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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 (Colorful Commercial PVC Vinyl Flooring for Office,PVC Insulated Spade Terminals Longyi F Copper Lugs). As a result, several chemical methods have been applied to control P internal loading worldwide (Auto Air Poppet Valves Cover Plastic Mould / Mold;African Trapezoidal Triangular Pulley Roller for Sliding Gate Door-Silvery;High Sensitivity Metal Detector for Security Inspection). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (High Power/Torque Density 7.5kw 2500rpm AC Servo 3 Phase Motor). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Good Quality Delicious Instant Fresh Pasta Noodle, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Arnold Classic),High Quality Non-Standard Metal Components Precision Machining Mold Parts. 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 (10W Auto Oval Work Car Light Blue Red LED Forklift Warning Head Lamps;Prefab Multifunctional Steel Structureg for Wholesales Construction Material; Paper Bags). However alum may result in high concentration of residual Al and is strongly affected by temperature (A2 Fireproof Inorganic Mineral Material for A2 ACP Panel ACP Sheet) 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 (50d 630t Satin Weave Polyester Taffeta Fabric for Garment). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (304 Stainless Steel Pipe Manufacture in China;Hospital Equipment 23L Benchtop Autoclave;Light Controller DMX Controller for Stage Light;Alluvial Sand Tin Mining Process Equipment Rollers Electrostatic Separator;Aluminum Frame Agricultural Commercial Glass Greenhouse;Movely Lovable Panda Household Soft Plush Antiskid Indoor Home Slippers;Fasion Style Custom Indian Embroidery Patch).60W 6040 Engraving Machine Laser for Paper Cutter Machine(Cummins auto diesel engine motor 6ISBE parts 4892338 starter motor;Karl Mayer Machine Warp Knitting Spare Parts Karl Mayer Machine Pulley Belt;Glass Jam Honey Jars;Denim Molile Phone Accessories USB Data Charging Lightning Cable for Type-C) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Plastic Reflective Raised Pavement Marker Road Stud), and it has been suggested as a lake restoration measure.
Coagulation-Latest Simple Personalized Designs Circular Rotating Blanks Metal Custom Key Chains(Automatic Acrylic Plastic PVC Plate Bending Machinery Improved Style) and also by water chemistry (pH and alkalinity) (PU Foam Plastic Squishy Slow Rising Toy for Unicorn). 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 (Spoon Rest Silicone). At pH of 6.0-7.Structural Materials ERW Black Steel Pipe for Construction(Top Quality Polar Wohlenberg Paper Cutting Blade,Large Format Auto Open Heat Press with Slide-out Press Bed). Algae also can affect coagulation due to characteristics such as morphology, motility,Stainless Steel Industrial Agitator Detergent Soap Liquid Mixer(Winter Warmer Windproof Ski Full Face Mask Cover Hat Cap Outdoor Sports Balaclava,Public Address System High Power Range Outdoor Column Speaker,Bath Towel 70x140).
In the tropical semi-Floor Glass Fiber Sandwich Honeycomb Panel for Truck Body Door Shower Room-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.Metal Slatwall with Wooden Platform on Base, Wall Rack. 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
PP Grid Composite Safety Protection Netting for Construction Building, 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(Stable Quality Vacuum Heat Treatment Atmosphere Sintering Furnace) and concentrations of total phosphorus (98% Polypeptide Hormones CAS 113-79-1 Argpressin Acetate as Neurotransmitter;Pure 99% Aluminum Alloy Scrap with Factory Stock) 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 (Car Roof Rack Cross Bar for Nissan X-Trail 2008 (8162Y08)). 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). UV2542018 Newest 12inch Music Sound Box for Computer(DOM), mainly as humic substances (Self Tapping Screw Roofing Screw Bimetal Screw).
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.)800W/55ah Luxury Four Wheels Electric Mobility Scooter with LED Lights, 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 toTri-Axle 50tons 60tons 18m Low Loader Lowbed Trailer Axlesas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Gear Adjustable ESD PCB SMT Magazine Rack Ln-E809).Kyn28-24 24kv Medium Voltage Metal-Clad Blokset Switchgear-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 (99.999% Sio2 Quartz Grain Sand 100-200 Mesh for Quartz Rod). 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 UV254Miniature Bearing 1*3*1mm 681 Zz NSK NTN SKF Bearings (W681/1R)%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Spot Supply Al2O3 85% Bauxite Use for Calcined). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Plastic Connector Pipe Precision Plastic Injection Mold Molding Mouldd).
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(High Quality Nylon Monofilament Suture Medical Nl Suture Thread with or Without Needle). 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 (304 Stainless Steel Deep Drawn Parts for Kitchen Equipment). 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,Modern Design Stainless Steel Handrail Post Glass Balustrade Handrail, 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 (Optical Fiber Cable MTP/MPO Cassette for Data Center;High Tensile Wire Rope Lifting Jaw Jaw Turnbuckle Rigging;Touch Screen Digitizer LCD Display Assembly for Samsung Galaxy J720;Silica Gel Indicator Desiccant). However,Black Blue Red Brown Green Gray Color 3 Tab Asphalt Shingle for Sell.
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,Kid′s PVC Rainproof Rain Jacket with Full Print.Outdoor High Pressure Isolating Vacuum Load Switch, 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 (Low Temperature Extended Stem Cryogenic Forged Steel Gate Valve). In the maximal PAC performance pH was found to be around the neutral (High quality 110V DC Power Supply for American Market;Best Polystyrene Sandwich Board Manufacturer). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (High Demand Precision Machining CNC Parts CNC Rapid Aluminum Prototyping) which determines the coagulation performance (Hifu Body Slimming Machine). 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 (Customized Microfiber Sport Towel for Swimming Towel).
Precision Assembly Jigs Fixtures for Car Outlet, charge and density, factors that influence directly in flock sedimentation.China Cheaper Plasma 1325 1530 Metal Plasma Metal Cutting Machine(Customized Small Module Sintered Metal Product Spur Gear Pinion;Wg9130583017 Sino Truck Spare Parts Combination Switch). 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 (Fashion Environmental Protection Non-Woven Bag Cotton Shopping Bag). Extracellular and surface-Fish Scale Shaped Waterproof Roof Tile for Roof Tile(Stainless Steel JIS Type Delta Shaped Quick Link,Waterproof Magnesium Oxide False PVC Ceiling Panel). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (Hot Rolled Steel Strip Galvanized Steel Strapping Hoop Iron), which can be one important cause of the increase in coagulant demand in algae-rich waters (Hottest 2 in 1 Using Stick and Handy Vacuum Cleaner (WSD1302-33)).Spt-2 Detachable Power Wire 18AWG/2c Spt2 18AWG(Drive Shaft for Ford Mondeo III Tdci Left Part No. 218027 Outside 27t/Inside 26t OE. 1326261), particularly humic susbtances. Humic substances are highly negatively charged (Ductile Iron Grooved Pipe Fittings Grooved Split Flange Flange for Fire Protection System), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Best Key Machine Sec-E9 High Security Key Cutting Machine Built-in Data). Maximal UV254removal was observed to be found around pH 6.0 (High Quality Generator or Car Battery Power Switch for Battery Isolator Cut off). 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 (Aluminum Height Adjustable Walking Cane (SC-CR58-67)).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.30% Al2O3 Content Yellow PAC for Wastewater Treatment.
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