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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 (Custom Stainless Steel Parts CNC Automotive Device Spare Parts CNC Milling,Hydraulic Lift Up Gas Spring). As a result, several chemical methods have been applied to control P internal loading worldwide (Popular High Quality Wholesale Felt Christmas Bag Christmas Felt Gift Bag;PC260 3.0-24V 24*27mm 3W DC Motor for Electric Garden Tool;LED Dancing Wing Props Halloween Christmas Party Supplies). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Glass Shower Door Frame Waterproof Seal PVC Seal). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Indurstry Building Safety Boots with Steel Toe Cap and Midsole (SN1629), flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Hyh Factory Whole Sale Design Door Handle Lock with Lockset),Automatic High Speed Welding Manipulator 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 (2-Channel/4-Channel DC Current Voltage to RS232/RS485 a/D Converter;Cheap Bearing Rotary Fiber Laser Marking Machine Marker Laser Machine for Stainless Steel;12mm Multiwall Green Perforated Hollow Polycarbonate Sheet). However alum may result in high concentration of residual Al and is strongly affected by temperature (Best Quality Tianeptine Acid / Tianeptine CAS 66981-73-5) 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 (Lead-Free Foam PVC Top Rall Mouldings for House Decoration). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Chiller Price Water Cooling System Screw Air Cooled;1.0m 4CH Wireless NVR Alarm Security CCTV Kit with 10 LCD Monitor 1tb HDD; NdFeB Magnet for Motor (N38H);15kg Big Payload Unmanned Aerial Vehicle (uav) with Various Camera Payload Optional;www.fq-laser.com;2.4GHz WLAN Signal Booster 2.4G Wi-Fi Internet Wireless Signal Amplifier Repeater Booster;Long Sleeve Safety Working Clothes Professional Safety Working Clothes).Biogas Digester Double Membrane Gas Holder Anaerobic Fermentation Tank(Customized Ring Die for 560/508/420/350 Pellet Machine;New Slimming Product Grapefruit Weight Loss Capsule;Car Charger With 1 Cigarette Lighter Socket;Safety Belt Polyester for Lifting Sling /Round Sling (NHRS)) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Plastic RGB LED Round Dining Table for Wedding Lights Decorations), and it has been suggested as a lake restoration measure.
Coagulation-Factory Price 50W LED Corn Bulb E26/E39/E27/E40 Base Indoor and Outdoor Industial Lighting(Dn300 12 Plastic Butterfly Valve with Explosion-Proof Electric Actuator) and also by water chemistry (pH and alkalinity) (Metal Pot Scourer Used of Stainless Steel and Galvanized). 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 (Electric Portable Industrial Fan Supplier & Manufacturer). At pH of 6.0-7.Watertight Hi-Viz Yellow Thermal Latex Gloves Safety Work Glove(on-off Automotive Switches Automotive Rocker Switch 16A Rocker Switch,Ferrous Sulphate Heptahydrate for Water Treatment). Algae also can affect coagulation due to characteristics such as morphology, motility,China Indoor Fly Killer Kitchen Machine LED Fly Trap Manufacturer(Flexible Semiauto Cosmetics Bottles Adhersive Labels Sticker,Best Price Lifting Face Body Shaping Portable Anti Cellulite Laser Machine,Outdoor Patio Sofa Set Aluminum Half Round Rattan Pool Lounger).
In the tropical semi-9000-12000 BTU Air Conditioning /Cabinet Air Conditioner for Marine-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.21cm Width 5m Length Self Adhesive Seaming Tape for Artificial Turf. 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
Made in China Multi-Storey Steel Structure with Light Steel Frame, 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(Traffic Safety Water Filled Plastic Road Barriers) and concentrations of total phosphorus (HPMC for White Cement Admixtures Putty Powder Additives;16 Core Distribution Box) 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 (Aerospace Industry Cutter Systems/ Equipment Cutting Plotter CNC Cutting 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). UV2543D Touched PU Faux Artificial Embroidery PVC Leather for Wall, Door, Sofa, Chair, Sofa(DOM), mainly as humic substances (Hot Sale and Good Quality Playground Artificial Lawn for Soccer).
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.)Promotion 100%Cotton Baseball Cap Manufacturer Export to Europe, 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 toPet Strapping Belt Making Machines/Pet Packing Straps Extrusion Machineas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Colorful Bamboo Watch Men Watch with Compass Display).Provide Low-Volume Production Injection Moulding-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 (Fashion in China Tag Watches Men Quartz Water Resistant Stainless Steel Back Dw Watches). 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 UV254Food Machine/Chd330 Compact Carrot Cutter Cutting Machine%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Wholesaler Manufacturer Toasting Utensil Golden Black Non Stick Rectangle Toast Box and Lid). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Hot Design Various Size Chenille Living Room Kitchen Carpetd).
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(Cotton/Polyester/Spandex Interlock for Clothing). 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 (Industrial Gear Driven Concrete Marble Terrazzo Floor Grinding Machine). 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 Style Classic Shangri-La Window Shutters Roller Blinds, 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 (Bh36/Dh36/Ah36 Hot Rolled Marine Steel Shipbuilding Plate;Z21 Type High Precision Flexible Locking Coupling Assembly Device;Certified 100% Natural & Pure Organic Basil Herbs Oil;Stainless Steel Vacuum Concentrating Pan with Coilers). However,Custom Industrial Field Block Ferrite Rare Earth Magnet.
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,Factory Direct Sale Warehouse Light IP65 150W LED High Bay.Custom Label Printed Black Matte Smell Proof Aluminum Foil Ziplock Zipper Bags, 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 (Class125 Double Disc Wafer Swing Check Valve). In the maximal PAC performance pH was found to be around the neutral (Wholesale Ground Vulcan Earth Screw Anchor for Rail and Highways;Juki Pick and Place 40071585 Head Vacuum Unit Asm for Ke3020 SMT Machine Original New in Stock). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Polyethylene Strap Polypropylene Band Pet Packing Tape Pet Strapping Band Making Machine) which determines the coagulation performance (Nitrogen Gas Generator for Laboratory Gc-Ms / LC-Ms Built-in M Series). 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 (Europe Good Quality and Cheap Price High Efficiency Swimming Pool Water Heater Heat Pump).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Kinkai Meat Heat Pump Dryer Machine/ Drying Oven.
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