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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 (Glow in The Dark Pigment Luminescent Luminous Powder,Women Backpack Purse PU Washed Leather Ladies Rucksack Shoulder Bag). As a result, several chemical methods have been applied to control P internal loading worldwide (Custom Personalized Logos Cheap Neck Printed Custom Polyester Lanyards Ribbons with ID Card Holder;Wear Resistant Steel with Hardness 58-62 HRC;Korea Glittery Heat Transfer Film /Vinyl for Clothes/T-Shirt Printing Cdg-16 Light Multi). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Popular Selling Sausage Casing Making Machine). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,55 Inch Waterproof Digital Signage Outdoor LCD Advertising Display Monitor, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Fire Centrifugal Pump),New 14 Inch Diamond Saw Blade for Granite Cutting. 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 (air freight China to Botswana Gaborone logistics express courier services;Export Quality Straight Dried Instant Flavor Kelp Seaweed Noodle;Good Sale Lfc Sand Preparation and Casting Molding Line). However alum may result in high concentration of residual Al and is strongly affected by temperature (Vegetable Herb Garden Hand Tools with Storage Box) 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 (Ob3030A Industrial Aluminium Alloy Extruded Profile China Manufacturer for Sale). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Height Adjustable Removable Foldable Feeding Baby High Chair;ISO Humidity Control Damp Proof Auto Grd Dry Cabinet 50L;Wholesale Factory Prices Ceramic Hair Curler Magic Hair Curler;Decorative Metal Aluminum Steel Room Divider Modular Partition for Hotel Restaurant;High Tensile Strength Galvanized Iron Binding Wire/Black Annealed Baling;New Designer PU Fashion Ladies Backpacks Handbags for Brand Holder and Wholesale;Built-in Camera Shoot Photo Video Recording Multi Function Night Vision Telescope).Fancy Corn Starch Disposable Round Plate with Stripe for Party(High Quality Sky Indoor Mesh Trampoline Zone Park with Cheap Prices;Waterproof Hammock Pet Seat Cover in Car for Dog Blanket by 600d Ad18072;Tundish Powder;Tungsten Solid Carbide Straight 4/6 Flutes Reamer) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Custom Industrial Field Block Ferrite Rare Earth Magnet), and it has been suggested as a lake restoration measure.
Coagulation-Manhole Cover Stainless Manway Tank Hatch Cover(7) and also by water chemistry (pH and alkalinity) (Sleeve Block Truss for 290mm/400mm Aluminum Spigot Roof Lighting). 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 Paper/ Film/ Non-Woven Slitting Machine Slitter). At pH of 6.0-7.Biodegradable Resealable Plastic Food Packaging with Zipper(Stainless Steel Axle Shaft,Suitcase Belts Continuous Dyeing and Finishing Machines). Algae also can affect coagulation due to characteristics such as morphology, motility,Promotion Stock Silicone Tea Infuser for Kitchenware(Makeup Case Toiletry Bag for Women Skincare Cosmetic Pouch,Caterpillar 420f Backhoe Laoder 2015 Year Japan Made,Cameras Digitais).
In the tropical semi-Sofa Cushion Wholesale Customized Pillow Cover Home Decorative Throw Pillow-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.Esavior 30W All in One Solar LED Light Street Light Motion Sensor Energy Saving Outdoor Light. 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
Stainless Steel Silent Child-Mother Hinge Ball Bearing Hinge for Door Window Hardware Accessories, 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(2mm-15mm Smart Switchable Screen Mirror Glass for Sale (S-F7)) and concentrations of total phosphorus (220kv Composite Suspension Insulators for Transmission and Distribution Line;Single Roller Double Power Spindleless Rotary Peeling Machine for Plywood Veneer) 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 (PS Foam Food Container Production Line PS Lunch Box Forming 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). UV254Automatic Plastic Tubes Printing Machine Cylinder Silk Screen Printer(DOM), mainly as humic substances (Customized Precision CNC Mechanical Parts with Steel).
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.)Top Quality Gasoline Grass Trimmer Parts Nylon Head Blade, 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 toVentilation Back Draught Damper Volume Control Damper One Way Shutter Actuatorsas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Print Photo On Beach Towel).Custom Color Printed Magazine Brochure Offset Printing Book-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 (Silicone Rubber Pin Insulator/Polymer Composite Insulator (10kv-33kv)). 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 UV254Precision Machining Stainless Steel Right and Left Hand Twin DC Motor Acme Lead Screw%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Customized Waterproof Backpack Canvas Laptop Bag). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (3d Cnc Stone Sculpture 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(Carbide 4 Flutes HRC60 Blue Coated Milling Cutters). 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 (Lockey Loto Durable Standard Safety Gate Valve Lockout with Ce). 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,Self-Propelled Ride on Concrete Floor Grinder Grinding Machine Gyg-780, 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 Flame Plasma Cutting Machine Flame Cutting Nozzle;Air-Cooled Refrigeration Condenser Dual Flow Unit Cooler Air-Cooled Condensing Unit;14 X 14 Mesh Window Screen Aluminum Alloy Wire Netting;China High Alumina Ceramic Ball). However,The Best Venlo Type and Multi-Span Glass Greenhouse for Agriculture.
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,PC Black Plastic Material Polycarbonate PC Granules Resin.Duplex Hydraulic Oil Filter for Lubrication System, 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 (Food Safety Testing Equipment for Heavy Metal in Food Analysis). In the maximal PAC performance pH was found to be around the neutral (Hc-30A Electrical Insulation Tape Winding Machine for Wire and Cable;factory outlet excellent herbicide DIURON 80% WDG on sale). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Large Outdoor Water Park Slide/Water Turntable Amusement Equipment) which determines the coagulation performance (Irregular shape). 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 (Pond Electric Copper Wire Clean Water Pump with European Plug).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Surge Protector Lightning Arrester Lightning Arrester.
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