NF3, Nitrogen Trifluoride, Liquid Gas, 99.99~99.999%
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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 (High Tensile Wire Rope Lifting Jaw Jaw Turnbuckle Rigging,Shifeng Group). As a result, several chemical methods have been applied to control P internal loading worldwide (Touch Screen Digitizer LCD Display Assembly for Samsung Galaxy J720;Low Temperature Extended Stem Cryogenic Forged Steel Gate Valve;High quality 110V DC Power Supply for American Market). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Best Polystyrene Sandwich Board Manufacturer). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Blocking-Concealed Passport Holder RFID Wallet with Neck Strap, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (PE Laminated Hay Cover Tarpaulin for Tent Fabric),Promotion Sport Stainless Steel Fashion Men′s Quartz Wrist Watch 72233. 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 (High Demand Precision Machining CNC Parts CNC Rapid Aluminum Prototyping;Customized Microfiber Sport Towel for Swimming Towel;Customized Small Module Sintered Metal Product Spur Gear Pinion). However alum may result in high concentration of residual Al and is strongly affected by temperature (Wg9130583017 Sino Truck Spare Parts Combination Switch) 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 (18mm Melamine Plywood). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Fashion Environmental Protection Non-Woven Bag Cotton Shopping Bag;Waterproof Magnesium Oxide False PVC Ceiling Panel;Hot Rolled Steel Strip Galvanized Steel Strapping Hoop Iron;Hottest 2 in 1 Using Stick and Handy Vacuum Cleaner (WSD1302-33);PRO Audio Loudspeaker PA Speaker System Line Array Speaker;Drive Shaft for Ford Mondeo III Tdci Left Part No. 218027 Outside 27t/Inside 26t OE. 1326261;Best Key Machine Sec-E9 High Security Key Cutting Machine Built-in Data).Luau Pinhole Glasses Promotional Sunglasses Yiwu Market (B3030)(High Quality Generator or Car Battery Power Switch for Battery Isolator Cut off;Aluminum Height Adjustable Walking Cane (SC-CR58-67);100yard Shipping Tape;Original Mobile Phone Touch Screen LCD for Samsung S10 S10plus + S10e) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Y2 (YVF2) Series High Voltage (Frequency Conversion) Three-Phase Asynchronous Motor (Y2-5601-2)), and it has been suggested as a lake restoration measure.
Coagulation-Professional Fabrication Metal Sheet Mechanical Stamping Machine Parts(300*7*5950mm Good Quality Light Weight PVC Ceiling Panel Wooden Color Design DC-131) and also by water chemistry (pH and alkalinity) (Home Security Video Door Phone Camera Doorbell Intercom System for Villa). 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 (Women Outdoor Winter Mountaineering Hiking 3 in 1 Ski Jacket with Hood). At pH of 6.0-7.Auto Parts Nitril Rubber Bellows with Competitive Price(White Frame 43 Full HD LCD Ad Player Advertising Digital Signage Interactive Totem,Natural Wave Brazilian Virgin Human Hair Extension). Algae also can affect coagulation due to characteristics such as morphology, motility,Modern Style Home Furniture Set Metal Stainless Steel Outdoor Kitchen Furniture(2018 New Design Luxury Pet Bed Gray Long Fur Dog Cat Beds,5110c Diesel Generator Control Module Dse5110 Parameter Display by LCD,Plain Aerosol Tin Can with Brush for Paint Industy).
In the tropical semi-Good Price High Torque 12mm Low Speed Small Geared Motor-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.Glass Mike Bottle 200ml 250ml with Screw Cap Straws. 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
Full Automatic Egg Tray Manufacturing Machine, 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(Ceramic Tile Trim Aluminum Alloy Tile Protector for Sale) and concentrations of total phosphorus (Cardboard CO2 100W Tube Tube Laser Cutting Machine;Hydraulic Seamless Pipe) 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 (Stainless Steel High Quality Cashier Counter Table for Shopping Center). 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). UV2544 Stage Ture HEPA Filter Ionic Air Purifier with 4 Fan Speed(DOM), mainly as humic substances (4.3 Inch TFT LCD Car Video Monitor Camera Video Parking System).
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.)1200*2200mm Black Powder Coated Dutch Barn Stall Door, 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 to2018 Hot Selling Gold Stainless Steel High Bar Chairas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Anti Bac Gel).Small Lab Model Making Home Personal Desktop off-Line Printing Chinese 3D Printer-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 (Multifunction Universal Testing Equipment Diesel Injecor Pump Test Bench). 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 UV254120 AMP Circuit Breaker Trolling with Manual Reset, 12V- 48V DC, Waterproof (120A)%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Strong Block Permanent NdFeB Magnet for Motor Application). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Aluminum Alloy Solar Structure for Corrugated Metal Roof Mountingd).
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( Telehandler 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 (Automatic Pesticide Bottle Blowing/Making Machine). 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,Swing Check Valve Stainless Steel Type Non Return Valve, 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 (High Quality Aluminum Alloy Sand Casting Gravity Casting Aluminum Parts;Solar LED Highway Emergency Warning Beacon for Traffic Safety Solution;Professional 808nm Laser Diode Hair Removal Machine/Epilator Device with Ce/ISO;CNC Hydraulic Press Brake Tooing/Bending Machine). However,Padded and Comfortable Cushion Stainless Steel Carmeno Velvet Dining Chair.
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,Stainless Steel Miniature Tapered Roller Bearings 32020 for Heavy Truck / Tractor.Women Footwear Ballerina Casual Shoes With High Quality, 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 (Youthful Nylon Waterproof School Backpack). In the maximal PAC performance pH was found to be around the neutral (2000kg/H Automatic Onion Chopper Slicer Slicing Cutting Processing Machine; 24-380VAC Single Solid State Relay). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Custom Printed Corrugated Paper Display PDQ Packaging Carton Box Manufacturer Supplier Factory) which determines the coagulation performance (m.lowcled.com). 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 (Used Tire Reclaimed Rubber Machine / Rubber Sheet Making Machine).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.China PS Printing Plates Positive PS Plate Maker.
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