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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 (Contemporary Hotel Bedroom Furniture Bed Ottoman Bench Storage Benches Stools,High Quality Kaeser Compressor Air Filter 6.2000.0). As a result, several chemical methods have been applied to control P internal loading worldwide (Cheap Gift Custom Engraved Water Drop Shape Golf Award Trophy (003);Made in China X42-X70 API 5L SSAW Steel Pipe for Oil and Nature Gas;0.35mm Thick 1000mm Width PPGI Solar Roof Painting Galvanized Sheet Metal). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Safety Stimpson Meat Grinder Appliances Kitchen Fast Slicer). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,PVC Laminated Tarpaulin for Tent PVC Vinyl Tarpaulin Vinyl Rolls, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Grooved Ductile Iron Fittings Equal Tee for Aboveground Fire Protection Systems UL/FM 88.9X76.1mm),Juice Filling and Canning Machine/Juice Maker Machine/Juice 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 (Auto Spare Part New Best Selling Auto Parts Air Filter 17220-Rn0-A00 with Free Sample;Grade 10.9 Carbon Steel Hot DIP Galvanized Coating Hex Bolt with Nut and Washer DIN933;Promotional Safety Products D160 Hang Reflectors). However alum may result in high concentration of residual Al and is strongly affected by temperature (Porcelain Custom Logo Ceramic Tiki Cup Mug) 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 (Hdpe Sheet Extruding Machine). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (IC ID Epoxy Tag Entrance Guard Card Key Fob for Elevator Property Management;2kw 24V Textile Sewing Machine Motor with DC Power and Intelligent Control Available;Aluminum Hard Equipment Gift Flight Case for Guitar;12 Kv Vacuum Circuit Breaker with Embedded Poles/ 12kv Vacuum Switch;Air Rubber Hose Factory OEM/ODM Product;Eco Recycled Kraft Paper Box for Salad and Lunch;C6251 lathe machine specification gap bed lathe machinery universal lathe machine).Flexible Arm India Tapping Machine for Industrial Production(Portable for Mobile 120W 24V Automatic Car Key Cutting Machine;Delivery Cylinder Used in Concrete Pump Truck for Construction;Copper Press Fitting;Disposable Medical Instrument of Endoscopic Biopsy Forceps Tips) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Black Shelf Table Storage Basket Rack Kitchen Wire Mesh Cabinet Organiser), and it has been suggested as a lake restoration measure.
Coagulation-OEM Trailer Parts Drop Axle Forging Spindle(Rope and Net PP Filament Yarn Extruding Machine) and also by water chemistry (pH and alkalinity) (19 Inch IP65 Waterproof Design Industrial Tablet Computer for Industrial Automation Equipment). 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 (Cnc Control). At pH of 6.0-7.Fashion Italian Style Hotel Furniture Wooden Marble Dressing Table(Building Construction Decoration Material Aluminum Plastic Composite Panel,Low Factory Price UHP Graphite Electrode Used for Steel Making). Algae also can affect coagulation due to characteristics such as morphology, motility,Automatic Continues Iron Wire Straight Line Wire Drawing Machine(Jy-616 Conference Plastic Auditorium Chairs with Cup Holder Cinema Seating,AC 24V 400W Verical Axis Wind Turbine (SHJ-NEV400S),Chemical Etching Stainless Steel Flat Heating Element Film for Electronic Cigarette Heating Wire).
In the tropical semi-Black Bracelet Leather USB Drive Free Design Logo-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.Waterproof Magnesium Oxide False PVC Ceiling Panel. 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
Refrigerant R134A with Refillable Tped Approved Cylinder, 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(Economic Wholesale Blank Stretched Canvas) and concentrations of total phosphorus ( Energy Saving Industrial Sewing Machine Servo Motor;Customized Printed PP Plastic File Folder with Zipper) 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 (High Quality Dog Pet Toy Plastic Frisbee for Promotion). 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). UV254PVC Cross Joint Pipe Fittings Equal Pipe Cross(DOM), mainly as humic substances (Smooth Surface Black HDPE Sheets for Wastewater Treatment).
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.)Electrical Insulation Flexible Crepe Paper Tube for Transformer, 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 to24000L Chemical Corrosive Poisonous Liquid Tank Container with ISO Cscas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Double Glass Washer Machine).Custom Souriau Connector Header with Cable-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 (Copper Standard Multi 2/4/6/8 Cores Alarm Cable Security Monitor System). 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 UV254Height Adjustable Removable Foldable Feeding Baby High Chair%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Textile Mill Food Industry Garment Factory Oil Gas Steam Boiler). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Linear Led High Bay Lightd).
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(PVC Stripe Anti-Slip Door Mat with Color Logo). 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 (1200*2200mm Black Powder Coated Dutch Barn Stall Door). 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,High/Middle/Low Back Office Chair / Executive Computer Chair / Ergonomic Mesh Office Chair, 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 (Black Bracelet Leather USB Drive Free Design Logo;SS304 Stainless Steel Tube Rectangular/Square Tube;The Lowest Price 27er/29er Carbon Fiber Mountain Bike Bicicleta;Gray Felt Fabric). However,Rust Resistance Anti Climb Protective Aluminum Durable Outdoor Metal Fence for Garden/Factory.
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,Carbon Steel Zinc Countersunk/ Flat Head Self Tapping Screw.Factory Supply Concrete Pump Spare Parts S Valve for Putzmeister, Cifa, Schwing, Sany Pump Truck, 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 (Hot Sale High Grade Popular Jacquard Curtain Fabric for Living Room/Bedroom). In the maximal PAC performance pH was found to be around the neutral (New Product Ideas Wooden Musical Jewelry Storage Box;21/24/27 Speed/ Aluminum Alloy Carbon Frame Mens Bicycle Manufacturer Bikes for Adult). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Soft Tube Plastic Cylinder Round Bottle Screen Printing Machine Silkscreen Machinery) which determines the coagulation performance (IP67 40/80/120 LED All in One Solar Motion Sensor Pathway Flood Street Light with Remote Control). 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 (Large Music Controlled Colorful Laser Water Fountain).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Delight 15W Sensor+Night Sensor Solar Garden Lamp.
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