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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 (Rubber Wheel Stopper Car Parking Blocks Rubber Speed Cushion,10g/15g Portable Cylinder High-Grade of Silver Acrylic Jar). As a result, several chemical methods have been applied to control P internal loading worldwide (Live Broadcast Camera 4K 3840X2160 Ultra HD IPS LCD Screen 17.3 LCD Display;Nylon Watch Bands with Metal Buckle 20mm Strap;High Precision Ultrasonic Vibro Screen for Refractory Material Separating). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (16mm Rotary Potentiometer with Switch for Audio Equipment). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Newest Robot Vacuum Cleaner with GPS, Camera, Built-in Virtual Wall, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Bosch Injector Gaskets Kit F00vc99002 F 00V C99 002 Common Rail Repair Kits Tool F00V C99 002),Flat Screen 15 17 19 24 32 Inch Smart HD Color LCD LED TV. 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 (4 Seat Lead Battery Powered Electric Beach Buggy Cart (DN-4);Hydraulic Cargo Freight Platform Lift for Industrial and Wearhouse;Kiet Brand High Efficiency Automatic Hydraulic Cam Dismounting Puller). However alum may result in high concentration of residual Al and is strongly affected by temperature (Dog Cat Car Products Travel Accessories Seat Pet Carrier Bag) 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 (Factory Price Refrigerant Gas R507 for Air-Conditioner). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Food Lunch Box 4 Compartment Aluminium Storage Box Disposable Aluminum Foil Container;Y32f-112lm8 Small and Light PCB Relays with High Power for Comunication Equipment; Door Mat;Made in China Multi-Storey Steel Structure with Light Steel Frame;Dogtag Pendant Die Casting Words on Gold Plating Dog Tags;Easy-to-Use School Office Invisible Stationery Tape;Commercial Tow-Able Diesel Portable Movable Rotary Screw Air Compressor).1616 Aluminum LED Strip Channel Surface Mount LED Extrusion(4 Cencter Set Lavatory Plastic Faucet (smooth and easy opening);Cold Storage Warehouse Rack with Good Quality;Anesthesia Sensor Suppliers for Sale;Brc Welded Wire Mesh Fence/3D Curvy Welded Wire Mesh Fence) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (A4), and it has been suggested as a lake restoration measure.
Coagulation-600d Polyester Trolley Luggage Soft Luggage Oxford Luggage Bag(High Efficiency Hook Type Shot Blasting Machine for Sale) and also by water chemistry (pH and alkalinity) (Non-Toxic RTV Silicone Sealant of Full Automatic Machine). 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 (Black Wizard Hat Ribbon for Customized Printed). At pH of 6.0-7.Export Quality Flavor Fresh Ramen Mixed Noodle with Turkey Sauce(High Tensile Forged Chain with Conveyor for Conveying System,M5 SMD with Internal Blind-Hole Thread with Pin (groove)). Algae also can affect coagulation due to characteristics such as morphology, motility,High Pressure Zirconia Ceramic Piston Rod Pump Ceramic(Interlocking Waterproof Removable Anti-Slip PVC Garage Floor Tile,Best Quality Popular Lovely Washable Pet Accessories Luxury Soft Dog Bed,Best Small Biomass Fireplace Pellet Stove (CR-10)).
In the tropical semi-Brown Shoes High Quality Strong Protection Working Shoes-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.700ml Leak Proof Fitness Plastic Protein Mixing Water Cup (HDP-0346). 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
4we5 Electrically Operated Directional Control Valves, 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(China Qingdao Factory Interlocking PVC Garage Floor) and concentrations of total phosphorus (Micropile Tube as Umbrella for Tunnel Portal Od139.7mm Wt9mm;Rexroth Directional Control Valve) 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 (Telescopic Aluminum Square Tent Pipe&Drape for Wedding/Event). 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). UV254Single Head High Speed Tubular Cap Embroidery Machine (TLC901)(DOM), mainly as humic substances (Ce Eco-Friendly 24V Electric Motor Operated SS304 Water Flow Control Valve for Drinking).
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.)Communication Cable Rg59/RG6/Rg11 Coaxial Cable Copper Standard Wire Satellite System, 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 toHook Vintage Weathered White Wall-Mounted Wood Coat Rack with Chalkboard Labelsas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Automatic Quilting Machine Products Made in China).High Speed LDPE Polyethylene Plastic Film Extrusion Machine-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 (Industrial Paraffin Wax/Powder/Slab/Paraffin Wax Chemical Formula). 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 UV254Telescopic Aluminum Square Tent Pipe&Drape for Wedding/Event%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Ouwave HVAC Scent Fragrance Systems Aroma Diffuser Electric Scent Machine). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Mini Handheld Sewing Machined).
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(Ci/Di/Ss/C954 Al Bronze Body Double Flange Butterfly Valve Pn10 Pn16 Pn25). 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 (Modular Concrete Batching Plant by Twin Shaft Mixer 3000/2000). 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,Oven and BBQ Digital Cooking Thermometer with Stainless Steel Probe, 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 (Whole Sale Banquet Tiffany Classic Stackable Gold Louis Dining Chair;Hidrotek Water Filter Cartridge with Sediment Carbon;9.7 Inch Poe Android Touch Screen Tablet with Vesa Mounting;Heavy Duty Stainless Steel or Zinc Plated Rubber Lined Pipe Clips). However,Caprolactam Grade Ammonium Sulphate (21%Min).
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,Micropile Tube as Umbrella for Tunnel Portal Od139.7mm Wt9mm.NdFeB Magnetic Strong Sintered N45 Rare Earth Permanent Neodymium Magnets for Motor, 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 (Stainless Steel Grade U2 U3 Stud Link Anchor Chain with Factory Price). In the maximal PAC performance pH was found to be around the neutral (Diesel Fuel Leak off Pipe for Mercedes-Benz;Automatic Plastic Pet Preform Injection Moulding Machine Price). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (High Quality Polyurethane Adhesive for Scrap Sponge) which determines the coagulation performance (Merino Wool Fabric Sleep Beauty Natural Modern Latex Mattress). 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 (Carbon Steel Carry Idler Belt Conveyor Guide Roller).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Concrete Road Cutting Machine, Road Cutter, Road Saw Machine.
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