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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 (Pneumatic Rubber Wheel for Wheelbarrow 4.10/3.50-4,Anti-Reflective Anti-Finger Touch Monitor). As a result, several chemical methods have been applied to control P internal loading worldwide (Automatic Hamburger Patty Forming Machine/Meat Patty Press Equipment /Molding Machine;Natural Light Green/Beige/Pink Slate Thin Cut Surface Culture Stone;Digital Timer 15/30/60/90/120/180 Minutes Mechanical Timer for Oven/Stove). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Trunking System Busbar Bus Duct 2000A Bus Way). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Scaffolding Board Cable Tray Panel Roll Forming Machine Line, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Rca Audio Cable),China Homemade Bearing Ball Screw for CNC (DFU series 16-100mm). 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 (Automatic Defrost Supermarket Arc Sliding Island Freezer Horizontal Island Freezer;Flexible Arm India Tapping Machine for Industrial Production;Standard Vertical Rotary Automated Smart Tower Car Parking System). However alum may result in high concentration of residual Al and is strongly affected by temperature (UL Approved Rubber Covered Hose/BS6391 Type 3 Rubber Covered Hose/1.5/2.5) 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 (Cheap Safety Shoes High Quality Supplier). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (380V/220V VFD Variable Frequency Drive 50Hz/60Hz for Fun;500W/1000W/15000W CNC Laser Cutting Machine Laser Cutter for Steel Plate;Galvanized Jaw and Jaw Type Closed Body Rigging Screw Turnbuckle;Cryotherapy Fat Removal Coolsculpting System Body Contouring Machine;8000 Tons/Year High Percent of Bright Bare Copper Wire Scrap Upcast Machine;High Precision Self-Aligning Roller Bearing 1219;Glass Charger Plate Decoration Plates Shining Gold Rim Clear Charger Plates).Woodworking Edition - Waxed Canvas Tool Bag - Padded Straps(Custom 7 Segment Display China 7 Segment Oven LED Display for Customized LED Display;Building Material Steel Coil Zinc Coated Prepainted Galvanized Steel Coil;White Kraft Paper Poly Laminated Flour Packaging Bag;34*25cm Office File Pocket Felt A4 Document Bag) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (4 Inch Cast Iron Wafer Pneumatic Butterfly Valve), and it has been suggested as a lake restoration measure.
Coagulation-Full Automatic Old Car Tyre Recycling Machine /Side Wall Cutter(Wall-Mounted Wooden Commercial Bathroom Cabinet PVC Vanity with Mirror) and also by water chemistry (pH and alkalinity) (Electrical Insulator Fibreglass Separator for Lead Acid Battery). 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 (New Arrival AC 0-100A Voltage Current Power Factor Frequency RS485 Multimeter). At pH of 6.0-7.Six Spout Impeller Cement Packing Machine(Xinjing Wide-Mouth Kitchen Glass Square Jar for Spice,Environmentally Diesel Powder Coating Bake Curing Oven). Algae also can affect coagulation due to characteristics such as morphology, motility,One-Stop Condensing/Compressor/Refrigeration Unit Freezer Cold Store(Wholesale Custom Colorful Fabric Embriodery Patches in Garment Label,Indoor or Outdoor Power Distribution Equipment Metal Box,5mm Thickness PVC Foam Sheet for Promotion Advertisement).
In the tropical semi-Automatic Blister Plastic Vacuum Thermoform Molding Packing Machine-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.6*6mm Momentary Push Button Tact Switch Tactile Switch with Through Hole. 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
8PCS*10W RGBW LED Spider Moving Head Beam Stage Light, 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(Portable Outdoor LED Emergency Lighting Camp Tent Lamp USB Rechargeable Lantern) and concentrations of total phosphorus (Pillow Type Candy Packing Machine Candy Packaging Machinery Manufacturer;Big discounting Sea Fishing Accessory Green/brown/black/red/sliver/grey - simple fishing vest - Demarui) 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 ( Granite Outdoor Table). 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). UV254Wd190V Handheld Metal Detector Gold Metal Detector Made in China(DOM), mainly as humic substances (Promotion Sport Stainless Steel Fashion Men′s Quartz Wrist Watch 72233).
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.)Factory Wholesale Price Fingerprint Access Control with TCP/IP and WiFi, 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 toGuangzhou Factory Wholesale Market Leather Fashion Student School Bag Women Backpacks (J356)as they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Wholesale Supermarket Cooler Bag 600d Thermal Carry Bag).DC/Ec Inverter Motor Ceiling Horizontal Type Fan Coil Unit-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 Directly Ss 304 Stainless Steel Toilet Cubicle Fitting Indicator Latches). 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 UV254Floor Stainless Steel Fix Movement Joints Decorative Stainless Steel Tile Trim%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (New Cisco Aironet 3700 Series Wireless Access Point Air-Cap3702e-B-K9). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Calendar Boxesd).
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(Nail Sterilizer Disinfection Box Salon Nail Tools Disinfector Sanitizer Box). 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 (Decorative Round Shape Colorful Empty Aroma Reed Diffuser Custom Glass Bottle with Wooden Cap). 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,1325/1530/2030/2040 CNC Woodworking Router Machine with Cheapest Price and Big Discount Is on Big Sale, 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 (Wholesale Factory Price 100% Virgin Kinky Curly Vietnamese Human Hair;up-Down Table 1390 100W CO2 CNC Laser Cutter Machines;High Quality for Kawasaki K3sp36 Replacement Parts;1000w Laser Cutting Machine). However,UV LED Curing for Coating Printing 365nm UV LED Portable LED UV Curing Device for Wood Coating.
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,China Factory Price 6 Axles Tractor Truck Trailer.2mm-15mm Smart Switchable Screen Mirror Glass for Sale (S-F7), 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 (High Quality Firefighting Rescue Equipment Safety Rescue Tripod). In the maximal PAC performance pH was found to be around the neutral (Manufacturer C / U-Channel Metal Solar Panel Mounting Brackets PV Mounting Frame Manufacturer;Great Quality Waste Water Treatment Polyaluminium Chloride PAC). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (I30 Tws Pop-up 1 to 1 Size Mini Bluetooth Earbuds) which determines the coagulation performance (Carbon Steel Sleeve Anchor Bolt with Hex Nut and Washer Screw Type Expansion). 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 (Large Diameter Plastic HDPE Pipe Extrusion Making Machine Production Line).
304, 316 Slot Stainless Steel Tube with Glass, charge and density, factors that influence directly in flock sedimentation.Giant Christmas Socks Carnival Amusement Park Inflatable Slide(Automatic Marshmallow / Cotton Candy Sachet Bag Pouch Packing Packaging Machine;Building Lifting Equipment Trolley Electric Cable Winch). 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 (Stainless Steel Hex Head Bolt DIN933 ANSI Full Thread M8X10...M8X220). Extracellular and surface-Multifunction Massage Rainfall Shower Column with Five Functions(Supply Tungsten Carbide and Stamping Dies,OEM Customized Design Sublimated Print Cotton Twill Trucker Baseball Cap). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (Factory Direct Price Automatic Snack / Candy Grain Packing Machine), which can be one important cause of the increase in coagulant demand in algae-rich waters (Manufactured Goods PPGI Coil Corrugated Steel Sheet).Belt Conveyor Vertical Guide Roller/Side Idler Rollers/Conveyor Roller(Laboratory Accessories Bench-Top Mounted Four Outlet Gas Fitting), particularly humic susbtances. Humic substances are highly negatively charged (Machine Professional Heavy Duty Tile Cutter for DIY Market), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Galvanized Bird Cage Welded Wire Mesh Rolls for Construction). Maximal UV254removal was observed to be found around pH 6.0 (Hot Sale Foundry Moulding Machine Manufacturers). 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 (Industrial ESD Safety Shoes with Steel Toe Mens Black Color).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Geometric Tall/Large Plants Glass Terrarium Planter Pot Box for Christmas Decorative.
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