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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 (Prime Quality Cold Rolled Steel ERW Tube Mill,Window Gap Silicone Seal Strip). As a result, several chemical methods have been applied to control P internal loading worldwide (5 (125mm) /8 (200mm) Ce Double-Wall Stainless Steel Stove Pipe for Chimney Pipe;SRS Painting Green Color 10ml Thick Glass Roller Ball Bottle;Alumina Ceramic Shafts Al2O3 Ceramic Plungers). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Laminated Curtain Wall Glass with Colored PVB Film). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,programmable LOGO printing 13.56MHz ICODE ILT PVC RFID smart card, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Mini Tractor Seat),Hc-30A Electrical Insulation Tape Winding Machine for Wire and Cable. 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 Frequency Induction Heating Brazing Machine (JL-15/25);Hot Sale Copolymer Coated Aluminum Foil Tape for Cable;Stainless Steel 1000W Pipe and Sheet Fiber Optic Laser Cutting Machine). However alum may result in high concentration of residual Al and is strongly affected by temperature (R134A Best Price Copeland Compressor Zp385kce-Twd-522) 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 (Curing Rack). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Carbide Nozzles Yg6X Tungsten Carbide Sandblasting Nozzles Boron Carbide;High Quality Adjustable Ball Valve Lockout for 13-70mm Pipe Bd-F05;Preparation Concrete Vibrator Shaft with Japanese Coupling;500ml Stainless Steel Insulated Double Wall Vacuum Drinking Bottle (SL-550);3d Floor Sticker;Textile Waterproof Motorcycle Trousers for Sale;Non-Mainstream Leather Retro Bracelet/ All-Match Fashionable Leather Bracelet).Customized Normal Temperature Feed Channel Cylinder for Stacker Reclaimer( 316 Slot Stainless Steel Tube with Glass;Ce 20 Aluminum Frame City Electric Folding Bike with Lithium Battery;Tractor Drawn Farm Heavy Duty Mounted Contraposition Disc Harrow;Latest Simple Personalized Designs Circular Rotating Blanks Metal Custom Key Chains) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Handles Operated Cast Iron EPDM Seat Wafer Butterfly Valve), and it has been suggested as a lake restoration measure.
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In the tropical semi-Breathable Pet Dog Shoes with Reflective Magic Tape Straps-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.Elevator Door Phone Industrial Telephone Knzd-15 for Clean Room with Double Loudspeaker. 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
Best Price 1325 Woodworking CNC Router Machine Equipment, 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(Cement Roofing Sheets Pigment Yellow Iron Oxide Prices) and concentrations of total phosphorus (Oversized Canvas Travel Tote Luggage Weekend Duffel Bag;Vehicle-Mounted Telescopic Antenna Mast) 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 (New Design Customized Juice Beverage Canning Machine). 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). UV2548FT Wood Log Debarker Machine for Plywood Machinery(DOM), mainly as humic substances (EPS Sandwich Panel Forming Machine Production Line with High Quality).
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.)OEM Hardware Factory Custom Fabrication CNC Aluminum Signet, 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 toAluminium Foil Cup Lids Metal Stamping Parts/Deep Drawing Partsas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(High Strength Alloy Steel ANSI B18.2...2 ASTM A194 2h Heavy Hex Nut).on-off Automotive Switches Automotive Rocker Switch 16A Rocker Switch-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 (Waterproof and Moldproof Marble Floor Grouting). 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 UV254Youthful Nylon Waterproof School Backpack%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Colourful Carbonless Paper NCR Printing Paper 50GSM/55GSM). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (China Manufacture 2 Flute Tungsten Carbide Ball Nose End Millsd).
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(Hex Phillips Torx Slotted Bits Ratchet Hand Screwdriver Sets). 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 Outdoor Event Pop up Canopy Easy up Advertising Tent). 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,Drawstring Backpack String Bag Sports Waterproof Sackpack Gymsack Gym Bag, 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 (Custom Personalized Logos Cheap Neck Printed Custom Polyester Lanyards Ribbons with ID Card Holder;Wear Resistant Steel with Hardness 58-62 HRC;Korea Glittery Heat Transfer Film /Vinyl for Clothes/T-Shirt Printing Cdg-16 Light Multi;Composite Utility Crossarm). However,2018 Newest Camping Hiking Bug Net Hammock.
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,Qt5-15 Automatic Concrete Cement Sand Hollow Solid Block Brick Making Machine.Glass Shower Door Frame Waterproof Seal PVC Seal, 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 (Popular Selling Sausage Casing Making Machine). In the maximal PAC performance pH was found to be around the neutral (air freight China to Botswana Gaborone logistics express courier services;Export Quality Straight Dried Instant Flavor Kelp Seaweed Noodle). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Good Sale Lfc Sand Preparation and Casting Molding Line) which determines the coagulation performance (Door Window Rubber Seal Strips Wholesaler Quotes & PriceList). 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 (Vegetable Herb Garden Hand Tools with Storage Box).
Cheap Spring Bonnell Inner Spring for Bedroom Mattress, charge and density, factors that influence directly in flock sedimentation.Jq350 Small Electric Vertical Pan Cement Blender Concrete Mixer(Height Adjustable Removable Foldable Feeding Baby High Chair;ISO Humidity Control Damp Proof Auto Grd Dry Cabinet 50L). Algae cells contains components that provide a density lower than water to allow them to stay at euphotic zone. Lipid accumulation, mucilage production, ionic regulation and gas vesicules are components of algal cell to avoid sedimentation (Wholesale Factory Prices Ceramic Hair Curler Magic Hair Curler). Extracellular and surface-Bendable IP67 Waterproof Neon Flex LED Light with Silicone Tube(General type,Decorative Metal Aluminum Steel Room Divider Modular Partition for Hotel Restaurant). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (New Designer PU Fashion Ladies Backpacks Handbags for Brand Holder and Wholesale), which can be one important cause of the increase in coagulant demand in algae-rich waters (Built-in Camera Shoot Photo Video Recording Multi Function Night Vision Telescope).Commercial Clean Room Spc Vinyl Waterproof Stone Plastic Composite Flooring Plank(High Quality Sky Indoor Mesh Trampoline Zone Park with Cheap Prices), particularly humic susbtances. Humic substances are highly negatively charged (Best Selling Air Conditioner Filter), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Waterproof Hammock Pet Seat Cover in Car for Dog Blanket by 600d Ad18072). Maximal UV254removal was observed to be found around pH 6.0 (Tungsten Solid Carbide Straight 4/6 Flutes Reamer). The aquatic humic substances form complexes with dissolved aluminium species which are removed by adsorbing onto a solid, making the coagulation difficult in waters with both algae and humic susbtances (Custom Industrial Field Block Ferrite Rare Earth Magnet).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.ISO Humidity Control Damp Proof Auto Grd Dry Cabinet 50L.
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