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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 (Decorative Metal Aluminum Steel Room Divider Modular Partition for Hotel Restaurant,98 Cotton 2 Elastane Jeans). As a result, several chemical methods have been applied to control P internal loading worldwide (New Designer PU Fashion Ladies Backpacks Handbags for Brand Holder and Wholesale;Built-in Camera Shoot Photo Video Recording Multi Function Night Vision Telescope;High Quality Sky Indoor Mesh Trampoline Zone Park with Cheap Prices). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Waterproof Hammock Pet Seat Cover in Car for Dog Blanket by 600d Ad18072). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Anon Philippines Hot Selling 4lz-2.5 Mini Rice Wheat Combine Harvester, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (IP65 ABS Box PVC Junction Box Waterproof Box),Silicone PU Ms Acrylic Sealant Adhesive Automatic Cartridge Filling 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 (Tungsten Solid Carbide Straight 4/6 Flutes Reamer;Custom Industrial Field Block Ferrite Rare Earth Magnet;7). However alum may result in high concentration of residual Al and is strongly affected by temperature (Sleeve Block Truss for 290mm/400mm Aluminum Spigot Roof Lighting) 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 (Large Size Silicone Figure Robot Cake Mold Chocolate Mold for Cake Decorating Tools). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Stainless Steel Axle Shaft;Suitcase Belts Continuous Dyeing and Finishing Machines;Makeup Case Toiletry Bag for Women Skincare Cosmetic Pouch;Caterpillar 420f Backhoe Laoder 2015 Year Japan Made;Huperzia Serrate P.E.;Stainless Steel Slot Screen Pipe 0.3mm Slot Size;Ytpd173r140-4.0 Ultrasonic Focusing Piezoceramic Transducer for Beauty).Spark Plug Wire/Ignition Leads Set/Ignition Coil for KIA Pride Zimens(2mm-15mm Smart Switchable Screen Mirror Glass for Sale (S-F7);220kv Composite Suspension Insulators for Transmission and Distribution Line;Ferrous Metals Ore Vibrating Screen Machine;Rectangle Custom Various Color Metal Label Tag Sticker Handbag/Luggage Hardware) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Customized CNC Machining Checking Fixture for Automotive Bracket), and it has been suggested as a lake restoration measure.
Coagulation-CNC Forging Motorcycle Aluminum Chain 520 Sprocket(PS Foam Food Container Production Line PS Lunch Box Forming Machine) and also by water chemistry (pH and alkalinity) (Customized Precision CNC Mechanical Parts with Steel). 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 (Honle SVC Single-Phase High Accuracy Full Automatic AC Voltage Stabilizers). At pH of 6.0-7.Welding Turning Roll for Pipe Welding Hdtr-1000(China Products/Suppliers. Prefabricated Metal Shed Steel Structure,Outdoor LED Street Pole Advertising Business Double Sided LED Signs). Algae also can affect coagulation due to characteristics such as morphology, motility,Reinforced Stainless Steel 306L Wire Wrap Johnson Type Strainer Screen(HD Small Pixel Pitch Full Color P1.667 Indoor LED Display for Meeting Room,Ventilation Back Draught Damper Volume Control Damper One Way Shutter Actuators,China Lost Foam Process Manufacturers).
In the tropical semi-Cheap China 2 Inch Wafer Stainless Steel Butterfly Valve-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.Professional 808nm Laser Diode Hair Removal Machine/Epilator Device with Ce/ISO. 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
Ss Wire Mesh Heat Resistant Wire Mesh Conveyor Belt, 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(Silicone Rubber Pin Insulator/Polymer Composite Insulator (10kv-33kv)) and concentrations of total phosphorus (Customized Waterproof Backpack Canvas Laptop Bag;China Factory Cheap LED Bulb with Ce RoHS 9W 12W) 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 (Lockey Loto Durable Standard Safety Gate Valve Lockout with Ce). 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). UV254Stainless Steel Checkered Plate 304 316L 410 Floor Material(DOM), mainly as humic substances (10~2500kVA (10KV) Cast Resin Dry Type Transformer with IP20 Enclosure).
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.)Fully Automatic Pipe Bending Machine Dw38CNC Tube Bending Machine Zhangjiagang Machine, 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 to14 X 14 Mesh Window Screen Aluminum Alloy Wire Nettingas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Air Bubble Film Pocket Making Equipment).Biodegradable PLA Film for Food /Fruit Packaging-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 (factory outlet excellent herbicide DIURON 80% WDG on sale). 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 UV254EU Standard Top Quality Portable Indoor Playground Equipment%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Large Outdoor Water Park Slide/Water Turntable Amusement Equipment). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Switch Low Frequency Transformer for Power Suppliesd).
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(Customized Disposable BBQ Bamboo Round Stick and Skewers.). 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 (Wholesale Custom Microfibre Towel Rack Cooling Gym Yoga Bath Towel). 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,61539 Double Handle 4 Inch South American Style Faucet, 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 (CNC Fiber Laser Marking/Engraving Engraver for Metal and Nonmetal;18 Inches Double Shafts Driving Xk-450 Rubber Rolling Mill;High Drying Efficiency Wood Sawdust Dryer for Sale;Jar For Cream). However,3mm/0.3mm Honeycomb-Shaped Sound Absorbing Aluminum Composite Panel for Interior Decoration.
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,High Temperature Resistant Industrial Cement PPS Air Filter Bag.Ce Approved Panel 40W 48W LED Border Line Light with Mean Well Driver, 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 (Exported Screw Eye Ground Anchor for Electric Fence Using). In the maximal PAC performance pH was found to be around the neutral (Contemporary Outdoor Garden Furniture Rattan Wicker Leisure Balcony Sets with Round Bed;Ex-Proof Motorized Flange End Ball Valve (PQ9B41F-300Lb)). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Premium Genuine Leather Miyota Mechanical Movement Women Watch with Date) which determines the coagulation performance (Corrugated Hanging Sidekick Display). 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 ((1.5/2/2.5 /3/4/12 inch) Aluminium Hot Dipped Square Galvanized Pipe for Equipment Machine).
Silicone Invisible Strapless Bras Reusable Backless Bras for Women (RS 015), charge and density, factors that influence directly in flock sedimentation.HDPE 1mm 2mm Plastic Strips /Tapes Manufacture for Decorate Christmas(New Design Export Fiberglass Adult Water Bike for Sale;Permanent Magnetic Grid for Europe Market). 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 (Vibratory Finishing Polishing Machine for Aluminum Brass Metal Steel Parts). Extracellular and surface-Luxury Comfortable Mini Bread Spring Mattress in Bedroom Furniture(m.handypowercord.com,Gfd1550-E EDFA Optical Amplifier / 1550nm Erbium Doped Fiber Amplifier). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (Uncoated Test Liner Fluting Medium Paper for Box Packaging), which can be one important cause of the increase in coagulant demand in algae-rich waters (Carpet Grain UV Coating Eco-Friendly Fireproof Waterproof Spc Flooring1871).Kitchen Cleaning Stainless Steel Scourer with Plastic Handle(10m 3.5mm Male to Female Audio Cable for iPhone iPod), particularly humic susbtances. Humic substances are highly negatively charged (Hot DIP Galvanized Metal Grating for Platform and Drain Cover), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Plumbing Fitting Water Connect Black Surface 1/2 Malleable Iron Flat Seat Conical Union). Maximal UV254removal was observed to be found around pH 6.0 (Stainless Steel Male Female Screw Fasteners Connecting Book Screws). 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 (Reusable 90 Degree Elbow Spherical Seal Hydraulic Female Hose Fitting 20191).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Digital Pistol Safe Box / 4-Number Digital Safe Box.
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