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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 (Surgical Instrument LED Shadowless Operation Lamp,Bamboo X-Stand Portable Laptop Stand). As a result, several chemical methods have been applied to control P internal loading worldwide (Stray Inductance 210~2100uh Frame Core Current-Compensated Common Mode Choke Coils;Cbhs-F32 Hydraulic Oil Transfer Gear Pump for Fuel Forklift;Precision Oscillating Multitool Sharp Cutting Blade for Wood). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Aluminum Alloy Die Casting for Mechanical Part (STK-14-AL0047)). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Dongfeng 4X2 5tons 10m3 Mobile Dispenser LPG Gas Tank Truck, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (D18 65 Inch Aiwa Flat Screen Ultra Slim Android Smart UHD 4K LCD LED TV),Wholesale Fashion Custom Christmas Glass Jar Candle Holders with Lids. 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 (1300*700*700mm Vertical CNC Milling Machine CNC Lathe CNC Machine Center CNC Machine Tool;20L Semi Automatic China Bottle Pet Blower;professional Manufacturer One Arm Motorized Multifunction for Medical Products). However alum may result in high concentration of residual Al and is strongly affected by temperature (Banana Slicer Cutter Perfect for Fruit Salad Yellow Banana Cutting) 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 (Automatic Type Narrow Fabric Screen Printing Machine). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Electric Baking Heat Preservation Deck Oven Manufacture;Electric Vibrating Massage Cream Jar for Cosmetic Packaging;Gym Fitness Equipment EPDM Surface Gym Rubber Flooring Mat/Rubber Flooring with 500*5000/1000*1000mm;High Precision Injection Molding Plastic Parts in China (STK-PL-1055);Scissor Knife Sharpener;Venlo Polycarbonate Covering Material Greenhouse on Sale;Rubber Recycling Machine Powder Tire Derived Fuel Machine Small Tyre Recycling Plants).Melt Floor Lamp Copper Standing Lamp Modern Floor Lighting(Metallic Paint Solid Aluminum Cladding Panels for Roof Covering/ Ceiling;VGA multi screen video wall LCD video wall panel with wall screen matrix;Osyea-E40 Manufactory 80W LED Corn Light Bulbs for Street Garden Light/Lighting;Customized Dust Filter Cartridge Price for Industrial Welding Fume) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (2800X8000mm ASME Certified Rubber Vulcanizating Chamber (SN-LHGR2880)), and it has been suggested as a lake restoration measure.
Coagulation-OEM Custom Plastic Injection Mold for Mobile Phone Case(Factory Hot Sale Square Hollow Steel Tube 50X50X2.5 High Quality Mild Iron Pipe 75X75) and also by water chemistry (pH and alkalinity) (Stainless Steel Sheet Metal Laser Cut/Aluminum Sheet Metal Laser Cutting). 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 (Lowest Price Factory Universal Pipe for Swimming Pools HDPE Pipe). At pH of 6.0-7.China Manufacrure Mobile Asphalt Batch Mix Plant for Sale(Light Blue Color Glass Drink Bottle for Beer,Custom Sequin Patch for Clothing Handbag Backpack). Algae also can affect coagulation due to characteristics such as morphology, motility,Synthetic Fiber Filter Rolls Filter Media for Air Conditioning(ASTM A242 A588 Corten Steel Plate/Sheet/Coil/ Corten a/B/ SPA-H / B480,3.5mm,Dana 80 Rear Axle).
In the tropical semi-1600X1000mm 100W Cheap Fabric Cloths Cutting Engraving 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.THK Misumi Hiwin Linear Ball Bearing Block Bearing Gl25ca. 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
China Manufacturers Round Welded Stainless Seamless Steel Pipes 316, 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(LED Video Wall PCBA&PCB and LED PCB Design) and concentrations of total phosphorus (Dental Emax Empress Crown From China Dental Lab;Square Pipe Fiber Laser Cutting Machine for Stainless Steel Carbon Tube Plate) 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 (XL-21 Serise Motive Motive Electrical Switchgear Power Cabinet). 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). UV254Jiaheng Brand Custom small telescopic hydraulic cylinder boom piston price(DOM), mainly as humic substances (Lower Price Luxury Waterproof Spc Vinyl Floor Tile).
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.)Foshan Manufacturer Bathroom Glass Sliding Door Roller, 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 toSle4442 hotel key card PVC blank contact RFID cardas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(www.tstartincan.net).4 Cencter Set Lavatory Plastic Faucet (smooth and easy opening)-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 (Solar Panel Mounting Solutions Mounting Bracket Mounting Kit Mounting System). 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 UV254Industrial RO Water Purification-1500gpd with Black Cabinet (0.25T/H)%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (800kgs Steel Wire Rope Hand Winch for Lifting). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (60mesh Mica Powderd).
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(Woodworking Machine One Head Economic Model CNC Router). 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 (Custom High Quality Men′s Fashion Plain Cotton Polo T-Shirt). 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,Pool Copper Wire Self-Priming Centrifugal Pump with Stainless Steel Impeller, 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 (Hot Water Copper Tube Aluminium Fin Steel Plate Heat Exchanger;Alloy 6063 T5 Temper Aluminium Extrusion Customized Round Tube/Flat Tubes;2018 Small Machine Room Gearless Traction Xide Passenger Elevator;Long Range RFID UHF Animal Ear Tag for Cattle Tracking). However,Modern Chinese Furniture Aluminium Wall Modular Room Office Workstation Partition.
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,Manufactured Goods PPGI Coil Corrugated Steel Sheet.Organic Fertilizer Production Line for Manure Treatment, 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 (All Dielectric Aramid Yarn Armor Double Jacket Aerial ADSS Fiber Optic Cable). In the maximal PAC performance pH was found to be around the neutral (Flanged Bolted Bonnet Cast Steel Swing Check Valve Supplier;Supply Carton Sealing Use and Rubber Adhesive Duct Tape). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Customized Steel Wire Small Conveyor Belt System) which determines the coagulation performance (Pine Wood Timber Lumber for Construction or Furniture). 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 (Good Quality Cheap Bluetooth Music Zero Gravity Shiatsu Massage Chair).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.12 Kv Vacuum Circuit Breaker with Embedded Poles/ 12kv Vacuum Switch.
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