Mirs Bay is a semi-enclosed bay neighboring the Zhujiang(Pearl)River estuary,one of the largest estuarine systems in the world.The long-term historical observational data(1994-2017)of temperature,salinity,dissolved ox...Mirs Bay is a semi-enclosed bay neighboring the Zhujiang(Pearl)River estuary,one of the largest estuarine systems in the world.The long-term historical observational data(1994-2017)of temperature,salinity,dissolved oxygen(DO),and biochemical parameters were used to examine the spatiotemporal distribution of hypoxia in Mirs Bay and adjacent coastal waters.Results show that bottom hypoxia varied seasonally and interannually.Hypoxia mainly occurred from June to September in Mirs Bay and the transition zone in the southern waters of Hong Kong,and the recorded hypoxia events have increased from 2007.The density difference between the bottom and surface layers was positively related to the bottom apparent oxygen utilization(AOU)(R=0.620,P<0.001)and negatively related to the bottom DO(R=0.616,P<0.001),indicating that water column stratification was an essential prerequisite for the formation of bottom hypoxia in summer.The bottom oxygen consumption and hypoxia had higher positive correlation with the seasonal thermocline(R=0.683,P<0.001)than the halocline(R=0.540,P<0.001),including in the area was affected by freshwater plume.The insignificant relationship between AOU and nutrients indicated that local eutrophication was not the only important factor in the formation of the hypoxic zone during summer.The decrease in phosphorous owing to the pollutant reduction policy and the increase in nitrate may have led to an increase in hypoxia events in the bay where waters therein are characterized by nitrogen-limitation.The increase in chemical oxygen demand in wastewater also promoted oxygen consumption.Compared to the adjacent coastal waters influenced by Zhujiang River plume water,the Mirs Bay experienced more hypoxia events.The high concentrations of ammonium and total Kjeldahl nitrogen in the sediment of Mirs Bay increased the oxygen depletion in the bottom water.The long residence time of the near-bottom water in Mirs Bay increased the risk of bottom hypoxia events,although the nutrient concentrations were lower than those in the transition zone.These factors lead to differences in hypoxia occurrence in Mirs Bay and adjacent coastal waters.展开更多
Excess reactive phosphorus(PO4)in waterways can lead to eutrophication.A low-cost approach to reducing PO4 levels in surface water was evaluated using the alum-based water treatment residual(Al-WTR)or Al-WTR augmented...Excess reactive phosphorus(PO4)in waterways can lead to eutrophication.A low-cost approach to reducing PO4 levels in surface water was evaluated using the alum-based water treatment residual(Al-WTR)or Al-WTR augmented with powdered activated carbon(PAC-WTR).Batch adsorption-desorption and continuous flow column experiments were performed to assess the specific adsorption capacities under various concentration and flow conditions.Both Al-WTR and PAC-WTR exhibited the ability to adsorb PO4.The overall,cumulative sorbed amount after a 28-d desorption step for Al-WTR was 33.93 mg/kg,significantly greater than the PAC-WTR value of 24.95 mg/kg(p<0.05).The continuous flow column experiments showed a theoretical PO4 uptake of 9.00 mg/g for Al-WTR and 7.14 mg/g for PAC-WTR over 720 h.When surface water was used,the Al-WTR and PAC-WTR columns removed 67.4%and 62.1%of the PO4,respectively.These results indicated that Al-WTR was more effective for in-field evaluation.展开更多
Phosphorus( P) has been recognized as a major limited nutrient responsible for the eutrophication of surface waters. Water treatment residuals( WTRs) are safe by-products of water treatment plants and are cost-efficie...Phosphorus( P) has been recognized as a major limited nutrient responsible for the eutrophication of surface waters. Water treatment residuals( WTRs) are safe by-products of water treatment plants and are cost-efficient adsorbents. In this study, batch experiments and column experiments based on WTRs were employed to study the characteristics of P adsorption and the effects of lowmolecular-weight organic acids( LMWOAs)( citric acid, oxalic acid,and tartaric acid) on P adsorption. Different models of adsorption were used to describe equilibrium and kinetic data. The adsorption data were fitted well by a pseudo-second order kinetic model. The adsorption process was determined to be controlled by three steps of diffusion mechanisms through the intra-particle model.The adsorption equilibrium was well described by the Langmuir,Freundlich,Redlich-Peterson,and Sips isotherm models. Batch and continuous flow experiments indicated that the LMWOAs exhibited inhibitory action,and as pH increased,the inhibitory action became weaker for all the three acids. The effect of LMWOAs concentration was not significant on inhibition. The effects of LMWOAs were closely related to reaction time.展开更多
Approximately 40% of biosolids （sewage sludge） produced in the U.S. are incinerated or landfilled rather than land applied due to concern over non-point source P （phosphorus） runoff. The objective of this study wa...Approximately 40% of biosolids （sewage sludge） produced in the U.S. are incinerated or landfilled rather than land applied due to concern over non-point source P （phosphorus） runoff. The objective of this study was to determine the impact of chemical amendments on WEP （water-extractable phosphorus） in applied treatments and DRP （dissolved reactive phosphorus） in runoff from biosolids-amended soils. Rainfall simulations were conducted in 2006 on field plots fertilized with biosolids that had been treated with alum [（A12804）3＂ 14H20], ferric chloride （FeC13） or an alum-based WTR （water treatment residual） at a rate of 20% （wt/wt） to reduce DRP in runoff. In 2007, rainfall simulations were conducted using WTR/biosolid blends of 15% and 30% （wt/wt） that were allowed to incubate for three weeks prior to application. Cumulative DRP runoff load observed for the 20% WTR treatment was not significantly different from other chemical treatments and resulted in a 45% reduction in DRP runoff as compared to the untreated biosolids application. Cumulative DRP runoff load in 2007 for the 15% and 30% WTR treatments resulted in significantly lower DRP loads compared to untreated biosolids and led to DRP runoff load reductions of 78% and 85% （compared to the untreated biosolids application）, respectively.展开更多
A large amount of residue from the water treatment process has gradually accumulated and thus caused serious environmental pollution in waterflood oilfields. The water treatment residue is a grey suspension, with a de...A large amount of residue from the water treatment process has gradually accumulated and thus caused serious environmental pollution in waterflood oilfields. The water treatment residue is a grey suspension, with a density of 1.08 g/cm^3, and mainly contains over 65% of light CaCO3, MgCO3, CaSO4, Fe2S3 and Ca（OH）2. This paper ascertains the effect of water treatment residue on core permeability and its application in oilfields. Coreflooding tests in laboratory were conducted in two artificial cores and one natural core. Core changes were evaluated by cast model image analysis, mercury injection method and scanning electron microscopy （SEM）. Fresh water was injected into another natural core, which was plugged with water treatment residue, to determine the effective life. The results indicate that the water treatment residue has a strongly plugging capability, a resistance to erosion and a long effective life, and thus it can be used as a cheap raw material for profile control. In the past 8 years, a total of 60,164 m^3 of water treatment residue has been used for profile control of 151 well treatments, with a success ratio of 98% and an effective ratio of 83.2%. In the field tests, the profile control agent increased both starting pressure and injection pressure of injectors, and decreased the apparent water injectivity coefficient, significantly improving intake profiles and lengthening average service life of injectors. 28,381 tons of additional oil were recovered from these corresponding oil wells, with economic benefits of ￥3,069.55×10^4 （RMB） and a remarkable input-output ratio of 8.6：1.展开更多
The influence of emulsified oil, suspended solids, Fe3＋, Fe2＋, cationic water clarifier and sulfate-reducing （SR） bacteria on the aggregation behavior of residual hydrophobic modified polyacrylamide in treated oil...The influence of emulsified oil, suspended solids, Fe3＋, Fe2＋, cationic water clarifier and sulfate-reducing （SR） bacteria on the aggregation behavior of residual hydrophobic modified polyacrylamide in treated oily wastewater from polymer flooding was studied by fluorescence spectroscopy and dynamic light scattering. The result of I1/I3 showed that the polarity of hydrophobic microdomains increased, whereas the size of the hydrophobic microdomains may be decreased, where the value of I1/I3 represents the ratio of the intensity of peak 11 （374.0 nm） to that of peak/3 （385.0 nm） of the vibration fine structure of pyrene monomer emission in residual polymer solution. The results of the ratio of I1 at 48 h to I1 at 0 h （I1,48h/I1,0h） indicated that oil and cationic water clarifier could inhibit the aggregation to some extent, while Fe2＋ and suspended solids were helpful for aggregation, and Fe3＋ and SR bacteria had no significant influence on the aggregation of polymer.展开更多
As safe byproducts of drinking water treatment processes,ferric and alum water treatment residuals（FARs） have the potential to be new phosphate（P） immobilization materials.In this study,batch experiments were cond...As safe byproducts of drinking water treatment processes,ferric and alum water treatment residuals（FARs） have the potential to be new phosphate（P） immobilization materials.In this study,batch experiments were conducted to investigate and compare the adsorption characteristics of three P species by FARs.The results showed that the kinetic processes of different P species＇ adsorption by FARs could be described by a pseudo second-order model.The ranking list of the initial adsorption rates with respect to different phosphates was pyrophosphate,phytate,orthophosphate,hexametaphosphate and glycerophosphate.Of the six models considered,the two-site Langmuir model most effectively described the adsorption characteristics of the various P species.Upon fitting the results,the maximum adsorption capacities were determined to be 40.24 mg/g for phytate,18.04 mg/g for pyrophosphate,17.14 mg/g for orthophosphate,15.86 mg/g for hexametaphosphate and 10.81 mg/g for glycerophosphate.In addition,the adsorption processes of the different P species were spontaneous endothermic processes and were favored at lower pH values.The pH dependency was found to be especially true for orthophosphate,where the adsorption capacity decreased by 1.22 mg/g with an increase in pH from 5 to 9.Fractionation of the adsorbed P species from the FARs demonstrated that Al-P and Fe-P were the dominating forms,constituting approximately 80%-90% of the total P fractions,which indicated that the adsorbed P species had a low leaching risk and could stably exist in the FARs.Therefore,the FARs could be effective in controlling pollution in water caused by different P species.展开更多
Batch experiments were conducted to investigate the phosphorus（P） adsorption and desorption on five drinking water treatment residuals（WTRs） collected from different regions in China. The physical and chemical cha...Batch experiments were conducted to investigate the phosphorus（P） adsorption and desorption on five drinking water treatment residuals（WTRs） collected from different regions in China. The physical and chemical characteristics of the five WTRs were determined. Combined with rotated principal component analysis, multiple regression analysis was used to analyze the relationship between the inherent properties of the WTRs and their P adsorption capacities. The results showed that the maximum P adsorption capacities of the five WTRs calculated using the Langmuir isotherm ranged from 4.17 to8.20 mg/g at a p H of 7 and further increased with a decrease in p H. The statistical analysis revealed that a factor related to Al and 200 mmol/L oxalate-extractable Al（Alox） accounted for 36.5% of the variations in the P adsorption. A similar portion（28.5%） was attributed to an integrated factor related to the p H, Fe, 200 mmol/L oxalate-extractable Fe（Feox）, surface area and organic matter（OM） of the WTRs. However, factors related to other properties（Ca,P and 5 mmol/L oxalate-extractable Fe and Al） were rejected. In addition, the quantity of P desorption was limited and had a significant negative correlation with the（Feox＋ Alox） of the WTRs（p 〈 0.05）. Overall, WTRs with high contents of Alox, Feoxand OM as well as large surface areas were proposed to be the best choice for P adsorption in practical applications.展开更多
A study on the removal of Co（Ⅱ） from aqueous solutions by water treatment residuals（WTR） was conducted in batch conditions. The sorption process of Co（Ⅱ） followed pseudosecondorder kinetics, with 30 hr require...A study on the removal of Co（Ⅱ） from aqueous solutions by water treatment residuals（WTR） was conducted in batch conditions. The sorption process of Co（Ⅱ） followed pseudosecondorder kinetics, with 30 hr required to reach equilibrium. Using the Langmuir adsorption isotherm model, a relatively high maximum sorption capacity of 17.31 mg/g Co（Ⅱ） was determined. The adsorption of Co（Ⅱ） was dependent on pH values and was affected by the ionic strength. Results show that Co（Ⅱ） adsorption was a spontaneous endothermic process and was favorable at high temperature. Most of the adsorbed Co（Ⅱ） stayed on the WTR permanently, whereas only small amounts of adsorbed Co（Ⅱ） were desorbed. The shifting of peaks in FT-IR spectra indicated that Co（Ⅱ） interacted with the WTR surface through strong covalent bond formation with Fe（Al）–O functional groups. It was concluded that WTR can be a suitable material from which to develop an efficient adsorbent for the removal of Co（Ⅱ） from wastewater.展开更多
Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a（NFS） made from drinking water treatment residuals...Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a（NFS） made from drinking water treatment residuals. The adsorption of phosphate on the NFS fitted well with the Freundlich isotherm and pseudo second-order kinetic models. At p H 7.0, the maximum adsorption capacity of 1.03 mg/g was achieved at 15°C corresponding to the wastewater temperature in cold months, and increased notably to 1.31 mg/g at 35°C.Under both acidic conditions（part of the adsorption sites was consumed） and basic conditions（negative charges formed on the surface of NFS, which led to a static repulsion of PO43-and HPO42-）, the adsorption of phosphate was slightly inhibited. Further study showed that part of the adsorption sites could be recovered by 0.25 mol/L Na OH. The activation energy was calculated to be above 8.0 k J/mol, indicating that the adsorption of phosphate on NFS was probably a chemical process. Considering the strong phosphate adsorption capacity and recoverability, NFS showed great promise on enhancing phosphate removal from the secondary treated wastewater in the filtration process.展开更多
Fe/Al drinking water treatment residuals（WTRs）, ubiquitous and non-hazardous by-products of drinking water purification, are cost-effective adsorbents for glyphosate. Given that repeated glyphosate applications coul...Fe/Al drinking water treatment residuals（WTRs）, ubiquitous and non-hazardous by-products of drinking water purification, are cost-effective adsorbents for glyphosate. Given that repeated glyphosate applications could significantly decrease glyphosate retention by soils and that the adsorbed glyphosate is potentially mobile, high sorption capacity and stability of glyphosate in agricultural soils are needed to prevent pollution of water by glyphosate.Therefore, we investigated the feasibility of reusing Fe/Al WTR as a soil amendment to enhance the retention capacity of glyphosate in two agricultural soils. The results of batch experiments showed that the Fe/Al WTR amendment significantly enhanced the glyphosate sorption capacity of both soils（p 〈 0.001）. Up to 30% of the previously adsorbed glyphosate desorbed from the non-amended soils, and the Fe/Al WTR amendment effectively decreased the proportion of glyphosate desorbed. Fractionation analyses further demonstrated that glyphosate adsorbed to non-amended soils was primarily retained in the readily labile fraction（Na HCO3-glyphosate）. The WTR amendment significantly increased the relative proportion of the moderately labile fraction（HCl-glyphosate） and concomitantly reduced that of the Na HCO3-glyphosate, hence reducing the potential for the release of soil-adsorbed glyphosate into the aqueous phase. Furthermore, Fe/Al WTR amendment minimized the inhibitory effect of increasing solution p H on glyphosate sorption by soils and mitigated the effects of increasing solution ionic strength. The present results indicate that Fe/Al WTR is suitable for use as a soil amendment to prevent glyphosate pollution of aquatic ecosystems by enhancing the glyphosate retention capacity in soils.展开更多
Drinking water treatment residuals（WTRs） have a potential to realize eutrophication control objectives by reducing the internal phosphorus（P） load of lake sediments. Information regarding the ecological risk of de...Drinking water treatment residuals（WTRs） have a potential to realize eutrophication control objectives by reducing the internal phosphorus（P） load of lake sediments. Information regarding the ecological risk of dewatered WTR reuse in aquatic environments is generally lacking, however. In this study, we analyzed the eco-toxicity of leachates from sediments with or without dewatered WTRs toward algae Chlorella vulgaris via algal growth inhibition testing with algal cell density, chlorophyll content, malondialdehyde content, antioxidant enzyme superoxide dismutase activity, and subcellular structure indices. The results suggested that leachates from sediments unanimously inhibited algal growth, with or without the addition of different WTR doses（10% or 50% of the sediment in dry weight） at different p H values（8–9）, as well as from sediments treated for different durations（10 or 180 days）. The inhibition was primarily the result of P deficiency in the leachates owing to WTR P adsorption, however, our results suggest that the dewatered WTRs were considered as a favorable potential material for internal P loading control in lake restoration projects, as it shows acceptably low risk toward aquatic plants.展开更多
Organic polymeric flocculants are commonly used in improving dredged sludge dewaterability, but less attention has been paid to residual water quality. In this paper, the effects of cationic etherified starch(CS) and ...Organic polymeric flocculants are commonly used in improving dredged sludge dewaterability, but less attention has been paid to residual water quality. In this paper, the effects of cationic etherified starch(CS) and poly-dimethyl diallyl ammonium chloride(PDDA) on dredged sludge dewatering efficiency and residual water quality of Baiyangdian lake were comprehensively investigated and evaluated by analytic hierarchy process(AHP). The results indicated that PDDA had stronger electrical effect and flocculation performance compared with CS, resulting in more efficient dewatering performance. PDDA can reduce the pollutants of discharged residual water, while CS significantly promoted the increase of NH_(4)^(+)-N and NO_(3)^(–)-N in the residual water. The increase of NH_(4)^(+)-N in the residual water of CS was due to the release of dredged sludge, while the increase of NO_(3)^(-)-N was introduced by CS leaching. AHP showed that PDDA performed better in flocculation treatment of dredged sludge than other organic polymers. This work provides a method for optimization of flocculation treatment for dredged sludge dewaterability.展开更多
This study analyzes water-level variability in Sansha Bay and its adjacent waters near Fujian, China, using water-level data observed from seven stations along the coast and wind data observed from a moored buoy near ...This study analyzes water-level variability in Sansha Bay and its adjacent waters near Fujian, China, using water-level data observed from seven stations along the coast and wind data observed from a moored buoy near Mazu Island. At super-to near-inertial frequencies, tides dominated the water-level variations, mainly characterized by semi-diurnal （prmafily M2, S2, and N2） and diurnal tides （primarily Kb O1）. The correlation coefficients between residual （non-tidal） water-level time series and the observed wind-stress time series exceeded 0.78 at all stations, hinting that the wind acting on the study region was another factor modulating the water-level variability. A cross-wavelet and wavelet-coherence analysis further indicated that （i） the residual water level at each station was more coherent and out-of-phase with the alongshore winds mostly at sub-inertial time scales associated with synoptic weather changes; and （ii） the residual water-level difference between the outer and inner bay was more coherent with the cross-shore winds at discrete narrow frequency bands, with the wind leading by a certain phase. The analysis also implied that the monsoon relaxation period was more favorable for the formation of the land-sea breeze, modulating the residual water-level difference.展开更多
Soil moisture characteristic curve （SMC） is a fundamental soil property and its direct measurement is tedious and time consuming. Therefore, various indirect methods have been developed to predict SMC from particle-...Soil moisture characteristic curve （SMC） is a fundamental soil property and its direct measurement is tedious and time consuming. Therefore, various indirect methods have been developed to predict SMC from particle-size distribution （PSD）. However, the majority of these methods often yield intermittent SMC data because they involve estimating individual SMC points. The objectives of this study were 1） to develop a procedure to predict continuous SMC from a limited number of experimental PSD data points and 2） to evaluate model predictions through comparisons with measured values. In this study, an approach that allowed predicting SMC from the knowledge of PSD, parameterized by means of the closed-form van Genuchten model （VG）, was used. Through using Mohammadi and Vanclooster （MV） model, the parameters obtained from fitting of VG to PSD data were applied to predict SMC curves. Since the residual water content （Or） could not be obtained through fitting of VG-MV integrated model to PSD data, we also examined and compared four different methods estimating 0r. Results showed that the proposed equation （MV-VG integrated model） provided an excellent fit to all the PSD data and the model could adequately predict SMC as measured in forty-two soils sampled from different regions of Iran. For all soils, the method in which Or Was obtained through parameter optimization procedure provided the best overall predictions of SMC. The two methods estimating Or with Campbell and Shiozawa （CS） model resulted in less accuracy than the optimization procedure. Furthermore, the proposed model underestimated the moisture content in the dry range of SMC when the value of 0r was assumed to equal zero. 0r could be attributed to the incomplete desorption of water coated on soil particles and the accurate estimation of 0r was critical in prediction of SMC, especially for fine-textured soils at high suction heads. It could be concluded that the advantages of our approach were the continuity, robustness, and independency of model performance on soil type, allowing to improve predictions of SMC from PSD at the field and watershed scales.展开更多
The Ordovician carbonate reservoirs in the Tahe Oilfield are highly heterogeneous, which have undergone multiple superimposed transformations by tectonic activities and karst processes, leading to an extremely complex...The Ordovician carbonate reservoirs in the Tahe Oilfield are highly heterogeneous, which have undergone multiple superimposed transformations by tectonic activities and karst processes, leading to an extremely complex fluid distribution. The geochemical characteristics of geofluids also display great disparities. Results show that the vertical distribution of oil and gas are continuous, however the oil-water interfaces in different blocks of the Tahe Ordovician Oilfield are numerous. Meteoric water infiltration is regarded as the main reason for the high oil-water interface and high water content to the north of Tahe Oilfield, especially in well blocks S78–S73. The isotopic values of deuterium-oxygen in the groundwater and carbon-oxygen from calcite veins confirm that formation water in Ordovician reservoirs of the Tahe Oilfield was a mix of meteoric water and connate water, and the proportion of meteoric water gradually increases from south to north, while connate water decreases. The Tahe Ordovician reservoirs are characterised by multiple hydrocarbon charges, and the general migrating direction is from southeast to northwest and from east to west. High production could be obtained in the northern area of the Tahe Oilfield since the oil layers are thick and oil is highly saturated. The residual water within the reservoirs is low, and heavy oil is dominant in this area. Only a small amount of pore water has been replaced by oil in the southern Tahe Oilfield, leading to low oil saturation and a high content of residual water. Crude oil is herein mainly of medium-light type. During the process of exploration in this region, acid fracturing reformation is usually required for wells to increase their output; however the yield is still low.展开更多
基金Supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(Nos.GML2019ZD0302,GML2019ZD0303)the National Natural Science Foundation of China(No.31971480)the State Key Laboratory of Tropical Oceanology Independent Research Fund(No.LTOZZ2103)。
文摘Mirs Bay is a semi-enclosed bay neighboring the Zhujiang(Pearl)River estuary,one of the largest estuarine systems in the world.The long-term historical observational data(1994-2017)of temperature,salinity,dissolved oxygen(DO),and biochemical parameters were used to examine the spatiotemporal distribution of hypoxia in Mirs Bay and adjacent coastal waters.Results show that bottom hypoxia varied seasonally and interannually.Hypoxia mainly occurred from June to September in Mirs Bay and the transition zone in the southern waters of Hong Kong,and the recorded hypoxia events have increased from 2007.The density difference between the bottom and surface layers was positively related to the bottom apparent oxygen utilization(AOU)(R=0.620,P<0.001)and negatively related to the bottom DO(R=0.616,P<0.001),indicating that water column stratification was an essential prerequisite for the formation of bottom hypoxia in summer.The bottom oxygen consumption and hypoxia had higher positive correlation with the seasonal thermocline(R=0.683,P<0.001)than the halocline(R=0.540,P<0.001),including in the area was affected by freshwater plume.The insignificant relationship between AOU and nutrients indicated that local eutrophication was not the only important factor in the formation of the hypoxic zone during summer.The decrease in phosphorous owing to the pollutant reduction policy and the increase in nitrate may have led to an increase in hypoxia events in the bay where waters therein are characterized by nitrogen-limitation.The increase in chemical oxygen demand in wastewater also promoted oxygen consumption.Compared to the adjacent coastal waters influenced by Zhujiang River plume water,the Mirs Bay experienced more hypoxia events.The high concentrations of ammonium and total Kjeldahl nitrogen in the sediment of Mirs Bay increased the oxygen depletion in the bottom water.The long residence time of the near-bottom water in Mirs Bay increased the risk of bottom hypoxia events,although the nutrient concentrations were lower than those in the transition zone.These factors lead to differences in hypoxia occurrence in Mirs Bay and adjacent coastal waters.
基金This work was supported by Ohio EPA 319(Grant No.17(H)EPA-17)and the Ohio Water Development Authority(Grant No.80-17).
文摘Excess reactive phosphorus(PO4)in waterways can lead to eutrophication.A low-cost approach to reducing PO4 levels in surface water was evaluated using the alum-based water treatment residual(Al-WTR)or Al-WTR augmented with powdered activated carbon(PAC-WTR).Batch adsorption-desorption and continuous flow column experiments were performed to assess the specific adsorption capacities under various concentration and flow conditions.Both Al-WTR and PAC-WTR exhibited the ability to adsorb PO4.The overall,cumulative sorbed amount after a 28-d desorption step for Al-WTR was 33.93 mg/kg,significantly greater than the PAC-WTR value of 24.95 mg/kg(p<0.05).The continuous flow column experiments showed a theoretical PO4 uptake of 9.00 mg/g for Al-WTR and 7.14 mg/g for PAC-WTR over 720 h.When surface water was used,the Al-WTR and PAC-WTR columns removed 67.4%and 62.1%of the PO4,respectively.These results indicated that Al-WTR was more effective for in-field evaluation.
基金National Water Pollution Control and Management Key Project,China(No.2009ZX07318-008-006)
文摘Phosphorus( P) has been recognized as a major limited nutrient responsible for the eutrophication of surface waters. Water treatment residuals( WTRs) are safe by-products of water treatment plants and are cost-efficient adsorbents. In this study, batch experiments and column experiments based on WTRs were employed to study the characteristics of P adsorption and the effects of lowmolecular-weight organic acids( LMWOAs)( citric acid, oxalic acid,and tartaric acid) on P adsorption. Different models of adsorption were used to describe equilibrium and kinetic data. The adsorption data were fitted well by a pseudo-second order kinetic model. The adsorption process was determined to be controlled by three steps of diffusion mechanisms through the intra-particle model.The adsorption equilibrium was well described by the Langmuir,Freundlich,Redlich-Peterson,and Sips isotherm models. Batch and continuous flow experiments indicated that the LMWOAs exhibited inhibitory action,and as pH increased,the inhibitory action became weaker for all the three acids. The effect of LMWOAs concentration was not significant on inhibition. The effects of LMWOAs were closely related to reaction time.
文摘Approximately 40% of biosolids （sewage sludge） produced in the U.S. are incinerated or landfilled rather than land applied due to concern over non-point source P （phosphorus） runoff. The objective of this study was to determine the impact of chemical amendments on WEP （water-extractable phosphorus） in applied treatments and DRP （dissolved reactive phosphorus） in runoff from biosolids-amended soils. Rainfall simulations were conducted in 2006 on field plots fertilized with biosolids that had been treated with alum [（A12804）3＂ 14H20], ferric chloride （FeC13） or an alum-based WTR （water treatment residual） at a rate of 20% （wt/wt） to reduce DRP in runoff. In 2007, rainfall simulations were conducted using WTR/biosolid blends of 15% and 30% （wt/wt） that were allowed to incubate for three weeks prior to application. Cumulative DRP runoff load observed for the 20% WTR treatment was not significantly different from other chemical treatments and resulted in a 45% reduction in DRP runoff as compared to the untreated biosolids application. Cumulative DRP runoff load in 2007 for the 15% and 30% WTR treatments resulted in significantly lower DRP loads compared to untreated biosolids and led to DRP runoff load reductions of 78% and 85% （compared to the untreated biosolids application）, respectively.
文摘A large amount of residue from the water treatment process has gradually accumulated and thus caused serious environmental pollution in waterflood oilfields. The water treatment residue is a grey suspension, with a density of 1.08 g/cm^3, and mainly contains over 65% of light CaCO3, MgCO3, CaSO4, Fe2S3 and Ca（OH）2. This paper ascertains the effect of water treatment residue on core permeability and its application in oilfields. Coreflooding tests in laboratory were conducted in two artificial cores and one natural core. Core changes were evaluated by cast model image analysis, mercury injection method and scanning electron microscopy （SEM）. Fresh water was injected into another natural core, which was plugged with water treatment residue, to determine the effective life. The results indicate that the water treatment residue has a strongly plugging capability, a resistance to erosion and a long effective life, and thus it can be used as a cheap raw material for profile control. In the past 8 years, a total of 60,164 m^3 of water treatment residue has been used for profile control of 151 well treatments, with a success ratio of 98% and an effective ratio of 83.2%. In the field tests, the profile control agent increased both starting pressure and injection pressure of injectors, and decreased the apparent water injectivity coefficient, significantly improving intake profiles and lengthening average service life of injectors. 28,381 tons of additional oil were recovered from these corresponding oil wells, with economic benefits of ￥3,069.55×10^4 （RMB） and a remarkable input-output ratio of 8.6：1.
基金supported by the Scientific Research Project of CNOOC(China)(Grant No.CNOOC-KJ 125 ZDXM 06 LTD NFGC 2014-01)
文摘The influence of emulsified oil, suspended solids, Fe3＋, Fe2＋, cationic water clarifier and sulfate-reducing （SR） bacteria on the aggregation behavior of residual hydrophobic modified polyacrylamide in treated oily wastewater from polymer flooding was studied by fluorescence spectroscopy and dynamic light scattering. The result of I1/I3 showed that the polarity of hydrophobic microdomains increased, whereas the size of the hydrophobic microdomains may be decreased, where the value of I1/I3 represents the ratio of the intensity of peak 11 （374.0 nm） to that of peak/3 （385.0 nm） of the vibration fine structure of pyrene monomer emission in residual polymer solution. The results of the ratio of I1 at 48 h to I1 at 0 h （I1,48h/I1,0h） indicated that oil and cationic water clarifier could inhibit the aggregation to some extent, while Fe2＋ and suspended solids were helpful for aggregation, and Fe3＋ and SR bacteria had no significant influence on the aggregation of polymer.
基金supported by the National Natural Science Foundation of China (No. 51278055,51179008)
文摘As safe byproducts of drinking water treatment processes,ferric and alum water treatment residuals（FARs） have the potential to be new phosphate（P） immobilization materials.In this study,batch experiments were conducted to investigate and compare the adsorption characteristics of three P species by FARs.The results showed that the kinetic processes of different P species＇ adsorption by FARs could be described by a pseudo second-order model.The ranking list of the initial adsorption rates with respect to different phosphates was pyrophosphate,phytate,orthophosphate,hexametaphosphate and glycerophosphate.Of the six models considered,the two-site Langmuir model most effectively described the adsorption characteristics of the various P species.Upon fitting the results,the maximum adsorption capacities were determined to be 40.24 mg/g for phytate,18.04 mg/g for pyrophosphate,17.14 mg/g for orthophosphate,15.86 mg/g for hexametaphosphate and 10.81 mg/g for glycerophosphate.In addition,the adsorption processes of the different P species were spontaneous endothermic processes and were favored at lower pH values.The pH dependency was found to be especially true for orthophosphate,where the adsorption capacity decreased by 1.22 mg/g with an increase in pH from 5 to 9.Fractionation of the adsorbed P species from the FARs demonstrated that Al-P and Fe-P were the dominating forms,constituting approximately 80%-90% of the total P fractions,which indicated that the adsorbed P species had a low leaching risk and could stably exist in the FARs.Therefore,the FARs could be effective in controlling pollution in water caused by different P species.
基金supported by the National Key Technology R&D Program(No.2012BAJ21B08)the National Natural Science Foundation of China(No.5127805551179008)
文摘Batch experiments were conducted to investigate the phosphorus（P） adsorption and desorption on five drinking water treatment residuals（WTRs） collected from different regions in China. The physical and chemical characteristics of the five WTRs were determined. Combined with rotated principal component analysis, multiple regression analysis was used to analyze the relationship between the inherent properties of the WTRs and their P adsorption capacities. The results showed that the maximum P adsorption capacities of the five WTRs calculated using the Langmuir isotherm ranged from 4.17 to8.20 mg/g at a p H of 7 and further increased with a decrease in p H. The statistical analysis revealed that a factor related to Al and 200 mmol/L oxalate-extractable Al（Alox） accounted for 36.5% of the variations in the P adsorption. A similar portion（28.5%） was attributed to an integrated factor related to the p H, Fe, 200 mmol/L oxalate-extractable Fe（Feox）, surface area and organic matter（OM） of the WTRs. However, factors related to other properties（Ca,P and 5 mmol/L oxalate-extractable Fe and Al） were rejected. In addition, the quantity of P desorption was limited and had a significant negative correlation with the（Feox＋ Alox） of the WTRs（p 〈 0.05）. Overall, WTRs with high contents of Alox, Feoxand OM as well as large surface areas were proposed to be the best choice for P adsorption in practical applications.
基金supported by the National Natural Science Foundation of China(No.51278055)the National Science and Technology Major Project(No.2012ZX07203-003)
文摘A study on the removal of Co（Ⅱ） from aqueous solutions by water treatment residuals（WTR） was conducted in batch conditions. The sorption process of Co（Ⅱ） followed pseudosecondorder kinetics, with 30 hr required to reach equilibrium. Using the Langmuir adsorption isotherm model, a relatively high maximum sorption capacity of 17.31 mg/g Co（Ⅱ） was determined. The adsorption of Co（Ⅱ） was dependent on pH values and was affected by the ionic strength. Results show that Co（Ⅱ） adsorption was a spontaneous endothermic process and was favorable at high temperature. Most of the adsorbed Co（Ⅱ） stayed on the WTR permanently, whereas only small amounts of adsorbed Co（Ⅱ） were desorbed. The shifting of peaks in FT-IR spectra indicated that Co（Ⅱ） interacted with the WTR surface through strong covalent bond formation with Fe（Al）–O functional groups. It was concluded that WTR can be a suitable material from which to develop an efficient adsorbent for the removal of Co（Ⅱ） from wastewater.
基金supported by the National Natural Science Foundation of China(No.21007050)the Science and Technology Nova Program of Shaanxi(No.2014KJXX-66)
文摘Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a（NFS） made from drinking water treatment residuals. The adsorption of phosphate on the NFS fitted well with the Freundlich isotherm and pseudo second-order kinetic models. At p H 7.0, the maximum adsorption capacity of 1.03 mg/g was achieved at 15°C corresponding to the wastewater temperature in cold months, and increased notably to 1.31 mg/g at 35°C.Under both acidic conditions（part of the adsorption sites was consumed） and basic conditions（negative charges formed on the surface of NFS, which led to a static repulsion of PO43-and HPO42-）, the adsorption of phosphate was slightly inhibited. Further study showed that part of the adsorption sites could be recovered by 0.25 mol/L Na OH. The activation energy was calculated to be above 8.0 k J/mol, indicating that the adsorption of phosphate on NFS was probably a chemical process. Considering the strong phosphate adsorption capacity and recoverability, NFS showed great promise on enhancing phosphate removal from the secondary treated wastewater in the filtration process.
基金supported by the National Natural Science Foundation of China (Nos.51278055, 51179008)the National Key Technology R&D Program (No.2012BAJ21B08)the National Public Benefit (Environmental) Research Foundation of China (No.201109009)
文摘Fe/Al drinking water treatment residuals（WTRs）, ubiquitous and non-hazardous by-products of drinking water purification, are cost-effective adsorbents for glyphosate. Given that repeated glyphosate applications could significantly decrease glyphosate retention by soils and that the adsorbed glyphosate is potentially mobile, high sorption capacity and stability of glyphosate in agricultural soils are needed to prevent pollution of water by glyphosate.Therefore, we investigated the feasibility of reusing Fe/Al WTR as a soil amendment to enhance the retention capacity of glyphosate in two agricultural soils. The results of batch experiments showed that the Fe/Al WTR amendment significantly enhanced the glyphosate sorption capacity of both soils（p 〈 0.001）. Up to 30% of the previously adsorbed glyphosate desorbed from the non-amended soils, and the Fe/Al WTR amendment effectively decreased the proportion of glyphosate desorbed. Fractionation analyses further demonstrated that glyphosate adsorbed to non-amended soils was primarily retained in the readily labile fraction（Na HCO3-glyphosate）. The WTR amendment significantly increased the relative proportion of the moderately labile fraction（HCl-glyphosate） and concomitantly reduced that of the Na HCO3-glyphosate, hence reducing the potential for the release of soil-adsorbed glyphosate into the aqueous phase. Furthermore, Fe/Al WTR amendment minimized the inhibitory effect of increasing solution p H on glyphosate sorption by soils and mitigated the effects of increasing solution ionic strength. The present results indicate that Fe/Al WTR is suitable for use as a soil amendment to prevent glyphosate pollution of aquatic ecosystems by enhancing the glyphosate retention capacity in soils.
基金supported by the National Natural Science Foundation of China(No.51278055)the Specialized Research Fund for the Doctoral Program of Higher Education(No.2012003110027)the National Key Technology R&D Program(No.2012BAJ21B08)
文摘Drinking water treatment residuals（WTRs） have a potential to realize eutrophication control objectives by reducing the internal phosphorus（P） load of lake sediments. Information regarding the ecological risk of dewatered WTR reuse in aquatic environments is generally lacking, however. In this study, we analyzed the eco-toxicity of leachates from sediments with or without dewatered WTRs toward algae Chlorella vulgaris via algal growth inhibition testing with algal cell density, chlorophyll content, malondialdehyde content, antioxidant enzyme superoxide dismutase activity, and subcellular structure indices. The results suggested that leachates from sediments unanimously inhibited algal growth, with or without the addition of different WTR doses（10% or 50% of the sediment in dry weight） at different p H values（8–9）, as well as from sediments treated for different durations（10 or 180 days）. The inhibition was primarily the result of P deficiency in the leachates owing to WTR P adsorption, however, our results suggest that the dewatered WTRs were considered as a favorable potential material for internal P loading control in lake restoration projects, as it shows acceptably low risk toward aquatic plants.
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment(No.2018ZX07110004)。
文摘Organic polymeric flocculants are commonly used in improving dredged sludge dewaterability, but less attention has been paid to residual water quality. In this paper, the effects of cationic etherified starch(CS) and poly-dimethyl diallyl ammonium chloride(PDDA) on dredged sludge dewatering efficiency and residual water quality of Baiyangdian lake were comprehensively investigated and evaluated by analytic hierarchy process(AHP). The results indicated that PDDA had stronger electrical effect and flocculation performance compared with CS, resulting in more efficient dewatering performance. PDDA can reduce the pollutants of discharged residual water, while CS significantly promoted the increase of NH_(4)^(+)-N and NO_(3)^(–)-N in the residual water. The increase of NH_(4)^(+)-N in the residual water of CS was due to the release of dredged sludge, while the increase of NO_(3)^(-)-N was introduced by CS leaching. AHP showed that PDDA performed better in flocculation treatment of dredged sludge than other organic polymers. This work provides a method for optimization of flocculation treatment for dredged sludge dewaterability.
文摘This study analyzes water-level variability in Sansha Bay and its adjacent waters near Fujian, China, using water-level data observed from seven stations along the coast and wind data observed from a moored buoy near Mazu Island. At super-to near-inertial frequencies, tides dominated the water-level variations, mainly characterized by semi-diurnal （prmafily M2, S2, and N2） and diurnal tides （primarily Kb O1）. The correlation coefficients between residual （non-tidal） water-level time series and the observed wind-stress time series exceeded 0.78 at all stations, hinting that the wind acting on the study region was another factor modulating the water-level variability. A cross-wavelet and wavelet-coherence analysis further indicated that （i） the residual water level at each station was more coherent and out-of-phase with the alongshore winds mostly at sub-inertial time scales associated with synoptic weather changes; and （ii） the residual water-level difference between the outer and inner bay was more coherent with the cross-shore winds at discrete narrow frequency bands, with the wind leading by a certain phase. The analysis also implied that the monsoon relaxation period was more favorable for the formation of the land-sea breeze, modulating the residual water-level difference.
文摘Soil moisture characteristic curve （SMC） is a fundamental soil property and its direct measurement is tedious and time consuming. Therefore, various indirect methods have been developed to predict SMC from particle-size distribution （PSD）. However, the majority of these methods often yield intermittent SMC data because they involve estimating individual SMC points. The objectives of this study were 1） to develop a procedure to predict continuous SMC from a limited number of experimental PSD data points and 2） to evaluate model predictions through comparisons with measured values. In this study, an approach that allowed predicting SMC from the knowledge of PSD, parameterized by means of the closed-form van Genuchten model （VG）, was used. Through using Mohammadi and Vanclooster （MV） model, the parameters obtained from fitting of VG to PSD data were applied to predict SMC curves. Since the residual water content （Or） could not be obtained through fitting of VG-MV integrated model to PSD data, we also examined and compared four different methods estimating 0r. Results showed that the proposed equation （MV-VG integrated model） provided an excellent fit to all the PSD data and the model could adequately predict SMC as measured in forty-two soils sampled from different regions of Iran. For all soils, the method in which Or Was obtained through parameter optimization procedure provided the best overall predictions of SMC. The two methods estimating Or with Campbell and Shiozawa （CS） model resulted in less accuracy than the optimization procedure. Furthermore, the proposed model underestimated the moisture content in the dry range of SMC when the value of 0r was assumed to equal zero. 0r could be attributed to the incomplete desorption of water coated on soil particles and the accurate estimation of 0r was critical in prediction of SMC, especially for fine-textured soils at high suction heads. It could be concluded that the advantages of our approach were the continuity, robustness, and independency of model performance on soil type, allowing to improve predictions of SMC from PSD at the field and watershed scales.
基金jointly supported by the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (No. PLC201002)the National Natural Science Foundation of China (No. 40839902)the National Science & Technology Major Project (Nos. 2011ZX05005-003-008HZ and 2011ZX05002-006-003HZ)
文摘The Ordovician carbonate reservoirs in the Tahe Oilfield are highly heterogeneous, which have undergone multiple superimposed transformations by tectonic activities and karst processes, leading to an extremely complex fluid distribution. The geochemical characteristics of geofluids also display great disparities. Results show that the vertical distribution of oil and gas are continuous, however the oil-water interfaces in different blocks of the Tahe Ordovician Oilfield are numerous. Meteoric water infiltration is regarded as the main reason for the high oil-water interface and high water content to the north of Tahe Oilfield, especially in well blocks S78–S73. The isotopic values of deuterium-oxygen in the groundwater and carbon-oxygen from calcite veins confirm that formation water in Ordovician reservoirs of the Tahe Oilfield was a mix of meteoric water and connate water, and the proportion of meteoric water gradually increases from south to north, while connate water decreases. The Tahe Ordovician reservoirs are characterised by multiple hydrocarbon charges, and the general migrating direction is from southeast to northwest and from east to west. High production could be obtained in the northern area of the Tahe Oilfield since the oil layers are thick and oil is highly saturated. The residual water within the reservoirs is low, and heavy oil is dominant in this area. Only a small amount of pore water has been replaced by oil in the southern Tahe Oilfield, leading to low oil saturation and a high content of residual water. Crude oil is herein mainly of medium-light type. During the process of exploration in this region, acid fracturing reformation is usually required for wells to increase their output; however the yield is still low.
