Mainstream Deammonification: Preliminary Experience Employing Granular AOB-Enriched Biomass at Low DO Values

The deammonification process represents one of the most convenient pathways for nitrogen removal from wastewater. A great deal of scientific articles dwells on the treatment of sidestream fluxes, whereas applications to mainstream waters represent a novel field. Among the general challenges of deammonification, one of the most important is the effective selection of ammonia oxidizers (AOB) over nitrite oxidizers (NOB), but also the typical slow start-up periods. In addition to such issues, mainstream deammonification has to face water temperatures and alkalinity reserves lower than those of sidestream fluxes and higher content of organic matter. An attempt was made to tackle such challenges by employing a lab-scale plant; low dissolved oxygen (DO) values (average 0.78 mg/L) and granular AOB-enriched biomass were used in order to address exclusion of nitrite oxidizers. The granules also allowed better biomass retention. The hydraulic retention time (HRT) was established initially at 24 h and later decreased to 12 h, as to possibly enhance the performance of the reactor. After 52 days of operation, Anammox biomass was also inoculated to the reactor. The results showed a maximum nitrogen removal efficiency of 54%. Moreover, little quantities of nitrates were observed throughout the experiment (<5 mg N/L twice, under the limit of quantification the rest of the sampling days), meaning that NOB out-selection techniques worked properly. Retention of biomass was also positively addressed and yielded a final SRT value of 15.6 days. Therefore, the proposed solution for mainstream deammonification was demonstrated to be promising and more research would be necessary to optimize it.     

Ca/CTS/FA复合材料对酸性大红的吸附研究

以粉煤灰（Fly ash,FA）为原料,通过负载壳聚糖和钙离子制备一种新型吸附剂（Ca/CTS/FA）用于酸性大红3R（Acid scarlet 3R,AS 3R）染料的吸附去除,考察了最佳吸附条件和吸附性能,探讨了吸附动力学、吸附热力学及复合吸附剂的再生。结果表明：水体pH、吸附剂投加量、吸附时间和振荡频率均对吸附有影响。在不同温度下,Ca/CTS/FA对AS 3R的吸附动力学均能用准二级吸附速率方程精确描述（R2=1.00）。不同温度下的等温吸附数据分别用Langmuir模型、Freundlich模型和Dubinin-Radushkevich（D-R）模型进行拟合,结果表明等温吸附行为更符合Langmuir模型,同时也较好地符合Freundlich模型和D-R模型;由D-R方程获得的平均吸附能、表观活化能及热力学研究均表明该吸附过程由化学吸附、物理吸附和氢键作用共同控制。热力学参数中吸附自由能变为负值、焓变为正值说明该吸附是吸热性质的自发过程。Ca/CTS/FA复合吸附剂能用0.01 mol·L-1 NaOH溶液再生,至少可循环使用8次以上,再生率均在99%以上。     

A model of ammonia volatilization from applied urea. I. Development of the model

Urea application to soil raises the pH and ammonium concentration, thus providing ideal conditions for ammonia volatilization. A mechanistic model is presented, which combines the process of ammonia volatilization with the simultaneous transformation and movement of urea and its products in soil, for predicting the concentration profiles of urea, ammoniacal-nitrogen and soil pH, and ammonia losses, following application of urea. The model consists of continuity equations describing the diffusion and reaction of urea, ammoniacal-nitrogen and soil base; it takes into account the volatilization of ammonia and the concurrent acidification of the soil surface; and considers a variable P_Co2 profile due to soil respiration and urea hydrolysis. The derivation of the continuity equations and their boundary conditions, calculations of ammonia volatilization, and appropriate methods for numerical solutions are described.     

Oxidation of quercetin by salivary components. Quercetin-dependent reduction of salivary nitrite under acidic conditions producing nitric oxide

Under acidic conditions, nitrite is protonated to nitrous acid (pK(a) = 3.2-3.4) that can be transformed into nitric oxide by self-decomposition and reduction. When sodium nitrite was mixed with quercetin at pH 1-2, quercetin was oxidized producing nitric oxide. In addition to quercetin, kaempferol and quercetin 4'-glucoside were also oxidized by nitrous acid, but oxidation of apigenin, luteolin, and rutin was slow compared to oxidation of the above flavonols. These results suggested that flavonols, which have a free hydroxyl group at carbon position 3, can readily reduce nitrous acid to nitric oxide. When the pH of saliva was decreased to 1-2, formation of nitric oxide was observed. The nitric oxide formation was enhanced by quercetin, and during this process quercetin was oxidized. These results indicate that there is a possibility of reactions between phenolics and nitrous acid derived from salivary nitrite in the stomach.     

MAJOR PATHWAYS FOR NITROGEN REMOVAL IN WASTE WATER STABILIZATION PONDS

A study on the factors influencing nitrogen removal in waste water stabilization ponds was undertaken in an eight-pond series in Werribee, Australia. Nitrogen species including Kjeldahl nitrogen, total ammonia nitrogen, nitrite and nitrate were monitored monthly from March 1993 to January 1994. At the same time, pH, temperature, chlorophylla content and dissolved oxygen were also recorded. Highest nitrogen removal occurred during the period with highest levels of chlorophylla content and dissolved oxygen, but the rate of nitrogen removal was not related to temperature and pH. Enhanced photosynthetic activities resulting from an increased phytoplankton abundance due to prolonged detention time caused an increase in dissolved oxygen, and created an optimum condition for nitrification to occur. In this process, ammonia was oxidized to nitrite and nitrate which were subsequently reduced to elemental nitrogen. Apart from nitrification-denitrification which was the major nitrogen removal pathway in the study system, algal uptake of ammonium, nitrate and nitrite as nutrient sources also contributed to the nitrogen removal. The role of phytoplankton and zooplankton in the treatment process in waste stabilization ponds was discussed.     

Response Surface Methodology for Modeling Bisphenol A Removal Using Ultrafiltration Membrane System

In this work, the effects of various operating parameters (pressure, pH, BPA concentration, and filtration time) toward bisphenol A (BPA) removal via ultrafiltration (UF) membrane system were investigated using response surface methodology (RSM). Historical data design of RSM was used to obtain the interaction between variables and response as well as optimizing the process. The analysis of variance (ANOVA) showed that the third-order polynomial model was significant in which pH and filtration time were identified as significant terms that influence BPA removal. The 3D response surface plots revealed the two-factor interaction between independent and dependent variables. The optimization process of the model predicted optimum conditions of 99.61% BPA removal at 1 bar, pH 6.7, 10 μg/L BPA concentration, and 10-min filtration time. The predicted optimum conditions for BPA removal were consistent with the obtained experimental values, indicating reliable application of historical data design RSM for modeling BPA removal in UF membrane system.     

Aggregate-related changes in network patterns of nematodes and ammonia oxidizers in an acidic soil

Nitrification plays a central role in global nitrogen cycle, which is affected by biological interaction between soil microfauna and microorganisms. However, the complexity of soil biotic communities made it difficult to reveal organizational principles of the community and the interactions among species. Here, we used the network analysis to decipher the interactions between nematodes and ammonia oxidizers within aggregate fractions under 10-year manure application, and examine their associations with soil variables and potential nitrification activity (PNA). Three aggregate fractions included large macroaggregates (>2000 μm, LA), small macroaggregates (250–2000 μm, SA), and inter-aggregate soil and space (<250 μm, IA). Aggregate factions showed a remarkable effect on association networks of nematodes and ammonia oxidizers. The average connectivity (avgK) and the number of edges in overall networks increased with increasing aggregate sizes, while the average geodesic distance (GD) followed the opposite trend. The LA network could be viewed as a better organized or a better operational soil food web with more functional interrelated members than the SA and IA networks. The modules related to PNA were significantly correlated and clustered together as meta-modules in networks of aggregate fractions. The role-shifts prevailed among the network members such as significant module memberships (MMs) and generalist/specialist operational taxonomic units (OTUs). A half of shared nodes were further identified as shared MMs, dominated by ammonia-oxidizing bacteria (AOB) especially for Nitrosospira cluster 3a and 10. Soil pH could explain partly the shift of module hubs in different networks, while grazing by bacterivores might account for three exclusively connecters related to Nitrososphaera clusters 1.1. The strongly coupled modules correlated positively to pH and total carbon (TC), regardless of aggregate fractions. The network analysis approach provided new insights into potential importance of network interactions between nematodes and ammonia oxidizers in soil nitrogen cycling.     

Spatial variation of ammonia volatilization from soil and its scale‐dependent correlation with soil properties

Quantitative predictions of ammonia volatilization from soil are useful to environmental managers and policy makers and empirical models have been used with some success. Spatial analysis of the soil properties and their relationship to the ammonia volatilization process is important as predictions will be required at disparate scales from the field to the catchment and beyond. These relationships are known to change across scales and this may affect the performance of an empirical model. This study is concerned with the variation of ammonia volatilization and some controlling soil properties: bulk density, volumetric water content, pH, CEC, soil pH buffer power, and urease activity, over distances of 2, 50, 500, and >2000 m. We sampled a 16 km × 16 km region in eastern England and analyzed the results by a nested analysis of (co)variance, from which variance components and correlations for each scale were obtained. The overall correlations between ammonia volatilization and the soil properties were generally weak: –0.09 for bulk density, 0.04 for volumetric water content, –0.22 for CEC, –0.08 for urease activity, –0.22 for pH and 0.18 for the soil pH buffer power. Variation in ammonia volatilization was scale‐dependent, with substantial variance components at the 2‐ and 500‐m scales. The results from the analysis of covariance show that the relationships between ammonia volatilization and soil properties are complex. At the >2000 m scale, ammonia volatilization was strongly correlated with pH (–0.82) and CEC (–0.55), which is probably the result of differences in parent material. We also observed weaker correlations at the 500‐m scale with bulk density (–0.61), volumetric water content (0.48), urease activity (–0.42), pH (–0.55) and soil pH buffer power (0.38). Nested analysis showed that overall correlations may mask relationships at scales of interest and the effect of soil variables on these soil processes is scale‐dependent.     

Neural Modeling of Greenhouse Gas Emission from Agricultural Sector in European Union Member Countries

The present paper discusses a novel methodology based on neural network to determine agriculture emission model simulations. Methane and nitrous oxide are the key pollutions among greenhouse gases being a major contribution to climate changes because of their high potential global impact. Using statistical clustering (k-means and Ward’s method), five meaningful clusters of countries with similar level of greenhouse gases emission were identified. Neural modeling using multi-layer perceptron networks was performed for countries placed in particular groups. The parameters that characterize the quality of a network are the predictive errors (mainly validation and test) and they are high (0.97–0.99). The use of sensitivity analysis allowed for identifying the variables that have a significant influence on the greenhouse gases emissions. The sensitivity analysis of the designed artificial neural network models shows a few dominant variables, affecting emissions with varied intensity: cattle and buffaloes, sheep and goat populations, afforestation as well as electricity consumption. The observed values were compared with those predicted by the models. The forecasted course of changes in the variable test is identical with the real data, which proves that the model highly matches to the observed data.     

Adsorption of Cadmium on Bed Sediments of River Hindon: Adsorption Models and Kinetics

The adsorption characteristics of cadmium on bed sediments ofriver Hindon in western Uttar Pradesh (India) have been studied.The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time, particlesize and temperature has been studied. The optimum equilibrationtime was found to be 60 min, which was independent of initialconcentration of cadmium ions. The adsorption curves were smoothand continuous leading to saturation, suggesting the possible monolayer coverage of cadmium ions on the surface of the adsorbent. The adsorption of cadmium increased with an increasein pH. Furthermore the adsorption of cadmium increased with increasing adsorbent concentration and decreased with adsorbentparticle size. The important geochemical phases, iron and manganese oxide, support the adsorption of cadmium ions. The adsorption data were analysed using the Langmuir and Freundlichadsorption models to determine the mechanistic parameters relatedto the adsorption process. Thermodynamic parameters, viz., freeenergy change, enthalpy change and entropy change, were alsodetermined. The negative values of free energy change (ΔG°) indicated the spontaneous nature ofthe adsorption and positive values of enthalpy change (ΔG°) suggested the endothermic nature ofthe adsorption process. The intraparticle diffusion of cadmium through pores in the adsorbent was found be the main rate-limiting step.     

Optimization of extraction conditions for active components in Hypericum perforatum using response surface methodology

Optimal conditions for extraction of Hypericum perforatum were determined using response surface methodology. A 3 x 4 x 4 full factorial design representing three extraction temperatures, four extraction times, and four solvent concentrations was executed. The overall extraction efficiency was defined by comparing either the total extractable material weight or the individual component peak area to the peak area of luteolin as internal standard. Of the tested variables, the extraction temperature most significantly affected extraction efficiency. Higher temperatures gave better extraction efficiencies, but high temperature also caused decomposition of hypericin. Within the test range, responses for most variables had local maxima. Optimum ranges of time and concentration for individual variables were overlaid. Considering all variables, optimum ranges for extraction time and extraction solvent concentration (percent ethanol in acetone) were 5.0-6.7 h and 44-74% at 23 degrees C, 5.4-6.9 h and 45-72% at 40 degrees C, and 5.3-5.9 h and 44-69% ethanol in acetone at 55 degrees C, respectively.     

Reducing sampling intensity in order to investigate spatial variability of soil pH,organic matter and available phosphorus using co-kriging techniques. A case study of acid soils in Eastern Croatia

Soil pH, hydrolytic acidity (HA), organic matter (OM) and plant available phosphorus (AP) are factors controlling the environmental-friendly soil management in agroecosystems. These parameters are highly variable in space. The objective of this work is to study spatial variability of pH, HA, OM and AP using several interpolation methods in Eastern Croatia. A total of 1004 (0–30 cm) soil samples were collected, and several univariate and multivariate interpolation performances were tested. The results showed that soils of the study area had high HA and AP, while pH and OM were low. The variogram analysis revealed different spatial structures among studied soil properties and demonstrate a need for variable-rate management. Soil pH and OM had lower spatial variability compared to AP and HA. Ordinary kriging was the most accurate method to estimate the studied variables. The incorporation of auxiliary variables increased the precision of the estimations for HA. Soil AP and OM showed different results for spatial prediction obtained by co-kriging. Overall, the incorporation of pH as auxiliary variable increased the prediction of the models. However, more co-variates should be incorporated in further models, in order to identify with more precision areas that need to be restored.     

Anammox反应器的启动及其菌群演变的研究

为了研究工艺条件对反应器内微生物多样性的影响,该论文采用城市污水处理厂活性污泥接种,通过培育硝化污泥,进行了启动厌氧氨氧化(Anammox)反应器的试验,并对启动过程中细菌的多样性变化作了跟踪研究。研究结果表明,以好氧活性污泥作为接种物,可成功地培育硝化生物膜;通过反应器运行条件的控制,硝化生物膜可从进行好氧氨氧化反应过渡到进行厌氧氨氧化反应。在此过程中,异养型细菌的数量大幅度下降,硝化细菌、反硝化细菌和厌氧氨氧化细菌的数量增大,推测它们都与厌氧氨氧化作用有关。运用PCR-DGGE技术证明,随着反应器运行时间的延长,菌群发生明显变化并呈现简化趋势。     

湖南典型双季稻田氨挥发对施氮量的响应研究

选择湖南典型双季稻田为对象,采用密闭室连续抽气法研究了不同施氮量下的氨挥发损失。结果表明,稻田氨挥发总量随施氮量增加而显著增加,在当地农民习惯施肥水平（早稻150 kg/hm2、晚稻180 kg/hm2）下,早稻氨挥发损失氮量占施氮量的39.8%,晚稻则达46.9%,双季稻平均氨挥发损失率达43.7%。氨挥发通量与田面水的NH+4-N浓度和 pH 之间均存在极显著的正相关关系。可见,氨挥发是该区域稻田氮素损失的最主要途径之一。     

稻麦轮作农田氮素循环的DNDC模型分析

基于长江中下游稻麦轮作体系的氮肥施用田间试验,采用Denitrification- Decomposition model (DNDC) 模型研究了气候条件、土壤属性、农业管理等输入因素的不确定性对子粒产量、作物氮吸收、氨挥发、N2O排放等预测结果的影响。结果显示:采用DNDC模型模拟的土壤氨挥发速率和N2O排放通量与田间实测结果较为吻合,氨挥发通量模拟值与实测值相关系数为0.688,N2O排放通量模拟值与实测值相关系数为0.528,均达极显著水平,表明DNDC模型预测农田土壤氮素具有较高可信度。模拟结果显示,气温和氮肥用量是影响作物产量和吸氮量的关键因素;土壤氨挥发主要受氮肥品种影响,并随氮肥用量增加而增加;土壤N2O排放主要受温度、土壤pH值、土壤有机碳含量的影响。为使DNDC能更有效地估算氨挥发和N2O排放,有必要获取更翔实的资料以减少输入数据的不确定性。     

Simultaneous automated determination of chloride,nitrite, nitrate,and ammonia in water and wastewater

An automated system capable of simultaneous determination of chloride, nitrite, nitrate, and ammonia in about 2 ml of fresh water or wastewater is described. The four compounds are determined using modifications of established colorimetric procedures. Results can be reported at a true rate of five samples per hour with a relative standard deviation at optimum concentrations of less than 2%. Detection limits are 1 ppm Cl for chloride and 1, 5, and 5 ppb N for nitrite, nitrate, and ammonia, respectively. Sample pH adjustment is not required from 0.0002 N H₂SO₄ (pH 3.7) to 0.005 N NaOH (pH 11.2). Fresh water and wastewater samples were analyzed for nitrite and ammonia by the proposed procedure and by the manual sulfanilic-naphthylamine and nesslerization method. Analysis by the student t-test showed no significant difference between the paired sets of data (P > 0.5). When potable and wastewater samples were spiked with sodium chloride, potassium nitrate, sodium nitrite, and ammonium chloride and analyzed, average recoveries were 99 to 103%.     

Competitive adsorption of humus acids and phosphate on goethite, gibbsite and two tropical soils

Competition in adsorption between humic acid (HA) or fulvic acid (FA) and phosphate on synthetic goethite, gibbsite and two tropical soils was studied. The results for both goethite and gibbsite showed that HA and FA competed strongly with phosphate for adsorption sites at low pH values. The soils showed a similar result with a reduction in phosphate adsorption resulting from the addition of HA at the pH of the soils. The competition between HA and phosphate at different pH levels is illustrated by comparing the adsorption envelopes for phosphate on goethite, gibbsite and the two soils in the presence and absence of HA. The trends observed may be explained by the relative positions of the maximum buffer-power (buffer capacity) of the organic acids and of phosphoric acid which are shown to lie in different pH ranges.     

不同施肥模式对设施生菜产量和氮损失的影响

  目的  探讨液体肥滴灌施肥模式和常规施肥模式对设施生菜产量和氮损失（氨挥发、氧化亚氮排放、硝态氮淋洗）的影响。  方法  采用田间小区试验,以日光温室生菜为对象,共设3个处理,分别为液体肥优化施肥模式（LF,170 kg hm?2 N,基肥不施氮肥 + 3次追肥）、固体水溶肥常规施肥模式（CF,200 kg hm?2 N,基肥 + 2次追肥）,以及不施氮对照（CK,0 kg hm?2 N,磷钾做基肥+清水滴灌）。安装水肥一体化设施进行追肥灌水,采用通气法和静态箱法收集并测定生菜生长季内氨挥发和氧化亚氮的排放。  结果  结果表明,与常规施肥处理（CF）相比,液体肥料处理（LF）在生长前期可以延迟氨挥发和氧化亚氮的排放高峰3 ~ 5 d,且在生长季内显著降低土壤氨挥发和氧化亚氮的排放量,减排率分别为24.6%和21.6%;应用液体肥料可以减少0 ~ 100 cm土层硝态氮残留21.0%,降低了氮素淋洗风险;与CF模式相比,LF模式在减氮15.0%的基础上,产量没有下降,氮肥利用率提高了32.4%。  结论  新型液体肥料优化施肥模式（LF）可以显著降低设施菜田氨挥发和氧化亚氮排放量,减轻土壤硝态氮淋洗风险,维持产量不降低并提高肥料利用效率,是一种节氮减排的绿色生产方式。     

施入粉煤灰和污泥对酸性淋溶土镉和铅吸附的影响

The safe recycling of fly ash (FA) and sewage sludge (SS) in the agricultural processes comprises an important environmental technology on waste management. Soils amended with FA and SS may change their ability to adsorb heavy metals due to either increase of soil pH or decomposition of sludge-borne organic matter. Thus, Cd and Pb sorption was investigated by 1-month incubation under soil moisture content at field capacity and room temperature with an acidic Typic Haploxeroalf from central Greece amended with varying amounts of FA and SS. Batch experiments were conducted by equilibrating the soil samples with CaCl₂ solutions containing 0-400 mg Pb L^-1 or 0-100 mg Cd L^-1. The results showed that the Freundlich equation described well the Cd and Pb sorption. Distribution coefficient (K_d) values of Pb were higher than those of Cd in all the treatments of this study. Application of FA increased K_d values for Cd and Pb to 8.2 and 2.3 times more than the controls, respectively. Simultaneous applications of FA and SS caused a K_d increase of 3.8 and 2.1 times compared to the treatments that received only SS for Cd and Pb, respectively. Treatment of SS alone did not significantly change Cd and Pb sorption compared to the controls. The sorption reactions seemed to be mainly affected by soil pH, which was revealed by the significant correlations of Cd and Pb sorption with soil pH. These suggested that fly ash was very useful as a low-cost adsorbent for Cd and Pb and could be used as an ameliorant for biosolid-amended acidic soils.     

寒旱地区生态沟渠基质去除氨氮和磷最优配比筛选及影响因素

基质是生态沟渠的重要组成部分,但在我国北方寒旱地区,由于高寒、降雨少、蒸发强等原因,导致土壤和水体中盐度较高,可供选择的基质种类较少,从而限制了生态沟渠技术在该地区的应用。选取天然沸石、麦饭石、无烟煤、炉渣、废砖块5种北方地区常见基质作为试验材料,通过静态吸附试验对选用材料进行氨氮和磷的吸附,并将吸附效果较好的3种基质组合成不同比例的生态沟渠基质试样,再次通过筛选试验确定出去除效果最好的基质比例组合,同时研究了温度、pH和盐度对最优基质组合去除氨氮和磷效果的影响。结果表明:废砖块、天然沸石、炉渣在质量比例为1∶1∶3时对氨氮和磷的去除率最优,均达到90%以上。随着温度的升高,氨氮的吸附量降低,磷的吸附量升高。pH对氨氮和磷的吸附效果有显著的影响,对磷的去除率随着pH升高而降低,对氨氮的去除率随着pH升高呈现先增后减的趋势,在pH=7时,氨氮去除效果最好,去除率为91.78%。氨氮和磷的去除效果均随着溶液盐度的增加而降低,对磷的吸附效果影响不明显,但对氨氮影响较大,表现为盐度低于1%时,溶液中氨氮的去除效果下降幅度并不明显,均在3%左右,而当盐度达到2%时,氨氮的去除率仅有68%,比盐度为0时的去除率(92%)降低了24%。