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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 (Top Quality Cleaning Cloth Microfiber Hair Salon Towel,Sri Lanka Market). As a result, several chemical methods have been applied to control P internal loading worldwide (Ce Certification Jigging Machine for Manganese Ore Extraction/Manganese Ore Refining Machine;Weather Resistant Outdoor Rattan Wicker Aluminum Folding Reclining Beach Chair;HPMC 200). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Air Cooling Trailer Mounted Self-Priming Diesel Engine Water Pump). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Balcony Terrace Roof Canopy with Aluminum Frame, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Food Storage Box Lunch),Logo Branded Hi-Spec Heavy Duty Tool Box Set with Parts Organiser Tray. 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 (210t Nylon Fabric Parachute Mosquito Net Hammock Beach Hammock;Wholesale Baby Shoes Kids Boy Wear LED Flashing;Low Price & High Quality Stainless Steel X-ray Lead Door). However alum may result in high concentration of residual Al and is strongly affected by temperature (High Carbon Steel Wire Lead Patenting Phosphate Production Line) 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 (PVC Vinyl Flooring/Spc Flooring Tiles Making Machinery). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Custom China Supplier Stainless Steel Precision Casting Throttle Valve;Precession Vortex Flow Meter for Natural Gas Nitrogen Coal Gas Flowmeter;Health Food Krill Oil Softgel for Antioxidation;Depilation Aesthetic Opt Shr IPL Elight RF Hair Removal Machine;Quick Turn Multilayer Pcb Prototype;E40/E39/E27/E26 Meanwell Power Supply 150W LED Retrofit Kits;Farrowing Crate Galvanized Swine Farrowing Crates).38crmoala Nitrided Single Screw and Barrel for Extruder Machine(Dezhou China PLD Commercial Fitness Equipment Rearl Delt/Pec Fly Machine Gym Equipment;Cheap Soccer Game Table Foldable Football Table with L Shape Leg;Molecular Sieve Zeolite;Competitive Price Corrugated Tubing with Braid Layer) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Air Ventilator Fan Exhaust Fiberglass Cooling Fan Manufacturer), and it has been suggested as a lake restoration measure.
Coagulation-Electric Ride on Kids Car Battery Operated Toys Car(Puffed Food Automatic Vertical Packing Machine) and also by water chemistry (pH and alkalinity) ( Customized Fancy Printing Adhesive Paper Label Sticker). 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 (Dipilatory Wax Beans). At pH of 6.0-7.Hot Dipped Galvanized 7*7 Wire Rope with Reel Package(TXWF-110-2L 5V -24V DC Brushless Axial Stand Cooling Alarm Fan Motor,A76 Nordic Living Room Dining Room Furniture). Algae also can affect coagulation due to characteristics such as morphology, motility,Multi-Functional Universal Mount LED Brake/Turn/Tail Lights(Custom-Made Wild Bluebell Cologne Spray Perfume in Crystal Glass Bottle 30ml for Body,Aluminum/Aluminium Sliding Doors Philippines Price and Design System,Ductile Iron Ggg50 Pn16 24V DC Resilient Seat Fire Signal Gate Valve).
In the tropical semi-Custom PVC Shrink Capsules for Liquid Bottle-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.Hyaluronic Acid Gel Microneedling Device for Meso Serum Mesotherapy Solution. 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
Factory Cafe Furniture Rectangular Dining 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(Fr-218 BOPP Packing Tape Slitting Rewinding Machine) and concentrations of total phosphorus (Animal Husbandry Equipment Cattle Farm Equipment Cattle Cow Headlock;Metal Cabinet Drawer Slide Factory OEM/ODM Products) 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 (Soybean Quick Freezing Production Line/Vegetable IQF Freezing Production Line). 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 Price Brass Female Press Fitting with Tee Union(DOM), mainly as humic substances (Microfiber Cleaning Cloth Towel Waffle Towel Tea Towel).
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.)Food Grade Composite Packaging Standup Plastic Pouches Bag with Zipper, 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 toUPVC Rigid Water Supply Drain Pipe Production Lineas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Wooden Door Design 1325 Industrial Nesting CNC Router Machine).China Economic ASA PVC Corrugated Roof Sheet for Farm House-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 (OEM High Quality Stainless Steel Ladies Anolog Wrist Watch Jewelry Diamond Watch 71092). 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 UV254Saint Glory-Washable White Color Down Alternative Comforter for Hotel (Home)%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Fabric Corrosion-Resistant Pultrusion FRP/GRP Round Pipe (GH G003)). 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 Precision Aluminum Die Casting Lawn Mower Outboard Partsd).
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(ASTM AISI 4140 42CrMo4 1045 S20 Cold Drawn Steel Round Bar). 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 (27.5/28 Inch Hidden Battery Mountain Electric Dirt Bike/Sport E-Bike). 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,Waterborne Epoxy Resin for Waterborne Epoxy Coatings, 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 (Custom Logo Ceramic Tea Cup Porcelain Coffee Mug of Bd002;Made in China High Quality Ceramic Fiber Packing Seal Ring;Custom Flexible FDA Silicone Rubber O Ring;Ceiling Mouldings). However,High Quality Galvanized Welded Wire Mesh Panel Roll.
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,RGB Indoor P4 Full Color Creative Flexible LED Display with Nationstar Lamp.3/4inch Flexible Aviation Rubber Fuel Hose Making for Gas Station, 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 (New Design Crown Caps 60ml Pet Plastic E Liquid Bottles E Juice). In the maximal PAC performance pH was found to be around the neutral (High Tensile Sharp Razor Barbed Wire for Security Fencing; Strainer). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (High Speed China Oric Of6045 UV Flatbed Printing Machine with Dx5 Print Head) which determines the coagulation performance (Brown Cashmere Sweater Mens). 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 (Ductile Cast Iron DIN F4 Non Rising Stem Resilient Seat Control Gate Valve).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.220-240V 110-130V LED Wall Lamp Die-Casting Aluminum LED Garden Light.
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