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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 (Ouwave HVAC Scent Fragrance Systems Aroma Diffuser Electric Scent Machine,Solar Panel System Adjustable Roof Mounting Front Legs). As a result, several chemical methods have been applied to control P internal loading worldwide (120 Grit Sand Blasting Media/Sandblasting Abrasives/Almandite/Garnet Sand 80 for Waterjet Cutting;Ci/Di/Ss/C954 Al Bronze Body Double Flange Butterfly Valve Pn10 Pn16 Pn25;Modular Concrete Batching Plant by Twin Shaft Mixer 3000/2000). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Virtual Reality Egg Game Machine Amusement Riding Machine for Sale). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Updated Stylish Peristaltic Biogas Pump Gas Booster Pump, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (High Quality PVC Ceiling Board Waterproof PVC Foam Sheet PVC Foam Sheet Manufacturer),Auto Parts High Quality Plastic Injection Moulding. 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 (Ad-P720 Hot-Selling Perfume Glass Bottle 100ml;Whole Sale Banquet Tiffany Classic Stackable Gold Louis Dining Chair;Hidrotek Water Filter Cartridge with Sediment Carbon). However alum may result in high concentration of residual Al and is strongly affected by temperature (9.7 Inch Poe Android Touch Screen Tablet with Vesa Mounting) 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 (Stainless Steel Tube/Steel Pipe AISI304/316L/201/202/430/410L). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Stainless Steel Grade U2 U3 Stud Link Anchor Chain with Factory Price;Diesel Fuel Leak off Pipe for Mercedes-Benz;Automatic Plastic Pet Preform Injection Moulding Machine Price;High Quality Polyurethane Adhesive for Scrap Sponge;Wholesale Inflatable Air Sofa Lazy Sleeping Bag with Tent;Carbon Steel Carry Idler Belt Conveyor Guide Roller;Rexroth Hydraulic Pump A8V55/80/107 Replacement Spare Parts).Wicker Willow Flower Garden Gardening Basket(Factory Supply Customized Sintered Inner Gear Rotor by Iron Alloy Powder;2750OE Hico 12.7mm Width Plastic Magnetic Stripe Card for VIP Card;Rigid Style Presentation Box with Lift off Lid;Quick Link Cotton Baling Wire with Single Double Loops Bale Tie Wire) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (High Automatically Vacuum Hydraulic Oil Filtration Equipment for Oil Recycling), and it has been suggested as a lake restoration measure.
Coagulation-Automatic Small Round Bottle Water Washing Filling Capping Machine(ASTM A792 PPGI PPGL Roof Sheet Cold Rolled Steel Coil) and also by water chemistry (pH and alkalinity) (Modular Functional L Shape Living Room Leather Sofa). 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 (500 Ton Injection Molding Machine). At pH of 6.0-7.Tungsten Carbide Cold Heading Dies for Screws and Nuts(Dish Plate Dryer and Sterilizer 60liter Using UV and Ozone,High Quality CNC Turning Center Parts Machinery Auto Parts). Algae also can affect coagulation due to characteristics such as morphology, motility,201 Stainless Steel Coil /Stainless Steel Sheet /Stainless Steel Plate(Factory Price Gerneral Usage Silicone Sealant,Transparent 240W SMD 3030 Outdoor LED Flood Lamp,2.4g Antenna).
In the tropical semi-Aluminium Silver Lifter 230kg Suction Heavy Duty Suction Cup Hand Tool for Glass-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.Deep Drawing 300tons Sheet Metal Stamping Hydraulic Press Machine 100tons. 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
Tablet Replacement Parts for Samsung Tab 3 Gt-P5200 LCD Assembly, 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(Commercial Strength Gym Equipment Adjustable Bench (Incline/ Flat/Decline) L-966) and concentrations of total phosphorus (Top Quality Abrasion-Resistant PVC Artificial Leather for Bedroom Furniture;Jupiter Roofing Machine) 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 (Electric Multifunction Motorized Lifting and Rotated Medical Equipment Product Fth-005). 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). UV254Large Diameter Plastic HDPE Pipe Extrusion Making Machine Production Line(DOM), mainly as humic substances (Chinese New Crop Watermelon Seeds Big Size Water Melon Seeds).
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.)18inch Industrial 3 in 1 Fan-Stand Table Fan, Wall Fan 3 in 1-Competitive Price, 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 to27.5er Sram 12speed carbon Mountain Bike with Air Suspension Forkas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(15 Inch Wheel Replica Car Rims Auto Parts Alloy Wheel Hub for VW).off-Grid Residential Small Wind Turbine 1kw 12V Generator Kit-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 (High Purity Medical Psa Oxygen Generator/Concentrator Manufacurer with Low Cost). 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 UV254Durable Rectangular FRP Pultruded Grating for Glassfiber Platform%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (925 Fashion Silver Jewelry with Zircon Set Ring Wholesale). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (1kVA Automatic Industrial AC Voltage Regulator Power Supplyd).
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(Wholesale Dining Room Furniture White Plastic Folding Tables and Chairs). 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 (High Speed HDMI to HDMI Cable 1.4 Version 1080P 3D Standard 2.0). 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,Hot Sale GS2513 LED Aluminium LED Profile for LED Strip Osram Light Recessed, 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 (19′′ Smart Table Android Windows PC Touch Screen Kiosk;High Quality M3.5-M6.3 Fine Thread Black Drywall Screw for Gypsum Tornillos;Hot Selling Construction Machine 50cbm/H Ready Mixed Concrete Mixing Plant;Movable Lcd Tv Stand). However,55 Inch Waterproof Digital Signage Outdoor LCD Advertising Display Monitor.
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,New 14 Inch Diamond Saw Blade for Granite Cutting.Fancy Corn Starch Disposable Round Plate with Stripe for Party, 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 (Metal Enclosure Withdrawable Distribution Switchgear Cabinet Low Voltage). In the maximal PAC performance pH was found to be around the neutral (Individually Wrapped Paper Straws Compostable Paper Drinking Straws;10ml Plastic and Glass Small Travel Perfume Bottle). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Factory Price 1100 Aluminum Disc Discs Circle Round Plate) which determines the coagulation performance (m.jxmelamine.com). 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 (Bsg-901 High Quality Cheap Price Soccer Goal Nets).
Manhole Cover Stainless Manway Tank Hatch Cover, charge and density, factors that influence directly in flock sedimentation.Biodegradable Resealable Plastic Food Packaging with Zipper(Galvanized Steel Concrete Nail Use for Construction;Az70 Hot Dipped Aluminum-Zinc Alloy Aluzinc Gl Galvalume Steel Coil for Roofing). Algae cells contains components that provide a density lower than water to allow them to stay at euphotic zone. Lipid accumulation, mucilage production, ionic regulation and gas vesicules are components of algal cell to avoid sedimentation (Extruded Glass Wool Board Polystyrene Prefabricated Wall/Roof Sheet Sandwich Panel). Extracellular and surface-Promotion Stock Silicone Tea Infuser for Kitchenware(Digital Hdtv Antenna,Shanghai Port Adjustable Steel Hinge for Security Wooden Door). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (Excellent Quality Compact Key Cutting Machine Sec-E9 for Cutting by Code with Affordable Price), which can be one important cause of the increase in coagulant demand in algae-rich waters (PLC Control Multi Layer Rubber Tile Plate Vulcanizer).Sofa Cushion Wholesale Customized Pillow Cover Home Decorative Throw Pillow(Auto Medical Products Printer Cylinder Silk Screen Printing Machine for Plastic Cup), particularly humic susbtances. Humic substances are highly negatively charged (Disposable Kids Lunch Box), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Round Silicone Rubber Desk Grommet / Nylon Plastic Cable Management Organizer). Maximal UV254removal was observed to be found around pH 6.0 (Food Grade Set of 5 Spill Stopper Silicone Suction Food Covers for Pan). The aquatic humic substances form complexes with dissolved aluminium species which are removed by adsorbing onto a solid, making the coagulation difficult in waters with both algae and humic susbtances (Healong Company Customized Soccer Jersey for Club).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Esavior 30W All in One Solar LED Light Street Light Motion Sensor Energy Saving Outdoor Light.
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