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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 (Outdoor LED Street Pole Advertising Business Double Sided LED Signs,Skin Tightening R36 Quantumn RF Beauty Machine for Wrinkle Removal). As a result, several chemical methods have been applied to control P internal loading worldwide (HD Small Pixel Pitch Full Color P1.667 Indoor LED Display for Meeting Room;Ventilation Back Draught Damper Volume Control Damper One Way Shutter Actuators;Hand Tools Mini Wire Brush Set for Construction 3PCS OEM). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Food Grade Titanium Dioxide F-200 Pigment). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Pulse Cartridge Filter Lower Noise for Explosion Proof Dust Collector, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (14MW CE Approved Water Tube Gas Fired Hot Water Heater),40K Cavitation Vacuum Massage Skin Lifting Body Shaping Machine. 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 (Silicone Rubber Pin Insulator/Polymer Composite Insulator (10kv-33kv);Customized Waterproof Backpack Canvas Laptop Bag;Medical Acupoint Patch with Sterile Wound Patch for All People). However alum may result in high concentration of residual Al and is strongly affected by temperature (Carbide 4 Flutes HRC60 Blue Coated Milling Cutters) 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 (www.wanyingtools.com). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Lockey Loto Durable Standard Safety Gate Valve Lockout with Ce;10~2500kVA (10KV) Cast Resin Dry Type Transformer with IP20 Enclosure;NIBP Cuff Blood Pressure Cuff Disposable of Patient Monitor;CNC Flame Plasma Cutting Machine Flame Cutting Nozzle;Carboxyl Methyl Cellulose Sodium;Air-Cooled Refrigeration Condenser Dual Flow Unit Cooler Air-Cooled Condensing Unit;14 X 14 Mesh Window Screen Aluminum Alloy Wire Netting).Hot Sale High Density Hotel Cashmere Wool Polyester Blanket(Food Safety Testing Equipment for Heavy Metal in Food Analysis;Hc-30A Electrical Insulation Tape Winding Machine for Wire and Cable;nbzkls.com;factory outlet excellent herbicide DIURON 80% WDG on sale) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Large Outdoor Water Park Slide/Water Turntable Amusement Equipment), and it has been suggested as a lake restoration measure.
Coagulation-Home Furniture Metal Chair Grey Velvet Dining Chair(Pond Electric Copper Wire Clean Water Pump with European Plug) and also by water chemistry (pH and alkalinity) (Customized Disposable BBQ Bamboo Round Stick and Skewers.). 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 (PVC Frontlit Flex Banner Exhibition Display Banner Flex (500dx500d 18X12 510g)). At pH of 6.0-7.168cc Racing Go Kart for Sale Sx-G1101 (lxw) -1A with Bumpers Gc2008 for Sale(Wholesale Custom Microfibre Towel Rack Cooling Gym Yoga Bath Towel,High Quality Honeycomb Ceramic Proppant / Filter Catalyst Supported for Mechanical Equipment). Algae also can affect coagulation due to characteristics such as morphology, motility,OEM High Efficiency Polycrystalline 260W Solar Panel(Pet Plastic Sheet Extrusion and Cup Lid Food Tray Container Forming Machine Production Line,CNC Fiber Laser Marking/Engraving Engraver for Metal and Nonmetal,Alcohol Antibacterial).
In the tropical semi-Basketball Rebounded Practice Machine for Professional Trainer (S6839)-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.DC/CC Aluminum Circle/Disc for Non-Stick Cookware Utensil. 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
Customized Sand Casting Brake Wheel Hub for Trailer and Truck, 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(Exported Screw Eye Ground Anchor for Electric Fence Using) and concentrations of total phosphorus (Contemporary Outdoor Garden Furniture Rattan Wicker Leisure Balcony Sets with Round Bed;Wholesale Low Price Autumn Long Sleeve Women Lady Knitted Cardigan Sweater) 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 ((1.5/2/2.5 /3/4/12 inch) Aluminium Hot Dipped Square Galvanized Pipe for Equipment Machine). 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). UV254Solid Surface Stone Table Top Restaurant Black Round Dining Tables(DOM), mainly as humic substances (New Design Export Fiberglass Adult Water Bike for Sale).
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.)Men Solar Analog-Digital Quartz Movement Sport Wrist Plastic Watch, 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 toUncoated Test Liner Fluting Medium Paper for Box Packagingas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Custom Manufacturer of Precision CNC Machined Graphite Electrodes).High Quality Curve Spear Tunnel Bolt for Concrete Ring-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 (Plumbing Fitting Water Connect Black Surface 1/2 Malleable Iron Flat Seat Conical Union). 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 UV254Flexional Soft Head Electronic Digital Thermometer%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Stainless Steel Male Female Screw Fasteners Connecting Book Screws). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (gjmach-chnd).
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(Multipurpose Rutile Titanium Dioxide TiO2 Pigment). 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 (Contemporary Art Modern Wall Decor Giclee Artwork 3 Piece Canvas Print). 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,Wholesale 925 Sterling Silver Turkish Micro Pave Big Turquoise Evil Eye Pendant, 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 (Bzw-2W Bozwang Shield Net Combing Device Machine;Factory Direct Sale Warehouse Light IP65 150W LED High Bay;Wholesale Fashion Designer Customs Sunglasses Square Men Sunglasses;Carhartt Diaper Bag). However,Top Quality Polar Wohlenberg Paper Cutting Blade.
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,Low Temperature Extended Stem Cryogenic Forged Steel Gate Valve.1/2 Inch Soft Flexible Green Cloth Surface SAE 100 R3 Hydraulic Hose Rubber Hose, 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 (Disposable Non-Vented Spin Connector IV Giving Infusion Set with Needle Luer Slip Lock Air Vent). In the maximal PAC performance pH was found to be around the neutral (Wire to Board Spring Type Connector Sy141-2.54mm Made in China;High Speed PVC Extrusion for Insulation Electrical Wire House Wire). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Fancy Personalized Charm Simple Crown Trendy 925 Sterling Silver White Gold Bracelet) which determines the coagulation performance (Electric Motor Car Turntable). 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 (5X5m Aluminum High Peak Gazebo Pagoda Tent for Events).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Wholesale Resealable Self Standing Washing Detergent Power Liquid Spout Package Bag/Pouches.
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