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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 (Pre Hot Dipped Galvanized Steel Pipe Cattle Fence,Natural Cotton Fabrics). As a result, several chemical methods have been applied to control P internal loading worldwide (Thermal Transfer Waterproof Tearproof Matt Silver Pet Label;Modern Leisure Chair for Europe;Silicone Grip Hand Forearm Strength Gripper Multi Colors Weights Rubber Ring Exerciser Gym). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Ribbed Colorful Wall Plug Anchor with Screw). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Banana Slicer Cutter Perfect for Fruit Salad Yellow Banana Cutting, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Key Hook),Blocking-Concealed Passport Holder RFID Wallet with Neck Strap. 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 (Modern Living Room Wood Frame Genuine Bonded Leather Chesterfield Sofa;New Baking Tool Creative Customized Silicone Toast Cake Mold;150-1000kg Commercial and Restaurant Cube Ice Maker Machine). However alum may result in high concentration of residual Al and is strongly affected by temperature (Littlefuse IC Fuse Cartridge Ceramic Electronic Component Nanosmdc012f-2) 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 (LED Supplier 150W Ceiling Lamp UFO LED Light High Bay). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal ( AC4900ca;Carbon Steel Heavy Structural Flat Washers Grade 10 DIN6916 Washers;Waterproof Antislip PVC S Mat PVC Z Mat for Bath Swimming Pool Factory Price;Steel Drilling Water Well Filter / Bridge Slot Screen Pipe;AC100-240V Compressor Truck Freezer;Astma312 TP304/Uns30400/X5crni18-10 Seamless Stainless Steel Round Hollow Bars;C-Type 2 Piece Tin Can Making Punch Press Machine).Promotion Sport Stainless Steel Fashion Men′s Quartz Wrist Watch 72233(Biobase -10~-25 Degree Upright Style Single Door Lab Deep Freezer;Powerful Bass and Nosie Cancelling Over Ear PS4 Gaming Headphone with Mic/Mute and Volume Control;Autumn And Winter Cat Bed;Custom Ductile Iron Casting Parts Gray Iron Sand Casting) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (High Quality Sand Paper for Sand Machine Brush (YY-170)), and it has been suggested as a lake restoration measure.
Coagulation-Luau Pinhole Glasses Promotional Sunglasses Yiwu Market (B3030)(Portable Trade Show Stand Tension Fabric Event Backdrop Display Stand From Tianyu) and also by water chemistry (pH and alkalinity) (Engineering Plastic Material). 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 (jinbinvalve.com). At pH of 6.0-7.Professional Fabrication Metal Sheet Mechanical Stamping Machine Parts(SAE 100 R1 R2 1sn 2sn Hydraulic Hose Assembly Fittings,GMP Certified Collagen Softgel for Fish Collagen). Algae also can affect coagulation due to characteristics such as morphology, motility,Auto Parts Nitril Rubber Bellows with Competitive Price(26000lm 200W LED High Bay Lamp Fixture for Gym House Factory,Luzhong-700 70HP 2WD Two Wheel Drive Farm Tractor,M008T50071)).
In the tropical semi-Modern Style Home Furniture Set Metal Stainless Steel Outdoor Kitchen Furniture-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.Good Price High Torque 12mm Low Speed Small Geared Motor. 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
Glass Mike Bottle 200ml 250ml with Screw Cap Straws, 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(Good Quality of 60t/D Wheat Flour Milling Plant) and concentrations of total phosphorus (Energy Saving One Step Automatic Tritan Pet Blow Molding Machine;Precast Concrete Structure Carousel) 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 (Heavy Duty Galvanized Stacking Steel Pallet Shelving with Posts). 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). UV254Full Automatic Egg Tray Manufacturing Machine(DOM), mainly as humic substances (Potato Chips Design Non-Toxic Silicone Baby Teether Toy).
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.)4 Stage Ture HEPA Filter Ionic Air Purifier with 4 Fan Speed, 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 toAutomatic Fresh Fruit Juice Bottle Natural Fruit Canning Machineas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Second-Hand 20 Benchtop Roland Versauv Lef-20 UV Flatbed Printer).1200*2200mm Black Powder Coated Dutch Barn Stall Door-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 (Multifunctional RF/40K Body Vacuum Roller Weight Loss Beauty Salon Cavitation Beauty Equipment). 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 UV254Small Lab Model Making Home Personal Desktop off-Line Printing Chinese 3D Printer%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Full Automatically Wp Line Powder Jet Mill Micronizer in Agriculture Field). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Best Price Wall Mounted Water Lightsd).
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(Plastic PE HDPE LLDPE LDPE Irrigation Water High Speed Pipe Extruder Making Machines). 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 (Power Transformer Voltage Transformer Pq2620 Series High Frequency Transformer). 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,120 AMP Circuit Breaker Trolling with Manual Reset, 12V- 48V DC, Waterproof (120A), 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 (American Double Hung Thermal Break Aluminum Window in China;Best Industrial Coal Fired Steam Boiler Manufacturer in China;7 Colorful 240 Degree Wide Lens Mini Speaker Smart WiFi Camera of Night Light Wc001y13;Multi-Function Small Tree Digging Shovel/Tree Machine). However,Swing Check Valve Stainless Steel Type Non Return Valve.
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,Padded and Comfortable Cushion Stainless Steel Carmeno Velvet Dining Chair.Stainless Steel Miniature Tapered Roller Bearings 32020 for Heavy Truck / Tractor, 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 (18X18 Asian Black Iron Square Tube/Black Square Steel Pipe Seamless). In the maximal PAC performance pH was found to be around the neutral (Luxury Modern Bathroom Furniture Sanitary Ware Solid Surface Basin;Monofilament Fishing Tackle Green Nylon Fish Net). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Used Fashion Summer Children′s Dress Unsorted) which determines the coagulation performance (201 304 316 430 Inox Profile Tube Hollow Section Stainless Steel Square Tube). 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 (Longboard or Skateboard Ball Bearings 608zz 608-2RS).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Chocolate High Speed Automatic Feeding and Packing Line.
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