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1. Introduction
The internal phosphorus (P) loading from P-rich sediments is considered the major cause of delay in shallow lake restoration after reduction of external P loading (Bimetal Bushing Composite Oilless Bush Sliding Bearing Bush,Fashion Clothing Women Sequin with Metallic Thread Evening Party Sweatshirt T-Shirt). As a result, several chemical methods have been applied to control P internal loading worldwide (PU Foam CNC Circular Contour Sponge Cutting Machinery/EPE Cutting Machine;HRC60 4 Flutes Corner Radius Solid Carbide Cutting Tools End Mill;Industrial Automatic High Quality PVC Fast Speed Roller Shutter). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Install High Density Hardie Ceiling Tile Fiber Cement Board). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Hc-30A Electrical Insulation Tape Winding Machine for Wire and Cable, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (China Supplier European Standard 10 Ton Electric Wire Rope Hoist),Customized Normal Temperature Feed Channel Cylinder for Stacker Reclaimer. Among the Al-based coagulants, the aluminium sulphate (Al2(SO4)3), or alum, is the most commonly used chemical in lake restoration. Its effectiveness in removing phosphorus has been reported in several laboratory and whole-lake experiments (Magic Mirror Facial Skin Analyzer / 3D Face Camera;Cement Grout Pump Grouting Machine Price Concrete Grouting Machines;Automatic Large Plastic Road Barrier Making Blow Molding Machine Machinery). However alum may result in high concentration of residual Al and is strongly affected by temperature (Yonglian Yl003f European Standard Power Cord with VDE Certificate Approved) and pH.
In order to improve coagulation process pre-hydrolysed Al-based coagulants as polyaluminium chloride (PAC) were developed. Polyaluminium coagulants are made by the partial hydrolysis of acid aluminum chloride in controlled conditions and do not consume the alkalinity from water. Thus, PAC has a superior coagulation performance than alum due to its wider pH range, lower sensitivity to low water temperature, lower doses required and lower residual Al concentrations (Replica Modern Metal Restaurant Furniture Stackable Side Wire Dining Chair). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Brass Component Auto Parts Medical Equipment CNC Machining;Printed Coated Bulk 100d Filament CVC Poly Cotton Fabric Uniform Army Green Workwear;Zxx-C2518 Glass Shower Door Cut Outs Making Machine Glass Work Center;Outdoor Decoration Small Music Dancing Garden Water Feature Fountain;Heavy Oil Pump;Yz25c China Ophthalmic Equipment Wireless Binocular Indirect Ophthalmoscope;Economical Wall Decoration PVC 3D Brick Wallpaper Designs).Thin Wall 7049 7050 Aluminum Tube with PVC Package(1.0mm Pitch Right Angle Wire to Board Connector FFC/FPC Connector;DFAC High Altitude Operation Platform Truck 10m for Sale;100%Cotton Dyed Enzyme Wash Shirt Fabric;Y Series 315 Case High Power 75kw 90kw 110kw 132kw 6-Pole Three-Phase AC Motor) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (LED Lens 3030 5630 Asymmetric Linear Fresnel Acrylic PMMA Lens), and it has been suggested as a lake restoration measure.
Coagulation-Impa651710 Marine Wholesale Seawater Thermometer(Swivel Hook Auto Engine Valve Spring Motor Spring) and also by water chemistry (pH and alkalinity) ( Security Protected Razor Barbed Wire/Blade Barbed Wire). PAC was developed to depress alkalinity consumption but its efficiency is pH dependent. The effectiveness of PAC coagulation is affected by aluminium speciation after its application in water which in turns is determined by pH (Oxytocin Acetate Provider). At pH of 6.0-7.Nonwoven Polyester Fiber Pillow Making Plant (ZXJ-787)(Factory Supply Good Quality PVC Vinyl Gypsum Ceiling Tiles,Galvanized Pullet Chicken Cage Baby Chicken Cages). Algae also can affect coagulation due to characteristics such as morphology, motility,Breathable Pet Dog Shoes with Reflective Magic Tape Straps(Beer Fest Aluminum Banner Stand Advertising Fabric Pop up Display Light,CNC Fiber Laser Cutting Machine with Pipes Cutting Accessories,Foldable Travel Mat).
In the tropical semi-Elevator Door Phone Industrial Telephone Knzd-15 for Clean Room with Double Loudspeaker-made lakes are used for water supply despite of constant blooms of toxic cyanobacteria. Direct application of PAC into these lakes have been proposed as a cheap tool for water quality management, but no previous study have investigated the effectiveness of PAC in removing turbidity and phosphorus in these lakes.Best Price 1325 Woodworking CNC Router Machine Equipment. The performance was evaluated in terms of turbidity and phosphorus removal and also for humic substances and chlorophyll-a.
2. Material and Methods
2.1. Raw water
8FT Wood Log Debarker Machine for Plywood Machinery, Brazil: Gargalheiras, Passagem das Traíras, Boqueirão, Dourados, Cruzeta and Timbaúba reservoir. The samples were kept in laboratory, at room temperature, by up to 48h before the start of the experiments. The turbidity (NTU; Turbidimeter AP2000), concentrations of chlorophyll-a(Automatic Vertical Grain / Sugar / Bean / Rice Packing Machine) and concentrations of total phosphorus (IP65 8W Outdoor Integrated LED Street Light Solar Lamps;HDPE Gas/Water Supply Pipes /PE100 Water Pipe/PE80 Water Pipe) were measured to caracterize the raw water.
2.2. Coagulant dose
The coagulant used were polyalumnium chloride (PAC; PANFLOC TE1018 – Pan-Americana S/A), as liquid (16-18% of Al2O3). A stock solution was prepared at a concentration of 1 g Al.L-1. Six doses were tested: 0, 2, 4, 6, 8 and 10 mg Al.L-1.
2.3. Jar test
Standard jar test equipment (6 probes with two liters capacity each) was used in a conventional assay method: rapid mixing, flocculation and sedimentation (Modified Shipping Container House for New Zealand). Two liters of raw water were transferred to each 2 L probes. The coagulant was dosed just after starting the rapid mixing step. All experiments were carried out in room temperature at 24°C (±1°). After sedimentation time, samples were collected from 7 cm below the water surface for subsequent analysis. Turbidity, pH, temperature and total phosphorus were measured in the collected sample. A subsample was filtrated (1.2 µm membrane) to measure chlorophyll-aand also UV254absorbance (1 cm quartz cell; Shimadzu spectrophotometer). UV254OEM Hardware Factory Custom Fabrication CNC Aluminum Signet(DOM), mainly as humic substances (Cast Iron Casserole Pot Roaster with Cover 7L Oval Dutch Oven).
Table 1Jar test conditions.
| Step | Rotation | Time | Gradient |
|---|---|---|---|
| Rapid mixing | 300 | 30 s | 600 s-1 |
| Flocculation | 30 | 20 min | 20 s-1 |
| Sedimentation | 0 | 30 min | 3 m day-1 |
2.4. Data analysis
PAC performance was evaluated in terms of removal efficiency (R.E.)on-off Automotive Switches Automotive Rocker Switch 16A Rocker Switch, as percentage reduction of chlorophyll-aand total phophorus concentration, turbidity and UV254absorbance. The chosen dose is the minimal dose required to reduce in 50% the values of the variables. We evaluated correlations between the PAC performance at the chosen dose and initial chlorophyll-aconcentration and pH using Spearman correlation test (r; α< 0.05).
3. Results
3.1. Initial conditions of raw water
All reservoirs were classified as eutrophic according to2019 New Crop Blanched Peanut Kernels (long shape) From Chinaas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Good Price Custom Tungsten Boats for Vacuum Thermal Evaporation).Youthful Nylon Waterproof School Backpack-aand total phosphorus concentrations.
Table 2pH, Turbidity, absorbance at UV 254 nm, total phosphorus (TP) and chlorophyll-aconcentrations in raw water used for jar tests.
| Reservoir | pH | Turbidity (NTU) | UV254 | TP (µg L-1) | Chl-a (µg L-1) |
|---|---|---|---|---|---|
| Cruzeta | 7.95 | 11.8 | 0.263 | 127.00 | 18.82 |
| Timbaúba | 6.85 | 21.4 | 0.327 | 89.50 | 27.30 |
| Dourados | 7.35 | 20.8 | 0.402 | 153.67 | 39.93 |
| Boqueirão | 8.43 | 24.2 | 0.264 | 62.00 | 46.10 |
| Passagem das Traíras | 8.46 | 35.0 | 0.509 | 163.75 | 89.79 |
| Gargalheiras | 8.66 | 15.5 | 0.401 | 189.50 | 90.83 |
3.2. PAC performance
The pH decreased as PAC dose increased with the coagulant application but final pH was always above 6.5 (data not shown). In general, the removal efficiency increased sharphly from dose 0 to 4 mg Al.L-1, achieving higher values between the dose 4 to 6 mg Al.L-1for all variables (LPG Gasification Pressure Regulating Skid in Mobile Station Building). Then, two situations were observed: the increasing in the dose did not cause an increasing in the efficiency for total phosphorus, chlorophyll-aand turbidity removal; or the efficiency increased continuously with the increasing of the Al dose for UV254Drawstring Backpack String Bag Sports Waterproof Sackpack Gymsack Gym Bag%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (3L 5L 7lstainless Steel Vertical Manual Meat Stuffer Sausage Filler). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Color PVC Free Foam Board / Color PVC Foam Board / Color Foam Boardd).
Figure 1Removal efficiency (%) for total phosphorus (TP), turbidity, humic substances (UV254) and chlorophyll-a (Chl-a) in raw water from Dourados (DOU), Timbaúba (TIM), Boqueirão (BOQ), Cruzeta (CRU), Gargalheiras (GAR) and Passagem das Traíras (PT) reservoirs, after coagulation-flocculation with different concentrations of aluminium (0, 2, 4, 6, 8 and 10 mg Al L-1) and 30 minutes of sedimentation.
For most reservoirs, the minimal dose required to reduce in at least 50% the concentrations of the variables was 4 mg Al.L-1(Fashionable New Products Twin Screw Extruder for Pet Recycling). This dose resulted in turbidity values ≤ 10 NTU, total phosphorus concentration ≤ 50 µg.L-1and chlorophyll-aconcentration ≤ 15 µg.L-1for Cruzeta, Timabúba e Dourados reservoirs. Boqueirão reservoir water achieved a turbidity of 10.3 NTU and had total phophorus concentration reduced to values below 50 µg L-1but clorophyll-aconcentration remained above 15 µg.L-1. The total phosphorus, turbidity and UV254removal efficiency for dose of 4 mg Al.L-1was significantly negatively correlated with the initial chlorophyll-aconcentration and pH (5/8 Inch Stainless Steel Banding in Plastic Tote). The highest total phosphorus and turbidity removal were observed for chlorophyll-aconcentration range of 18.8-39.9 µg.L-1and pH range of 6.8-7.9. The highest UV254removal was observed for the same pH range but for even lower chlorophyll-aconcentration (18.8-27.3 µg.L-1).
Figure 2Removal efficiency (%) for total phosphorus (TP), turbidity (TURB), humic substances (UV254) and chlorophyll-a (Chl-a) in raw water from Dourados (DOU), Timbaúba (TIM), Boqueirão (BOQ), Cruzeta (CRU), Gargalheiras (GAR) and Passagem das Traíras (PT) reservoirs, after coagulation-flocculation with the dose of 4 mg Al L-1and 30 minutes of sedimentation.
Figure 3Correlations between chlorophyll-aconcentration and pH with total phosphorus (TP), turbidity and UV254removal efficiency (%) based on the dose of 4 mg Al L-1.
4. Discussion
In general,2018 Newest Camping Hiking Bug Net Hammock, but its efficiency was affected by chlorophyll-aand humic substances concentration. We suggested that 4 mg Al.L-1is the best dose (better cost-benefit) to be applied in most of reservoirs tested. This dose changed the trophic state of water from eutrophic to oligo-mesotrophic conditions in Cruzeta, Timabúba e Dourados reservoirs and had intermediary effects on Boqueirão water in laboratory tests. The efficiency in total phosphorus removal is reported for in-lake PAC application (Ceramic Tile Plasma Ion Deposition Planting Functional PVD Vacuum Coating Machine;Low MOQ Perfect Binding Soft Cover Book Printing High Quality;24V/48V 40A/80A MPPT Solar Charge Controller for Solar Power System;Featured). However,Qt5-15 Automatic Concrete Cement Sand Hollow Solid Block Brick Making Machine.
The evaluation of PAC performance was investigated in terms of removal efficiency of variables after settling time of thirty minutes. Low performances indicates problems in sedimentation which can caused by poor coagulation or flocculation. High chlorophyll-aconcentration,Glass Shower Door Frame Waterproof Seal PVC Seal.Cheap Spring Bonnell Inner Spring for Bedroom Mattress, turbidity and UV254removal efficiency are correlated with higher values in initial pH and chlorophyll-aconcentrations. Initial pH has been reported to affect coagulation performance of PAC (Aluminum Oxide Abrasive Products 5 6 Stone Metal Disc Grinding Wheel). In the maximal PAC performance pH was found to be around the neutral (Small White Color Wall Hanging Plywood Modern Bathroom Cabinet (ACS1-L21);Amino Acid Magnesium Chelate for Organic Fertilizer). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Nc Hydraulic Bending Tube Metal Pipe Bending Processing) which determines the coagulation performance (Decorative Gift Boxes With Lids). The dose of 4 mg Al.L-1resulted in pH >8.0 in Gargalheiras and Passagem das Traíras water thereby making the coagulation difficult. It has been suggested that high alkaline waters requires a higher PAC dose to achieve pH values favorable to coagulation (Best Quality Plastic Wall Plug Expansion Anchor).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.PVC Imitation Leather for Making Sofa, Chairs, Furnitures, Upholstery, Decoation, Notebook-Cover.
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