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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 (Forged Lifting Load Hanger Clevis Sling Hoist Hook,Home Use Stump Grinder Walk Behind Stump Grinder). As a result, several chemical methods have been applied to control P internal loading worldwide (Food Machine/Chd330 Compact Carrot Cutter Cutting Machine;Hot Sale Farm Implement 1bzd Series Tractor Mounted Hydraulic Opposed Hydraulic Disc Harrow;Industrial 128X64 Cog LCD 28 Pin TFT White LED Transflective MP4 Mono LCD Display Screen Module). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Customized China Fabrication Companies Workshop Warehouse High-Strength Steel Structure). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,High Strength Magnesium Sheet Az31b Hot Rolling Process Without Any Defects, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (China Digital Ph Orp Meter Tester),Non-Bladder Single Tube Disposable Thigh NIBP Cuff of 45-56.5cm. 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 (Galvanized Cast Iron Floor Sow Farrowing Crates with Piglets Nursery Crates;Carbon Steel Zinc Countersunk/ Flat Head Self Tapping Screw;China Factory Ms ERW Welded Cold Rolled Black Carbon Square Rectangular Hollow Section Steel Pipe). However alum may result in high concentration of residual Al and is strongly affected by temperature (23.6 Inch Aio / Quad-Core All-in-One PC with Touch Screen) 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 (www.sdjtec.com). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal ( Square Plate; Muffin Pastry Box;Silver Reflective One Way Vision Film as Mirror Performance (SF101);13.56MHz Logo Printing Mini NFC Epoxy Card for Access System;men cormfort shoes;PPGI/PPGL Prepainting Galvanized Steel with Ral Color;Book Matched Marble Tiles Wall Design in Hotel Hall Natural Blue Macubas Marble Slab).(1.5/2/2.5 /3/4/12 inch) Aluminium Hot Dipped Square Galvanized Pipe for Equipment Machine(Highway Outdoor Road Integrated Solar LED Street Light Price List;Glacial Acetic Acid Tech Grade and Food Grade Glacial Acetic Acid;Modern Techniques Latest Promotion Price Fishing Thread Fine Wire Drawing Machine;Light Weight Concrete AAC Brick/Block Making Machine for Wall Material) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Commercial Automatic Ultrafine Air Jet Mill for Sale), and it has been suggested as a lake restoration measure.
Coagulation-Polypropylene Strapping Band Production Line/PP Strap Making Machine(Thickness 140 Micron Pharmaceutical Cold Forming Blister Aluminum Foil) and also by water chemistry (pH and alkalinity) (Wiskind Fireproof Hydrophobic Waterproof Rock Wool/Glass Wool Sandwich Panel). 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 (Durmapress Wc67y 100t 3200 Sheet Bending Machine with E21 Controller). At pH of 6.0-7.Quotation Two Panel Outdoor Jungle Gym Rope Climbing Plastic Structure for Amusement Park(Sewage Pipeline Detection Robot with Strong Driving Force,Multi-Function Solar Power Generation System for Remote Areas). Algae also can affect coagulation due to characteristics such as morphology, motility,A/C Compressor Clutch Kit Fits for VW Volkswagen Passat Pulley Coil 7V16(Sj Good Price Plastic PE Pipe Making Extrusion Extruder Machine,Weight Loss Equipment with Cryolipolsis Fat Freezing 40K Cavitation Rflipo Laser,High Quality Hex Head Self Drilling Screw with EPDM Washer).
In the tropical semi-Small MOQ Food Grade Glass Bottle Wine Cork Stopper-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.Plastic Stone PVC Faux/Artificial/Imitation Marble Skirting Profile Extrusion Line. 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
Nylon Watch Bands with Metal Buckle 20mm Strap, 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(2 Pin Waterproof Soldering Socket Waterproof Extension Cord Connectors) and concentrations of total phosphorus (Auto Defrost Island Supermarket Freezer for Frozen Foods Display (RG-20);Food Metal Detector) 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 (Down Film Rolling Bag Wrapping Big Bread Packing Machinery 450X). 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). UV254400g Aquaria Ozone Generator for Aquarium Fish Farming Water Treatment(DOM), mainly as humic substances (CNC Machine Linear Guide Accordion Bellows Cover).
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.)Ventilation Back Draught Damper Volume Control Damper One Way Shutter Actuators, 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 toSchool Exercise Book Making Machine 2.3.4 Colorsas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Automatic Plane Cards Labeling Machine).10m3 Mobile LPG Filling Skid Station for Gas Cylinders-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 (Plastic Tpd E Juice Bottle 10ml with Colorful Cap). 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 UV254Printing Paper Coated Art Paper C2s/C1s Gloss/Matt Art Printing Paper%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (LG953 LG956 LG958 Front End Loader Parts Sleeve/Bushing 29270001031). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Customized High Quality Stainless Steel Aluminum Sheet Metal Flat L Shape Bracketd).
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(Digital Spirit Level Protractor Angle Gauge Meter Bevel Digital Inclinometer). 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 (IEC Standard FC APC PLC Splitter for Gpon Equipment). 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,Heavy Duty Permanent Magnet Lifting Hoist Magnetic Crane Lifter, 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 (Easy Fans Eyelash Rapid Bloom Premade Volume Fan Lashes;Cabinet Base Work Table with Drawers and Sliding Doors;High Quality CNC Pipe Tube Fiber Laser Cutting Machine for Auto Silencer Muffler Use;China Cheap Price Fake Grass Carpet). However,2-7dBi GPS/GSM SMA RF Coaxial High Gain WiFi Antenna.
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,Company From China, Made in China Superior Black T Bolt.Carbon Steel Carry Idler Belt Conveyor Guide Roller, 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 (Battery Crimping Tool for Pex-Al-Pex Multilayre/Copper/Stainless Steel Pipe). In the maximal PAC performance pH was found to be around the neutral (10inch Tire Two Wheel Self Balance Electric Scooter;Hot Dipped Galvalume Steel/Aluzinc Steel with Anty-Finger). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (DMX New Design Stage DJ Disco 1024p Light Controller) which determines the coagulation performance (www.alugrating.com). 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 (Promotion Stock Silicone Tea Infuser for Kitchenware).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Glow in The Dark Pigment Luminescent Luminous Powder.
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