Effect of nitrogen and phosphorus on the water quality in the Three Gorges Reservoir Area during and after its construction

A survey concerning the concentration of the nutrients in the Three Gorges Reservoir Area was carried out. This paper presents the parameters(NO 3 - N, NO 2 - N, Kjeldahl N, non ionic ammonia, P PO 4 and TP) determined at 16 sampling sites from 1997 to 1999 The dominant soluble nitrogen form was NO 3 - N followed by Kjeldahl N, NO 2 - N and non ionic ammonia. Mean values of NO 3 - N, NO 2 - N, Kjeldahl N and non ionic ammonia ranged from 0 50 to 2 37 mg/L, 0 022 to 0 084 mg/L, 0 33 to 0 99 mg/L and 0 007 to 0 092 mg/L respectively. Mean values of P PO 4 at most sampling sites were higher than 0 1 mg/L for subject to eutrophication. The major factors influencing the concentrations of N and P might be agricultural runoff, municipal and industrial effluents. In addition, 6 kinds of soil were sampled at the area where would inundated after the dam completed. Two approaches were adopted to simulate the N and P release from the inundated soils. The results showed that the soils would release nitrogen and phosphorus to the overlying water when the soils were inundated. The characteristics of soil affected the equilibrium concentrations of N and P between the soil and the overlying water.

Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons(PAHs) in Guanting Reservoir sediments, China

The Guanting Reservoir lost its function as the second biggest drinking water source for Beijing due to the pollutions from the upstream flow of Yongding River in 1997 From 1998, lots of studies were carryied out to renew the function of Guanting Reservoir as domestic drinking water source before 2008 Olympic Games. This is the first time that polycyclic aromatic hydrocarbon concentrations in the surface sediment of Guanting Reservoir have been analyzed. A distinctive spatial distribution of PAHs was observed. Sediments from four sites along Inlet of Yongding River to reservoir bam had PAHs concentrations of 1377—2855 μg/g dw in descending order. The composition of PAHs is investigated and used to assess petrogenic, combustion and naturally derived of the sediments samples of Guanting Reservoir. Special PAHs ratios, such as phenanthrene/anthracene(P/A) and fluoranthene/pyrene(Fl/Pyr) were calculated to assess the relative importance of different origins. The data confirmed a relatively high level of petrogenic contamination in four sites. These high PAHs levels were associated with the input of untreated and partially treated industrial sewage. In addition, the concentrations of PAHs compounds of samples indicated that sediments of reservoir were most likely to pose potential biological impairment.

Kinetics study of aqueous sorption of phenanthrene to humic acids and sediments

The sorption behavior was determined for a model polycyclic aromatic hydrocarbon(PAH), i.e., phenanthrene(PHN), from water to three humic acids(HAs) and three sediments in different reacting time. The chemical compositions of HA samples were measured using cross polarization magic angle spinning carbon 13(CPMAS 13 C NMR along with elemental analysis. The dissolved humic substances dissociating from solid HAs and sediments were characterized by 1 H NMR. The experiments indicated that the sorption modes and mechanisms of natural sorbents for PHN varied significantly between short(<7 d) and long contact time and the reaction time should be taken into consideration in studying the overall sorption process. The sorption capacity( K ′ f) and exponent( n ) might be relative to the properties of dissolved humic materials in initial stage but the solid aromatic organic matter after long time reaction. According to the experiments performed in this investigation and the previous researches, a conceptive sorption model was established.

Seed yeast cultivation for salad oil manufacturing wastewater treatment

The mixture of five yeast strains obtained from soil could remove about 85% TOC of oil rich wastewater in batch test. While the highest MLSS was obtained at an N∶C of 1∶5, the oil removal decreased with the increase of N∶C during yeast sludge cultivation. Ammonium chloride was the best nitrogen source for yeast cultivation from the viewpoint of yeast growth and oil utilization. An ammonia concentration of over 1300 mg/L led to mass death of yeast at a pH of 5. The ammonia concentration should be controlled at a level of 1000 mg/L or lower.

Phosphorus removal by the multipond system sediments receiving agricultural drainage in a headstream watershed

Wetland systems in headstream watersheds are important to control the nonpoint source pollutant phosphorus. Experiments were conducted using intact sediment-water columns obtained from the multipond system in Liuchahe watershed of Chaohu Lake to determine its capacity to retain P. It was found that pond sediments had strong P retention ability. For the Hill pond, Village pond and Rice pond, their retention coefficient(A) were 288.3, 279.2 and 260.8 L/m2, respectively. The equilibrium P concentration(EPC_w) were 0.016, 0.028 and 0.018 mg/L, respectively. The Hill pond indicated the highest P retention ability. P retained in the pond sediments indicated high stable degree. P removal from the overlying water column into the pond sediments followed a first-order kinetic model. Under the experimental hydrological conditions, the retention time had a positive correlation with the P loading. The multipond system could provide enough retention time to retain P in drainage runoffs. At the P levels evaluated, the sediments of the multipond system are effective sinks to retain P from nonpoint source runoffs.

Adsorption of zinc on manganite(γ-MnOOH): particle concentration effect and adsorption reversibility

The adsorption and desorption processes of Zn(Ⅱ) on γ-MnOOH as a function of particle concentrations(C p) were studied. An obvious C p effect was observed in this adsorption system. The degree of adsorption hysteresis increased greatly with the increasing of C p, indicating that the extent of the real metastable-equilibrium states deviating from the ideal equilibrium state was enhanced with the increasing of C p. The C p-reversibility relationship confirmed the metastable-equilibrium adsorption(MEA) inequality(Pan, 1998a), which was the core formulation of the MEA theory. Because the MEA inequality was based on the basic hypothesis of MEA theory that adsorption density Γ is not a state variable, the C p-reversibility relationship gave indirect evidence to the basic hypothesis of MEA theory.

Removal of heavy metals from aqueous solution by carbon nanotubes: adsorption equilibrium and kinetics

Carbon nanotubes prepared by catalytic chemical vapor deposition of hydrocarbon at 650℃ show good adsorption capability of Pb 2+ , Cu 2+ and Cd 2+ ions from aqueous solution after oxidized with concentrated nitric acid at 140℃ for 1 h. The specific surface area and particle size distribution of the as-grown and oxidized CNTs were studied by BET method and laser particle analyzer. Three kinetic models, that is, first-, pseudo second- and second-order, were used to investigate the adsorption data and the pseudo second-order model can represent the experimental data better than two others. The equilibrium data fitted well with the Langmuir model and showed the following adsorption order: Pb 2+ >Cu 2+ >Cd 2+ .

Double catholyte electrochemical approach for preparing ferrate-aluminum: a compound oxidant-coagulant for water purification

Ferrate is an excellent water treatment agent for its multi functions in oxidation, disinfection, coagulation and adsorption, but its coagulation ability depends on its dosage and is after its oxidation. This paper focuses on preparing a new kind of ferrate combined with alum to enhance its coagulation function for water purification. An effective electrolysis reactor was designed and employed in the test. Some key parameters in the process of electrolysis concerning the preparation efficiency, such as the current density, temperature and alkalinity were also investigated. The proper conditions for ferrate alum preparation were determined. Under the condition of 5V given voltage, 6h electrolyzing interval, below 2% alum concentration (in weight), a combined liquid ferrate alum products was successfully prepared, which contained 0.0294 mol/L FeO 2- 4 and 0.0302 mol/L total soluble ferron with 2% Al 2O 3. There was no insoluble ferron produced by controlling an optimum electrochemical condition.

Spatial and temporal variability of agricultural pollutants in an agricultural headwater stream within a multipond system, southeastern China

The spatial and temporal variability of nutrients and suspended solids were investigated for two years in a 1.8 km agricultural headwater stream, located by Chaohu Lake, southeastern China. The stream form was greatly modified by human activities into channelized, pond and estuary shapes. The stream could be divided into 4 channelized reaches(1.3 km), a pond reach(0.15 km) and 3 estuary reaches(0.36 km). It was found that nutrients and TSS concentrations in the stream showed temporal variability, and higher concentrations occurred in months with high precipitation and intensive agricultural activities. And, retention of total nitrogen(TN), nitrate(NO- 3-N), ammonium(NH+ 4-N) and total suspended solids(TSS) predominantly occurred in the pond reach and estuary reaches with larger width and low current velocity. Pollutants retained in these reaches accounted for more than 50% of those retained in whole stream. The retention mostly happened in the rain-runoff events and it was 7 to 27 times than that in base flow. The results showed that the channelized reach was the most important source for pollutants release under either runoff or base flow, and its release accounted for more than 90% of whole stream release. There was a high spatial variability of nutrients retention in different channelized reaches. The channelized reach directly discharging into the pond did always retain nutrients and TSS under base flow and runoff conditions, whereas the other channelized reaches performed differently in different hydrological conditions. The high spatial and temporal variability of nutrients and TSS in the stream indicated that anthropogenic disturbance of the agricultural headwater stream, such as channelization and excavation, would be expected to decrease the capacity of nutrients retention in the stream.

Endocrine disrupting effects on Chinese rare minnow(Gobiocypris rarus) fed with field collected Limnodrilus sp.

The potential endocrine disrupting effects and other toxicity effects on aquatic biota resulted from food uptake was simulated by feeding the laboratory cultured rare minnow(Gobiocypris rarus) with field collected Limnodrilus sp. The results indicated that the food chain processes affected significantly the growth, slightly reduced gonadosomatic indices, and elevated hepatosomatic indices. There was an obvious vitellogenin(VTG) induction, which generally only occurred in mature female, in the serum of juvenile rare minnow and mature male when fed with Limnodrilus sp. In addition, the rare minnow feeding on Limnodrilus sp. had significantly high renal indices, it meant obvious renal hyperplasia. The present work suggested that Limnodrilus sp. from field water may contain toxic pollutants and could lead to endocrine disruption effects to the predators. It was concluded that endocrine disruptors may not only be assimilated through water, but also be bioconcentrated through food web. The results also suggested the importance of food selection in conducting the study of endocrine disruption effects using sensitive species.

Photodegradation mechanism of two dyes: the influence of adsorption behavior on the novel TiO_2 particles

The relationship between adsorption behavior and photocatalytic mechanism of the two dyes was investigated. Adsorption isotherms showed that the adsorption of cationic pink FG was Langmuir type behavior, while the reactive brilliant red k-2G was Freundlich type behavior. The increasing pH favored the adsorption of FG but have little effect on the photodegradation. The increasing pH favored the adsorption and the photodegradation of k-2G. The presence of scavenger of h + vb and OH· radical potassium iodide inhibited the degradation of k-2G, free radicals scavenger tetranitromethane inhibited the photodegradation of FG. These results indicated that the photodegradation of FG mainly via free radicals in solution, and the photodegradation of k-2G was mainly on the catalysts surface or near the interface of solid and solution by react with h + vb and surface-bound OH·. The different effect of SO 2- 4, HCO - 3 on the adsorp tion and photodegradation of two dyes confirmed these results.

Physicochemical interaction and its influence on deep bed filtration process

The capillary model was used to analyze the hydraulic conditions in the deep bed filtration process. The physicochemical interaction forces between the filter media and suspended particles and their influence on deep bed filtration process were also studied theoretically. Through the comparison of the hydraulic and physicochemical forces, the key influencing factors on the filtration process were proposed and investigated. Pilot study of the micro-flocculation deep bed filtration was carried out in the No. 9 Potable Water Treatment Plant of Beijing, and the experimental results of hydraulic head loss, particle distribution and entrapment were presented. The theoretical prediction was reasonably consistent with the experimental results under different conditions, which indicated that the regulation and control of micro-flocculation and deep bed filtration could be realized by the evaluation of the physicochemical interactions. Further theoretical and experimental research should be carried out to investigate the interaction mechanism and its application in the deep bed filtration and other cases.

Bubble performance of a novel dissolved air flotation(DAF) unit

ES-DAF, a novel DAF with low cost, high reliability and easy controllability, was studied. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied in detail by using a newly developed CCD imagination through a microscope. Compared with M-DAF under the same saturation pressure, ES-DAF can produce smaller bubble size and higher bubble volume concentration, especially in lower pressure. In addition, the bubble size decreases with the increase of reflux ratio or decrease of superficial air-water ratio. These results suggested that smaller bubbles will be formed when the initial number of nucleation sites increases by enhancing the turbulence intensity in the saturation system.

Effective removal of microcystins using carbon nanotubes embedded with bacteria

Adsorption of microcystins (MCs) by carbon nanotubes (CNTs) and clay materials was studied. Compared with various clays tested, CNTs showed a much stronger ability to adsorb MC-RR and LR that were two typical types of microcystins found in China. At initial 21.0 mg/L of MC-RR and 9.5 mg/L of MC-LR in solution, the adsorption amounts of MC-RR and LR by CNTs were 14.8 and 6.7 mg/g that were about five times higher than those by the clay ma-terials of sepiolite, kaolinite and talc, etc. In the presence of CNTs and the bacterial Ralstonia solanacearum that was firstly isolated and used for the biodegradation of MCs by the authors, a remarkable removal of MCs from water were observed. The mechanism was that CNTs could absorb large amount of both MCs and the embedded R. solanacearum so that, even when diluted by a large amount of water, the con-centrations of both organic pollutants and the added bacteria could be largely enhanced on the surface of CNTs where a concerted biodegradation reaction was effectively conducted. This finding could be important for the further development of practical techniques to eliminate MCs from polluted drinking waters.

Determination of trophic relationships within a Bohai Bay food web using stable δ^(15)N and δ^(13)C analysis

This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from ?25.38‰ to ?11.08‰ showing a relative low enrichment in the food web from Bohai Bay. The mean δ 13C of mullet is higher than that of other organisms, and this might be due to that mullet is migration fish and feeds mainly on inshore sources. δ 15N ranged from 4.08‰ to 13.98‰, and showed a step-wise en- richment with trophic level of 3.8‰. The δ 15N enrichment factor was used to construct an isotopic food web model to establish trophic relationships within this marine food web. According to this model, exact trophic levels of all organisms were estimated as 1.46?2.10, 1.91?3.32, 2.55?4.23 and 2.98?4.28 for plankton, invertebrates, fishes, and seabirds.

Surface characteristics of modified carbon nanotubesand its application in adsorption from aqueous solution

Carbon nanotubes (CNT) were modified bynitric acid oxidation. Infrared spectroscopy (IR) demon-strated that hydroxyl (—OH) and carbonyl (—C== O) func-tional groups were introduced to the surface of modifiedCNT. Micrometrics ASAP 2000 measurement showed that the surface area of modified CNT was slightly increased.Furthermore, the Pb2+ adsorption behavior on the surface of modified CNT has been investigated. The results indicate that the modified CNT has an exceptional adsorption capa-bility for Pb2+ removal. The adsorption isotherms are well described by the Langmuir equation under test temperatures and the kinetics level is three.

Photoelectrochemical synergetic degradation of Acid Orange II with TiO_2 modified β-PbO_2 electrode

Electrochemically assisted photocatalysis is an effective approach to improve photocatalytic efficiency. In this paper, modified β-PbO2 electrode was prepared by TiO2 co-deposition and characterized by SEM and XRD. Then 2.0 g TiO2 modified β-PbO2 electrode (2.0 g TiO2 involved in the 200 mL co-deposition solution) was used in electrochemically assisted photocatalytic degradation of Acid Orange II and the influence of initial pH values was investigated when the potential applied across the electrodes was 1.5 V. When the potential applied was 2.5 V, the difference of the degradation process and the final products were studied. The results indicated that 2.0 g TiO2 modified β-PbO2 electrode was different from the unmodified one in that the β-PbO2 crystals became finer and the electrode became more compact and more uniform. The synergetic effect in electrochemically assisted photocatalytic degradation of Acid Orange II was observed and degradation efficiency and TOC removal were the highest at initial solution pH 2.0. By UV-visible spectral analysis, it was proved that photoelectrochemical synergetic degradation of Acid Orange II went through the step of producing main product maleic acid for the solution at the initial pH 2.0 within 2 h, but the degradation was slow for the solution at the initial pH 12.0.

Effects of Ca on the distribu-tion, structure and morphol-ogy of aluminum species in polyaluminum chloride

The flocculation efficiency of polyaluminum chloride (PAC) is closely related to the distribution and structure of its Al species, and Al13 is the optimal species in PAC for flocculation. A series of PAC containing Ca was prepared by adding Ca before and after the basifying reac- tion. The effects of Ca on the Al species were studied by Al 27 nuclear magnetic resonance (NMR) and atomic force micro- scope (AFM) techniques. The experimental results show that the introduction of Ca increases the content of Alm and Al13 in PAC and decreases their chemical shifts in NMR spectra due to the electric repulsion between the positive Ca species and Al species and the formation of Al-O-Ca complexes. With the rise of Ca/Al molar ratio, the Al species in PAC tend to scatter. It is observed that the formerly branch-aggregated clusters are tending to form granule-aggregated ones whose diameter gets smaller and smaller, and the floccule aggre- gates are formed at a higher Ca/Al molar ratio. The intro- duction of Ca to PAC, which increases the Al13 content, is certainly to enhance the flocculation efficiency of PAC in water treatment.