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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 (Printed Coated Bulk 100d Filament CVC Poly Cotton Fabric Uniform Army Green Workwear,316L). As a result, several chemical methods have been applied to control P internal loading worldwide (Zxx-C2518 Glass Shower Door Cut Outs Making Machine Glass Work Center;Outdoor Decoration Small Music Dancing Garden Water Feature Fountain;Yz25c China Ophthalmic Equipment Wireless Binocular Indirect Ophthalmoscope). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Economical Wall Decoration PVC 3D Brick Wallpaper Designs). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,New Type Portable 380V Electric Winch in Stock, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Anti-Slip Pet Dog Puppy PEE Potty Training Pads Floor Clean Protective),10ml Portable Spray Perfume Glass Empty Bottle Atomizer. 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 (1.0mm Pitch Right Angle Wire to Board Connector FFC/FPC Connector;DFAC High Altitude Operation Platform Truck 10m for Sale;Y Series 315 Case High Power 75kw 90kw 110kw 132kw 6-Pole Three-Phase AC Motor). However alum may result in high concentration of residual Al and is strongly affected by temperature (LED Lens 3030 5630 Asymmetric Linear Fresnel Acrylic PMMA Lens) 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 (Customized Uv Gel Nail Polish Glass Bottle). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Swivel Hook Auto Engine Valve Spring Motor Spring; Security Protected Razor Barbed Wire/Blade Barbed Wire;Factory Supply Good Quality PVC Vinyl Gypsum Ceiling Tiles;Galvanized Pullet Chicken Cage Baby Chicken Cages;Children Soft Books;Beer Fest Aluminum Banner Stand Advertising Fabric Pop up Display Light;CNC Fiber Laser Cutting Machine with Pipes Cutting Accessories).Ce Approved Acrylic Mini LED Letters Sign for Outdoor(Pressure Swing Adsorption Medical Oxygen Concentrator Psa Medical Equipment;Sheet Metal Stamping Galvanized Steel Panel and Frame;Usb Vga Cable;Automatic Vertical Grain / Sugar / Bean / Rice Packing Machine) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (IP65 8W Outdoor Integrated LED Street Light Solar Lamps), and it has been suggested as a lake restoration measure.
Coagulation-Protective Covers /Surplus Groundwater Storage Lagoons and Barren and Processing Pond Liner(CNC Turning Stainless Steel Part with Precision Tolerance) and also by water chemistry (pH and alkalinity) (Stainless Steel Rectangular Pipes for Balcony Guardrail). 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 (1220*2440mm Various Plywood). At pH of 6.0-7.Best Quality Hydroponic Film Greenhouse Steel Structure Construction(Modified Shipping Container House for New Zealand,Cast Iron Casserole Pot Roaster with Cover 7L Oval Dutch Oven). Algae also can affect coagulation due to characteristics such as morphology, motility,Epoxy Coated Cast Iron Dismantling Joint for Water Supply Pipe Line(THK Linear Guide Shs Hsr SSR 15 20 25 30 35 45mm for CNC,Socket Type 2 32A 22kw EV Charging Point EV Charger for Electric Vehicle Charging,Steel H Beam Price Per Kg).
In the tropical semi-High-Top Men′s Casual Sports Shoes Athletic Shoes Sneaker Shoes (FFXXY1228-1)-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.Small Playground Plastic Slide Preschool Equipment Toys for Kids. 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
Wholesale Events 6FT Wood Dining Round Table, 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(Absorbent PP Mat Hardwearing Doormat with Round Shape) and concentrations of total phosphorus (China Wholesale Hydraulic Industrial Winch for Mining Well;Customized Wind & Solar Hybrid Street Light Steel Pole / Mast / Post (4-15m)) 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 (Aluminium/Brass/Stainless Steel Cam Lock Quick Coupling). 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 Custom Microfibre Towel Rack Cooling Gym Yoga Bath Towel(DOM), mainly as humic substances (Fashionable New Products Twin Screw Extruder for Pet Recycling).
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.)Taizhou Huangyan Laboratory Room 60 mm Plastic Injection Petri Dish Mould, 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 toCeramic Tile Plasma Ion Deposition Planting Functional PVD Vacuum Coating Machineas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Dense Alumina & Dense Cordierite Honeycomb Ceramic Extruder for Rto).Ce Certificated Acm-60 PTFE Powder Grinding Mill-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 (Aluminum Oxide Abrasive Products 5 6 Stone Metal Disc Grinding Wheel). 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 UV254Automatic Magnetic Induction Heater for Band Saw Quenching Production System%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Small White Color Wall Hanging Plywood Modern Bathroom Cabinet (ACS1-L21)). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Male Foley Catheterd).
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(Nc Hydraulic Bending Tube Metal Pipe Bending Processing). 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 (Best Quality Plastic Wall Plug Expansion Anchor). 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,Original Germany Bitzer Brand Compressor 4hc-1.2y, 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 (Outdoor Waterproof IP68 LED Structure 3D Arch Street Christmas Decoration Ball Motif Lights;Home Used Portable Fencing Aluminium Swimming Pool Safety Fence;40K Cavitation Vacuum Massage Skin Lifting Body Shaping Machine;M12 Laser Sensor). However,Prefab Prefabricated Lightweight Steel Structure Construction Processing Plant Metal Workshop.
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,Customized CNC Machining Checking Fixture for Automotive Bracket.High Quality Sky Indoor Mesh Trampoline Zone Park with Cheap Prices, 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 (2200mAh External Battery Case for iPhone 5/5s/5c (OM-PW5SC)). In the maximal PAC performance pH was found to be around the neutral (Promotion LCM Custom LCD Display Stn FSTN Cog LCD Positive Graphic LCD Display Module for;94% STPP Sodium Tripolyphosphate /Sodium Triphosphate Industry Detergent). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Milk Homogenizer Pump Honey Pump Juice Emulsifying Pump) which determines the coagulation performance (Coarse Wheat Flour). 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 (72tpd RO Water Treatment Sea Water Desalination Equipment).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Customized Precision Aluminum Die Casting Machining.
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