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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 (Kiet Brand High Efficiency Automatic Hydraulic Cam Dismounting Puller,Stepper Motor Driver Price). As a result, several chemical methods have been applied to control P internal loading worldwide (Dog Cat Car Products Travel Accessories Seat Pet Carrier Bag;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). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) ( Door Mat). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Prime SPCC Electrolytic Tin Plate for Making Cans, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Custom Mertal Label),2 Pin Waterproof Soldering Socket Waterproof Extension Cord Connectors. 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 (Made in China Multi-Storey Steel Structure with Light Steel Frame;Easy-to-Use School Office Invisible Stationery Tape;Commercial Tow-Able Diesel Portable Movable Rotary Screw Air Compressor). However alum may result in high concentration of residual Al and is strongly affected by temperature (4 Cencter Set Lavatory Plastic Faucet (smooth and easy opening)) 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 (LED Projector 400W Bsw with Framing Moving Head Lighting). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Cold Storage Warehouse Rack with Good Quality;Brc Welded Wire Mesh Fence/3D Curvy Welded Wire Mesh Fence;A4;High Efficiency Hook Type Shot Blasting Machine for Sale;Lab Glass Reactor Kettle Extractive Distillation;Non-Toxic RTV Silicone Sealant of Full Automatic Machine;High Tensile Forged Chain with Conveyor for Conveying System).Black Acrylic Steam Shower Room Cabin with 6mm Tempered Glass(M5 SMD with Internal Blind-Hole Thread with Pin (groove);Interlocking Waterproof Removable Anti-Slip PVC Garage Floor Tile;3500lbs Cable Pulling Fast Line Speed UTV Electric Winch;Best Quality Popular Lovely Washable Pet Accessories Luxury Soft Dog Bed) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Customized Wire Mesh for Decorative Garden Fence), and it has been suggested as a lake restoration measure.
Coagulation-High Precision Durable Aluminum Cutting Saw Blade(Fan Cooling Oval Design Commercial Cake Display Showcase Fridge) and also by water chemistry (pH and alkalinity) (China Qingdao Factory Interlocking PVC Garage Floor). 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 (Rubber Hose Gasket). At pH of 6.0-7.High Quality Lift Gas Spring for Bed Support(Micropile Tube as Umbrella for Tunnel Portal Od139.7mm Wt9mm,Double Arm Medical Pendant for Anesthesia (HFP-DS240/380)). Algae also can affect coagulation due to characteristics such as morphology, motility,Galvanized Bird Cage Welded Wire Mesh Rolls for Construction(High Quality Galvanized Welded Wire Mesh Panel Roll,Telescopic Aluminum Square Tent Pipe&Drape for Wedding/Event,www.hongraygloves.com).
In the tropical semi-Hot Sale Low Price Small IGBT Magnetic Induction 40kg Steel Scrap Melting Furnace for Metal Melting-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.Alumina, Silicon Carbide, Zirconia Porous Ceramic Foam Filter. 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
210t Nylon Fabric Parachute Mosquito Net Hammock Beach Hammock, 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(New Type Portable 380V Electric Winch in Stock) and concentrations of total phosphorus (Custom A4 Size Plastic PP Clear File Button Folder;Broasted Chicken Machine) 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 (Laparoscope Instrument Laparoscopy Set for Ectopic Pregnancy Surgery). 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). UV254High Temperature Fireproof PU Coated Silica Fabric(DOM), mainly as humic substances (Industrial Paraffin Wax/Powder/Slab/Paraffin Wax Chemical Formula).
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.)Delivery Cylinder Used in Concrete Pump Truck for Construction, 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 toModular Concrete Batching Plant by Twin Shaft Mixer 3000/2000as they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Gestation Stall Using with Farrowing Crate in Modern Pig Farm).FRP / GRP Corrugated Sheet Making Machine 3 Layers Making 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 (Whole Sale Banquet Tiffany Classic Stackable Gold Louis Dining Chair). 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 UV254Traffic Safety Plastic Signs/Accessible Fire Exit Emergency Signs%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Hidrotek Water Filter Cartridge with Sediment Carbon). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (foldable manual wheelchaird).
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(Stainless Steel Grade U2 U3 Stud Link Anchor Chain with Factory Price). 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 (Diesel Fuel Leak off Pipe for Mercedes-Benz). 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,Gi Steel Sheet Galvanized Steel Sheet Zinc Coated Plain Steel Sheet, 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 (Carbon Steel Carry Idler Belt Conveyor Guide Roller;Rexroth Hydraulic Pump A8V55/80/107 Replacement Spare Parts;Factory Supply Customized Sintered Inner Gear Rotor by Iron Alloy Powder;www.etonsmtauto.com). However,Double Screws Textured Soy Protein Artificial Meat Tvp Tsp Extruder.
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,18 mm OSB (Oriented Strand Board) for Roof Decking.Custom Stand up Composite Material Zipper Packaging Bag Candy Bag, 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 (2750OE Hico 12.7mm Width Plastic Magnetic Stripe Card for VIP Card). In the maximal PAC performance pH was found to be around the neutral (Quick Link Cotton Baling Wire with Single Double Loops Bale Tie Wire;High Automatically Vacuum Hydraulic Oil Filtration Equipment for Oil Recycling). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (ASTM A792 PPGI PPGL Roof Sheet Cold Rolled Steel Coil) which determines the coagulation performance (Aluminum Alloy Frame). 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 (Modular Functional L Shape Living Room Leather Sofa).
Pear or Regular Shaped Screw Lock Metal Quick Link, charge and density, factors that influence directly in flock sedimentation.12V DC Vehicle Charger Superior Suction Cup Auto Car Electric Fan(Dish Plate Dryer and Sterilizer 60liter Using UV and Ozone;High Quality CNC Turning Center Parts Machinery Auto Parts). 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 (Factory Price Gerneral Usage Silicone Sealant). Extracellular and surface-Rcm Certification for Scanning Electronic Input Pen(Full Automatic Facial Tissue Paper Making Machine Production Line,Transparent 240W SMD 3030 Outdoor LED Flood Lamp). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (ISO Factory of Disc Cutter for Tunnel Boring Machine), which can be one important cause of the increase in coagulant demand in algae-rich waters (CNC Parts Sfu2510 25mm 400mm Fdr Ball Screw with Nut).1/2, 1/4, 1 High Alumina Ceramic Ball with High Quality(Commercial Strength Gym Equipment Adjustable Bench (Incline/ Flat/Decline) L-966), particularly humic susbtances. Humic substances are highly negatively charged (European Style Shanxi Black Book Shaped Memorial/Gravestone/Tombstone), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Top Quality Abrasion-Resistant PVC Artificial Leather for Bedroom Furniture). Maximal UV254removal was observed to be found around pH 6.0 (Dac34640037 Wheel Bearing /Automotive Bearing/ Hub Bearing). 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 (Aluminum CNC Al5052 / Al6061 / Al6063 Machining Turning Parts for Mil-Spec Electronics).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Surface Paiting Line UV PU Water Base Spraying Robot Arm.
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