Treatment Of Eutrophic Water Research Articles

Full-scale dissolved air flotation (DAF) equipment for emergency treatment of eutrophic water.

Eutrophication of urban rivers has caused severe environmental problems due to the pollution from point and diffuse sources. Although eutrophication can be alleviated by reducing the input to the river system, fast-treating terminal control technologies, especially under emergent situations, should be developed to reduce risks induced by eutrophication. The present study developed an emergency purification device based on dissolved air flotation (DAF) technology. After equipment commissioning and parameter optimization for applications in the field of engineering, the device was found to effectively remove total phosphorus, chlorophyll a, chemical oxygen demand, and turbidity in water by controlling the coagulant dosage and adjusting the gas-liquid mixing pump parameters. Dissolved air in water could enhance dissolved oxygen, and dissolved oxygen in polluted rivers could be raised from 0.2-2 mg/L to 3-3.5 mg/L. Removal of total nitrogen was poor because the majority of nitrogen contents were dissolved. Finally, DAF has been proven to be a promising technology due to its ease of implementation, low equipment investment requirement, and low operation cost.

Application of Mg–Al-modified biochar for simultaneous removal of ammonium, nitrate, and phosphate from eutrophic water

Water eutrophication is a serious environmental problem worldwide. Biochar derived from the thermochemical treatment of biomass, particularly the modified biochar, can be used as a new type of adsorbent for environmental management. In this study, Mg–Al-modified soybean straw biochars (Mg/BC, Al/BC, and Mg–Al/BC) were prepared to remove NH4+, NO3−, and PO43− from eutrophic water. Brunauer–Emmett–Teller analysis, X-ray diffraction spectroscopy, scanning electron microscopy, and Fourier transform infrared techniques were used to characterize the physical and chemical properties of the biochar. The single-solute-adsorption properties and adsorption kinetics of NH4+, NO3−, and PO43− were initially examined. Results showed that the maximum adsorption capacities for NH4+ (0.70 mg/g), NO3− (40.63 mg/g), and PO43− (74.47 mg/g) were achieved on Mg–Al/BC, Al/BC, and Mg/BC, respectively. The bi-solute-coadsorption and tri-solute-coadsorption properties of NH4+, NO3−, and PO43− were then studied to simulate the adsorption in actual eutrophic water. Mg/BC and Al/BC can be used to treat eutrophic water contaminated with PO43− and NO3−, respectively. Mg–Al/BC could effectively improve the quality of water whereNH4+, NO3−, and PO43− coexist. Therefore, the Mg–Al-modified biochars can be used as an excellent adsorbent for the treatment of eutrophic water.

Sedimentation and resuspension modelling in free water surface constructed wetlands

Eutrophication is a widespread problem that is being tackled from many perspectives and the recently applied technology of constructed wetlands is being used in the treatment of eutrophic water. However, process-based models to simulate their performance are scarce, so in this work a mechanistic model was developed to simulate the removal of total suspended solids, phytoplankton and total phosphorus in free water surface constructed wetlands treating eutrophic water. The model represents the influence of the main factors of the biotope and biota on these water quality variables, and particular attention is paid to resuspension produced by wind and by avifauna. Likewise, the effect of emergent vegetation cover in sedimentation, resuspension and phytoplankton growth is included. Phytoplankton is considered to store phosphorus internally in order to use it when growing, and the contribution of phytoplankton concentration to the suspended solids budget is included. The software AQUASIM was used to calibrate and validate the model in two full-scale constructed wetlands treating eutrophic water from Lake l′Albufera de València (Spain) for three years. The simulated data and field measurements showed satisfactory adjustments for the three studied variables. The budgets obtained for each variable reveal that sedimentation and resuspension are the main processes in total suspended solids performance. Sedimentation of organic particulate phosphorus is the most important process in total phosphorus removal. The sum of the effect of resuspension by avifauna and by wind increases by more than 50% the quantity of solids that enters the water column. The model reveals that simulating the effects of the emergent vegetation cover and resuspension is crucial for representing the performance of the studied variables.

Removal Characteristics of Organic Pollutants from Eutrophic Raw Water by Biological Pretreatment Reactors

Two biological contact oxidation reactors, cascade biofilm reactor (CSBR) and one-step biofilm reactor (OSBR), were used in this paper for pretreatment of eutrophic water from Lake Taihu in China. The CSBR was more effective and stable for eutrophic water treatment than OSBR, in terms of extracellular microcystin-LR,chlorophyll-a, DOC, and biodegradable dissolved organic carbon (BDOC) removal. Removal efficiencies of extracellular microcystin-LR andchlorophyll-a were 75.8% and 59.7% in CSBR and 60.5% and 53.0% after 2 h in OSBR. CSBR had much higher removal efficiency (34.3%) than OSBR (22.7%) for DOC, and CSBR could remove 67% BDOC, accounting for 34% of total DOC in source water. 11.5% of DOC was removed through means other than biological degradation, such as biofilm adsorption and bioflocculation. In CSBR at 5.5~13°C, 57.5% of atrazine was removed at 2 h hydraulic retention time, with background concentration of 136.5 ng/L. Meanwhile, removal efficiencies of three phthalic acid esters (PAEs) (dimethyl phthalate, di-(2-ethylhexyl) phthalate, and di-n-butyl phthalate) were 78.7%, 52.4%, and 85.3%, respectively. Only 35.2% of polycyclic aromatic hydrocarbons (PAHs) could be removed by CSBR with initial concentration of 21.5 μg/L. The results indicated that CSBR is effective in low-molecular-weight organic pollution pretreatment and provides benefits in terms of effluent quality.

Evaluation of disinfection by-product formation potential (DBPFP) during chlorination of two algae species — Blue-green Microcystis aeruginosa and diatom Cyclotella meneghiniana

Microcystis aeruginosa (blue-green alga) commonly blooms in summer and Cyclotella meneghiniana (diatom) outbreaks in fall in the reservoirs that serve as drinking water sources in Southeast China. Herein, an evaluation of disinfection by-product formation potential (DBPFP) from them during chlorination should be conducted. Five DBPs including trichloromethane (TCM), trichloronitromethane (TCNM), dichloroacetonitrile (DCAN), 1,1-dichloropropanone (1,1-DCP) and 1,1,1-trichloropropanone (1,1,1-TCP) were monitored. The formation potential of TCM and TCNM was enhanced with the increase of reaction time and chlorine dosage, whereas that of DCAN, 1,1-DCP and 1,1,1-TCP increased first and then fell with continuing reaction time. M. aeruginosa showed higher DBPFP than C. meneghiniana, the yield of DBPs varied with components of algal cells. The DBPFP order from components of M. aeruginosa was cell suspension (CS)≈intracellular organic matter (IOM)>extracellular organic matter (EOM)>cell debris (CD), which indicated that IOM was the main DBP precursors for M. aeruginosa. The yields of DBPs from components of C. meneghiniana were in the order of CS>IOM≈CD≈EOM, suggesting that three components made similar contributions to the total DBP formation. The amount of IOM with higher DBPFP leaked from both algae species increased with the chlorine dosage, indicating that chlorine dosage should be considered carefully in the treatment of eutrophic water for less destroying of the cell integrity. Though fluorescence substances contained in both algae species varied significantly, the soluble microbial products (SMPs) and aromatic protein-like substances were the main cellular components that contributed to DBP formation for both algae.

Effects of Fructus ligustri lucidi on the growth, cell integrity, and metabolic activity of the Microcystis aeruginosa.

Agricultural waste has been used in the treatment of cyanobacterial bloom because of its environmental friendly and cost-efficient characteristics. In this work, the effects of Fructus ligustri lucidi (FLL) on the growth inhibition, physiological properties, algicidal property, and cell ultrastructure of Microcystis aeruginosa were investigated for the first time. The alga was efficiently inhibited by FLL at the dosages from 0.25 to 4.0gL(-1), and the Chl-a fluorescence and metabolic activity of cells also declined gradually. During 25days incubation time, the inhibition ratio of 0.25gL(-1) dosage increased from 8 to 68%, the percentage of intact cells decreased from 94.4 to 59.8%, the inhibition ratio of 2.0 and 4.0gL(-1) dosages was nearly 100%, and the cell membranes were completely broken. The results of Chl-a, propidium iodide (PI) staining, fluorescein diacetate (FDA) staining, and transmission electron microscopy (TEM) assays were consistent with that of growth inhibition tests. The new medium test with the PI staining test suggested that FLL may act as an algicidal agent which can inhibit the growth of M. aeruginosa in the acute time. Consequently, FLL could be an excellent choice in the treatment of eutrophic water.

Brackish Eutrophic Water Treatment by Iris pseudacorus L.-Planted Microcosms: Physiological Responses of Iris pseudacorus L. to Salinity

Iris pseudacorus L. has been widely used in aquatic ecosystem to remove nutrient and has achieved positive effects. However, little is known regarding the nutrient-removal performance and physiological responses of I. pseudacorus for brackish eutrophic water treatment due to high nutrients combined with certain salinity levels. In this study, I. pseudacorus-planted microcosms were established to evaluate the capacity of I. pseudacorus to remove excessive nutrients from fresh (salinity 0.05%) and brackish (salinity 0.5%) eutrophic waters. The degradation of total nitrogen and ammonia nitrogen were not affected by 0.5% salinity; 0.5% salinity promoted the degradation of nitrate nitrogen while severely inhibited the degradation of total phosphorus. Additionally, 0.5% salinity was found to induce stress responses quantified by measuring six physiological indexes. Compared to 0.05% salinity, 0.5% salinity resulted in significant decreases in the chlorophyll a, b and total chlorophyll contents of I. pseudacorus which closely related to photosynthesis (p < 0.05). Furthermore, the higher proline, malondialdehyde contents and antioxidant enzyme activities were detected in I. pseudacorus exposed to 0.5% salinity, which provided protection against reactive oxygen species. The results highlight that the cellular stress assays are efficient for monitoring the health of I. pseudacorus in salinity shock-associated constructed wetlands.

Role of biologic components in a novel floating-bed combining Ipomoea aquatic, Corbicula fluminea and biofilm carrier media

A novel floating-bed incorporated with water spinach (Ipomoea aquatica), Asiatic clam (Corbicula fluminea), and carrier media supported biofilm was developed for eutrophic water purification. The contributions of each biologic component to the removals of total nitrogen (TN), total phosphorus (TP) and Chl.a were examined. The nutrient removals due to the direct uptake by either water spinach or Asiatic clam were less than 10%, suggesting a negligible role of biologic assimilation and leaving the biofilm as the indispensable biologic component in the floating-bed. Chl.a was reduced mainly by Asiatic clams via filter-feeding. Meanwhile, the digestion and excretion of Asiatic clams benefited the proliferation of nitrifying and denitrifying bacteria, resulting in the improvement of TN removal. In summary, the synergetic effects of water spinach, Asiatic clams and biofilms would promote the eutrophic water treatment performance of floating-bed in comparison with the conventional floating-bed with vegetation as the single biologic component.

Effects of light intensity and magnesium supplementation in pretreatment cycle on ammonium removal from wastewater of photobioreactor using a biofilter composed of the aerial microalga Trentepohlia aurea

Application of a laboratory-scale photobioreactor containing a biofilter composed of the aerial microalga Trentepohlia aurea to the removal of ammonium from synthetic wastewater was assessed to determine whether the system could be applied to water purification and the treatment of eutrophic water. The removal efficiency of the photobioreactor was tested after ten biofilter sheets (total dry weight cells: 50 mg) were cycled in nitrogen-free Bold’s basal (BB) medium for 72 h (pretreatment cycle). The ammonium removal ability was significantly enhanced when the photobioreactor was operated after performing the pretreatment cycle using nitrogen-free BB medium supplemented with magnesium. Moreover, the illumination conditions during the treatment were shown to affect the nitrogen removal ability, and this ability was strongly dependent on the concentrations of organic compounds (e.g., α-ketoglutarate and pyruvate) for assimilating the nitrogen source in the T. aurea biofilter.

Synthesis of mesoporous graphene and tourmaline co-doped titania composites and their photocatalytic activity towards organic pollutant degradation and eutrophic water treatment

Mesoporous graphene and tourmaline co-doped titania composite was prepared using a direct sol–gel co-condensation combined with solvothermal treatment technique. The composite exhibited a three-dimensional (3D) interconnected mesostructure and anatase phase-structure with a large surface area (218 m2 g− 1) and uniform pore size. Compared with pure titania, the photocatalytic activity of the composite was enhanced significantly towards aqueous organic pollutant rhodamine B and norfloxacin degradation under simulated sunlight irradiation. Subsequently, this composite was successfully applied to the actual eutrophic water treatment.

Fate of 15NO3− and 15NH4+ in the Treatment of Eutrophic Water Using the Floating Macrophyte, Eichhornia crassipes

Use of the floating aquatic macrophyte, , to improve eutrophic water quality is practiced on a large scale in China. Limited information is available on the relative importance of the biological NO or NH removal process during the treatment of eutrophic water using . To investigate the key process responsible for the removal of NO and NH, N-NO (9.98 atom % [at.%] N) or N-NH (10.08 at.% N) was added to obtain eutrophic water with or without the cultivation of . In the unplanted water, considerable proportions of the added N-NO (27.13 ± 4.87%) or N-NH (42.08 ± 7.22%) were assimilated by the developed algae. The growth of controlled algae development in the planted water. Furthermore, the cultivation of stimulated gaseous loss of N by microbial denitrification (8.61 ± 1.70% NO-N loss from N-NO-labeled water). Apart from N loss by denitrification, considerable proportions of the added N-NO (62.01 ± 6.93%) or N-NH (76.76 ± 6.21%) were assimilated into the macrophyte N pools. The fine root detritus of contained a proportion of N (4.37 ± 1.39% in NO-labeled water, 2.03 ± 0.52% in NH-labeled water) that will be returned to the water after decomposition. In addition to N loss via NO emission, an unaccounted proportion of N could be mainly due to gaseous loss as N by denitrification (25.00% in N-NO-labeled water with Eichhornia crassipes)

Environmental and economic analysis of application of water hyacinth for eutrophic water treatment coupled with biogas production

The proliferation of water hyacinth is currently controlled by removing it from a water body and disposing it by landfill in China. Using water hyacinth to remove nutrients from water bodies and to produce biogas is another technically feasible option for the control of water hyacinth, but its environmental and economic performances are not well understood. This study collected data from an experimental biogas plant to develop a lifecycle analysis and a cost benefit analysis for the control of water hyacinth proliferation in a eutrophic lake in China. Comparison was made between the alternative option of using water hyacinth for biogas production and the current practice of disposing it in landfills. The results reveal that the biogas option is economically feasible with a positive energy balance. The removal of water hyacinth to produce biogas can contribute to water quality improvement and GHG emission reduction whose values, however, depend on the processing scale of the biogas plant. Since both the current approach and the biogas option can remove nutrients from water bodies, the additional value of water quality improvement resulting from the biogas option is only possible when the processing scale of the biogas plant is greater than the amount of water hyacinth disposed by landfill. The emission of methane deserves attention when water hyacinth is disposed by landfill. The biogas option can respond to China's policies on water pollution control, renewable energy development, and energy saving and emission reduction.

Comparison of ozone and hydrogen peroxide/ozone for the treatment of eutrophic water

Tests carried out on eutrophic waters using ozone and peroxone (peroxide and ozone) indicated that an applied ozone concentration of between 1 and 1.5 mg/l (ozone:DOC ratio of 0.2 to 0.5) was generally required before significant removals of natural organic matter surrogate parameters and micropollutants were obtained. Peroxone produced the same effect as ozone used alone, but the maximum effect occurred at a lower ozone concentration when using peroxone. Peroxide to ozone ratios greater than 0.3 to 0.5 were not found to increase the benefit derived from the addition of peroxide.

Comparison of ozone and hydrogen peroxide/ozone for the treatment of eutrophic water

Tests carried out on eutrophic waters using ozone and peroxone (peroxide and ozone) indicated that an applied ozone concentration of between t and 1.5 mg/I (ozone:DOC ratio of 0.2 to 0.5) was generally required before significant removals of natural organic matter surrogate parameters and micropollutants were obtained. Peroxone produced the same effect as ozone used alone, but the maximum effect occurred at a lower ozone concentration when using peroxone. Peroxide to ozone ratios greater than 0.3 to 0.5 were not found to increase the benefit derived from the addition of peroxide.