Comparison of useful terrestrial and aquatic plant species for removal of nitrogen and phosphorus from domestic wastewater

To develop a low cost and energy-saving wastewater treatment technique in combination with resource recycling and amenity functions, we constructed a plant bed filter ditch in which useful terrestrial and aquatic plants can be utilized for nitrogen and phosphorus removal from wastewater. Screening studies were conducted to evaluate and compare the effectiveness of 20 kinds of plant species which are economically important or exhibit on aesthetic value, including 13 terrestrial species, for domestic wastewater treatment. Artificial wastewater containing 20 mg L^-1 of Nand 3.3 mg L^-1 of P, was supplied to the ditch at the rate of about 1.41–2.08 g m^-2 d^-1 for N and 0.20–0.33 g m^-2 d^-1 for P. The experiments were performed in a glass house with windows opened from April to November. The ditches showing high Nand P removal rates were planted with plants which exhibited high biomass production rates. In the case of the papyrus ditch, Nand P removal rates exceeded 0.8 g m^-2 d^-1 for N and 0.15 g m^-2 d^-1 for P from late spring to autumn, in the case of the kenaf ditch and sorghum ditch, from summer to autumn and in the case of the Italian ryegrass ditch and barley ditch, in early spring. These findings indicated that efficient wastewater treatment can be performed consistently except in the winter season, by cultivating these plants in an appropriate combination in the ditches.     

Evaluation of useful plants for the treatment of polluted pond water with low N and P concentrations

Eutrophication of ponds for agricultural use has begun to adversely affect rice production and the residential living environment in Japan. Cultivation of useful terrestrial and aquatic plant species in plant-bed filter ditches enables to treat domestic wastewater in addition to resource recycling and amenity functions. We evaluated the ability of several plant species, Italian ryegrass (Lolium multiflorum Lam.), hanana (Brassica campestris L. var.), African marigold (Tages erecta L.), sorghum (Sorghum vulgare Pers.), kenaf (Hibiscus cannabinus L.), papyrus (Cyperus papyrus L.), and reed (Phragmites communis Trin.), to remove nitrogen and phosphorus from polluted pond water whose N and P concentrations were much lower than those in domestic wastewater. Artificial pond water containing 2.5 mg L^-1 of N and 0.5 mg L^-1 of P was supplied to ditches at a loading rate of 1.1 g m^-2 d^-1 for N and 0.21 g m^-2 d^-1 for P. Italian ryegrass, papyrus, or kenaf in ditches removed N and P more effectively than other plants. The average removal rate of Italian ryegrass in ditches was 0.62 g m^-2 d^-1 for N and 0.10 g m^-2 d^-1 for P, that of papyrus 0.81 g m^-2 d^-1 for N and 0.15 g m^-2 d^-1 for P, and that of kenaf 0.73 g m^-2 d^-1 for N and 0.11 g m^-2 d^-1 for P. The influence of N and P concentrations on the removal rates of Italian ryegrass, papyrus, and kenaf was studied. Concentrations at a removal rate of zero were 0.2–0.3 mg L^-1 for N and 0.01–0.03 mg L^-l for P. At low concentrations, the plant removal rates increased sharply with the rise in the concentration. When N concentrations exceeded 0.3–0.6 mg L^-1 and P concentrations 0.10–0.45 mg L^-1, the removal rates were high and less affected by the concentration. It was considered that these plant species could be used most efficiently at the concentrations where removal rates are less restricted.     

Treatment of Hydroponics Wastewater Using Constructed Wetlands in Winter Conditions

Hydroponics culture generates large amounts of wastewater that are highly concentrated in nitrate and phosphorus but contains almost no organic carbon. Constructed wetlands (CWs) have been proposed to treat this type of effluent, but little is known about the performance of these systems in treating hydroponic wastewater. In addition, obtaining satisfactory winter performances from CWs operated in cold climates remains a challenge, as biological pathways are often slowed down or inhibited. The main objective of this study was to assess the effect of plant species (Typha sp., Phragmites australis, and Phalaris arundinacea) and the addition of organic carbon on nutrient removal in winter. The experimental setup consisted of 16 subsurface flow CW mesocosms (1 m², HRT of 3 days) fed with 30 L?d¹ of synthetic hydroponics wastewater, with half of the mesocosms fed with an additional source of organic carbon (sucrose). Carbon addition had a significant impact on nitrate and phosphate removal, with removal means of 4.9 g m^-2?d^-1 of NO₃-N and 0.5 g m^-2 d^-1 of PO₄-P. Planted mesocosms were generally more efficient than unplanted controls. Furthermore, we found significant differences among plant treatments for NO₃-N (highest removal with P. arundinacea) and COD (highest removal with P. australis/Typha sp.). Overall, planted wetlands with added organic carbon represent the best combination to treat hydroponics wastewater during the winter.     

Characterisation of agricultural drainage ditch sediments along the phosphorus transfer continuum in two contrasting headwater catchments

Purpose

This study investigated the phosphorus (P) source, mobilisation and transport potential of ditch bed sediments as well as surrounding field and bank soils in two agricultural headwater catchments with contrasting soil drainage capacities. This information is important for discerning the potential for ditches to attenuate or augment transfers of P from upstream sources and thus for developing appropriate management strategies for these features.

Materials and methods

Phosphorus sources were characterised using the Mehlich3-P, water-soluble P and total P tests. Phosphorus mobilisation potential was characterised using the Mehlich3-AL/P, Mehlich3-Ca/P and DESPRAL P tests. Phosphorus transport potential was characterised using data collected on the presence/absence of surface water in ditches during field surveys and downstream turbidity data.

Results and discussion

Ditch sediments had similar P source contents (Mehlich3-P, water-soluble P and total P) to the surrounding field soils and higher P contents than bank soils. However, calcium contents of sediments in the poorly drained catchment reflected the deep sub-soils rather than the surrounding field and bank soils. Mehlich3-Al/P and Mehlich3-Ca/P contents of ditch sediments in the well (non-calcareous) and poorly (calcareous) drained catchments respectively indicated potential for P retention (above thresholds of 11.7 and 74, respectively). However, sediments were less aggregated than field soils and may mobilise more particulate P (PP) during rain events. Nevertheless, the majority of surveyed ditches dried out from March to September 2011; thus, their potential to mobilise PP may be less important than their capacity to attenuate soluble and PP during this time.

Conclusions

In these and similar catchments, soluble P attenuation and particulate P mobilisation should be maximised and minimised, respectively, for example, by cleaning out the sediments before they become saturated with P and encouraging vegetation growth on ditch beds. This study also highlighted the influence of deep sub-soils on soluble P retention in ditches and thus the utility of characterising soils below depths normally included in soil classifications.

     

沟渠及塘堰湿地系统对稻田氮磷污染的去除试验

为研究原位状态下灌区沟渠及塘堰湿地系统对稻田氮磷污染的去除效应和规律,在湖北省漳河灌区选取农沟-斗沟尺度的3段典型排水沟渠和一处塘堰,分别于2009-2010年5—9月水稻生育期在沟渠和塘堰进出水口采集水样进行氮磷浓度化验分析。结果表明,灌区农沟-斗沟尺度典型排水沟渠对总氮、硝态氮、铵态氮、总磷整体去除率分别为44．6％、9．9％、37．3％、35．1％;塘堰对总氮、硝态氮、铵态氮、总磷的平均去除率分别为15．2％、15．6％、30．2％、-6．5％。典型沟渠和塘堰对氮磷污染的去除表现出一定的抗冲击自修复性。原位条件下,由于排水沟中水力停留时间都不长,使得种植不同植被的沟段之间对氮磷的去除效应差异性不明显。塘堰湿地系统中植被的选育及其管理对去除稻田排水氮磷污染具有重要意义。     

Phosphate Leaching from Intact Soil Column in Response to Reducing Conditions

Iron(III)(hydr)oxides can dissolve under reducing soil conditions. Simultaneously, oxide-associated inorganic phosphate is released to the soil solution. In this study, the effect of reducing soil conditions on phosphate leaching from transient waterlogging clayey soil is evaluated. We applied glucose solutions (either 100 or 1000 mg glucose-C L^-1) at a steady flow rate of 0.63 mm h^-1 to a saturated intact column of structured Alfisol (diam. 0.5 m, height 1.0 m). Effluent concentrations of iron(II) and reactive orthophosphate (P_i) increased slightly during 5 d of low glucose application, reaching values of 2.5 mg Fe L^-1, and 0.02 mg PO₄-P L^-1, respectively. During 10 d of high glucose application, the iron(II) concentration increased to 14 mg Fe L^-1 and fluctuations in the P_i-concentration between 0.002 and 0.1 mg PO₄-P L^-1 were observed. The fluctuations in P_i-concentration are ascribed to interactions between progression of the glucose front, and P_i-mobilization/resorption processes at the walls of macropores. The daily P-losses during low and high glucose applications averaged 0.3 mg PO₄-P m^-2 d^-1, and 0.5 mg PO₄-P m^-2 d^-1, respectively. Comparisons with a parallel topsoil study suggest that subsoil exerts a strong control on leaching – probably via resorption – of P_i mobilized in the topsoil.     

Impact of Soil Sorption Characteristics and Bedrock Composition on Phosphorus Concentrations in two Bohemian Forest Lakes

Phosphate (PO₄-P) sorption characteristics of soils and bedrock composition were determined in catchments of two mountain lakes, Ple?né Lake (PL) and ?ertovo Lake (CT), situated in the Bohemian Forest (Czech Republic). The aim was to explain higher terrestrial P export to mesotrophic PL compared to oligotrophic CT. Concentrations of Al and Fe oxides were the dominant parameters affecting soil ability to adsorb PO₄-P. Depending on concentrations of Al and Fe oxides, P sorption maxima varied from 9.7 to 70.5 mmol kg^?1 and from 7.4 to 121 mmol kg^?1 in organic and mineral soil horizons, respectively. The catchment weighted mean PO₄-P sorption capacity was 3.4 mol m^?2 and 11.9 mol m^?2 in the PL and CT soils, respectively. The higher PO₄-P sorption capacity in the CT catchment was predominantly associated with higher pools of soil and Fe oxides. The CT bedrock (mica schist) released one order of magnitude less P than the PL bedrock (granite) within a pH range of catchment soils (pH_CaCl2 of 2.5–4.5). The higher ability of PL bedrock to release P and the lower ability of PL soils to adsorb PO₄-P thus contributed to the higher terrestrial P loading of this lake.     

排水沟塘分布特性及与农田水力联系对水质净化能力的影响

湿地是一种能够有效治理农业非点源污染的生态设施;在一些无法建设人工湿地的地区,现存的排水沟塘系统具有类似湿地的水质净化效果。为研究排水沟塘的分布以及其与农田水力联系对其水质净化能力的影响,该文以扬州市江都区昭关灌区为例,首先通过实地调查,明确研究区不同形式沟塘的分布规律,确定沟塘与农田逐级详细水力联系,然后建立理论分析模型,分别计算考虑与不考虑水力联系2种情况下,沟塘的污染物去除能力。结果表明,考虑水力联系后,污染物去除能力为不考虑水力联系的70%~84%;水质净化作用主要集中在一些面积较大的支沟和池塘。从农田排水的角度考虑,尺寸较大沟塘会出现一定的水力冗余,但是从水质改善的角度看,则有必要保留。研究区可通过较为简单的工程措施来优化水力联系,提高其污染物的去除能力。     

Losses of Soil Carbon upon a Fire on a Drained Forested Raised Bog

We studied the consequences of a fire that affected 29 ha of a drained forested raised bog in Tver oblast, Central European Russia. The drainage network consisted of open 1-m-deep ditches with 60 to 160 m ditch spacing. The groundwater level (GWL) varied within the studied drained bog. We used the method of assessing the loss of soil carbon (C) based on the difference between the ash concentration in the burnt peat of the upper layer and underlying unburnt layers. The carbon loss was higher near the drainage ditches than in the sites remote from ditches. The sample median values of carbon loss (kg C/m²) were estimated at 0.37 near the drainage ditches and at 0.22 for the remote sites with a distance of 160 m between ditches. They increased to 2.23 and 0.79 near and far from the drainage ditches for 106 m ditch spacing, and ranged from 1.13 to 2.10 near the drainage ditches and were equal to 0.45 at the remote sites for 60 m ditch spacing. The maximum loss of C was at the bog margin with the 70-cm-deep GWL; the sample median was equal to 2.97 kg C/m². The results obtained for C loss from the wildfire on the raised bog agree with the estimates obtained by other authors (1.45–4.90 kg C/m²) and confirm the importance of taking such loss into account in the estimates of the carbon budget of peat soils (Histosols).     

Soil and Minespoil Fill as Media for Renovation of Nitrogen and Phosphorus in Domestic Wastewater

Development of Appalachian coal mining regions of the USA has been severely hampered by lack of domestic waste disposal technologies suited to fills. The suitability of on-site wastewater treatment and disposal systems (OSWTDS) in fill material is uncertain due to the effects of surface mining on soil physical properties. This research was conducted to evaluate the potential for renovation of N and P present in domestic wastewater by fills produced from mining operations. Nitrogen and P were chosen because of their potential adverse environmental impacts. Soil-fill (a mixture of Jefferson, fine-loamy, siliceous, mesic Typic Hapludult and Muskingom, fine-loamy, mixed, mesic Typic Dystrochrept soils) and minespoil (spoil)-fill (blasted rock material associated with the Taggart Marker and Low Splint Bench coal seams of the Upper Middle Wise Formation) were used in this study. Septic tank effluent (STE) and sand filter effluent (SFE) were applied to spoil-fill columns at four loading rates (0, 5.4, 10.8, and 21.6 L m^-2d^-1) and spoil-fill columns at one loading rate (21.6 L m^-2d^-1) for a period of 20 wk. Renovation of wastewater was assessed by determining the concentration of N and P present in column leachate. Reduction of inorganic N (NO₃ ^- + NH₄ ⁺), based on N/Cl ratios, ranged from 14.9 to 32.1% after the varying application rates of STE and SFE passed through the soil columns. However, leachate NO₃ ^--N concentrations were still above the 10 mg^-1 drinking water standard. The quantity of P emerging from the spoil-fill columns (3.0 mg P L^-1) was higher than anticipated and may be related to the indigenous P present in the minespoil. Sorption of P in the soil-fill column decreased with increased STE and SFE application (reductions ranged from 99.1 to 74.4%). Results from this study indicate that there is potential for renovating wastewater in OSWTDS in selected soil-fill areas in reclaimed minelands.     

Optimization of Petroleum Refinery Wastewater Treatment by Vertical Flow Constructed Wetlands Under Tropical Conditions: Plant Species Selection and Polishing by a Horizontal Flow Constructed Wetland

Typha latifolia-planted vertical subsurface flow constructed wetlands (VSSF CWs) can be used to treat petroleum refinery wastewater. This study evaluated if the removal efficiency of VSSF CWs can be improved by changing the plant species or coupling horizontal subsurface flow constructed wetlands (HSSF CWs) to the VSSF CW systems. The VSSF CWs had a removal efficiency of 76% for biological oxygen demand (BOD₅), 73% for chemical oxygen demand (COD), 70% for ammonium-N (NH₄⁺-N), 68% for nitrate-N (NO₃^?-N), 49% for phosphate (PO₄^3?-P), 68% for total suspended solids (TSS), and 89% for turbidity. The HSSF CWs planted with T. latifolia further reduced the contaminant load of the VSSF CW-treated effluent, giving an additional removal efficiency of 74, 65, 43, 65, 58, 50, and 75% for, respectively, BOD₅, COD, NH₄⁺-N, NO₃^?-N, PO₄^3?-P, TSS, and turbidity. The combined hybrid CW showed, therefore, an improved effluent quality with overall removal efficiencies of, respectively, 94% for BOD₅, 88% for COD, 84% for NH₄⁺-N, 89% for NO₃^?-N, 78% for PO₄^3?-P, 85% for TSS, and 97% for turbidity. T. latifolia strived well in the VSSF and HSSF CWs, which may have contributed to the high NH₄ ⁺-N, NO₃^?-N, and PO₄^3?-P removal efficiencies. T. latifolia-planted VSSF CWs showed a higher contaminant removal efficiency compared to the unplanted VSSF CW. T. latifolia is thus a suitable plant species for treatment of secondary refinery wastewater. Also a T. latifolia-planted hybrid CW is a viable alternative for the treatment of secondary refinery wastewater under the prevailing climatic conditions in Nigeria.     

宁夏引黄灌区排水沟水环境质量及其影响因素

[目的]探明宁夏引黄灌区排水沟水环境质量及其影响因素,旨在为排水沟水体污染综合整治提供一定的理论依据。[方法]搜集2009—2015年排水沟水环境因子指标和以地级市为单元的社会经济指标数据,选取高锰酸盐指数、化学需氧量、氨氮、总磷、生化需氧量、挥发酚、氟化物、氰化物、硫化物作为水质综合污染指数的评价因子,采用相关分析法和灰关联法分析研究社会经济指标对排水沟水质的影响程度。[结果]南干沟水质呈现逐年好转趋势,银新干沟水质和清水沟水质急剧恶化,其他排水沟的综合污染指数变化趋势较平稳,且水质总体状况较好;排水沟水质与社会经济指标的相关性和关联度都较高:中干沟与化肥使用量相关系数高达0.998,南干沟与工业废水排放总量相关系数高达0.983;永二干沟与农业耗水量的关联度高达0.793 41,南干沟与工业废水排放总量的关联度高达0.755 69。[结论]排水沟的水质变化趋势受农业面源污染和工业废水的影响较大;以地级市为单位,综合污染指数与社会经济指标的相关性大小依次为吴忠市、银川市、中卫市、石嘴山市;相关分析与灰关联分析结果有较好的一致性,且运用二者结合分析了影响排水沟的最主要影响因子;总体上,农业生产对银川市和石嘴山市排水沟水质影响较大,工业生产对吴忠市和中卫市排水沟的影响较大,且农业生产导致的农业面源污染比工业生产产生的工业废水对排水沟水质状况影响程度大。     

模拟降雨条件下垄沟坡度对溶解态氮磷流失的影响

为揭示不同垄沟坡度对径流中溶解态氮、磷流失的影响,采用人工模拟降雨试验,设置4个垄沟坡度处理(0°,9°,18°和27°),研究了不同垄沟坡度对径流中速效磷(PO_4~(3-)—P)、硝态氮(NO_3~-—N)和铵态氮(NH_4~+—N)浓度和流失量的影响;并利用Inorganic—N/PO_4~(3-)—P、NO_3~-—N/PO_4~(3-)—P和NH_4~+—N/PO_4~(3-)—P 3种氮磷比,评价不同处理的富营养化风险。结果表明:(1)在降雨过程中,4个垄沟坡度处理径流中PO_4~(3-)—P、NO_3~-—N和NH_4~+—N浓度随时间均呈锯齿状变化;其流失量随时间变化均呈先增加后以锯齿状变化的趋势,且波动幅度大,最大值(16.60,1 020.73,48.35 mg)分别出现在垄沟坡度为0°,0°和9°处理。(2)4个垄沟坡度处理间相比较,径流中PO_4~(3-)—P和NH_4~+—N流失量均表现为0°9°27°18°,其浓度最大值(0.50,1.08 mg/L)和最小值(0.37,0.76 mg/L)均分别出现在垄沟坡度为9°和18°处理;而径流中NO_3~-—N浓度和流失量均在垄沟坡度0°处理时为最大值(30.68 mg/L和64.16 mg/m~2),18°处理时为最小值(21.78 mg/L和42.22 mg/m~2)。(3)Inorganic—N/PO_4~(3-)—P率和NH_4~+—N/PO_4~(3-)—P率表明4个垄沟坡度处理径流中均存在一定的富营养化风险。其中,垄沟坡度为0°处理的径流富营养化风险水平最高,27°处理的径流富营养化风险水平最低。研究结果可为横坡垄作的水土流失及养分流失评价、预测以及防治提供科学依据。     

Nutrient Fluxes in Sediment (NH4 + and PO4 -3) in N.W. Coastal Lagoon Mexico Associated with an Agroindustrial Basin

In order to balance the impact of agricultural development on land around coastal lagoons with the protection of aquatic resources, knowledge of the role of the sedimentary phase in the entrapment or availability of nutrients in the water column in areas affected by agroindustrial outlets is important. The Ensenada del Pabellon coastal on the Pacific coast of Mexico was chosen to be analyzed. The input of ammonium and orthophosphate from sediment using semicontrolled benthic chambers near a sugar cane factory outlet was compared to non altered sediment. Phosphate and ammonia loading from agroindustrial outlets has been the primary cause of eutrophication. The inputs of ammonium and orthophosphates from the sediment to the water column depend on their concentration in the agroindustrial outlet's waste water, the local morphology, the tide, and biotic assimilation, in order of importance. Sediment in non-altered revealed maxima of 7.8 mg m^-2 d^-1 of NH⁺ ₄ and 1.4 mg m^-2 d^-1 of PO^-3_₄, whereas in one outlet that greatly transfigures the environment, maxima of 223 mg m^-2 d^-1 of NH⁺ ₄ and 67 mg m^-2 d^-1 of PO^-3_₄ were recorded, which represent an increase greater than 20 times the normal diffusion. These figures varied markedly in space and time. Results from the study indicated that existing levels of nutrient could endanger the future of this ecosystem, including its sustainable fisheries.     

Variability of water quality in a riparian wetland with interacting shallow groundwater and surface water

Lowland catchment hydrology is dominated by shallow groundwater with complex interactions between groundwater and surface water. In lowland catchments of N Germany, a high fraction of agricultural land is drained and therefore influenced by fast water transport to discharge systems with resulting alterations to water quality. The investigated catchment area “Kielstau” (approx. 50 km²) in the N of Schleswig‐Holstein serves as an example. Detailed investigations on the interactions between groundwater, river, and ditch‐water quality were evaluated at a drained riparian wetland area (0.15 km²) used as grassland in the central part of this catchment. The water quality in the drainage ditches showed variability dependent on their hydrological integration. At the far‐from‐river end, groundwater and ditch‐water quality were in most parameters much more alike than at the close‐to‐river end. The composition of ditch water at the close‐to‐river end of the ditch was determined by transformation processes and dilution which took place along the ditch much more than exfiltration processes like those that were dominant at the far‐from‐river end. In most cases, the mean NH concentrations were higher in the groundwater than in the ditches, but the highest concentrations were found all along the time in the close‐to‐river sampling points and in the river. The highest NO concentration was observed in a ditch influenced by an adjacent arable field as well as in the river. The concentrations of phosphate and total P were lower in groundwater than in the ditch water.     

人工布设基质对农田排水沟水质的影响

本研究选择宁夏灵武农场的典型排水支沟进行人工布设基质,在沟中布设土壤、炉渣、秸秆、锯末4种基质处理及铲草处理和对照(不做任何处理),研究分析了基质对农田排水沟水质的影响。对基质的组分分析表明,锯末显著地吸附盐分和全氮,吸附量分别达0.4 g.kg 1和0.3 g.kg 1,土壤、炉渣、秸秆均明显地释放盐分,释放量为5.3~50.8 g.kg 1;秸秆显著地释放有机碳,释放量达54.0 g.kg 1;4种基质对全磷吸附效果不明显。水质分析表明,除秸秆处理和对照外,盐分(TDS)在其他处理下显著减少,而化学需氧量(COD)、总氮(TN)、总磷(TP)、NO3-N和NH4+-N浓度在锯末和土壤处理下均有不同程度的减小。对于整条试验沟道,农田退水中TDS、TN、TP的浓度随着在沟道迁移距离的增加呈明显减小的趋势,至出水断面时浓度分别为0.60~0.80g.L 1、0.24~0.33 mg.L 1和0.04~0.09 mg.L 1。田间沟道试验说明,农田排水沟能有效地截留农田退水污染物,选择适合的基质进行人工布设实际可行,有助于发挥农田排水沟的生态功能。     

Phosphate Sorption to Macropore Wall Materials and Bulk Soil

Preferential flow through macropores may allow reactive solutes to travel long distances in soil. The amount of solute transported is expected to depend on the ability of the macropore wall materials to retain the solute from the bypassing solution. From a loamy sand soil, samples of bulk Ap-horizon, bulk Btg-horizon, earthworm burrow lining, and both iron-depleted and iron-enriched materials from glossic fracture walls were obtained. The different soil materials were shaken for 5 min, 2 hr and 7 d in 0.01 M CaCl₂ with initial P concentrations from 0 to 3.3 mg H₂PO₄ ^--P L^-1 at pH 5. The resulting changes in solution P-concentration were interpreted in terms of P-desorption or P-sorption. Burrow lining and bulk-Ap were poor P sorbents, especially at short contact times (5 min and 2 hr). They were unable to sorb P at concentrations below approximately 1 mg PO₄-P L^-1. In contrast, fracture wall materials and bulk-Btg were much stronger sorbents. They removed P from solutions having P-concentrations of only about 0.03 mg PO₄-P L^-1. The results of the study suggest that environmentally critical concentrations of dissolved P_i will be leached more easily through earthworm burrows than fractures, and that sorption characteristics of bulk soil may deviate strongly from sorption characteristics of macropore wall materials.     

混合浮床对南海湖湿地富营养化水体修复的作用

[目的]探究植物的交互作用对生态浮床去除N,P效率的影响,为后期南海湖湿地规模化建设提供理论依据。[方法]在自然开放水域条件下,选取适合于北方生长的3种挺水植物水葱、千屈菜、风车草为浮床植物,以高密聚乙烯空心塑料基盘为植物载体,建立单一种植与交叉混合种植两种浮床体系,在南海湖湿地保护区进行为期90 d的水质处理,研究植物生长特性及浮床净化效果。[结果] 10月份收割时,混合浮床中水葱和风车草的分蘖数分别达26和30株,生物量(鲜重)分别为1.43和1.98 kg/株。风车草浮床N累积量最好,达110.6 g/m~2,水体TN去除率34.9%。混合浮床P累积量最好,达26.02 g/m~2,水体TP去除率43.3%。[结论]植物的交互作用对植株的分蘖繁殖有一定促进作用,但不改变植物自身N,P吸收能力,植物体对N,P的累积量受生物量影响较大,3种植物在混合浮床中的整株N,P累积量要高于单植物浮床,混合浮床可作为针对南海湖富营养化水体修复的浮床形式推广使用。     

Performances of Methyl Blue and Arsenic(V) Adsorption from Aqueous Solution onto Magnetic 0.8Ni0.5Zn0.5Fe2O4/0.2SiO2 Nanocomposites

Washing-down parlours and standing areas, following milking on dairy farms, produce dairy soiled water (DSW) that contains variable concentrations of nutrients. Aerobic woodchip filters can remove organic matter, nutrients and suspended solids (SS) in DSW, but the effluent exiting the filters may have to be further treated before it is suitable for re-use for washing yard areas. The performance of a single-layer sand filter (SF) and a stratified SF, loaded at 20 L m^?2 day^?1, to polish effluent from a woodchip filter was investigated over 82 days. Average influent unfiltered chemical oxygen demand (COD_T), total nitrogen (TN), ammonium–N (NH₄–N), ortho-phosphorus (PO₄–P) and SS concentrations of 1,991?±?296, 163?±?40, 42.3?±?16.9, 27.2?±?6.9 and 84?±?30 mg L^?1 were recorded. The single-layer SF decreased the influent concentration of COD_T, TN, NH₄–N, PO₄–P and SS by 39, 36, 34, 58 and 52 %, respectively. Influent concentrations of COD_T, TN_T, NH₄–N, PO₄–P and SS were decreased by 56, 57, 41, 74 and 62 % in the stratified SF. The single-layer SF and the stratified SF were capable of reducing the influent concentration of total coliforms by 96 and 95 %, respectively. Although a limited amount of biomass accumulated in the uppermost layers of both SFs, organic and particulate matter deposition within both filters affected rates of nitrification. Both types of SFs produced final water quality in excess of the standards for re-use in the washing of milking parlours.     

基于沟渠库厂联合运用的金属矿区酸性废水防控措施研究

[目的]金属矿区酸性矿山废水外排防控一直是个难题。探索酸性矿山废水源头控制与末端治理相结合的防控技术体系,为金属矿区酸性废水的防控提供新的解决思路。[方法]以广东省大宝山矿区为研究案例,坚持"源头防控,末端治理"的原则,构建基于沟渠库厂联合运用的酸性废水综合防控技术体系。[结果]建设截排水系统实施雨污分流,从源头上减少酸性废水产生量;清淤腾空拦泥库调蓄库容2.81×106 m3,并建设4.50×104 t/d处理规模的污水处理厂,对酸性废水进行未端治理,达到在5a一遇降雨条件下丰水期酸性废水不外排的防控目标。[结论]通过沟(截水沟)、渠(排水渠)、库(拦泥库)、厂(污水处理厂)的联合运用,可以控制酸性矿山废水在设计标准下不外排,该技术体系可用于类似矿山酸性废水的治理。