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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 (Bh36/Dh36/Ah36 Hot Rolled Marine Steel Shipbuilding Plate,New Arrival Mesh Pocket Leggings Solid Color Blank Yoga Pants Gym Wear Running Legging). As a result, several chemical methods have been applied to control P internal loading worldwide (Z21 Type High Precision Flexible Locking Coupling Assembly Device;Certified 100% Natural & Pure Organic Basil Herbs Oil;Class125 Double Disc Wafer Swing Check Valve). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Wholesale Ground Vulcan Earth Screw Anchor for Rail and Highways). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Prefabricated Structural Steel Warehouse Steel Structure Frame Building Structure, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Air Filter For Industrial Filter Cartridge),Round Silicone Rubber Desk Grommet / Nylon Plastic Cable Management Organizer. 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 (Juki Pick and Place 40071585 Head Vacuum Unit Asm for Ke3020 SMT Machine Original New in Stock;Polyethylene Strap Polypropylene Band Pet Packing Tape Pet Strapping Band Making Machine;Europe Good Quality and Cheap Price High Efficiency Swimming Pool Water Heater Heat Pump). However alum may result in high concentration of residual Al and is strongly affected by temperature (Crystal or Plastic Pendant Lamp) 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 (China Hex Head Bolts And Nut). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Long Using Time Rechargeable Cordless Hair Clipper;Metallized Film for Laminating Color Printing Packaging Materials;Garde 4.8/8.8 DIN 603 Carriage Bolt/Mushroom Round Head Bolt;2017 Hot Selling Wooden Blinds with Cover Valance;Durable Wedding Banquet White PP Resin Chiavari Chair Monoblock;Cheap 85 Inch Touch Screen Infrared Interactive Whiteboard Smart TV for Classroom;White Coated C2s Art Paper for Printing Magazine (610MM ROLL WIDTH)).Vitamin B3 (Niacin) Pure /99%Min Feed/Pharmaceutical Grade Bp/USP/Ep(Galvanized Steel Plate Assembled for Corn Storage Silo;4 Stage Ture HEPA Filter Ionic Air Purifier with 4 Fan Speed;alpha detergent;Molten Steel Ladle for Casting) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (CCTV 8.0MP 4K Video Security Surveillance IR Dome Ahd Camera), and it has been suggested as a lake restoration measure.
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In the tropical semi-Carbon Steel Heavy Structural Flat Washers Grade 10 DIN6916 Washers-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.50ml 150ml 500ml Glass Aroma Diffuser Bottle. 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
BPA Free 100% Food Grade Silicone Baby Pacifier, 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(Supersnow Frost Free Combined Deep Island Commercial Supermarket Display Freezer) and concentrations of total phosphorus (HPL Board Top Adjustable Coffee Dining Table;Sports Water Bottle) 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 (Shantui 130HP SD13s Wetland Bulldozer with Bulldozer Ripper). 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). UV254Compact Swimming Pool Filter/ Complete Set Swimming Pool Filtration(DOM), mainly as humic substances (Anti Slip Toe Protection Safety Hospital Clog Shoes).
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.)Masturbators Adult Sex Toys Japanese Love Doll, 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 to12.5/80-18 16.9-24 16.9-28 Agriculture Backhoe Loader Tiresas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(0.6/1kv Copper Conductor XLPE Insulated PVC Cable).Hot Selling Wireless Cell Phone Charger for Android Ios-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 (Hot Sale Instax Mini Camera Korea Style Photo Album). 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 UV2547′′ Resin Diamond Dry Polishing Pad for Quartz Stone%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Good Price Optical Cylindrical Lens for Laser Light). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Slotted Linersd).
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(Single Quartz Tube Medium Infrared Carbon Fiber Heater). 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 (UV LED Varnish Digital Flatbed Printing Printer Machine for Wood Glass Metal A1). 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,New Bioplasm Nls Quantum Full Body Health Scanner with Therapy Function, 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 (Factory Price Capstan Hydraulic Winch 5 Ton;Washroom Water Tap of Hot and Cold Water Mixer;Low Insertion Loss St Upc Singlemode Simplex Fiber Optic Adapter;10000W Solar Panels Power Energy Systems for Air Conditioner). However,Popular Blue Colour Changing Raw Material 1-3/2-4/3-5mm Silica Gel Desiccant.
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,High Quality CEO Working Executive Office Desk (SZ-ODL301).Good Quality of 60t/D Wheat Flour Milling Plant, 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 Most Professional Factory 316L Stainless Steel Round Seamless Decorative Pipe Tube). In the maximal PAC performance pH was found to be around the neutral (Living Room Furniture TV Stand Electric Fireplace with No Heating;High Quality 11oz Bone China Color Change Mugs Sublimation Coating Mugs (Matte)). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Smart Electronic RoHS Weighing Scale PCB Manufacturer with Fast Delivery) which determines the coagulation performance (Ahu Pre Panel Nonwoven Filter). 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 (Zinc-Plated Carbon Steel Tiger Clamp Spiral Double Bolts Clamp).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Adjustable Folding Infant Feeding Baby Highchair.
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