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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 (Good Cleaner Cotton Rope Mop Wood Mop Stick,Semifinished 1.499 Short Corridor Progressive Optical Lens UC). As a result, several chemical methods have been applied to control P internal loading worldwide (Customized Cast Iron Ak41 Type V-Belt Pulley for 4L;Red Enamel Cast Iron Fondue Pot with Forks;Automatic White Cardboard Paper Roll to Sheet Cutting Machine). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Rust Resistance Anti Climb Protective Aluminum Durable Outdoor Metal Fence for Garden/Factory). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Home Furniture Metal Chair Grey Velvet Dining Chair, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (FHD 1080P Wireless 4G Solar Power IP Camera Outdoor Low Power Consumption Surveillance DIY Camera),168cc Racing Go Kart for Sale Sx-G1101 (lxw) -1A with Bumpers Gc2008 for Sale. 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 (3mm Poplar Plywood with Fancy Veneer Directly;Farm Seed Spreader / Tractor Fertilizer Spreader for Sale;Industry Basket Washing Machine Crate Washer). However alum may result in high concentration of residual Al and is strongly affected by temperature (Colorful Mobile Phone Accessory Dull Polish Back Cover PC Phone Case for Meizu Note 6) 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 (Stick Silicone Spoon Rest). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Steel Jacket Steam Insulation Pipe for High Tempertature Heating;6.2mmx6.2mmx4.3mm SMD Waterproof Tact Switch;PP Yarn Water Filter Cartridge for Large Flow Rate;2019 New Products Wall-Mounted Household Natural Gas Alarm Low Power;Non-Woven Nipple Cover;Taizhou Huangyan Laboratory Room 60 mm Plastic Injection Petri Dish Mould;High Density White Magic Sponge Magic Eraser Melamine Foam Cleaning Sponge Car Cleaning Sponge).OEM High Efficiency Polycrystalline 260W Solar Panel(Hot Sale 1: 1 High Quality Same Sound Effect Bluetooth Earphone Airpods for Apple iPhone; 42′ LG LED TV Backlight Lens Strips/Bars/Spears;Full Embossing Color Printing Facial Tissue Napkin Paper Product Line for Hot Sale; Drying Equipment) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Customized Acrylic Plastic Sign Board Design Customized Size), and it has been suggested as a lake restoration measure.
Coagulation-Basketball Rebounded Practice Machine for Professional Trainer (S6839)(Solar PV Detached 30W 12inch Roof Mount Solar Ventilation Attic Vent (SN2014003)) and also by water chemistry (pH and alkalinity) (Chinese 1kw Vertical Axis Wind Turbine for Home Use). 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 (Good quality High Pressure Blower Fan Industrial Blower - AD2540 - Zhuohui). At pH of 6.0-7.DC/CC Aluminum Circle/Disc for Non-Stick Cookware Utensil(2.45 2.45. inch OLED display 304X96 DOT Matrix MONO OLED, Temperature Controller Thermostat 110V for Cabinet Use). Algae also can affect coagulation due to characteristics such as morphology, motility,Customized Sand Casting Brake Wheel Hub for Trailer and Truck(11kv 15kv 33kv Pole-Mounted Hermetically Seal Distribution Transformer,Customized Epoxy Plated Super Power Neodymium Magnet Bonded Magnetic,3.5 Inch TFT LCD 320X240 RGB 50pin 450CD TFT LCD Display Screen).
In the tropical semi-Solid Surface Stone Table Top Restaurant Black Round Dining Tables-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.Men Solar Analog-Digital Quartz Movement Sport Wrist Plastic Watch. 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
High Quality Curve Spear Tunnel Bolt for Concrete Ring, 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(20FT T11 T14 Transport Tank Container Motor Oil ISO Tank Container) and concentrations of total phosphorus (Customized EPS/EPP Mold From Factory with ISO;m.gsbracefactory.com) 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 (Wooden Grain Siding Plank for Villa Integrated House). 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). UV254Flexional Soft Head Electronic Digital Thermometer(DOM), mainly as humic substances (Touch Screen Handheld PDA Barcode Scanner with 4G Bluetooth WiFi Camera GPS).
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.)Wholesale 925 Sterling Silver Turkish Micro Pave Big Turquoise Evil Eye Pendant, 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 toHigh Quality Viscose Rayon Embroidery Threadas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Hair Brush Sponge Twist Wave Barber Tool for Magic Twist Curl Sponge).Top Quality Polar Wohlenberg Paper Cutting Blade-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 (Rubber Wheel Stopper Car Parking Blocks Rubber Speed Cushion). 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 UV254Low Temperature Extended Stem Cryogenic Forged Steel Gate Valve%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Live Broadcast Camera 4K 3840X2160 Ultra HD IPS LCD Screen 17.3 LCD Display). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Engraving Gravure 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(High Precision Ultrasonic Vibro Screen for Refractory Material Separating). 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 (16mm Rotary Potentiometer with Switch for Audio 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,1/2 Inch Soft Flexible Green Cloth Surface SAE 100 R3 Hydraulic Hose Rubber Hose, 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 (Kiet Brand High Efficiency Automatic Hydraulic Cam Dismounting Puller;Dog Cat Car Products Travel Accessories Seat Pet Carrier Bag;Food Lunch Box 4 Compartment Aluminium Storage Box Disposable Aluminum Foil Container;Cinnamon Bark Extract Powder for Lowering Blood Pressure). However,Yg15/Yg8 Mirror Polished Hip Sintered Tungsten Carbide Wire Guide Rollers.
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,Green&Health High Quality Modular Cold Room Storage for Fruits and Vegetable.Street Lighting 50W 100W 150W 200W LED Street Lamp Source Outdoor LED Street Light, 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 (Y32f-112lm8 Small and Light PCB Relays with High Power for Comunication Equipment). In the maximal PAC performance pH was found to be around the neutral ( Door Mat;Made in China Multi-Storey Steel Structure with Light Steel Frame). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Easy-to-Use School Office Invisible Stationery Tape) which determines the coagulation performance (Metal Embossing). 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 (Commercial Tow-Able Diesel Portable Movable Rotary Screw Air Compressor).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Durable Soft Polishing Wheel for Polishing Wood and Plastic.
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