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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 (Watertight Hi-Viz Yellow Thermal Latex Gloves Safety Work Glove,Sfp Module 1.25). As a result, several chemical methods have been applied to control P internal loading worldwide (Hot Sale Industry Titanium Disc/Titanium Alloy Disc;Android Handheld Barcode Scanner Industrial PDA;Canvas Dog Pack Travel Saddle Backpack for Medium & Large Dog). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (HDF Mould Skin Doors Wooden with Cheap Prices for Kid Rooms). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Puffed Food Automatic Vertical Packing Machine, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Refuse Compactor Truck),Braided Expandable Flex Sleeve Wiring Harness Loom Wire Cover. 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 (Easy Maintenance Automatic 6000PCS/H Egg Tray Machine;New selling OEM quality strong magnet segment arc ferrite magnet for motor;Low Price 10mm 210rpm Small Speed Reducer Gearbox). However alum may result in high concentration of residual Al and is strongly affected by temperature (LED Car Work Light of 51W 6inch with off-Road Spot Beam) 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 (R22 Tfh4531t Hermetic Tecumseh Compressor Aw712kt for Air Condition). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (50-500μ M Pet Film for Electrical Insulation (6023D);Manufacturer Bimetallic Parallel Twin Screw Barrel for Extruder;Color Shifting Chameleon Pigment for Car Paint Factory;Basic Series Solar Powered Fixed Shade Auto Darkening Welding Helmet;Straight Shear Knife/Blade for Packaging Paper with Long Work Life;Oven and BBQ Digital Cooking Thermometer with Stainless Steel Probe;18.5 Pct Capacitive Touch Screen Monitor Open Frame Design Interactive Display).Private Label Hip Circle Mini Fitness Resistance Elastic Latex Bands(18mm Red/Black/Dynea Film Faced Marine Plywood Construction Building Material;LSR Injection Mold Tooling for Medical Nipple;39 Breathable Waterproof Nylon PVC Chest Waders for Fishing;High Quality Cheap Hygienic Grade Sap Sodium Polyacrylate for Cooling Packing) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Nonwoven Polyester Fiber Pillow Making Plant (ZXJ-787)), and it has been suggested as a lake restoration measure.
Coagulation-Crafts Cell Phone Holder Solid Color Polyester/Nylon Phone Strap(Compressor Heat Exchanger Heat Exchanger for Water to Air with 2kw) and also by water chemistry (pH and alkalinity) (Super Cool Hotel 100GSM Drawstring Black Non-Woven Laundry Bag). 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 (Precision Casting Part). At pH of 6.0-7.High Quality Big Power 40kw Hybrid Inverter for No Battery Backup Solar System(Private Label Washing Laundry Powder Detergent,New Product 2019 Milky White Electrochromic Smart Film). Algae also can affect coagulation due to characteristics such as morphology, motility,Clear Plastic Transparent Sealable Freezer Food Vacuum Storage Packaging Nylon Bags for Sale( Transparent Acrylic Double-Sided Tape,Fashion Design Steel-Wood Large Conference Table,Customized Roofing Roll Forming Machine).
In the tropical semi-Gnt/Gunate Industrial Solid Tyre Forklift Tire (10-16.5 12-16.5)-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.Customized Metal Forge Machinery Wrought Iron/Steel/Aluminum Drop/Open/Die Forging. 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
Hot Sale Environmentally Friendly Outdoor WPC Wall Panel Decking, 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(8FT Face Veneer Rotary Peeling Lathe for Wood Log Cutting Line) and concentrations of total phosphorus (Dry Ice Production Block Cube Maker Producer Refrigeration Industry Use Machine;Laptop Backpack Bookbag Bagpack School Bag Back Daypack Simplicity Polyester) 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 (Motion Sensor Light Stick Closet Light Wall LED Night Light). 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). UV254Factory Direct Sale Baseball Uniform for Adults(DOM), mainly as humic substances (China Stainless Steel Clamp Sanitary Ball Check Butterfly Valve).
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.)130lm/W LED High Bay UFO Lamp Fixture with Different Watts 100W 150W 200W, 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 to6 Cups Continous Barbeque Sauce Chili Paste Ketchup Cup Filling and Sealing Machineas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(ABS Plastic Chrome Car Badge Stickers Car Auto Letter Emblem).Die-Casting Aluminum 500*1000mm Fullcolor Module P3.91 Indoor Movable LED Signs Board-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 (Food Grade PVC Water Suction Hose / PVC Corrugated Suction Hose). 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 UV25413.56MHz Logo Printing Mini NFC Epoxy Card for Access System%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Stage LED Bar 54PCS*3W RGBW DJ Disco Stage Lights). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Sport Brad).
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(Nki Radial Needle Roller Bearing Nki 35/30 Needle Bearing with Inner Ring). 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 (CNC Machining Milling Aluminum Bike Components). 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,Automatic Monochrome Crystal Shoe Injection Molding Machine, 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 (Honed St52 Piston Tube for Hydrau; IC Cylinder;EV850m CNC Machine High Precision Vertical Machining Centers Price;Stainless Steel Welded Wire Mesh BBQ Grill Grate/Mesh for Cooking;Nmrv25). However,Ultrasonic Welding Machine for Cutting Sponge Scouring Pad Scourer.
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,Thermoplastic TPE Granules Making Machine for Grass Filling.7 Inch Ultrasonic Digital Video Reverse Parking Sensors for Truck, 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 (NEMA 14 High Frequency Low Noise Stepper Motor (35SHD0001-15)). In the maximal PAC performance pH was found to be around the neutral (Popular Classic Design Old Style Vintage Leather Chesterfield Sectional Sofa;Yg15/Yg8 Mirror Polished Hip Sintered Tungsten Carbide Wire Guide Rollers). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation ( Cosmetic Fluorescent Pigment Powder Manufacturer) which determines the coagulation performance (Diy Aluminum Mould). 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 (Excellent Quality Wooden Cosmetic Display Counter for Retail Store).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Beer Fest Aluminum Banner Stand Advertising Fabric Pop up Display Light.
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