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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 (8FT Wood Log Debarker Machine for Plywood Machinery,Hollywood Bathroom Mirror Lights). As a result, several chemical methods have been applied to control P internal loading worldwide (Aluminium Foil Cup Lids Metal Stamping Parts/Deep Drawing Parts;China Magic Panel Matrix 36X15W Single LED Controllable LED Beam Moving Head Light;2 Storey Worker Living Block Container House Supplier). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Waterproof and Moldproof Marble Floor Grouting). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Ruipai High Quality Plastic Recycling Extruder, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Fashionable Safe Steam Hair Straightener Brush),Laser Therapy Apparatus Predominantly 810nm Laser Output for Laser Therapy Pain Relief. 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 (Colourful Carbonless Paper NCR Printing Paper 50GSM/55GSM;Qgd Series 3 Inch Deep-Well Submersible Electric Screw Water Pump;Hex Phillips Torx Slotted Bits Ratchet Hand Screwdriver Sets). However alum may result in high concentration of residual Al and is strongly affected by temperature (Custom Outdoor Event Pop up Canopy Easy up Advertising Tent) 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 (Bpa Free Liquid Silicone Rubber Big Teat). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (High Quality Folding Training Study Table with Wheels Sf-10f;Glow in The Dark Pigment Luminescent Luminous Powder;Custom Personalized Logos Cheap Neck Printed Custom Polyester Lanyards Ribbons with ID Card Holder;Wear Resistant Steel with Hardness 58-62 HRC;Fence Galvanized Steel Pipe Square/Rectangular/Round/Oval Tube;Korea Glittery Heat Transfer Film /Vinyl for Clothes/T-Shirt Printing Cdg-16 Light Multi;Popular Selling Sausage Casing Making Machine).ASTM A335 P11 Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service(air freight China to Botswana Gaborone logistics express courier services;Export Quality Straight Dried Instant Flavor Kelp Seaweed Noodle;Laboratory Pipette Filter Tip;Good Sale Lfc Sand Preparation and Casting Molding Line) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Vegetable Herb Garden Hand Tools with Storage Box), and it has been suggested as a lake restoration measure.
Coagulation-PPR Hot Pipe for Building Materials (PN16, PN20)(Height Adjustable Removable Foldable Feeding Baby High Chair) and also by water chemistry (pH and alkalinity) (ISO Humidity Control Damp Proof Auto Grd Dry Cabinet 50L). 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 (Flow Control Valve). At pH of 6.0-7.High Quality Curved Bend Car Rearview Mirror Glass(Wholesale Factory Prices Ceramic Hair Curler Magic Hair Curler,Decorative Metal Aluminum Steel Room Divider Modular Partition for Hotel Restaurant). Algae also can affect coagulation due to characteristics such as morphology, motility,Rice Cracker Core Filling Snacks Food Making Machinery(New Designer PU Fashion Ladies Backpacks Handbags for Brand Holder and Wholesale,Built-in Camera Shoot Photo Video Recording Multi Function Night Vision Telescope,Outdoor Stylidh Canvas Mens Single Strap Shoulder Bag Sh-16031133).
In the tropical semi-Fabric/ Cloth Insertion SBR/ EPDM/ Nitrile/ Neoprene/ FKM/ Natural Anti-Slip Rubber Flooring-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.Luxury Fashion Lady Women Shoulder Tote Bag Leather Evening Handbag. 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
600L Stainless Steel Beer Fermentation Tank 3-Vessels Brewhouse, 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(Tungsten Solid Carbide Straight 4/6 Flutes Reamer) and concentrations of total phosphorus (Custom Industrial Field Block Ferrite Rare Earth Magnet;Transfer Label For Glass) 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 (Stainless Steel Axle Shaft). 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 Baby Shoes Kids Boy Wear LED Flashing(DOM), mainly as humic substances (Suitcase Belts Continuous Dyeing and Finishing Machines).
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.)Stainless Steel 304 316 Railing Fittings Casting Round Tube Plate, 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 toYtpd173r140-4.0 Ultrasonic Focusing Piezoceramic Transducer for Beautyas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Industrial Water Hose).Non-Smoke E7018 E6018 Welding Rod Carbon Steel Welding Electrodes-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 (Rectangle Custom Various Color Metal Label Tag Sticker Handbag/Luggage Hardware). 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 UV254Factory Direct Seal Y14f General Power Relay 5 Pins%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Customized CNC Machining Checking Fixture for Automotive Bracket). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (10pin Pin Headerd).
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(Customized Precision CNC Mechanical Parts with Steel). 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 (China Products/Suppliers. Prefabricated Metal Shed Steel Structure). 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,30L 600W Dental / Lab Ultrasonic Cleaner Washer Ultrasound Cleaning Machines, 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 (Ventilation Back Draught Damper Volume Control Damper One Way Shutter Actuators;Hand Tools Mini Wire Brush Set for Construction 3PCS OEM;Food Grade Titanium Dioxide F-200 Pigment;Cheap Trampolines For Sale). However,G95 LED Filament Bulb Light Lamp 8W 110-130V/220-240V Edison Bulb with Ce RoHS.
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,Lockey Loto Durable Standard Safety Gate Valve Lockout with Ce.FRP Fiberglass Underground Septic Tank for Effluent Treatment, 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 (Silicone Rubber Pin Insulator/Polymer Composite Insulator (10kv-33kv)). In the maximal PAC performance pH was found to be around the neutral (Customized Waterproof Backpack Canvas Laptop Bag;Medical Acupoint Patch with Sterile Wound Patch for All People). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Carbide 4 Flutes HRC60 Blue Coated Milling Cutters) which determines the coagulation performance (www.miracle-leather-bag.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 (Lockey Loto Durable Standard Safety Gate Valve Lockout with Ce).
Pgz1000 Crystal Industry Pneumatic Scraper Bottom Discharge Flat Basket Filter Centrifugal Separator, charge and density, factors that influence directly in flock sedimentation.Inflatable Floating Water Playground Water Island for Commercial Business Usage(10~2500kVA (10KV) Cast Resin Dry Type Transformer with IP20 Enclosure;NIBP Cuff Blood Pressure Cuff Disposable of Patient Monitor). Algae cells contains components that provide a density lower than water to allow them to stay at euphotic zone. Lipid accumulation, mucilage production, ionic regulation and gas vesicules are components of algal cell to avoid sedimentation (CNC Flame Plasma Cutting Machine Flame Cutting Nozzle). Extracellular and surface-Solid Carbide Straight Slot Reamer with Inner Cooling Hole(Electric 80r New Design 24V DC Gear Motor with Od 63mm (SLT-63ZYT),Air-Cooled Refrigeration Condenser Dual Flow Unit Cooler Air-Cooled Condensing Unit). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation (14 X 14 Mesh Window Screen Aluminum Alloy Wire Netting), which can be one important cause of the increase in coagulant demand in algae-rich waters (Food Safety Testing Equipment for Heavy Metal in Food Analysis).Balaclava Hood Ski Bike Cycling Face Mask Cap Fleeces Helmet(Hc-30A Electrical Insulation Tape Winding Machine for Wire and Cable), particularly humic susbtances. Humic substances are highly negatively charged (100kVA/80kw Cummins Emergency Use/Marine/Water Cooling/Electric Starting/Boat Generator), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (factory outlet excellent herbicide DIURON 80% WDG on sale). Maximal UV254removal was observed to be found around pH 6.0 (Large Outdoor Water Park Slide/Water Turntable Amusement Equipment). The aquatic humic substances form complexes with dissolved aluminium species which are removed by adsorbing onto a solid, making the coagulation difficult in waters with both algae and humic susbtances (Pond Electric Copper Wire Clean Water Pump with European Plug).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Commercial Promotion White Inflatable Party Tent for Exhibition.
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