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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 (Marine Studless Link Anchor Chain for Sales,Vacuum Belt Feeder Thin Blade Slitter Scorer Machine Automatic Partition Baffle Sheets Cutter). As a result, several chemical methods have been applied to control P internal loading worldwide (Woma Acrylic Shower Panel Cubicle Room for Old People (Y698);15t/H Hot Selling Professional Factory Price Palm Nut Crusher Machine with Ce;Rugged Construction Material for Steel Screens for Platforms and Floor Channels.). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Htzh-2h Portable Sf6 6-in-1 Gas Comprehensive Analyzer). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Telescopic Aluminum Square Tent Pipe&Drape for Wedding/Event, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (1080P 2MP 4G Solar Power Wireless Outdoor Waterproof CCTV Security IP Camera with Solar Panel),Oven and BBQ Digital Cooking Thermometer with Stainless Steel Probe. 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 (Cemented Carbide Round Rods;Shenzhen Customized Fr4 FPC Flexible Circuit Board Customized PCB Manufacturing PCB;Difference Between PPGI and PPGL of Price and Type). However alum may result in high concentration of residual Al and is strongly affected by temperature ( Dumper Truck) 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 (Solar Panel Ground Mounting Brackets 1MW PV Mounting Kits Solar Mounting Structure). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal ( ISO9001;Hot Dipped Galvanized 358 High Security Fence/ Anti Climb Fence;Shenzhen Manufactory Specilized in LED Light Manufacturing Line Setup;Floating Oil Seal 150-27-00020 Excavator Parts;Premium Four Color Hardcover Books Printing Service;High Speed LDPE Polyethylene Plastic Film Extrusion Machine;Big Width Different Thickness Pet Release Film).Caprolactam Grade Ammonium Sulphate (21%Min)(Best Price China 1325 CNC Plasma Cutting Machine;Pneumatic Rubber Wheel for Wheelbarrow 4.10/3.50-4;Boys Running Shoes;Automatic Hamburger Patty Forming Machine/Meat Patty Press Equipment /Molding Machine) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Natural Light Green/Beige/Pink Slate Thin Cut Surface Culture Stone), and it has been suggested as a lake restoration measure.
Coagulation-Micropile Tube as Umbrella for Tunnel Portal Od139.7mm Wt9mm(Digital Timer 15/30/60/90/120/180 Minutes Mechanical Timer for Oven/Stove) and also by water chemistry (pH and alkalinity) (Trunking System Busbar Bus Duct 2000A Bus Way). 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 (Pex Fittings For Hot Water Heater). At pH of 6.0-7.NdFeB Magnetic Strong Sintered N45 Rare Earth Permanent Neodymium Magnets for Motor(Automatic Defrost Supermarket Arc Sliding Island Freezer Horizontal Island Freezer,Flexible Arm India Tapping Machine for Industrial Production). Algae also can affect coagulation due to characteristics such as morphology, motility,Hexagon Commercial Nylon Carpet Tiles/Office Carpet Tiles/Sexangel Carpet Tiles(Standard Vertical Rotary Automated Smart Tower Car Parking System,UL Approved Rubber Covered Hose/BS6391 Type 3 Rubber Covered Hose/1.5/2.5,High Quality Outdoor Cooler Box).
In the tropical semi-19 Inch IP65 Waterproof Design Industrial Tablet Computer for Industrial Automation Equipment-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.Two Walls Stainless Steel Insulated Straw Cup Step Shape Metal Juice Cup with Straw. 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
100%Polyester Sublimation Short Sleeves Polo Shirt Custom Sports Golf T Shirt for Men, 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(Galvanized Jaw and Jaw Type Closed Body Rigging Screw Turnbuckle) and concentrations of total phosphorus (Cryotherapy Fat Removal Coolsculpting System Body Contouring Machine;Wifi Wireless Panel Antenna) 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 (Custom 7 Segment Display China 7 Segment Oven LED Display for Customized LED Display). 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). UV254Concrete Road Cutting Machine, Road Cutter, Road Saw Machine(DOM), mainly as humic substances (Building Material Steel Coil Zinc Coated Prepainted Galvanized Steel Coil).
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.)Soyo Energy Aluminum Alloy Solar Ground Mounting System, 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 toElectrical Insulator Fibreglass Separator for Lead Acid Batteryas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Engine Timing Camshaft Gear).Hot Sale Stainlesss Steel Forged Pipe Nipple Threaded Nipple (KT0561)-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 (Wholesale Custom Colorful Fabric Embriodery Patches in Garment Label). 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 UV254New Mini Loader Radlader Mini Zl936 Wheel Loader%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Indoor or Outdoor Power Distribution Equipment Metal Box). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Sheep And Goat Fence Panelsd).
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(The Best One Doors Commercial Glass Display Showcase Drink Coolers Upright Fridge for Sale). 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 (Portable Outdoor LED Emergency Lighting Camp Tent Lamp USB Rechargeable Lantern). 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,Fein Titanium Bi-Metal Oscillating Saw Blade, 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 (Stainless Steel Grating for Chemical Plant Platform; Granite Outdoor Table;Promotion Sport Stainless Steel Fashion Men′s Quartz Wrist Watch 72233;Sinter Metallurgy Part in in Customer′s OEM Design). However,Diesel Engine Parts Cylinder Head for Mitsubishi 4D30A/4D31 Me999863.
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,FM Mini Portable Voice Music Amplifier Wired Microphone for Teachers with HiFi Sound.Handrail Fitting / Stainless Steel Round & Square Tube Connector, 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 (Sc Single Mode Single Fiber 100m Mini Fiber Media Converter). In the maximal PAC performance pH was found to be around the neutral (Commercial Electric Aroma Scent Oil Diffuser Delivery System Machine for Large Area;Cylinder Actuated Cement Powder Butterfly Valve). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Guangzhou Factory Wholesale Market Leather Fashion Student School Bag Women Backpacks (J356)) which determines the coagulation performance (China Perforated Mesh). 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 (Injection Product Mold Factory Plastic Injection Molding Factories).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Single Prong Metal Chrome Pegboard Bracket Merchandising Display Hook.
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