Abstract  A field experimental project was set up in southern Sweden to assess the effects of controlled drainage on hydrology and environment. Controlled drainage makes it possible to vary the drainage intensity with the variation in drainage requirement during season by controlling the height of a riser in the drain outlet and thus to a certain degree control the amount of outflow of solutes via the drainage system. During periods with low drainage demand, the riser in the drain outlet can be raised and the groundwater level in field will rise up to the level of the riser before the discharge takes place. Three plots, each with an area of 0.2 ha (40 m x 50 m) were installed on a loamy sand. One plot was drained by conventional subsurface drainage (CD) and two plots were drained by controlled drainage (CWT). The plots contained four lateral drain tubes, at 10 m spacing and placed at 1 m depth. Each plot was isolated by a double layer of plastic sheeting placed in the back-filled trenches to a depth of 1.6 m to prevent lateral leakage and subsurface interactions. Measurements of precipitation, drain outflow and soil and air temperatures were carried out hourly. Groundwater levels were measured and samples of drain outflow were collected twice a month for nitrogen and phosphorous analyses. Mineral nitrogen contents in soil were measured three times a year.Controlled drainage had a significant hydrological and environmental effect during the 2 years of measurement (1996-1998). Compared with CD, the total drain outflow from CWT was 79% less in Year 1 and 94% in Year 2. The total reduction in nitrate losses with CWT corresponded to the reduced outflow rates. Compared with CD, the total amounts of nitrate in drain outflow were 78% less in Year 1 and 94% in Year 2. The highest concentrations of nitrate were measured at the time of the largest outflow rates. The phosphorous losses were 58% less for CWT as compared to the CD values in Year 1 and 85% less in Year 2. The reduction in nitrogen content in the soil profile during the winter season was 60-70% less in CWT than in CD.

Abstract    Nitrogen nutrition in cyanobacteria is regulated by NtcA, a transcriptional activator that is subject to negative control by ammonium. Using Synechococcus sp. strain WH7803 as a model organism, we show that ntcA expression was induced when cells were exposed to nitrogen stress but not when they were subjected to phosphorus or iron deprivation.

Abstract  Cyanotoxins, a group of hepatotoxins and neurotoxins produced by cyanobacteria, pose a health risk to those Who use surface waters as sources for drinking water and for recreation. Little is known about the spatial and seasonal occurrence of cyanotoxins in Lake Ontario and other lakes and ponds within its watershed. Within the embayments, ponds, rivers, creeks, shoreside, and nearshore and offshore sites of Lake Ontario, microcystin-LR concentrations were low in May, increased through the summer, and reached a peak in September before decreasing in October. Considerable variability in microcystin-LR concentrations existed between and within habitat types within the Lake Ontario ecosystem. In general, the average microcystin-LIR concentration was two orders of magnitude lower in embayment (mean=0.084 mu g/L), river (mean=0.020 mu g/L, and shoreside (mean 0.052 mu g/L) sites compared to upland lakes and ponds (mean = 1.136 mu g/L). Concentrations in the nearshore sites (30-m depth) and offshore sites ( 100-m depth) were another order of magnitude lower (mean=0.006 mu g/L) than in the creek/river, bay/pond, and shoreside habitats. Only 0.3% (2 of 581) of the samples taken in Lake Ontario coastal Waters exceeded the World Health Organization (WHO) Drinking Water Guideline of 1 mu g microcystin/L for humans. In contrast, 20.4% (20 of 98) of the samples taken at upland lakes and ponds within the watershed of Lake Ontario exceeded WHO Guidelines. No significant relationship between nitrate and microcystin-LR concentrations was observed in Lake Ontario even though a significant positive relationship existed between phosphorus and phycocyanin and microsystin-LR concentrations. At all upland lake site (Conesus Lake) in the Ontario watershed, the development of a littoral Microcystis Population was not observed despite high nutrient loading (P and N) into the nearshore zone, well-developed nearshore populations of filamentous Spirogyra and Zygnema, the occurrence of Dreissena spp., and the known Occurrence of Microcystis and microcystin production in the pelagic waters of Conesus Lake. (C) 2009 Elsevier Inc. All rights reserved.

Abstract  Between 2000 and 2006, the New Hampshire Department of Environmental Services and the University of New Hampshire collected water quality samples at 25 to 40 stations per year in a 56.5-km(2) estuary as part of the Environmental Protection Agency's National Coastal Assessment program. Due to the high density of stations, probabilistic statistics for the estuary could be calculated with low uncertainty. The proportions of the estuary exceeding thresholds in each year were calculated for temperature, salinity, dissolved oxygen, chlorophyll a, nitrogen as nitrate and nitrite, nitrogen as ammonium, phosphorus as orthophosphate, total suspended solids, and fecal coliform bacteria. These values were tested for trends over time and correlations with climate variables. The same statistical tests were applied to monthly grab sample data from a representative station in the estuary. The outcomes of the statistical tests on the two datasets were compared to determine if they provided similar information to coastal managers. Trends and correlations were equally likely to be detected using the probability-based data and the fixed station data, but the results were different for the two datasets. The differences were likely due to the distributed nature of the probability-based sampling design, which places stations in all sections of the estuary. In addition, expressing the probabilistic datasets as estimated proportions reduced variability in volatile parameters, such as bacteria, relative to the grab sample dataset. It will be important to develop tools to rectify trends from probability-based surveys with fixed station monitoring to provide clear information to managers.

Abstract  At a watershed in an intensively farmed region of Brittany, France, nutrient concentrations and loads in surface water were examined over a 10-yr period. The annual nitrate and total phosphorus concentrations were compared with rainfall and land use to evaluate the major factors affecting the nutrient losses. The watershed was characterized by heavy fertilization. The mean nutrient concentration was determined as the sum of instantaneous fluxes of nutrients over the desired time period divided by the water flux over the same time period. Resulting data are presented to show the monthly and annual nitrate and total phosphorus concentrations. The results show no statistical evidence of a trend for the monthly mean NO sub(3) and total P loads. In terms of NO sub(3), the percent area of the watershed covered by corn had the largest absolute impact on the annual concentration, but rainfall also played a major role, as the drier years corresponded to the lowest annual NO sub(3) concentrations. Most of the excess P was stored in the soil profile.

Abstract  Agriculture is a major cause of non-point source water pollution in the Midwest. Excessive nitrate, phosphorous, and sediment levels degrade the Mississippi River and Gulf of Mexico. In this research we ask, to what extent can citizen involvement help solve the problem of non-point source pollution. Does connecting farmers to farmers and to other community members make a difference in moving beyond the status quo? To answer these questions we examine the satisfaction level of Iowa farmers and landowners with their current conservation measures as a proxy for willingness to change. A survey of 360 conservation minded farmers obtained from a random sample of 75 HUC (Hydrologic Unit Code) 12 Iowa watersheds reveals that 27% of the variance among farmers' perception of adequacy of their conservation practices is explained by a combination of beliefs about the seriousness of water pollution, personal, civic, and expert connections. The more farmers talk with other farmers the more likely they are satisfied with their conservation efforts. However, the more frequently farmers talk to friends and neighbors that don't farm, the more likely they are to not be satisfied with their conservation efforts. Further, the more social organizations farmers belong to-e.g., more non-farmers they interact with in a group setting-the more likely they are to be dissatisfied with their level of effort being adequate to protect local water bodies. These findings suggest the personal and civic connections among farmers and communities are important in explaining perceptions of how adequate conservation measures are. These perceptions have implications for farmers' willingness to go beyond current actions and more actively engage in solving local watershed problems and explain why they may not currently be engaged in additional actions.

Abstract  In the Upper Saint-Laurent region of Quebec, Canada, the growth, performance, and nutrient status of two willow species were compared when cultivated under short-rotation intensive culture (SRIC) on extensive sites with different characteristics. In addition, the impact of fertilization with wastewater sludge on yields after the first rotation cycle was examined. The willow species were Salix viminalis and S. discolor. The sites had different soil characteristics, one of which was well drained, and the other two were poorly drained. While diameter growth was similar for the two species, S. viminalis grew significantly taller than S. discolor. The fertilization treatment induced a significant increase in diameter of both species on all experimental sites, while effects on stem height were variable. Both species had comparable masses and leaf area on all plots, but the leaves were smaller and lighter on the sandy site compared with the two clayey sites. Both species used nitrogen more efficiently on the sandy site, and fertilization induced a decrease in the efficiency of N utilization. Foliar N and magnesium contents and concentrations were generally lower on the sandy site, while both species tended to have similar phosphorus, potassium, and calcium contents and concentrations regardless of the plantation site. Dried and granulated wastewater sludge was determined to be a good fertilizer for willows under SRIC.

Abstract  Loss of phosphorus (P) from agriculture contributes to the eutrophication of surface waters. We have assessed the magnitude and controls of P leaching and the risk of colloid-facilitated transport of P from sandy soils in Muenster. Concentrations of soluble reactive P in drainage water and groundwater were monitored from 0.9 to 35 m depth. Total P concentrations, P saturation, and P sorption isotherms of soil samples were determined. Concentrations of dispersible soil P and colloidal P in drainage water and groundwater were investigated. The concentrations of soluble reactive P in drainage water and groundwater were close to background concentrations (< 20 kg P l super(-1)). Median concentrations in excess of 100 kg P l super(-1) were found down to 5.6 m depth at one of four research sites and in the lower part of the aquifer. Experimentally determined equilibrium concentrations and the degree of P saturation were good predictors of P concentrations of drainage water. Large concentrations of dispersible P were released from soil with large concentrations of oxalate-extractable P and addition of P induced further dispersion. Colloidal P was transported in a P-rich subsoil when there was a large flow of water and after nitrate had been flushed from the soil profile and total solute concentrations were small. We conclude that the concentration of soluble reactive P in drainage water is controlled by rapid adsorption in the sandy soils. Subsurface transport of dissolved P contributes substantially to the loss of P from the soils we investigated. Accumulation of P in soils increases the risk of colloid-facilitated leaching of P.

Abstract  This paper describes the hydrochemistry of a lowland, urbanised river-system, The Cut in England, using in situ sub-daily sampling. The Cut receives effluent discharges from four major sewage treatment works serving around 190000 people. These discharges consist largely of treated water, originally abstracted from the River Thames and returned via the water supply network, substantially increasing the natural flow. The hourly water quality data were supplemented by weekly manual sampling with laboratory analysis to check the hourly data and measure further determinands. Mean phosphorus and nitrate concentrations were very high, breaching standards set by EU legislation. Although 56% of the catchment area is agricultural, the hydrochemical dynamics were significantly impacted by effluent discharges which accounted for approximately 50% of the annual P catchment input loads and, on average, 59% of river flow at the monitoring point. Diurnal dissolved oxygen data demonstrated high in-stream productivity. From a comparison of high frequency and conventional monitoring data, it is inferred that much of the primary production was dominated by benthic algae, largely diatoms. Despite the high productivity and nutrient concentrations, the river water did not become anoxic, and major phytoplankton blooms were not observed. The strong diurnal and annual variation observed showed that assessments of water quality made under the Water Framework Directive (WFD) are sensitive to the time and season of sampling. It is recommended that specific sampling time windows be specified for each determinand, and that WFD targets should be applied in combination to help identify periods of greatest ecological risk. (c) 2015 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.

Abstract  Dairy cow pastures and feeding areas around barns can be a significant source of nonpoint source pollutants to nearby streams. To help document the significance of these sources, nutrient export in streamflow from a 56.7-ha, mostly agricultural, watershed located in southwestern North Carolina was monitored from August 1994 to January 1996. Total nitrogen and phosphorus export rates from the upper, predominantly pasture, part of the watershed were 18.0 and 1.4 kg/ha/yr, respectively, as measured by weekly grab sampling and 18.7 and 4.9 kg/ha/yr, respectively, as measured from storm event monitoring. Nitrogen and phosphorus export rates for the area between the monitoring sites, which included overgrazed cow holding and feeding areas and farm buildings, were 376 and 86 kg/ha/yr, respectively, for grab sampling and 351 and 160 kg/ha/yr, respectively, for storm event monitoring. To estimate the amount of reduction from nonpoint source controls necessary to effect a significant reduction in pollutant loading, statistical analyses of the load data were conducted. The analyses for the five pollutants monitored showed that total suspended solids would require the greatest reduction (34.6 percent for weekly grab and 33.6 percent for storm) in loading after the implementation of controls for statistical significance. Nitrate plus nitrite was found to require the least reduction (12.6 percent for weekly grab). Pollutant export rates computed from weekly grab samples and storm event samples used separately were compared to corresponding export rates computed from combining grab and storm event samples to assess the differences in monitoring schemes.

Abstract  Sources of organic pollution to Kingston Harbour were assessed by monthly sampling at 22 rivers, gullies and discharge pipes emptying into the harbor between August 1996 and July 1997. These sources were divided into point and non-point sources and coupled with underground water and industrial flow assessed from 1992 and 1996 data. Organic pollution signatures were coliform bacteria, total suspended solids (TSS), biochemical oxygen demand (BOD), nitrite + nitrate nitrogen and phosphate phosphorous. Sewage is by far the most important contributor of organic pollution to Kingston Harbour, regardless of the signature used. The continuity and concentrations at the outfall of the Greenwich and Western sewage treatment plants render these two areas as the most significant point sources of pollution to the harbor. River flow is the second largest point source of organic pollution to the harbor; the degree of its contribution depending on rainfall since only at high flow does it make major contributions. Poor watershed management, extensive agriculture inputs from few, but large industries, large and growing residential areas and the length of the river creates problems. When the rivers are at low flow, industries and groundwater become major non-point sources of different pollutants. During periods of high water flow the gullies are small, but significant non-point sources of most pollutants. Fifty-five to 70% of the contributions of total suspended solid (TSS) is associated with sewage, while 23-30% is associated with a range of industries. Under high flow conditions, < 20% of TSS is associated with the outflow from rivers and gullies, while under low flow conditions, rivers and gullies make no meaningful contribution. Of the contributions of biochemical oxygen demand (BOD), 29-50% is associated with sewage, while 24-40% with industries. Under high flow conditions, 40% of BOD is associated with river outflow, while under low flow conditions, rivers make no meaningful contribution. Of the contributions of nitrate nitrogen, 55-65% is associated with sewage, approximately 30% is associated with ground water and < 20% associated with flow from rivers and gullies under high flow conditions. River and gully outflow under low flow conditions make no meaningful contribution. Of the contributions of phosphate phosphorous, 75-90% is associated with sewage and < 20% associated with high flow conditions from river and gully outflow. At low flow, industries and ground water make no meaningful phosphate phosphorous contribution. Having identified, quantified and ranked the sources of organic pollution to Kingston Harbour, recommendations are suggested for the improvement of the water quality. Among these are a reduction and/or cessation of sewage discharges to the harbor coupled with the use of a predictive hydrodynamic three-dimensional model and an ongoing monitoring program.

Abstract  The Caernarvon structure, which came into operation in 1991, was the largest of 6 diversions which delivered freshwater from the Mississippi river to Breton sound. A survey of water quality in the sound commenced 3 years prior to operation of the Caernavon diversion and continued until 1994, with 2 additional field trips in 1996. Nitrate plus nitrite, total Kjeldahl nitrogen (TKN), ammonium, total phosphorus, total suspended solids and salinity were determined in samples taken at monthly intervals from 7 stations in Breton sound. A significant decrease in total nitrogen, TKN and salinity was the only immediate impact of the diversion. Reduction in salinity had been an early objective for the diversion. Nitrate plus nitrite was rapidly assimilated by the system and suspended sediments were rapidly trapped within a few kilometres of the diversion. Loading rates of nitrate-nitrite and total nitrogen were 5.6-13.4 g per m2.year and 8.9-23.4 g per m2.year, respectively, with removal efficiencies of 88-97 and 32-57 per cent, respectively. Total phosphorus had a loading rate of 0.9-2.0 g per m2.year with a removal efficiency of 0-46 per cent. These removal rates and the fact that dissolved oxygen remained high suggested that increased diversion flows from the Mississippi river could be used in an effort to increase nutrients and sediment transfer to the lower reaches of Breton sound. The need for such transfers was to increase vertical accretion and maintain marsh elevation above the relative sea level rise in the area. There are 57 references.

Abstract  Long-term changes and inter-annual variability in inorganic nutrient concentrations of the Skagerrak Coastal Water (North Sea off Arendal, Norway) were studied. The Jutland Coastal Water mass and the Kattegat Surface Water mass both contribute 75% and 25%, respectively, to the Skagerrak Coastal Water. Inorganic nutrient levels in Jutland Coastal water have been increasing since the 1980s, with nitrate levels and the nitrogen:phosphorus ratio nearly doubling. Most of this increase is caused by contributions from German Bight Water-a parent water of Jutland Coastal Water. Large inter-annual variability in nitrates is due partly to river runoff. Phosphates and silicates are less variable, and probably are not as heavily influenced by river runoff as nitrates are.

Abstract  The aim of this study was to investigate the effects of one kind of food industry effluent, cassava stillage and its anaerobic fermentation liquid, on biological nutrient removal (BNR) from municipal wastewater in anaerobic-anoxic-aerobic sequencing batch reactors (SBRs). Experiments were carried out with cassava stillage supernatant and its anaerobic fermentation liquid, and one pure compound (sodium acetate) served as an external carbon source. Cyclic studies indicated that the cassava by-products not only affected the transformation of nitrogen, phosphorus, poly-β-hydroxyalkanoates (PHAs), and glycogen in the BNR process, but also resulted in higher removal efficiencies for phosphorus and nitrogen compared with sodium acetate. Furthermore, assays for phosphorus accumulating organisms (PAOs) and denitrifying phosphorus accumulating organisms (DPAOs) demonstrated that the proportion of DPAOs to PAOs reached 62.6% (Day 86) and 61.8% (Day 65) when using cassava stillage and its anaerobic fermentation liquid, respectively, as the external carbon source. In addition, the nitrate utilization rates (NURs) of the cassava by-products were in the range of 5.49-5.99 g N/(kg MLVSS⋅h) (MLVSS is mixed liquor volatile suspended solids) and 6.63-6.81 g N/(kg MLVSS⋅h), respectively. The improvement in BNR performance and the reduction in the amount of cassava stillage to be treated in-situ make cassava stillage and its anaerobic fermentation liquid attractive alternatives to sodium acetate as external carbon sources for BNR processes.

Abstract  Bioaugmentation was used to upgrade the nitrification process in a full-scale municipal WWTP with an A2/O system. A mixture of nitrifying bacteria was inoculated into the bioreactor for a final concentration of 1% (v/v). The upgrade process took 25 days, and the NH4+-N removals reached 94.6% (increased at least by 75%). The effluent concentrations of COD and NH4+-N stabilized at <30 mg/L and <4 mg/L even when the corresponding influent concentrations were over 300 mg/L and 60 mg/L, which met the first-class requirement of the National Municipal Wastewater Discharge Standards of China (COD ≤ 50 mg/L, NH4+-N ≤ 5 mg/L). The succession of the microbial community showed the enhanced NH4+-N removal efficiency mainly resulted from the persistence of introduced ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), which increased from 0% to 0.4% and from 0.01% to 2.1%, respectively. This bioaugmentation was shown as an effective technology for upgrading or retrofitting conventional systems to tertiary-level.

Abstract  RATIONALE: The isotopic tracer technique is widely used to identify the sources and fate of nitrogen (N) in order to understand the N cycle and contamination in water environments. The stable isotope ratio of ammonium is expected to greatly enhance the tracing analysis by combining it with the traditional nitrate isotope ratio. Diffusion followed by gas-phase trapping is the most commonly applied method for ammonium isotope ratio measurement. Although dissolved organic nitrogen (DON) is abundant in natural water and its breakdown in the diffusion procedure has been reported, the interference of DON with the measurement of ammonium isotope ratios has not been fully examined.

METHODS: This study aims to test the effect of DON contamination by using organic N compounds, viz. humic acid and alanine. A series of diffusion experiments was conducted at a temperature of 80°C for a maximum of 7 days. Ammonia was transferred from alkaline solution and trapped with an acidic filter. This method was applied for samples with ammonium concentrations between 0.5 and 2.0 mg-N/L.

RESULTS: There was no difference between the ammonium N stable isotope ratios for samples with and without added DON compounds; the fractionation between the observed value and the actual value was negligible, in the range of 0.2 to 1.0‰. The modifications of previous studies, i.e. shorter diffusion period, no vigorous shaking and using gas-phase trapping, successfully avoided any breakdown of DON in fresh water samples.

CONCLUSIONS: The modified method provides high precision and accuracy and it is recommended for the analysis of anthropogenically influenced water samples, such as paddy fields, ground water, rivers and lakes.

Abstract  Although Nitrobacter winogradskyi is an important chemoorganotrophic organism for the study of nitrite-oxidizing bacteria physiology as well as nitrification, until now, the mixotrophic medium for this organism growth has not been optimized, comprehensively. In this study, we aimed to improve the growth medium of N. winogradskyi using the one-factor-at-a-time (NaNO2 , glycerol, pH) method. In addition, a further experimental design was carried out based on central composite design with response surface methodology. Different combinations of the three cultural parameters were fitted by multiple regression analysis to calculate the predicted response. Our results suggest that optimal culture condition for the growth of N. winogradskyi was a modified DSMZ 756a medium containing NaNO2 (5·74 g l-1 ) and glycerol (37·88 mmol l-1 ), pH 7·83, a temperature of 28°C and agitation at 120 rev min-1 . The results from a validation experiment (bacterial growth: OD600 1·0293) were close to the value predicted by the quadratic model (OD600 1·0994). In addition, we uncovered the potential mechanism at the cellular and ultrastructural levels. The results indicated that glycerol in the media enhanced the rate of cell division and cell growth by increasing the accumulation of polyphosphates and phosphorus, and high concentrations of NaNO2 provided sufficient energy for growth and contributed to the generation of carboxysomes in cells for CO2 fixation.

SIGNIFICANCE AND IMPACT OF THE STUDY: Due to the extremely slow growth rate and the low growth yield of ammonia-oxidizing bacteria and NOB (nitrite-oxidizing bacteria), nitrification is still the rate-limiting step of nitrogen cycle in the current research. Nitrobacter winogradskyi, an important NOB, participates in the second step of nitrification in water and soil. This study reported an optimized culture condition for N. winogradskyi, which increased the growth yield by 5·06 times than that in the basal medium and uncovered the potential mechanism. We expect our study will contribute to the research on water and soil nitrogen cycle. In addition, the optimized culture conditions have the potential to be suitable for the chemoorganotrophic growth of other nitrifiers.

Abstract  Poly-γ-glutamic acid (γ-PGA) is an important multifunctional biopolymer with various applications, for which adenosine triphosphate (ATP) supply plays a vital role in biosynthesis. In this study, the enhancement of γ-PGA production was attempted through various approaches of improving ATP supply in the engineered strains of Bacillus licheniformis. The first approach is to engineer respiration chain branches of B. licheniformis, elimination of cytochrome bd oxidase branch reduced the maintenance coefficient, leading to a 19.27% increase of γ-PGA yield. The second approach is to introduce Vitreoscilla hemoglobin (VHB) into recombinant B. licheniformis, led to a 13.32% increase of γ-PGA yield. In the third approach, the genes purB and adK in ATP-biosynthetic pathway were respectively overexpressed, with the AdK overexpressed strain increased γ-PGA yield by 14.69%. Our study also confirmed that the respiratory nitrate reductase, NarGHIJ, is responsible for the conversion of nitrate to nitrite, and assimilatory nitrate reductase NasBC is for conversion of nitrite to ammonia. Both NarGHIJ and NasBC were positively regulated by the two-component system ResD-ResE, and overexpression of NarG, NasC, and ResD also improved the ATP supply and the consequent γ-PGA yield. Based on the above individual methods, a method of combining the deletion of cydBC gene and overexpression of genes vgB, adK, and resD were used to enhance ATP content of the cells to 3.53 μmol/g of DCW, the mutant WX-BCVAR with this enhancement produced 43.81 g/L of γ-PGA, a 38.64% improvement compared to wild-type strain WX-02. Collectively, our results demonstrate that improving ATP content in B. licheniformis is an efficient strategy to improve γ-PGA production.

Abstract  The mature landfill leachate containing high ammonia concentration (>1000 mg/L) is a serious threat to environment; however, the low COD to TN ratio (C/N, <3) strongly inhibits the denitrification process and poses a severe obstacle for efficient treatment. Herein, two kinds of acidogenic liquids, fermented from oil-removed food waste and oil-added food waste, were first applied as external carbon sources for the biological nitrogen removal from mature landfill leachate in an aerobic/anoxic membrane bioreactor. "Acidogenic liquid b" served quite better than commercial sodium acetate, considering the higher denitrification efficiency and the slightly rapider denitrification rate. The effect of C/N and temperature were investigated under hydraulic retention time (HRT) of 7 d, which showed that C/N ≥ 7 (25 °C) was enough to meet the general discharge standards of NH4+-N, TN and COD in China. Even for some special areas of China, the more stringent discharge standards (NH4+-N ≤ 8 mg/L, TN ≤ 20 mg/L) could also be achieved under longer HRT of 14 d and C/N ≥ 6. Notably, the COD concentration in effluent could also be well reduced to 50-55 mg/L, without further physical-chemical treatment. This proposed strategy, involving the high-value utilization of food waste, is thus promising for efficient nitrogen removal from mature landfill leachate.

Abstract  Nitrification plays a crucial role in global nitrogen cycling and treatment processes. However, the relationships between the nitrifier guilds of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) are still poorly understood, especially in freshwater habitats. This study examined the physiological interactions between the AOB and NOB present in a freshwater aquarium biofilter by culturing them, either together or separately, in a synthetic medium. Metagenomic and 16S rRNA gene sequencing revealed the presence and the draft genomes of Nitrosomonas-like AOB as well as Nitrobacter-like NOB in the cultures, including the first draft genome of Nitrobacter vulgaris. The nitrifiers exhibited different growth rates with different ammonium (NH4+) or nitrite concentrations (50-1,500 μM) and the growth rates were elevated under a high bicarbonate (HCO3-) concentration. The half-saturation constant (Ks for NH4+), the maximum growth rate (μmax), and the lag duration indicated a strong dependence on the synergistic relationships between the two guilds. Overall, the ecophysiological and metagenomic results in this study provided insights into the phylogeny of the key nitrifying players in a freshwater biofilter and showed that interactions between the two nitrifying guilds in a microbial community enhanced nitrification.

Abstract  Two lab-scale nitrifying sequencing batch biofilm reactors, with (SBBR_CN) or without the addition of organics (SBBR_N), were operated to investigate potential roles of acyl homoserine lactone (AHL) based quorum sensing. AHLs of N-[(RS)-3-Hydroxybutyryl]-L-homoserine lactone, N-hexanoyl-L-homoserine lactone (C6-HSL) and N-octanoyl-L-homoserine lactone (C8-HSL) were detected in both reactors. C6-HSL and C8-HSL were also detected in batch experiments, especially with stimulated nitrite oxidizing bacteria activities. Quorum sensing affected biofilm formation mainly through the regulation of extracellular protein production. By the metagenomics analysis, many identified genera and species could participate in quorum sensing, quorum quenching and extracellular polymeric substances (EPS) production. A high quorum quenching activity was obtained in SBBR_CN, whereas a high quorum sensing activity in SBBR_N. Nitrosomonas-like ammonia oxidizing bacteria, Nitrospira-like nitrite oxidizing bacteria and Comammox harbored genes for AHL synthesis and EPS production. Possible relationships among AHLs synthesis, biofilm formation and nitrifiers activity were proposed.

Abstract  Plant sterols are important multifunctional lipids, which are involved in determining membrane properties. Sterol C24 methyltransferase2 (SMT2) governs the pattern of phytosterols synthesized in higher plants. In this study, the spinach sterol C24 methyltransferase2 (SoSMT2) cDNA was cloned by RT-PCR and RACE-PCR. The full length of SoSMT2 consists of 1614 bp, including a 278 bp 5'-untranslated region (UTR), a 1086 bp open reading frame (ORF), and a 250 bp 3'-UTR. The SoSMT2 gene encodes a polypeptide of 361 amino acid residues with a predicted molecular mass of 40.47 kDa. RT-PCR analysis indicated that the expression of SoSMT2 was induced by excess nitrate in the root and shoot of spinach. The transcript level of SoSMT2 was decreased by NaCl treatment. In contrast, dehydration, and H2O2 treatment increased the transcript levels of SoSMT2. To examine the biological roles of SoSMT2 in stress responses, transgenic Arabidopsis plants that constitutively overexpress SoSMT2 under the control of cauliflower mosaic virus 35S promoter were generated. The germination rate of transgenic seeds was higher than wild type (WT) in MS medium supplemented with 160 mM nitrate. When seedlings were transferred to MS liquid medium with 160 mM nitrate for 0, 8, 24 and 48 h, the transgenic plants showed lower levels of MDA and H2O2 contents, compared with WT plants. Additionally, transgenic plants had relatively higher SOD, CAT and POD activities and soluble sugar contents than WT plants under nitrate stress with the increasing of treatment time. These data suggest that SoSMT2 is involved in nitrate tolerance in spinach. (C) 2015 Elsevier B.V. All rights reserved.

Abstract  Soil analysis for small farms in developing countries is often inconvenient and prohibitively expensive, yet the information gained from these soil tests could result in significant benefits. Based on tests done on a limited range of soils, the pressurized hot water (PHW) extraction coupled with colorimetric or turbidimetric analysis is a promising alternative. Before this extraction and analysis can be used in developing countries, testing is needed across the range of soils found in these countries. At Brigham Young University (BYU), 228 soils from Guatemala and Morocco were analyzed for NO3-N, phosphorus (P), and potassium (K) using standard methods (water-CTA, Olsen-molybdic acid and ammonium acetate atomic- absorption, respectively). Results were correlated to values obtained from the PHW extraction coupled with colorimetric or turbidimetric analytical procedures. The relationships between these tests were good (r(2) values of 0.96, 0.71, and 0.52 for NO3-N, P, and K, respectively). In an additional study comparing several P extraction methods for Guatemala soils, relationships between PHW-extractable P and Olsen-, Bray I-, and Mehlich I-extractable P (r(2) values of 0.75, 0.67, and 0.46, respectively) suggest that PHW is a promising P-extraction procedure for use in Guatemala. Overall, PHW extraction and accompanying analyses are a less expensive alternative to current soil nutrient extraction and analysis procedures for the soils of Morocco and Guatemala.

Abstract  The influence of different fertilizer forms and rates on nitrogen, phosphorus and potassium contents, nitrate accumulation and yield in red head chicory (Cichorium intybus var.foliosum L.) was investigated. Field fertilization trials were set up at two localities in Northwest Croatia in 1999 and 2000. Trials were laid out according to the Latin square scheme in five fertilization treatments: manure 5 kg/m(2), three rates of complex mineral fertilizer NPK (5:20:30) - 50, 100 and 150 g/m(2), and an unfertilized control variant. The results of investigations indicate that there were no significant differences between treatments in the plant nitrogen and phosphorus contents. Significant fluctuations of the chicory potassium content (3.27-4.75% K) depending on the fertilization variant were recorded only in 1999 while in 2000 all values (4.13-5.12% K) were uniform. Plant nitrate levels were influenced by weather conditions more significantly than by the form and rates of fertilizers. All the recorded values are within the limits tolerated for leafy vegetables. Comparing the trial years, yields were generally higher in 1999 (1.58-4.95 kg/m(2)) than in 2000 (0.40-2.70 kg/m(2)). No significant differences in yield were recorded between the application of stable manure and the lowest mineral fertilizer rate.

Abstract  Reducing nitrate loads from corn and soybean, tile-drained, agricultural production systems in the Upper Mississippi River basin is a major challenge that has not been met. We evaluated a range of possible management practices from biophysical and social science perspectives that could reduce nitrate losses from tile-drained fields in the Upper Salt Fork and Embarras River watersheds of east-central Illinois. Long-term water quality monitoring on these watersheds showed that nitrate losses averaged 30.6 and 23.0 kg nitrate N ha yr (Embarras and Upper Salt Fork watersheds, respectively), with maximum nitrate concentrations between 14 and 18 mg N L. With a series of on-farm studies, we conducted tile monitoring to evaluate several possible nitrate reduction conservation practices. Fertilizer timing and cover crops reduced nitrate losses (30% reduction in a year with large nitrate losses), whereas drainage water management on one tile system demonstrated the problems with possible retrofit designs (water flowed laterally from the drainage water management tile to the free drainage system nearby). Tile woodchip bioreactors had good nitrate removal in 2012 (80% nitrate reduction), and wetlands had previously been shown to remove nitrate (45% reductions) in the Embarras watershed. Interviews and surveys indicated strong environmental concern and stewardship ethics among landowners and farmers, but the many financial and operational constraints that they operate under limited their willingness to adopt conservation practices that targeted nitrate reduction. Under the policy and production systems currently in place, large-scale reductions in nitrate losses from watersheds such as these in east-central Illinois will be difficult.