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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 ( 42′ LG LED TV Backlight Lens Strips/Bars/Spears,Wholesale Best Light Weight 3 in 1 Outdoor Windproof Waterproof Jacket for Men). As a result, several chemical methods have been applied to control P internal loading worldwide ( Drying Equipment;Customized Acrylic Plastic Sign Board Design Customized Size;Solar PV Detached 30W 12inch Roof Mount Solar Ventilation Attic Vent (SN2014003)). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Chinese 1kw Vertical Axis Wind Turbine for Home Use). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,3D Finish Soundproof Movable Partition Wall for Meeting Room, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Garments Polo Shirt Kids),1.0 Ton Small Backhoe Crawler Mini Excavator Digger Machine for Sale. 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 (2.45 2.45. inch OLED display 304X96 DOT Matrix MONO OLED; Temperature Controller Thermostat 110V for Cabinet Use;11kv 15kv 33kv Pole-Mounted Hermetically Seal Distribution Transformer). However alum may result in high concentration of residual Al and is strongly affected by temperature (Customized Epoxy Plated Super Power Neodymium Magnet Bonded Magnetic) 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 (Q700 Xiaomi Qi 10W Wireless Fast Charger for iPhone Samsung Cell Phone). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (High Quality Precision Aluminum Automatic Lathe CNC Machining Parts;200m Deep Top Driving Tractor Mounted Water Well Drill Equipment;20FT T11 T14 Transport Tank Container Motor Oil ISO Tank Container;Customized EPS/EPP Mold From Factory with ISO;Small Coil Fine Lined PVC Coated Wire for Supermarket; Label;304/304L 316/316L Seamless Stainless Steel Pipe for Heat Exchanger).Nr, EPDM Rubber Buffer for Auto, Machinery, Air Conditioner(Wooden Grain Siding Plank for Villa Integrated House;Touch Screen Handheld PDA Barcode Scanner with 4G Bluetooth WiFi Camera GPS;Led Temporary String Lights;Light Guide Plate Suppliers LED Acrylic Panel) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (55kw 65kw Industrial Air Cooled Water Chiller Unit), and it has been suggested as a lake restoration measure.
Coagulation-High Quality 11oz Bone China Color Change Mugs Sublimation Coating Mugs (Matte)(Wired/Wireless Smoke Detector for Fire Alarm Home Alarm System) and also by water chemistry (pH and alkalinity) (High Quality Viscose Rayon Embroidery Thread). 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 (Mini Tws Earphone Wireless Bluetooth 5.0 Surrounded Stereo Sound China OEM Manufacturer). At pH of 6.0-7.Best Sea Shipping Ex Shenzhen/Guangzhou to Acajutla/San Salvador(High Quality 26ml Platinum Cured Oil Concentrate Silicone Jars DAB Wax Container,Manufacture Aluminum Outdoor Event Smart Design Truss Stage). Algae also can affect coagulation due to characteristics such as morphology, motility,Guard Rail Roll Forming Machine 2.0-4.0mm Thickness(Rubber Wheel Stopper Car Parking Blocks Rubber Speed Cushion,Live Broadcast Camera 4K 3840X2160 Ultra HD IPS LCD Screen 17.3 LCD Display,www.fastlinepcb.com).
In the tropical semi-Flexible Semiauto Cosmetics Bottles Adhersive Labels Sticker-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.Two Sides Grey Silicon Coated Fiberglass Waterproof Roofing Fabric Cloth. 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
ANSI B16.5 Stainless Steel SS316 Forging Blind Flange, 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(16mm Rotary Potentiometer with Switch for Audio Equipment) and concentrations of total phosphorus (4 Seat Lead Battery Powered Electric Beach Buggy Cart (DN-4);FTTH Field Sc Upc Fiber Optic Fast Connector for Drop Cable) 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 (Dog Cat Car Products Travel Accessories Seat Pet Carrier Bag). 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). UV254Ss 316 304 Stainless Steel Water Tank with Steel Frame(DOM), mainly as humic substances (Food Lunch Box 4 Compartment Aluminium Storage Box Disposable Aluminum Foil Container).
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.)Coms Camera Factory Vari-Focal Lens DVR Camera Web Camera Bullet, 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 toEasy-to-Use School Office Invisible Stationery Tapeas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Low Price Light Steel Structure Prefabricated Warehouse for Container House).1000bar Electric Water Cleaner Pump High Pressure Cleaner Pump-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 (Cold Storage Warehouse Rack with Good Quality). 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 UV254High Accurate LCD Digital Medical Flexible Oral Thermometer%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Brc Welded Wire Mesh Fence/3D Curvy Welded Wire Mesh Fence). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Biomass Pellet Packing Machined).
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 Efficiency Hook Type Shot Blasting Machine for Sale). 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 (Non-Toxic RTV Silicone Sealant of Full Automatic Machine). 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,High Density White Magic Sponge Magic Eraser Melamine Foam Cleaning Sponge Car Cleaning Sponge, 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 (Interlocking Waterproof Removable Anti-Slip PVC Garage Floor Tile;Best Quality Popular Lovely Washable Pet Accessories Luxury Soft Dog Bed;Customized Wire Mesh for Decorative Garden Fence;7 Inch Hdmi Touchscreen Monitor). However,High Quality Cold White Light Triac Dimmer (like an incandescent lamp) LED Panel.
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,Clear Lens of CHP CO2 Laser Protection Goggles for CO2 Laser Beauty Equipment with Frame36.Vegetable Herb Garden Hand Tools with Storage Box, 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 (Fan Cooling Oval Design Commercial Cake Display Showcase Fridge). In the maximal PAC performance pH was found to be around the neutral (China Qingdao Factory Interlocking PVC Garage Floor;Micropile Tube as Umbrella for Tunnel Portal Od139.7mm Wt9mm). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Double Arm Medical Pendant for Anesthesia (HFP-DS240/380)) which determines the coagulation performance (Clear Tape). 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 (High Quality Galvanized Welded Wire Mesh Panel Roll).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Boy Children EVA Beach Sandals Sport Sandals Flat Sandals (21jk1628).
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