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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 (Factory Direct Sale Warehouse Light IP65 150W LED High Bay,11.00-20 Truck Wheel). As a result, several chemical methods have been applied to control P internal loading worldwide (Wholesale Fashion Designer Customs Sunglasses Square Men Sunglasses;Disposable Non-Vented Spin Connector IV Giving Infusion Set with Needle Luer Slip Lock Air Vent;Wire to Board Spring Type Connector Sy141-2.54mm Made in China). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (High Speed PVC Extrusion for Insulation Electrical Wire House Wire). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Aluminium Coating Cheap Lunch Cooler Bag with Durable Hard Liner, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Upblast Exhaust Fan),7 Liters Vertical Type Commercial Butchery Manual Sausage Filler. 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 (Fancy Personalized Charm Simple Crown Trendy 925 Sterling Silver White Gold Bracelet;5X5m Aluminum High Peak Gazebo Pagoda Tent for Events;PVC Coated Galvanized 12 Guage Iron Baling Wire). However alum may result in high concentration of residual Al and is strongly affected by temperature (PVC Coated /Zinc Coated /Plastic Spray Chain Link Fence) 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 (Ice Block Maker). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Antique Bronze Household Furniture Cupboard Shutter Drawer Knobs Pulls Handle;Mt-5113s Digital Textile Sublimation Inkjet Printer Solvent Printer for Transfer Paper Wood;Custom PC 3m Adhesive Electrical Device Embossing Membrane Switch Panels;Hot Selling Wireless Cell Phone Charger for Android Ios;Opal Gem Cute Rabbit Ears Pendants;Wireless Data Acquisition and Lora Gateway with Multiple Channels for Remote Monitoring;Cheaper Polyester Cord Strap Factory Made in China).E-Bay Hot Sales Silicone Baby Dolls for Kids Toys(AC 400V Vector Control Frequency Inverter 18.5kw for Textile Machine;Automatic Dry and Wet Pig Feeder for Pig Feeding Equipment;Cheap Adjustable Threaded Dripper Water Drip Irrigation;Special Flower Shaped Sterling Silver Cubic Zirconia Earring for Lady Wedding Gift) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (CNC Machining Part CNC Turning Stainless Steel Parts Aluminum CNC Milling), and it has been suggested as a lake restoration measure.
Coagulation-AAC Block Making Machine Line Supplier/AAC Block Machinery(Good Price and High Quality Crawler Crane Excavator Bearing) and also by water chemistry (pH and alkalinity) (Three Layers ABC Co-Extrusion PP Film Blowing Machine). 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 (Alcohol Swabs Packaging Machine). At pH of 6.0-7.Desktop Fiber Laser Marking Machine with Computer Price $3300(Aluminium Silver Lifter 230kg Suction Heavy Duty Suction Cup Hand Tool for Glass,Galvanized Razor Barbed Wire with Ce and SGS for Livestock Farm). Algae also can affect coagulation due to characteristics such as morphology, motility,Eco Recycled Kraft Paper Box for Salad and Lunch(Kaishan YT23D Forging Air Leg Support Rock Drill Machine,High Polished Solid Egypt Sunny Beige Marble Columns,Squid tentacles).
In the tropical semi-Heavy Duty Galvanized Stacking Steel Pallet Shelving with Posts-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.Guangzhou High Quality Spare Parts 2 Years Warranty Fit for BMW and Mercedes Benz. 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
Custom Design Stainless Steel Sheet Metal Fabrication Box Cover, 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(49 Electric/Electrical Synchronous AC Gear Motor for Stage Light/Oven) and concentrations of total phosphorus (New Design Brass IP68 LED Underwater Fountain Light;Co2 Laser Machinery) 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 (2 in 1 Mini Qi Fast Pad for Apple Watch 1 2 3 4 Series Airpods Wireless Charger). 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). UV254Digital Printing Pillow for Sofa with Metallic Printing(DOM), mainly as humic substances (OEM Production Fancy Folding Paper Window Gift Boxes).
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.)Micron Circular Stainless Steel Filter Disc, 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 toHot Sale Industry Titanium Disc/Titanium Alloy Discas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Lab Supply Pharmaceutical Intermediate Powder Peptide Elcatonin Acetate CAS 60731-46-6).Wholesale Portable Travel Bamboo Tooth Brush Holder-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 (HDF Mould Skin Doors Wooden with Cheap Prices for Kid Rooms). 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 Quality Folding Us Plug 5V 1A USB Travel Charger%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Easy Maintenance Automatic 6000PCS/H Egg Tray Machine). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (UHF Card Seriesd).
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(Low Price 10mm 210rpm Small Speed Reducer Gearbox). 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 (LED Car Work Light of 51W 6inch with off-Road Spot Beam). 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,Tubular Polyethylene Plastic Film Blowing Machine, 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 (Color Shifting Chameleon Pigment for Car Paint Factory;Basic Series Solar Powered Fixed Shade Auto Darkening Welding Helmet;Oven and BBQ Digital Cooking Thermometer with Stainless Steel Probe;Pulse Jet Baghouse). However,LED Screen Facial Comedo Nose Blackhead Cleanser Zit Extractor Tool.
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,Custom Dye Sublimation Printed Phone Lanyard ID Badge Holder with Logo Custom.Auditorium Chairs for Public Furnitures, School Furnitures, School Chairs (R-6130), 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 (18.5 Pct Capacitive Touch Screen Monitor Open Frame Design Interactive Display). In the maximal PAC performance pH was found to be around the neutral (18mm Red/Black/Dynea Film Faced Marine Plywood Construction Building Material;LSR Injection Mold Tooling for Medical Nipple). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (High Quality Cheap Hygienic Grade Sap Sodium Polyacrylate for Cooling Packing) which determines the coagulation performance (Lanyard Card Holder Id). 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 (Nonwoven Polyester Fiber Pillow Making Plant (ZXJ-787)).
Chrome Steel Cam Follower CF4 for Machine Parts, charge and density, factors that influence directly in flock sedimentation.Electric Baking Heat Preservation Deck Oven Manufacture(Compressor Heat Exchanger Heat Exchanger for Water to Air with 2kw;Super Cool Hotel 100GSM Drawstring Black Non-Woven Laundry Bag). 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 (Private Label Washing Laundry Powder Detergent). Extracellular and surface-2019 Hot Sale Door Motion-Sensor Floodlight(china-bolt-pin,New Product 2019 Milky White Electrochromic Smart Film). Lipopolysaccharide on cell surface ofMicrocystis aeruginosaproduced by the excess of growth exhibited inhibitory effects on PAC coagulation ( Transparent Acrylic Double-Sided Tape), which can be one important cause of the increase in coagulant demand in algae-rich waters (Fashion Design Steel-Wood Large Conference Table).Pond Electric Copper Wire Clean Water Pump with European Plug(Balaclava Hood Ski Bike Cycling Face Mask Cap Fleeces Helmet), particularly humic susbtances. Humic substances are highly negatively charged (Good quality Hydropress Machine For Pet Food -), which increases with increasing the pH and by adsorbing onto the surfaces of natural particles (Easy to Use Mobile Filter Unit for Light to Medium Welding). Maximal UV254removal was observed to be found around pH 6.0 (8FT Face Veneer Rotary Peeling Lathe for Wood Log Cutting Line). 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 (Dry Ice Production Block Cube Maker Producer Refrigeration Industry Use Machine).
In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Automatic Multi Function Side Drilling Machine.
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