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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 (Paint Bucket Plastic Injection Mold Design Manufacture Chemicals Container Mould,Factory Customized High Quality Silicone PVC Car Key Cover for Various Car Models). As a result, several chemical methods have been applied to control P internal loading worldwide (17inches Travel Computer Backpack Bag Water Resistant Business Laptop Backpack;Decoration Building Material Prepainted Corrugated Galvanized Roofing Sheet Steel Plate;Vertical Multi-Head Weigher Meat Packing/Packaging Machine (PMW-420E)). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Summer Mesh Bulk Ankle Socks Cheap Mens Dress Socks). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,2 in 1 Baby Feeding Chair Kids Eating High Chair, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Cheap Metal Roofing Sheet),Lifting and Hoisting Industrial Manual Chain Lever Block Vt. 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 (Three-Way Car Horn Air Compressor 12V 24V;Kg316t Digital Programmable Timer DIN Rail 220VAC 25A Timer Switch for Electric Appliance;PVC Pipe Extrusion Line CPVC UPVC Drainage Pipe Production Line). However alum may result in high concentration of residual Al and is strongly affected by temperature (Inconel 625 2.4856 Polished Nickel Alloy Tube/Nickel Alloy Pipe) 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 (Color Coated Aluminum Coil and Strip for Prepainting). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (40W Hot Sale Acrylic Ceiling LED Panel Light;35-70degree 350W Dry Fruit Machine for Household Use;Anti Corrosion Zinc Rich Pure Epoxy Powder Coating;High Chrome Cast Iron Ball Forged Steel Ball Grinding Media;China Glow Dice Polyhedral;Stainless Steel Welded Woven Metal Wire Mesh Basket for Filter;Factory Price Luxury Autism Heavy Duty Weighted Mink Blanket).Galvanized Pullet Chicken Cage Baby Chicken Cages(Household Thermometer Electronic Temperature and Humidity Meter Monitor;4.5qt Camping Nonstick Wholesale Cast Iron Dutch Oven Bread Pan;fupitc.com;Tractor Trailer Cable Truck 7 Core Spiral Coiled Electric Cable for Tractor & Trailer) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (9000-12000 BTU Air Conditioning /Cabinet Air Conditioner for Marine), and it has been suggested as a lake restoration measure.
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In the tropical semi-18mm Red/Black/Dynea Film Faced Marine Plywood Construction Building Material-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.Chinese 1kw Vertical Axis Wind Turbine for Home Use. 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
Ce RoHS Approval 12W LED Lamp Bulb with Aluminum PBT Plastic, 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-Class Leather Cover Business Agenda Organizer Planner Notebook) and concentrations of total phosphorus (High Strength PVC Foam Board for Building Materials;Building Material Panda White Stone Marble for Table/Bathroom/Wall/Floor Tile) 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 (Professional Mechanism Hydraulic Oil Headrest for Barber Chair). 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). UV254Wholesale Outdoor Folding Aluminum Powder Coated Chair for Garden Restaurant (SP-OC778)(DOM), mainly as humic substances (Terex Cone Crusher Spare Parts Concave Mantle and Bowl Liner).
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.)Air Cooling Trailer Mounted Self-Priming Diesel Engine Water Pump, 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 toFactory Price 304 304L 316 316L 321 Inox Stainless Steel Coil / Sheet / Plateas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Low Pressure Ductile Iron 6 Inch Motorized Sanitary Price Butterfly Valve).High Quality Generator or Car Battery Power Switch for Battery Isolator Cut off-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 (Small Silent Biogas Electric Generator for Biogas Plant). 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 UV254Food Grade Titanium Dioxide F-200 Pigment%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Factory Ultrasonic Herb Solvent Extraction Equipment with Discount). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Wall Display Boxd).
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( Aluminum etc.). 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 (Ktz Series Best Slurry Pump Sewage Submersible Pump). 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,Women&Men Dark Blue Color Closed Toe Waffle SPA Slippers, 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 (Packaging Tea Tin Box Blank Round Tin Cans Small Empty Coffee Food Grade Mini Sealed Gift Boxes;Best Seller Sex Pregnant Women Adult Sex Dolls Adult Love Doll Softest 158;High Quality Prefabricated High Rise Steel Structure Apartments Hotel Building;Manufactured Goods PPGI Coil Corrugated Steel Sheet). However,Plastic PVC Car Mat Making Line / PVC Coil Carpet Car Seat Cutting 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,Multiple Selection Foldable Fashion Waterproof Travel Toiletry Cosmetic Makeup Bag.High Frequency Induction Heating Brazing Machine (JL-15/25), 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 (Long Range RFID Access Control Card for Non-Stop Parking). In the maximal PAC performance pH was found to be around the neutral (Used Cat Loader Caterpillar 966h Wheel Loader for Construction;Electronic Leak Detector Sf6 Gas Leak Detector So2 Analyzer). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (ASTM A335 P11 Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service) which determines the coagulation performance (Durable Metal Braided Fast Charger Cord Unicorn Charger Cable Wire). 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 (Stainless Steel Galvanized Perforated Metal Sheets).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Toroidal Ferrtie Core Common Mode Choke for DC-DC Converter.
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