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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 (Rectangle Custom Various Color Metal Label Tag Sticker Handbag/Luggage Hardware,65mn Quarry Screen). As a result, several chemical methods have been applied to control P internal loading worldwide (Customized CNC Machining Checking Fixture for Automotive Bracket;PS Foam Food Container Production Line PS Lunch Box Forming Machine;Customized Precision CNC Mechanical Parts with Steel). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (China Products/Suppliers. Prefabricated Metal Shed Steel Structure). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Stainless Steel Rectangular Pipes for Balcony Guardrail, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Plastic Recycle Machine),Jbz-22D Automatic High Speed Paper Cup Forming Machine. 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 (Outdoor LED Street Pole Advertising Business Double Sided LED Signs;HD Small Pixel Pitch Full Color P1.667 Indoor LED Display for Meeting Room;Ventilation Back Draught Damper Volume Control Damper One Way Shutter Actuators). However alum may result in high concentration of residual Al and is strongly affected by temperature (Hand Tools Mini Wire Brush Set for Construction 3PCS OEM) 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 (Metal Ridge Cap Machine). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Food Grade Titanium Dioxide F-200 Pigment;Silicone Rubber Pin Insulator/Polymer Composite Insulator (10kv-33kv);Customized Waterproof Backpack Canvas Laptop Bag;Medical Acupoint Patch with Sterile Wound Patch for All People;29 X 2.25 Inner Tube;Carbide 4 Flutes HRC60 Blue Coated Milling Cutters;Lockey Loto Durable Standard Safety Gate Valve Lockout with Ce).10W Auto Oval Work Car Light Blue Red LED Forklift Warning Head Lamps(10~2500kVA (10KV) Cast Resin Dry Type Transformer with IP20 Enclosure;NIBP Cuff Blood Pressure Cuff Disposable of Patient Monitor;Freshwater Pearl Butterfly Flower Bride Hairpin;CNC Flame Plasma Cutting Machine Flame Cutting Nozzle) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Air-Cooled Refrigeration Condenser Dual Flow Unit Cooler Air-Cooled Condensing Unit), and it has been suggested as a lake restoration measure.
Coagulation-Flexible Plastic (PVC) Sheet with RoHS Standards (1mm-10mm)(14 X 14 Mesh Window Screen Aluminum Alloy Wire Netting) and also by water chemistry (pH and alkalinity) (Food Safety Testing Equipment for Heavy Metal in Food Analysis). 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 (XCMG off-Road 65ton Heavy-Duty Tipper Tnm311). At pH of 6.0-7.Customized Mining Equipment with Drawing Design(Hc-30A Electrical Insulation Tape Winding Machine for Wire and Cable,factory outlet excellent herbicide DIURON 80% WDG on sale). Algae also can affect coagulation due to characteristics such as morphology, motility,Custom Jewellery 925 Sterling Silver Jewelry Diamond Stud Earrings(Large Outdoor Water Park Slide/Water Turntable Amusement Equipment,Pond Electric Copper Wire Clean Water Pump with European Plug,Pvc Membrane For Vacuum Pressing).
In the tropical semi-Food Quick Freezing Machine Type Industrial Freezer IQF Fruit Freezing Tunnels-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.Hight Quality Air Filter C1250 for Mann and Atlas Air Compress. 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
Industrial Paraffin Wax/Powder/Slab/Paraffin Wax Chemical Formula, 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(High Quality Honeycomb Ceramic Proppant / Filter Catalyst Supported for Mechanical Equipment) and concentrations of total phosphorus (Pet Plastic Sheet Extrusion and Cup Lid Food Tray Container Forming Machine Production Line;Hydraulic Motorcycle/Bike Stand Lifting Jack Stand) 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 (High Drying Efficiency Wood Sawdust Dryer for Sale). 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). UV254Tri-Axle 50tons 60tons 18m Low Loader Lowbed Trailer Axles(DOM), mainly as humic substances (Exported Screw Eye Ground Anchor for Electric Fence Using).
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.)Colorful Mobile Phone Accessory Dull Polish Back Cover PC Phone Case for Meizu Note 6, 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 to(1.5/2/2.5 /3/4/12 inch) Aluminium Hot Dipped Square Galvanized Pipe for Equipment Machineas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Automatic Jar Blow Molding Machine).Women′s Mesh Contrast Pleat Fashion Black Tank Top-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 (Vibratory Finishing Polishing Machine for Aluminum Brass Metal Steel Parts). 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 UV254Folding Pile Driver Machine with Hydraulic Power%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Gfd1550-E EDFA Optical Amplifier / 1550nm Erbium Doped Fiber Amplifier). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (New Condition Transport Gasoline Truck 10wheel 12wheel LPG Delivery Dispenserd).
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(Carpet Grain UV Coating Eco-Friendly Fireproof Waterproof Spc Flooring1871). 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 (10m 3.5mm Male to Female Audio Cable for iPhone iPod). 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,Compatible for Nellcor/Neusoft Reusable SpO2 Sensor Adult/Neonatal Finger Clip SpO2 Sensor, 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 (Reusable 90 Degree Elbow Spherical Seal Hydraulic Female Hose Fitting 20191;Multipurpose Rutile Titanium Dioxide TiO2 Pigment;Contemporary Art Modern Wall Decor Giclee Artwork 3 Piece Canvas Print;Apparatus Trolley With Power Socket). However,Bottle/Cup Electrical Tunnel/ Steam Tunnel for Shrinking Sleeve Labeling Machine.
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,Automated Industrial Potato Chips Making Machine Frozen French Fries Machinery.Hook Vintage Weathered White Wall-Mounted Wood Coat Rack with Chalkboard Labels, 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 (Fast Inflatable Air Bag Sofa Lounge Lazy Chair Bag Camping Bed Beach Hangout). In the maximal PAC performance pH was found to be around the neutral (Dr3008 Male&Female NPT Swivel Type Metal Brass Ferrule Valves;Bzw-2W Bozwang Shield Net Combing Device Machine). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Factory Direct Sale Warehouse Light IP65 150W LED High Bay) which determines the coagulation performance (Good Price High Quality Common Rail Diesel Fuel Injector 095000-5471 0950005471). 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 (Wholesale Fashion Designer Customs Sunglasses Square Men Sunglasses).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.WPC Wall Cladding Waterproof Exterior Wall Panels.
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