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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 (Automatic Multi Function Side Drilling Machine,Metal Oxide Nanoparticles). As a result, several chemical methods have been applied to control P internal loading worldwide (Yh1650 15′′ Retractable Cable Wire Trigger Key Lock Gun Lock;Hot Selling Mini Am RF Security Hard EAS Pencil Tag for Clothing Store;7.00-20 Tube Rim TBR Truck Steel Wheel with TS16949/ISO9001: 2000). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (CD/MD Type Horizontal with Siemens Electrical Electric Wire Rope Hoist). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Qgd Series 3 Inch Deep-Well Submersible Electric Screw Water Pump, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Pin Lead High Pulse PP Film Capacitors for IGBT Mould),Ankle Support Brace Foot Guard Sport Injury Wrap Elastic Splint Strap Protect. 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 (Hot Sale Alkaline Water Purifier Water Machine Alkaline Water Ionizer or Alkaline Water Generator; Wp30;Integrated Circuit Printed Circuit Board China Trusted PCB Manufacturer). However alum may result in high concentration of residual Al and is strongly affected by temperature (Copper Wire Multi Cores 4/6/8 Shielded Alarm Cable Security System) 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 (Men Watches 2018 Watches Men Automatic Mx503m Details). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (DC/Ec Inverter Motor Ceiling Horizontal Type Fan Coil Unit;Cylinder Borosilicate Glass Cooking Oil Bottle with Spout;Simple Design High Quality Cotton Velour Disposable SPA Hotel Travel Slippers with Logo;China New Design TPU/PVC Layflat Flexible 6 Light Duty Suction Hose;Remote Unlock WiFi Smart Video Doorbell IR Night Vision Wireless Video Door Phone;Braided Expandable Flex Sleeve Wiring Harness Loom Wire Cover;2019 Multi-Funtion Mobile Talkie Walkie Sport Smart Phone Case for Outdoor Walkie Talkie).Universal Cable Fault Testing Instrument Tester / Analyzer(100%RPET Micro Fiber Fabric/Peach Skin Fabric/Eco-Friendly and Recycled Fabric in Low Carbon;Stainless Steel Short Pitch Precision Single Roller Chain (B series);Buy Hdmi Cable;2019 New Style Plastic Toothbrush with Cheap Price for Hotel Use) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes ( Solvent PVC-Free Wall Paper), and it has been suggested as a lake restoration measure.
Coagulation-3600 Rpm Concrete Machinery Ride on Power Trowel Factory(Custom Men′s Plain Cotton Short Sleeve Oversize Plus T-Shirt) and also by water chemistry (pH and alkalinity) (Quotation Two Panel Outdoor Jungle Gym Rope Climbing Plastic Structure for Amusement Park). 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 (Portable Veterinary Anesthesia Machine). At pH of 6.0-7.20 Cavity Pet Preform Mould with Competitive Price(Easy Installation Decorative Terracotta Louver Wall for Cladding,Industrial Use Sandwich Panel Container for Offices/Construction Sites). Algae also can affect coagulation due to characteristics such as morphology, motility,Hot Fine Steel Mesh with Simple Waterproof Couple Quartz Watch(Beauty Equipment Face Lifting Hifu Equipment,Detachable Anti-Spill Creative Buoyancy Water Drinking Bowl for Dog Cat,Good Price and Quality Soda Ash Light/Dense in Glass Making).
In the tropical semi-Pneumatic Air Fitting Female Straight for PU&PA Hose (Metric Size-R(PT) Thread Type)-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.New Product PVC Insulation Tape, Fire Resistance Electrical Tape, PVC Electrical Tape (BK-1-217). 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
Tsautop 1.52*18m/Roll Chameleon Pearl Car Wrap Trailer Wrap Cost, 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(24W RGB LED Outdoor Inground Light IP67 Deck Paver Lamp Spot Floor Light DMX512) and concentrations of total phosphorus (Safety Bike for Cool Design Children Bike/Bicycle;2Ton Automatic Welding Positioner) 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 (Top Quality Disposable Dental Surgical Suction Sterile Aspiration/ Aspirator Tips). 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). UV254Modern Leisure Chair for Europe, America and Asia with Armrests(DOM), mainly as humic substances (Customized Logo Personalized PVC Cup Coaster with Gift Box).
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.)Customized Cutting Tool Solid Carbide Tool Taps (TS-100002), 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 toWire Rope Clips Us Type Galvanized Drop Forged Cable Clampas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(custom RFID key fob).Three Lines Production Three Side Seal Pouch Making Machine-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 (Retro Vintage Old Black Malleable Iron Floor Flange for DIY Home Pipe Furniture). 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 Price Crankshaft Position Sensor 90919-05043%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (7′′ Resin Diamond Dry Polishing Pad for Quartz Stone). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (RFID Reader/Antenna Circular 9dBi 6-8 Meters EU/Us Standard for Vehicle Access Managementd).
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(High Quality 200W IP66 China LED Flood Light). 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 (High Quality Meat Pie Making Machine with Different Mould Shape). 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,Food Grade PVC Water Suction Hose / PVC Corrugated Suction Hose, 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 (Hot Sale Touching Operation Outdoor A8 Mini Stereo Portable Wireless Bluetooth LED Speaker;Hex Washer Heaf Self-Drilling Screw with Steel and Rubber Washer;Stainless Steel 4.8/8.8/10.9 Galvanized Non-Standard/Machine/Auto Parts/Spare Parts Screw;Double Layer 12V 5050 LED Strip Light with Ce RoHS). However,Karl Mayer Machine Warp Knitting Spare Parts Karl Mayer Machine Pulley Belt.
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,Textile Screen Printing Mesh Polyester Material.Hot Selling HOWO Heavy Truck 371HP Dump Truck, Tipper, Dumper 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 (China Factory Price 6 Axles Tractor Truck Trailer). In the maximal PAC performance pH was found to be around the neutral ( Juki SMT Chip Mounter;High Precision Die Cast Aluminum Manufacturers with CNC Machined). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Opgw Fiber Optical Cable 12 Cores/ 24cores / Outdoor Cable) which determines the coagulation performance ((Midtech Industry) Plastic PE Ocean Marine Pedal Profile Extrusion/Extruder Making Machine). 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 (Ceramic Foam Filter for Water Purification).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.220V Square Synchronous Grill Rotisserie Motor for Gas Cooker.
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