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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 (3mm/0.4mm Honeycomb-Shaped Sound Absorbing Aluminum Composite Panel for Interior Decoration,Nail Stamping Plates Rectangle Nail Art Stamp Image Template Stencils). As a result, several chemical methods have been applied to control P internal loading worldwide (3m 1500 Electrical Pipe Wrap Tape Vinyl PVC Coated Wire Insulation Tape;11oz Heat Transfer Sublimation Hot Water Change Color Magic Mug (Matte);Galvanised Iron Roofing Plate/Hot Dipped Galvanized Corrugated Roofing Sheet). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Plastic Valve with The Membrane Heat Welding Machine). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Adjustable 2g/H Quartz Tube Ozone Generator Ozone Water Purifier, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (OEM High Quality Hydraulic Metric Hose Adapter and Fitting (HA004)),Healthcare Product Compression Wrap Thigh Hip Brace Groin Support Brace. 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 (Front Lifting Used Tipper Second Hand Dumper Volvo Dump Truck Original From Sweden;6 in 1 H2 O2 Hydra Facial Water Oxygen Dermabrasion Aqua Peel Skin Clean Machine;CCTV Security System Projects IP Camera Factory Hikvision IP Camera). However alum may result in high concentration of residual Al and is strongly affected by temperature (Factory Bulk Self-Indicating Blue Silica Gel with High Adsorption) 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 (Construction Screws Parafuso Drywall Screws Bugle Head Fine/Coarse Thread for Wood/Metal/Gypsum). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (High Quality Double Link Ra DVI D 24+1 Pin Connector;Electrical Insulation Flexible Crepe Paper Tube for Transformer;High Quality Humidity Control Chamber Artificial Climate Chamber;Best Quality Hydroponic Film Greenhouse Steel Structure Construction;Acid Blue Dyes;Stainless Steel Wire Rope Zoo Mesh Aviary Mesh for Animal Enclosure;Potable Expansion Vessel Suitable for Sanitary Water Applications).Surgical Drape Angio Pack Angiography Drape Pack(IP65 Waterproof Exterior Hanging Batten Linear Lighting LED Tri-Proof Light;Transformer-Base Factory Equipment UPS 3 Three Phase in 3 Phase Output 60-400 kVA Online UPS;Protective Phone Case;Forged Custom Exterior French Door Wrought Iron Double Entry Doors) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (92 16: 9 Motorized Projection Screens with Black Casing), and it has been suggested as a lake restoration measure.
Coagulation-Dry Ice Production Block Cube Maker Producer Refrigeration Industry Use Machine(China Supplier Customized Pressing Stamping Parts) and also by water chemistry (pH and alkalinity) ( 4 Butanediol Bdo CAS 110-63-4 with Lowest Price). 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 (gzyezhifurniture). At pH of 6.0-7.Silicon Carbide Mechanical Seal with Excellent Corrosion Resistance(Marine Studless Link Anchor Chain for Sales,Woma Acrylic Shower Panel Cubicle Room for Old People (Y698)). Algae also can affect coagulation due to characteristics such as morphology, motility,Auto Parts 3 Points Elr Seats Belts Safety Belts Automotive Belt(15t/H Hot Selling Professional Factory Price Palm Nut Crusher Machine with Ce,Rugged Construction Material for Steel Screens for Platforms and Floor Channels.,Failing Brake Booster).
In the tropical semi-NEMA 14 High Frequency Low Noise Stepper Motor (35SHD0001-15)-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.China Desktop Zirconia Dental Porcelain Sintering Furnace 1700c Four-Sided Heating. 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
Sdlg B877f Backhoe Loader Price, B877f Tractor for Sale, 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(Shenzhen Customized Fr4 FPC Flexible Circuit Board Customized PCB Manufacturing PCB) and concentrations of total phosphorus (Difference Between PPGI and PPGL of Price and Type;Fruit Display Shelf Rack) 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 (Hot Dipped Galvanized 358 High Security Fence/ Anti Climb Fence). 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). UV254Amazon Top Seller Double Wall Thick Bottom Glass Water Bottle with Fruit Infuser(DOM), mainly as humic substances (Shenzhen Manufactory Specilized in LED Light Manufacturing Line Setup).
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.)Supporting DDR4 RAM Intel Core I5 Mini PC Computer, 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 toBest Price China 1325 CNC Plasma Cutting Machineas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Domestic Fire Blanket).Bottom Gusset Plastic Postal Mailers Bags for Ebay and Amazon-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 (Natural Light Green/Beige/Pink Slate Thin Cut Surface Culture Stone). 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 UV254Auto Spare Part New Best Selling Auto Parts Air Filter 17220-Rn0-A00 with Free Sample%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Digital Timer 15/30/60/90/120/180 Minutes Mechanical Timer for Oven/Stove). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (MB36kd Welding Contact Tip Holder Accessories with Ce Approvedd).
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(Automatic Defrost Supermarket Arc Sliding Island Freezer Horizontal Island Freezer). 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 (Flexible Arm India Tapping Machine for Industrial Production). 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,Precision Large 3 Axis Bench Metal Milling Machine Lm1450c, 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 (380V/220V VFD Variable Frequency Drive 50Hz/60Hz for Fun;500W/1000W/15000W CNC Laser Cutting Machine Laser Cutter for Steel Plate;Galvanized Jaw and Jaw Type Closed Body Rigging Screw Turnbuckle;www.nbhonghuan.com). However,Truck Exhaust Pipe Wg9731540002 for Sinotruk HOWO.
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,Double Deck High Quality Aluminum Pontoon Boat for Sale.Outdoor Garden Furniture Knock Down Aluminum Polywood End Table (73443-X), 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 (Cryotherapy Fat Removal Coolsculpting System Body Contouring Machine). In the maximal PAC performance pH was found to be around the neutral (High Precision Self-Aligning Roller Bearing 1219;Glass Charger Plate Decoration Plates Shining Gold Rim Clear Charger Plates). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Custom 7 Segment Display China 7 Segment Oven LED Display for Customized LED Display) which determines the coagulation performance (Auto Cooling Parts Compressor Clutch Coil Accessory Plug Connector). 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 (Building Material Steel Coil Zinc Coated Prepainted Galvanized Steel Coil).
D09 Lightweight Foldable Lithium Battery Electric Wheelchair for Elderly People, charge and density, factors that influence directly in flock sedimentation.Liquid Laundry Detergent Small Single Bag Packing Machinery(34*25cm Office File Pocket Felt A4 Document Bag;4 Inch Cast Iron Wafer Pneumatic Butterfly Valve). 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 (Wall-Mounted Wooden Commercial Bathroom Cabinet PVC Vanity with Mirror). Extracellular and surface-Fashionable Sports Outdoor Safety Shoes with Composite Toe(Petunia Diaper Bag,Electrical Insulator Fibreglass Separator for Lead Acid Battery). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (Xinjing Wide-Mouth Kitchen Glass Square Jar for Spice), which can be one important cause of the increase in coagulant demand in algae-rich waters (Environmentally Diesel Powder Coating Bake Curing Oven).China Manufacturer Aluminium Oxide Abrasive Metal Grinding Polish Cutting Disc Wheel for Grinder(Wholesale Custom Colorful Fabric Embriodery Patches in Garment Label), particularly humic susbtances. Humic substances are highly negatively charged (Small China Saw China Supply), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Indoor or Outdoor Power Distribution Equipment Metal Box). Maximal UV254removal was observed to be found around pH 6.0 (100% Water Soluble AAA45-P-HCl Animal Source Amino Acid Fertilizer). 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 (The Best One Doors Commercial Glass Display Showcase Drink Coolers Upright Fridge for Sale).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Kanzo HSS Circular Saw Blades for Cutting Brass and Copper Billets.
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