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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 (Street Lighting 50W 100W 150W 200W LED Street Lamp Source Outdoor LED Street Light,military caps). As a result, several chemical methods have been applied to control P internal loading worldwide (Jfe-9243 9 Motors Stainless Steel Glass Straight Line Grinding Machine;Custom Clear Acrylic Chinese Tea Table (BTR-Q1012);Stainless Steel Electric Heating Mixing Kettle for Food Industry). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (High Efficiency Nylon Fiber Separator in Waste Tire Recycling Line). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Solid Wood Countertop Wood Table Top Wood Island Top Wood Bar Top Wood Table Top, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (www.sunhogloves.com),Steel Toe Cap Men Leather Safety Shoes Footwear Ufe019. 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 (High Quality C5/C3 Grinding Ball Screw From Taiwan;High Speed Wheel Hub Bearing/Automotive Wheel Bearing Units/Wheel Bearing;Manufacturer of Various Color Graduation Tassel Honor Cords). However alum may result in high concentration of residual Al and is strongly affected by temperature (CNC Router Machine Heavy Duty Steel Frame 2030 CNC Router) 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 (Professional Custom Shiny Silver 3D Letters Metal Brand Logo Plate). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Makute Electric Power Planer Woodworking Wood Cutting 82mm 600W;China Label Screen Printing Machine Suppliers; Water;Ring Die Sawdust Wood Pellet Making Machine Line;Babble Express Bag;Honkon Beauty SPA Skin Tighter and Acne Removal Mesogun Injector Beauty Machine;Prime SPCC Electrolytic Tin Plate for Making Cans).High-Class Leather Cover Business Agenda Organizer Planner Notebook(Large Size 300mm Low Noise 55dB IP44 Air Blower for Public Places;Microfiber Wiping Lens Cleaning Cloth for Glasses;Professional Manufacturer of AC Motor Frequency Inverter 4kw 380/400V;Double Layer Waterproof and Durable Asphalt Shingle Roof Tile Roofing Shingles) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (2018 Amusement Park Children Outdoor Playground Equipment for School (HS806001)), and it has been suggested as a lake restoration measure.
Coagulation-Rebar Splicing of Reinforcement Bars Complying with Aci-318(Small Industrial Sewage Treatment Unit for Industrial Wastewater Treatment) and also by water chemistry (pH and alkalinity) (Low Cost Commercia Plastic Polycarbonate Used Agricultural Greenhouse for Sale). 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 (High-Quality Spherical Roller Bearings 22205-230/750). At pH of 6.0-7.55 65 75 86 98 Inch 3D LCD Touch Screen Smart Board TV All in One PC for Meeting Room & Classroom( Disc-Chain Automatic Feeding System,20% White Vinegar Available for Agricultural or Cleaning Purposes). Algae also can affect coagulation due to characteristics such as morphology, motility,Slip on Blind Weld Neck Stainless Steel Flange Including Welding Neck Flange(Dart Extrusion Machinery Making Twin Screw Extruder,100% Fabric Advertising Display See Through Mesh Banner Windproof,Home Textile Ins Style Active Printing Ab Pattern 4 PC Cotton Comforter Set).
In the tropical semi-Industrial Unit Cooler / Evaporative Air Cooler / Evaporator-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 Model Polished Porcelain Glazed Marble Ceramic Floor Tiles for Project. 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
Bottles Juice Glass Bottles Liquid Filling Line Beverage Processing Machinery, 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(ISO SGS Certified 100% Natural Spirulina Powder) and concentrations of total phosphorus (55 Inch Waterproof Digital Signage Outdoor LCD Advertising Display Monitor;Low Sulfur Graphitized Petroleum Coke) 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 (Disposable Take out Paper Food Salad Sushi Lunch Box Container). 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). UV254Stainless Steel Black Matt Kitchen Faucet(DOM), mainly as humic substances (99.95% Pure Metal Molybdenum Mo Sputtering /Sputter Target for Magnetron Sputtering).
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.)Ceramic Components Applied in Machinery Industry, 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 toOutdoor 4 LEDs RGB Landcape Spotlight Solar LED Lawn Lightas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Car Chamois Cloth).Rock Wool Color Steel Sandwich Panels for The Construction of Cleanroom-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 (Fire Retardant Fire Retardant Coating Diatom Ooze Used Sepiolite Powder Sepiolite Fiber Sepiolite). 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 UV254Wall Mounted Bathroom Tissue Holder Toilet Paper Towel Roll Holder%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Fiberglass Heat Fire Resistant Welding Welders Blanket Cover Protective Fabric). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Soda Ash Light 99.2%d).
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(China Metal Cooling Fan for Dry-Type Transformer). 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 (Superior Fabric Core Conveyor Belts Vulcanizing Press From China). 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,Ride on Concrete Power Trowel Machine with Suitable Seat, 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 (Naked Mango Premium E-Liquid|Nicotine Salt for Electric Cigarette;Tempered/Toughened Glass/Window/Shower Door Float Glass (T-TP);Hsc8 6-4A Mini-Type Self-Adjustable Crimping Plier;OEM/ODM Luxury Glass Perfume Bottle of Experienced Designer). However,Concrete Grinding Plate for Abrasive Machines of Abrasive Disc.
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,Duplex Parallel Connection Bag Filter for Filtering Drinking Mineral Water.China New Design TPU/PVC Layflat Flexible 6 Light Duty Suction Hose, 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 (High Density Wood Grain Fiber Cement Board). In the maximal PAC performance pH was found to be around the neutral (1 1/4 Inch Abrasive Resistant High Pressure Sandblasting Hose 12bar;Dumpling Wrapper Machine Dough Pressing Machine Dough Sheet Cutter to Do Tortilla Flat Bread). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Cow Horse Trailer Ramp Stall Stable Rubber Mat) which determines the coagulation performance (Casting Iron Balance Valve). 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 (Hydrochloric Acid (HCl) ).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Monofilament Fishing Tackle Green Nylon Fish Net.
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