程,构建"WQ+Veg"水质模块,耦合MIKE21水动力结果,模拟永年洼人工湿地种植前后湖区流速及NH3-N、 TN、 TP等水质指标的变化。在有加密监测的断面上,模拟有植物的2017年情景相比无植物的2016年情景,NH3-N、TN和TP平均下降了14.9%、7.33%和14.3%,与监测结果较为一致。在永年洼出水口处2017年相比2016年,NH3-N、TN和TP的去除率提高了7.2%、5.3%和9.1%。模型描述的反应过程清晰,可考虑湿地植物类型、分布、面积等条件下水质氮磷的响应,为大尺度湿地修复的布局及设计提供研究工具,同时为湿地水质净化效果评估提供依据。     

Nitrogen dynamics in a constructed wetland system treating landfill leachate.

A pilot scale treatment system was established in 2002 at the Laflèche Landfill in Eastern Ontario, Canada. The system consists of a series of treatment steps: a stabilisation basin (10,000 m3), a woodland peat trickling filter (5,200 m2), a subsurface flow constructed wetland planted in Phragmites sp. (2,600 m2), a surface flow constructed wetland planted in Typha sp. (3,600 m2) and a polishing pond (3,600 m2). The system operates from May to December with leachate being recycled within the landfill during the winter months. Hydraulic loading was increased three-fold over four operating seasons with nitrogen and organic mass loading increasing six-fold. Excellent removal efficiencies were observed with 93% BOD5, 90% TKN and 97% NH4-N removed under the highest loading conditions. Almost complete denitrification was observed throughout the treatment system with NO3-N concentrations never exceeding 5mg L(-1). The peat filter reached treatment capacity at a hydraulic loading of 4cm d(-1) and organic loading rate of 42 kg BOD ha(-1) d(-1), which is consistent with design criteria for vertical flow wetland systems and intermittent sand filters, The first order plug flow kinetic model was effective at describing TKN and ammonium removal in the SSF and FWS wetlands when background concentrations were taken into account. Ammonium removal k-values were consistent with the literature at 52.6 and 57.7 yr(-1) for the SSF and FWS wetlands, respectively, while TKN k-values at 6.9 and 7.7 yr(-1) were almost an order of magnitude lower than literature values, suggesting that leachate TKN could contain refractory organics not found in domestic wastewater.     

Experimental study of a novel hybrid constructed wetland for water reuse and its application in Southern China

A new type of hybrid constructed wetland (CW), consisting of both vertical-baffled flow wetland (VBFW) and horizontal subsurface flow wetland (HSFW), has been deployed in Southern China to naturally accelerate the removal of organic matter and nitrogen. The hybrid CW system is characterised by a combination of continuous baffled flow vertical wetland and 'S' pattern horizontal subsurface flow wetland with natural aeration ditches to increase the concentration of dissolved oxygen in the HSFW bed. An internal circulatory system from the HSFW effluent back to the VBFW may optionally be operated to enhance the biological denitrification effect. Cyperus alternifolius is the main macrophyte in the wetland bed. The performance of the hybrid CW was studied with a pilot-scale system and three full-scale systems for municipal sewage treatment in Southern China. The results suggest that this new hybrid CW can achieve removal efficiencies of chemical oxygen demand, suspended solids, ammonia nitrogen, total nitrogen, and total phosphorus of better than 83.6, 95.0, 71.7, 64.5 and 68.1% respectively, with a specific wetland bed area of 0.70-0.93 m(2) PE(-1). The mean effluent concentrations of these parameters would meet the regulatory discharge limits for wastewater treatment systems (GB18918, 2002) and reuse in the context of agricultural irrigation solutions in China.     

Using a compact combined constructed wetland system to treat agricultural wastewater with high nitrogen.

The objectives of this study were to find appropriate conditions for nitrogen removal by a compact combined constructed wetland system and to evaluate the removal rate constant in a tropical climate. This study will present suitable operating conditions for a combined system to treat pig farm wastewater containing high ammonia-nitrogen. Four laboratory-scale combined constructed wetland units (0.5 x 1.0 x 1.0 m3): vertical flow vegetated bed over horizontal flow sand bed, were operated under an average temperature of 24 degrees C. Pig farm wastewater with COD and NH4-N concentration of 1034 and 448 mg/L in average was fed to the system at different HLR from 2 to 8 cm/day. The performance of the system when operated with a vertical flow bed followed by a horizontal flow bed or vice versa did not show a significant difference but under high HLR, nitrogen removal efficiencies were clearly reduced. Nitrobacter and Nitrosomonas were found in a large number in vertical flow beds and the same for denitrifier bacteria in a horizontal flow beds. Removal rate constants for nitrification (kNH4+ -N) were 0.0413 m/d for H-Vmode and 0.0339 m/d for V-H mode. Removal rate constants for denitrification (kNOx-N) were 0.0979 m/d for H-Vmode and 0.0399 m/d for V-H mode, respectively.     

Effects of solid retention time on the performance of submerged anoxic/oxic membrane bioreactor.

In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH(4+)-N to NO(3-)-N was readily achieved over a feed NH(4+)-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study.     

不同基质和植物人工湿地净化效果试验

分别以高炉渣、瓜子片、碎石为基质,美人蕉、黑三棱草、野茭白为植被构建人工湿地模拟系统,对其净化效果进行试验研究。结果表明,种植植物的湿地系统比未种植植物的湿地系统净化效果好,不同植物同种基质湿地系统对不同指标的净化效果各不相同,如不同植物对NH3-N和TN的净化效果从高到低顺序为:黑三棱草,美人蕉,野茭白;同种植物不同基质湿地系统对不同指标的净化效果也不同,不同基质对NH3-N和TN的净化效果从高到低顺序为:碎石,高炉渣,瓜子片。对NH3-N和TN浓度较高的污染环境,采用碎石为基质、黑三棱草为植被的人工湿地系统效果最佳。     

Performance of a combined eco-system of ponds and constructed wetlands for wastewater reclamation and reuse.

An on-site study on the operational performance of a combined eco-system of ponds and SF constructed wetland for municipal wastewater treatment and reclamation/reuse in Donging City, Shandong, China was carried out from January 2001 through October 2003. The removal efficiencies for various main parameters were: TSS 84.8 +/- 7.3%, BOD5 87.2 +/- 5.3%, CODCr 70.2 +/- 18.6%, TP 52.3 +/- 23.1%, and NH(3)-N 54.8 +/- 23.9% with effluent concentration of TSS 9.12 +/- 5.12 mg/l, BOD5 6.44 +/- 4.58 mg/l, CODCr, 42.8 +/- 6.7 mg/l, TP 0.94 +/- 0.27 mg/l and NH(3)-N 7.95 +/- 2.36 mg/l. In addition, the removal efficiencies for faecal coliforms and total bacteria were > 99.97% and > 99.998% respectively, which well meet Chinese National standards for effluent quality of municipal wastewater treatment plants. The composition of TSS was closely related to CODCr and BOD5 variations, and nitrification-denitrification is the major mechanism of nitrogen removal both in ponds and in wetlands. In addition, sedimentation also played an important role in the removal of TSS, nitrogen, phosphorus and BOD5. The removal efficiencies of various parameters, the number of species and biomass of biological community in the system increased gradually with the ecological maturation.     

A mass balance study on nitrification and deammonification in vertical flow constructed wetlands treating landfill leachate.

A laboratory-scale, mass-balance study was carried out on the transformation of nitrogenous pollutants in four vertical flow wetland columns. Landfill leachate containing low organic matter, but a high concentration of ammoniacal-nitrogen, was treated under dissolved oxygen concentrations close to saturation. Influent total nitrogen (TN) comprised ammoniacal-nitrogen with less than 1% nitrate and nitrite, negligible organic nitrogen, and very low BOD. Nitrification occurred in three of the four columns. There was a substantial loss of total nitrogen (52%) in one column, whereas other columns exhibited zero to minor losses (< 12%). Nitrogen loss under study conditions was unexpected. Two hypotheses are proposed to account for it: (1) either the loss of TN is attributed to nitrogen transformation into a form (provisionally termed alpha-nitrogen) that is undetectable by the analytical methods used; or (2) the loss is caused by microbial denitrification or deammonification. By elimination and stoichiometric mass balance calculations, completely autotrophic nitrogen-removal over nitrite (CANON) deammonification is confirmed as responsible for nitrogen loss in one column. This result reveals that CANON can be native to aerobic engineered wetland systems treating high ammonia, low organic content wastewater.     

The effect of a vertical flow filter bed on a hybrid constructed wetland system.

Data from 18 sampling wells in Kodij?rve horizontal subsurface flow (HSSF) constructed wetland (CW) (South Estonia) is presented and differences in purification efficiencies inside the HSSF CW are calculated. Temporarily anaerobic conditions in the Kodij?rve HSSF system did not allow efficient removal of BOD7, NH4-N, Ntot and Ptot. In 2002 a vertical subsurface flow filter was constructed to enhance aeration. The design of the system was based simply on the oxygen demand of the wastewater and on the aeration potential of vertical flow wetlands. The vertical flow system has shown satisfactory results. The purification efficiency of BOD7 in the Kodij?rve CW has improved significantly and there has been a slight increase in purification efficiencies of NH4-N and Ntot. On the ohther hand, the removal efficiency of Ptot has decreased significantly. Although, the mass loading rates have increased, mass removal rates of all four parameters have improved significantly. Nevertheless, optimization of the constructed wetland system is essential in order to meet effluent standards during wintertime.     

Degradation of organic matter from domestic wastewater with loofah sponge biofilm reactor

A laboratory-scale oxic biofilm reactor using loofah sponge as support material was carried out to study its start-up characteristics and the optimum operation parameters in removing organic matter and nitrogen from domestic wastewater. It took no more than 10 days to complete microbiological cultivation and acclimation, indicating that the natural loofah sponge was a superior support material compared with some conventional ones. The influence parameter experiments showed that the hydraulic retention time (HRT) had a significant influence on the COD and NH(3)-N removal efficiencies, the average COD and NH(3)-N removal efficiencies were 83.7 and 96.9% respectively when the temperature was 25 ± 2 °C, the influent flow rate was 0.21 L/h and the HRT was 7.5 h. The loofah sponge biofilm system had a strong tolerance to organic shock loading in the present experiment. Additionally, it was found that domestic wastewater could be preferably treated with 88.9% of COD and 98.7% of NH(3)-N removal efficiencies with the corresponding influent concentrations of 260.0 and 26.8 mg/L, respectively. The observations obtained in the present study indicated that the loofah sponge was an excellent natural support material, potentially feasible for the present system for the treatment of the decentralized domestic wastewater.     

The role of plant uptake on the removal of organic matter and nutrients in subsurface flow constructed wetlands: a simulation study.

Plants in constructed wetlands have several functions related to the treatment processes. It is generally agreed that nutrient uptake is a minor factor in constructed wetlands treating wastewater compared to the loadings applied. For low loaded systems plant uptake can contribute a significant amount to nutrient removal. The contribution of plant uptake is simulated for different qualities of water to be treated using the multi-component reactive transport module CW2D. CW2D is able to describe the biochemical elimination and transformation processes for organic matter, nitrogen and phosphorus in subsurface flow constructed wetlands. The model for plant uptake implemented describes nutrient uptake coupled to water uptake. Literature values are used to calculate potential water and nutrient uptake rates. For a constructed wetland treating municipal wastewater a potential nutrient uptake of about 1.9% of the influent nitrogen and phosphorus load can be expected. For lower loaded systems the potential uptake is significantly higher, e.g. 46% of the nitrogen load for treatment of greywater. The potential uptake rates could only be simulated for high loaded systems i.e. constructed wetlands treating wastewater. For low loaded systems the nutrient concentrations in the liquid phase were too low to simulate the potential uptake rates using the implemented model for plant uptake.     

垂直流人工湿地中污染物昼夜及沿程变化规律

利用垂直潜流人工湿地单元模型探讨COD、TN和NH4+-N质量浓度在一昼夜之中随时间及深度的变化规律。结果表明:垂直潜流人工湿地中污染物去除率的变化呈一定的周期性,昼夜差距较大。COD、NH4+-N和TN的去除率在15:00达到最大,夜间最小。COD和NH4+-N质量浓度在表层(距湿地底部60～90cm段)迅速降低,底部变化幅度较小。TN浓度沿程的降低趋势很明显。湿地中COD、NH4+-N和TN质量浓度的变化趋势与DO显著相关,DO质量浓度越高,越有利于有机物和氮的去除。     

Experimental study on water-saving and emission-reduction effects of controlled drainage technology

Field experiments and laboratory analysis were carried out to determine the effects of controlled drainage(CTD) and conventional drainage(CVD) technologies on drainage volume, concentrations of NHt4-N, NO 3-N, and total phosphorus(TP), nitrogen and phosphorus losses, rice yield,and water utilization efficiency. Results show that CTD technology can effectively reduce drainage times and volume; NHt4-N, NO 3-N, and TP concentrations, from the first to the fourth day after four rainstorms decreased by 28.7%e46.7%, 37.5%e47.5%, and 22.7e31.2%, respectively,with CTD. These are significantly higher rates of decrease than those observed with CVD. CTD can significantly reduce nitrogen and phosphorus losses in field drainage, compared with CVD; the reduction rates observed in this study were, respectively, 66.72%, 55.56%, and 42.81% for NHt4-N, NO 3-N, and TP. Furthermore, in the CTD mode, the rice yield was cut slightly. In the CVD mode, the water production efficiencies in unit irrigation water quantity, unit field water consumption, and unit evapotranspiration were, respectively, 0.85, 0.48, and 1.22 kg/m3, while in the CTD mode they were 2.91, 0.84, and 1.61 kg/m3 din other words, 3.42, 1.75, and 1.32 times those of CVD. Furthermore, the results of analysis of variance(ANOVA) show that the indicators in both the CVD and CTD modes, including the concentrations of NHt4-N, NO 3-N, and TP, the losses of NHt4-N, NO 3-N, and TP, irrigation water quantity, and water consumption, showed extremely significant differences between the modes, but the rice yield showed no significant difference.     

两种复合垂直流人工湿地污水处理对比研究

构建下行流-上行流、下行流-下行流两套复合人工湿地处理生活污水,考察不同运行方式下两套湿地系统污染物净化效果。结果表明,下行流-上行流复合系统适合在较低水力负荷[0.6m3/（m^2.d）]下运行,系统连续进水5天的出水效果很好,COD、TP、氨氮、TN的去除率分别为75%-95%、65%-85%、45%-80%、45%-80%。下行流-下行流复合系统耐水力负荷冲击能力强,适合在高水力负荷[1.2m3/（m^2.d）]下运行,COD、TP、氨氮、TN的去除率分别为70%-95%、40%-85%、50%-90%、50%-80%;其水流方式较下行流-上行流复合系统水流方式更利于复氧,有利于高水力负荷下COD、氨氮的降解。研究成果为实际中人工湿地处理生活污水的运行操作提供了依据和参考。     

Modelling and evaluation of nitrogen removal performance in subsurface flow and free water surface constructed wetlands.

With the aim of protecting drinking water sources in rural regions, pilot-scale subsurface water flow (SSF) and free water surface flow (FWS) constructed wetland systems were evaluated for removal efficiencies of nitrogenous pollutants in tertiary stage treated wastewaters (effluent from the Pasak?y biological nutrient removal plant). Five different hydraulic application rates and emergent (Canna, Cyperus, Typhia sp., Phragmites sp., Juncus, Poaceae, Paspalum and Iris) and floating (Pistia, Salvina and Lemna) plant species were assayed. The average annual NH4-N, NO3-N and organic-N treatment efficiencies were 81, 40 and 74% in SSFs and 76, 59 and 75% in FWSs, respectively. Two types of the models (first-order plug flow and multiple regression) were tried to estimate the system performances. Nitrification, denitrification and ammonification rate constants (k20) values in SSF and FWS systems were 0.898 d-1 and 0.541 d(-1), 0.486 d(-1) and 0.502 d(-1), 0.986 d(-1) and 0.908, respectively. Results show that the first-order plug flow model clearly estimates slightly higher or lower values than observed when compared with the other model.     

中水湿地去氮效果研究

以山东省平阴中水湿地为研究对象,通过对湿地水体、底泥的氨态氮(NH3-N)、硝态氮(NO3--N)沿程变化的分析,研究湿地对中水中氮(N)的去除效果。结果表明:湿地对水体中NH3-N的去除效果较好,而作为水体中N主要存在形式的NO3--N沿水流方向却呈增加趋势,微生物硝化作用强烈。底泥中总氮(TN)沿水流方向也呈增加趋势,累计效应比较明显。研究结果为湿地设计的进一步改进提供理论支持。     

WRSIS系统中稻田田面水和地下排水中氮素的动态变化特征

在江苏高淳县WRSIS系统中进行田间试验,对不同氮肥施用量下稻田田面水和地下排水中氮素动态变化特性进行分析。结果表明:施肥1 d后田面水TN和NH4+-N质量浓度值达到最大,随着时间推移,质量浓度迅速下降,施肥7 d后TN质量浓度下降70%~76%,NH4+-N质量浓度下降83.5%~85.5%。田面水中ρ(NH4+-N)/ρ(TN)和ρ(NO3--N)/ρ(TN)具有相似变化规律,先升后降,且ρ(NH4+-N)/ρ(TN)显著大于ρ(NO3--N)/ρ(TN)。地下排水中氮素以NO3--N为主,施肥后NO3--N质量浓度在3.0~19.0 mg/L的范围内;NH4+-N质量浓度较低,整个生育期质量浓度都在1.1 mg/L以下。田面水和地下排水中氮素质量浓度均随着施肥量的增加而增加。施肥7 d内是防止氮素大量流失的关键时期,需要控制排水;同时减少氮肥施用量能显著减少氮素地表流失和地下渗漏损失量。     

官厅水库人工湿地系统水质净化效果研究

官厅水库黑土洼人工湿地系统经过一年多的运行，经历了严寒冬季的考验，获取了1万多组监测数据。通过对BOD5等指标去除率分析，人工湿地对Orth—D、TP、CODMn去除率较多，TN、NH4^＋-N、NO^-3-N处理效果一般。建议二期工程进一步改进工艺，促进有机物的降解。     

Feasibility study on the removal of nitrous compounds with a hollow-fiber membrane biofilm reactor.

The objective of this study was to develop an integrated nitrogen treatment system using autotrophic organisms. A treatment system consists of an aerobic hollow-fiber membrane biofilm reactor (HfMBR) and anaerobic HfMBR. In the aerobic HfMBR, a mixture gas of air and O2 was supplied through the fibers for nitrification. Denitrification occurred in the anaerobic HfMBR using H2 as the electron donor. The treatment system was continuously operated for 190 days. NH4-N removal efficiencies ranging from 95% to 97% were achieved at NH4-N concentrations of influent ranging from 50 to 100 mg N/L. When glucose was added to the influent, the simultaneous nitrification and denitrification occurred in the aerobic HfMBR, and nitrogen removal rates were changed according to the COD/NH4-N ratio of influent. In the anaerobic HfMBR, autotrophic denitrification using H2 occurred and the removal rates achieved in this study were 23-58 mg N/m2 d. In this study, the achieved removal efficiency was lower than other study findings; however, the result suggested that this hybrid HfMBR system can be used effectively for nitrogen removal in oligotrophic water.