Factors affecting water colour removal by tyrosinase

Tyrosinase obtained from Agaricus bisporus was used to catalyze the decolourization of two reactive dyes: reactive yellow 15 (RY15) and reactive blue 114 (RB114). A 3³ factorial design was used to evaluate the effects of enzyme concentration, pH of the reaction medium and temperature on the decolourization yield. From fitted mathematical models, response surfaces were determined and the best decolourization conditions obtained were 25?°C, enzyme concentration of 200?U/L and pH 7.0. At these conditions, a maximum decolourization of 36 and 20% for RY15 and RB114, respectively, was obtained. In order to improve decolourization, aeration of the media, enzyme type (crude or lyophilized) and additives (CaCl₂ or CaCO₃) were evaluated. The lyophilized enzyme without any protective compound presented a better performance. The aeration was a very important factor confirming that oxygen was limiting the reaction. The aeration of the medium with lyophilized tyrosinase improves the dye decolourization to more than 90%.     

Supplementing Bacillus sp. RS1 with Dechloromonas sp. HZ for enhancing selenate reduction in agricultural drainage water

Cost and efficiency are two important factors considered in the remediation of Se-contaminated agricultural drainage water through bacterial reduction of soluble Se(VI) to insoluble Se(0). Bacillus sp. RS1 isolated from rice straw was assessed for its ability to use inexpensive molasses to reduce Se(VI) in agricultural drainage water containing NO3- levels of 0, 50, 100, 250, and 500 mg/L. The results showed that Se(VI) (1000 microg/L) was almost entirely reduced to Se(IV) (62.7%) and Se(0) (36.4%) by Bacillus sp. RS1 in synthetic agricultural drainage (SAD) water without the presence of NO3-. The reduction Se(VI) to Se(0) was limited in the SAD water with NO3- levels of 100, 250, and 500 mg/L. The addition of Dechloromonas sp., a NO3- reducer, to the SAD water not only increased NO3- removal, but also enhanced Se(VI) reduction by Bacillus sp. RS1. During an 8-day experiment, 98-99% of the added Se(VI) was reduced to Se(0) with small amounts of Se(IV) and Se(-II) in the SAD water containing 100 and 250 mg/L NO3-. The addition of Dechloromonas sp. HZ to the natural agricultural drainage water also significantly increased the reduction of Se(VI) (748 microg/L) by Bacillus sp. RS1, with a production of Se(0) (65%) and Se(-II) (32%). These results suggest that a combination of Bacillus sp. RS1 with Dechloromonas sp. HZ has great potential with the use of inexpensive molasses to remediate Se-contaminated agricultural drainage water containing relatively high NO3- levels.     

Effect of zero-valent iron and a redox mediator on removal of selenium in agricultural drainage water

Effective and economical removal of selenium (Se) in agricultural drainage water is very important in Se bioremediation. Zero-valent iron (ZVI) and a redox mediator [anthraquinone-2,6-disulfonate (AQDS)] were assessed for their ability to enhance the removal of Se(VI) or Se(IV) (500 µg/L) in synthetic drainage water by Enterobacter taylorae. The results showed that E. taylorae was capable of using inexpensive sucrose to remove Se from the drainage water. During a 7-day experiment, Se(VI) was almost entirely reduced to Se(0) and transformed to organic Se in the drainage water with sucrose levels of 500 to 1000 mg/L. Addition of ZVI to the drainage water increased the removal of total soluble Se to 94.5-96.5% and limited the production of organic Se. Addition of AQDS to the drainage water with or without ZVI decreased Se(VI) removal, but enhanced the removal of Se(IV), suggesting that E. taylorae only can use anthrahydroquinone-2,6-disulfonate (AHQDS, a reduced form of AQDS) to respire Se(IV), and not Se(VI). These results show that ZVI has promising application potential in the bioremediation of Se in Se-contaminated water.     

Factors affecting the export of nitrate-nitrogen from drainage basins in southern Ontario

The export of nitrate-N from 21 watersheds near Toronto, Ontario was measured over a 25-month period. The annual average loss ranges from 1.41 to 7.31 kg ha⁻¹. Analysis of these data indicated a very significant correlation between nitrate exports and percentage of each watershed in crops and abandoned agricultural land. A number of soil and topographic variables also had significant correlations with stream nitrate levels. The causal relationships underlying these simple correlations are difficult to evaluate because of considerable multicollinearity between land use and watershed physiography. The separate analysis of stream discharge indicated that agricultural watersheds have lower mean annual discharges (1 s⁻¹ km⁻²) than those watersheds containing extensive areas of forest and abandoned agricultural land. Variations in annual discharge therefore tended to reduce the contrast in nitrate exports between agricultural and non-agricultural watersheds. The influence of watershed characteristics on nitrate levels exhibited considerable seasonal contrasts. During summer low flow conditions nitrate concentration and loss were not correlated with watershed land use, and instead were affected primarily by localised pollution sources and by biological processes within the streams.     

Managing selenium-contaminated agricultural drainage water by the integrated on-farm drainage management system: role of selenium volatilization

The Integrated on-Farm Drainage Management (IFDM) system was designed to dispose of selenium (Se)-contaminated agricultural irrigation drainage water through the sequential reuse of saline drainage water to grow crops having different salt tolerance. This study quantified the extent of biological volatilization in Se removal from the IFDM system located in the western San Joaquin Valley, California. Selenium volatilization from selected treatment areas, including pickleweed (Salicornia bigelovii Torr.), saltgrass (Distichlis spicata L.), bare soil, and the solar evaporator, was monitored biweekly using an open-flow sampling chamber system during the pickleweed growing season from February to September 1997, and monthly from September 1997 to January 1998. Biological volatilization from the pickleweed section removed 62.0 +/- 3.6 mg Se m(-2) y(-1) to the atmosphere, which was 5.5-fold greater than the Se accumulated in pickleweed tissues (i.e., phytoextraction). The total Se removed by volatilization from the bare soil, saltgrass, and the solar evaporator was 16.7 +/- 1.1, 4.8 +/- 0.3, and 4.3 +/- 0.9mg Se m(-2) y(-1), respectively. Selenium removal by volatilization accounted for 6.5% of the annual total Se input (957.7mg Sem(-2) y(-1)) in the pickleweed field, and about 1% of the total Se input (432.7 mg Se m(-2) y(-1)) in the solar evaporator. We concluded that Se volatilization under naturally occurring field conditions represented a relatively minor, but environmentally important pathway of Se removal from the IFDM system.     

Factors affecting selectivity during dissolved organic matter removal by anion-exchange resins

Anion-exchange processes have received increased attention in recent years as efficient alternatives for removing disinfection byproduct precursors. In this research the preferential uptake of different dissolved organic matter (DOM) components, and hence the resulting reactivity after treatment, is shown to depend on the initial molecular weight (MW) distribution and the sulfate concentration. MW distribution is important because size-exclusion phenomena can occur in ion-exchange sorption, leading to the preferential uptake of low (ca. 1000 Da) MW species. Sulfate competition can reverse resin preference for low-MW species. DOM components that compete best with sulfate combine ionogenic group affinity and entropy-assisted adsorption. Entropy-assisted sorption, whereby sorption is promoted by the entropy gained from the desolvation of hydrophobic DOM moieties, is shown to be significant for two surface water sources. Entropic contributions are most significant when resin dosages are low and competition between DOM components and between DOM and sulfate are high. DOM components having MW near 1 kDa are sufficiently large to have significant hydrophobic moieties to promote entropy-assisted sorption and sufficiently small to enable access to exchange sites. Total uptake and preferential removal of specific UV absorbance (SUVA), an indicator of DOM reactivity, will thus depend on the initial MW distribution, how SUVA depends on MW, and the sulfate concentration.     

The occurrence and removal of nitrogen in subsurface agricultural drainage from the San Joaquin Valley, California

During the years 1967–1973 there have been extensive studies of subsurface agricultural drainage in the San Joaquin Valley of California. These studies, by cooperating state and federal agencies, were to determine the composition and quantity of drainage waters produced from irrigated agriculture, to evaluate possible methods of removing problem constituents (mainly nitrogen) from these waters, and to obtain an idea of the effectiveness of the treatment methods studied for reducing the waters biostimulatory content with respect to potential receiving waters. The results of the studies indicated that on an annual average, the drainage waters will probably contain about 20 mg NO₃-N I⁻¹ even after 50 years of leaching and that most of the nitrogen is derived from native soil nitrogen. Treatment studies demonstrated that the nitrogen could be reduced from 20 to 3–5 mg N I⁻¹ by any one of several biological treatment processes including bacterial denitrification (filter and pond), algae growth and harvesting, and by a combination plant growth—bacterial denitrification (“symbiotic”) process. Cost estimates for the processes studied ranged from $10 to $36 1000⁻¹ m³ (1969 dollars). Laboratory algal assays demonstrated that the nitrogen removal systems studied effectively reduced the drainage waters biostimulatory content.     

Factors affecting the extraction of polar environmental constituents from water

Factors affecting the extraction of polar environmental constituents from water have been investigated using polar weathering products from Ekofisk crude oil as test substances. Such factors include pH, choice of solvent and chemical nature of the polar constituents.Continuous extraction using ethyl acetate resulted in good reproducibility and showed a high efficiency compared to the more direct methods using a separatory funnel.     

Factors affecting the extraction and analysis of polynuclear aromatic hydrocarbons in water

Factors expected to affect the efficiency of extraction of Polynuclear Aromatic Hydrocarbons (P.A.H.) from environmental water samples have been systematically investigated. Such factors include the initial concentration of P.A.H., the presence of suspended solids and prolonged storage of the sample prior to analysis. Extraction efficiencies between 30 and 85% have been found and these data make possible more accurate measurements of levels of P.A.H. in water. Analyses of environmental water samples have been performed using both Thin layer chromatography (TLC) and Gas-liquid chromatography (GLC). Accuracy of analysis was assessed by addition of P.A.H. to environmental water samples before extraction. Thin layer chromatography was found to be the better procedure for the compounds analysed, and avoided the need for purification of the solvent extract prior to analysis.     

Simultaneous removal of nitrate and arsenic from drinking water sources utilizing a fixed-bed bioreactor system

A novel bioreactor system, consisting of two biologically active carbon (BAC) reactors in series, was developed for the simultaneous removal of nitrate and arsenic from a synthetic groundwater supplemented with acetic acid. A mixed biofilm microbial community that developed on the BAC was capable of utilizing dissolved oxygen, nitrate, arsenate, and sulfate as the electron acceptors. Nitrate was removed from a concentration of approximately 50 mg/L in the influent to below the detection limit of 0.2 mg/L. Biologically generated sulfides resulted in the precipitation of the iron sulfides mackinawite and greigite, which concomitantly removed arsenic from an influent concentration of approximately 200 ug/L to below 20 ug/L through arsenic sulfide precipitation and surface precipitation on iron sulfides. This study showed for the first time that arsenic and nitrate can be simultaneously removed from drinking water sources utilizing a bioreactor system.     

Factors affecting pH change in alkaline waste water treatment—I

The pH of wastewater in various stages of its purification depends mainly upon the equilibria of carbonic acid. Thus relations between pH and the concentrations of carbon dioxide, bicarbonate and carbonate can be formulated. Corrections for the non-ideal character of the sewage are necessary.

With some restrictions the concept of alkalinity can be used for these pH relations.

Several (bio)chemical and physical processes occurring in biological purification affect the concentrations of carbon dioxide and (bi)carbonate.

Processes studied are carbon dioxide desorption, oxidation of organic matter and nitrification.

Models are proposed for the calculation of the effluent pH and the values so obtained are compared with the available experimental results.     

Factors affecting bulk to total bacteria ratio in drinking water distribution systems

Bacteria in drinking water systems can grow in bulk water and as biofilms attached to pipe walls, both causing regrowth problems in the distribution system. While studies have focused on evaluating the factors influencing the bacteria in bulk water and in biofilms separately, there is a need for understanding biofilm characteristics relative to the bulk water phase. The current study evaluated the effects of chlorine and residence time on the presence of culturable bacteria in biofilms relative to that in bulk water. The results showed that when no chlorine residual was present in the system, the median ratio of bulk to total bacteria was 0.81, indicating that 81% of the bacteria were present in bulk water, whereas only 19% were present in the biofilm. As chlorine concentration increased to 0.2, 0.5, and 0.7 mg/L, the median percentage of bacteria present in bulk water decreased to 37, 28, and 31, respectively. On the other hand, as the residence times increased to 8.2, 12, 24, and 48h, the median percentage of bacteria present in bulk water increased to 7, 37, 58, and 88, respectively, in the presence of a 0.2mg/L chlorine residual. The common notion that biofilms dominate the distribution system is not true under all conditions. These findings suggest that bulk water bacteria may dominate in portions of a distribution system that have a low chlorine residual.     

Factors affecting the adsorption of polio virus to magnetite in water and wastewater

The process of magnetic filtration involves the use of magnetite for the removal of various pollutants from water and wastewater. A study was undertaken to investigate the interaction between magnetite and polio virus. It was found that the adsorption process was enhanced by the presence of cations, conformed to the Freundlich isotherm, and did not vary significantly when the pH was varied from 5 to 9. The influence of two wastewater effluents on the adsorption process was also studied and their interference with the adsorption of polio virus to magnetite is discussed.     

Assessment of in-stream phosphorus dynamics in agricultural drainage ditches

The intensive agricultural systems in the Midwestern United States can enrich surface waters with nutrients. Agricultural drainage ditches serve as the first and second order streams throughout much of this region, as well as other highly productive agricultural areas in humid regions throughout the world. This project was conducted to evaluate in-stream processing of soluble P (SP) in agricultural drainage ditches. Soluble P injection studies were conducted at seven sites along three drainage ditches (298 to 4300 ha drainage area), and one site on a third-order stream that receives the discharge from the agricultural ditches (19,000 ha drainage area) by increasing the SP concentration in the ditch water by approximately 0.25 mg L^− 1. Sediments collected from smaller watersheds contained greater amounts of Mehlich 3 and exchangeable P (ExP), silt and clay size particles, and organic matter. Phosphorus uptake lengths (S_net) ranged from 40 to 1900 m, and SP uptake rates (U) ranged from 0.4 to 52 mg m^− 2 h^− 1. Phosphorus S_net was correlated with ditch geomorphological (i.e. width) and sediment properties (i.e. organic matter, ExP, and equilibrium P concentration; r² = 1.00, P < 0.001), indirect drainage in the watershed (r² = 0.92, P < 0.001), and the amount of small grains, forest, urban area, alfalfa and corn (r² = 1.00, P < 0.0001). Agricultural drainage ditches actively process nutrients and could potentially be managed to optimize this processing to minimize SP export from these landscapes.     

Kinetic study for phosphate removal from water by recycled date-palm wastes as agricultural by-products

The presence of excessive amounts of nutrients including phosphates in water is undesirable. They cause the deterioration of water quality and problems in many natural and engineering systems. The recycling of agricultural waste materials as biosorbents for contaminants removal provides a cheap and ecological means to reduce wastes. This study explored the use of date palm wastes for the effective removal of phosphate from aqueous solutions. Granular date stones (GDS) and palm surface fibres (PSF) as raw abundant waste materials were examined for PO₄ ^-3 removal from aqueous solution. The experimental work was performed in a batch mode to investigate the influence of initial phosphate concentration, contact time, and pH of solution on phosphate biosorption. The FT-IR spectra for the waste materials display many adsorption peaks, confirming the complex nature of the GDS and PSF. Phosphate percentage removal up to 87 and 85% were obtained at initial PO₄ ^-3 concentration of 50 mg as P/L using GDS and PSF, respectively. Due to their low cost and high capability, these types of waste can be used for cost-effective removal of phosphate from wastewater.     

纸面稻草(麦秸)/石膏复合板的应用性能研究

纸面稻草(麦秸)/石膏复合板(SGB)与纸面石膏板(PGB)相比,在物理力学方面,纸面稻草(麦秸)/石膏复合板的静曲强度、弹性模量大于纸面石膏板,只有内结合强度小于纸面石膏板;在应用性能上,除在腻子附着力小于纸面石膏板外,纸面稻草(麦秸)/石膏复合板的握螺钉力、乳白胶胶合性能、硬度、均布载荷均高于纸面石膏板。在总体性能上,纸面稻草(麦秸)/石膏复合板优于纸面石膏板,替代市场上工业化生产的纸面石膏板是可行的。     

Factors affecting phosphate adsorption to aluminum in lake water: implications for lake restoration

Treatment of lake inlets or lake sediments with aluminum (Al) is being increasingly used for lake restoration but only few studies exist concerning competitive substances that might influence phosphate (PO(4)(3-)) removal from lake water. Therefore, chemical interferences of several ions (magnesium, silicate, chloride and humic acid) on PO(4)(3-) adsorption to Al(OH)(3) were studied. Interference of each ion was studied in artificial lake water, and the complex interactions occurring in natural water were studied in water from 30 Danish lakes at pH 7 in both cases. In the artificial lake water Al:P ratio was high as sediment P-pools were the targets while in the natural lake water Al addition was generally lower as only P present in the water was targeted (i.e. inlet water). The single-ion experiments evidenced that silicate (>200 microM) and humic acids significantly decreased the effectiveness of PO(4)(3-) adsorption to Al(OH)(3) by 10-13% at 450 microM Si and 17% at 1 mM C, respectively. NaCl did not influence adsorption of PO(4)(3-) to Al(OH)(3), however, PO(4)(3-) removal was slightly reduced in seawater, mainly due to the presence of Mg(2+). The studies on interferences in natural lake water showed that as long as the PO(4)(3-) concentration was low (<5 microM), silicate competed with PO(4)(3-) for adsorption sites on Al(OH)(3) but at higher PO(4)(3-) concentrations, color and DOC (as indicators of HA) were the main variables decreasing PO(4)(3-) removal from lake water. Inhibition of PO(4)(3-) precipitation in natural lake water appeared complex and did not allow for a simple calculation of Al dose from the concentration of potentially competitive ions. Recommendation for lake management is therefore still that precipitation assays should be carried out for any type of inlet or lake water prior to Al application.     

Influence of pH,salinity, and selenium on the growth of Aeromonas veronii in evaporation agricultural drainage water

Aeromonas veronii was isolated from seleniferous agricultural drainage water and characterized in terms of growth kinetics under changing environmental parameters [i.e. pH, selenium (Se) and salinity (electrical conductivity, EC)] that simulated evaporation. Aeromonas veronii metabolized peptone and was active in volatilizing Se, principally as dimethyl selenide (DMSe). Other volatile products produced included dimethyl disulfide, methyl selenol, dimethyl selenosulfide and dimethyl diselenide. The rate of Se volatilization correlated with the growth of A. veronii, with the highest levels of DMSe released during the exponential phase of growth. The C assimilated was primarily respired as CO₂ or incorporated into cell biomass with a small fraction used in the alkylation of Se. The maximum growth rate (μ_max) for A. veronii was 0.23 h⁻¹ at pH 7.94, 10 μg Se 1⁻¹, and EC of 3.9 dS m⁻¹ and decreased to 0.06 h⁻¹ with increasing salt content (40.2 dS m⁻¹), pH (8.53) and Se (500 μg l⁻¹). Salinity appeared to be the dominant inhibitory factor as observed by a decrease in growth rate and mass of cells. The range in salt content that was most inhibitory to the growth rate of A. veronii was from EC 11.7 to 40.2 dS m⁻¹. As drainage waters evaporate in holding facilities, salinity tends to increase having serious ecological effects on the growth of A. veronii.     

Five year water and nitrogen balance for a constructed surface flow wetland treating agricultural drainage waters

The performance of a constructed surface flow wetland in reducing diffuse N pollution coming from croplands is being investigated in an ongoing experiment, begun in 1998 in NE Italy. The 0.32 ha wetland is vegetated with Phragmites australis (Cav.) Trin. and Typha latifolia (L.). It receives drainage water from 6 ha of land managed for an experiment on drainage systems, where maize, sugarbeet, winter wheat and soybean are cultivated. During the period 1998-2002, the wetland received from 4698 to 8412 mm of water per year (on average, about 9 times the environmental rainfall); its water regimen was discontinuous and flooding occurred on a variable number of days per year (from 13 to 126). Nitric nitrogen was the most important form of element load. Its concentration in the inflow water over time was rather discontinuous, with median values ranging from 0.2 (in 2001) to 4.5 (in 2000) mg L(-1). Inflow nitric N concentrations were occasionally in the 5-15 mg L(-1) range. Concentrations reduced passing through the wetland, with a more evident effect in the last year. Over 5 years, the wetland received slightly more than 2000 kg ha(-1) of nitrogen, 87% in nitric form mostly from farmland drainage. The remaining 13% of N was applied as organic slurry directly onto the wetland, with 5 distributions during 1998 to assess wetland performance in treating occasional organic loads. Field drainage loads had a discontinuous time pattern and occurred mostly during autumn-winter, with the exception of the 2001-2002 season which was a very dry. The wetland discharged 206 kg ha(-1) of N, over the 5-year period, with an apparent removal efficiency of about 90%. The disappearance was mostly due to plant uptake (1110 kg ha(-1)) and soil accumulation (570 kg ha(-1)), with the contribution of denitrification being estimated at around 7%.