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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 (Hot Sale Industry Titanium Disc/Titanium Alloy Disc,Lovely 5FT5 Real Sex Doll with Stainless Steel Skeleton). As a result, several chemical methods have been applied to control P internal loading worldwide (Android Handheld Barcode Scanner Industrial PDA;Canvas Dog Pack Travel Saddle Backpack for Medium & Large Dog;HDF Mould Skin Doors Wooden with Cheap Prices for Kid Rooms). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Easy Maintenance Automatic 6000PCS/H Egg Tray Machine). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Micro Water Tank Level Transducer for Wall Hung Gas Boiler, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (High Reliable and Precision Metal Film Resistor),Economical Small Bench Metal Mini CNC Lathe (CK6130 CK6132). 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 (New selling OEM quality strong magnet segment arc ferrite magnet for motor;Low Price 10mm 210rpm Small Speed Reducer Gearbox;LED Car Work Light of 51W 6inch with off-Road Spot Beam). However alum may result in high concentration of residual Al and is strongly affected by temperature (50-500μ M Pet Film for Electrical Insulation (6023D)) 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 (Kids Play Kitchen Set). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Manufacturer Bimetallic Parallel Twin Screw Barrel for Extruder;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;Prefab Housing and Steel Structure Building Manufacturer Hot Sale Prefab Building;18.5 Pct Capacitive Touch Screen Monitor Open Frame Design Interactive Display;18mm Red/Black/Dynea Film Faced Marine Plywood Construction Building Material).250ml Empty Refillable Pet Material Plastic Shampoo Bottle(LSR Injection Mold Tooling for Medical Nipple;High Quality Cheap Hygienic Grade Sap Sodium Polyacrylate for Cooling Packing;Gamma Pga - R-Pga Factory & Manufacturer;Nonwoven Polyester Fiber Pillow Making Plant (ZXJ-787)) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Compressor Heat Exchanger Heat Exchanger for Water to Air with 2kw), and it has been suggested as a lake restoration measure.
Coagulation-High Speed Automatic Cleaning Scourer Making Machine Manufacturer(Super Cool Hotel 100GSM Drawstring Black Non-Woven Laundry Bag) and also by water chemistry (pH and alkalinity) (Private Label Washing Laundry Powder Detergent). 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 (Pet Bottle Orange Juice Making Machine/ Tea Manufacturing Equipment /Automatic Tea Bottling Plant). At pH of 6.0-7.Magnetic Badge Holder Rectangle Magnet Button Badge Maker(New Product 2019 Milky White Electrochromic Smart Film, Transparent Acrylic Double-Sided Tape). Algae also can affect coagulation due to characteristics such as morphology, motility,Multi-Viewing Biological Microscope with Good Price(Fashion Design Steel-Wood Large Conference Table,Balaclava Hood Ski Bike Cycling Face Mask Cap Fleeces Helmet,Bespoke Iron Gates).
In the tropical semi-0.8mm Ar Coated Tempered Glass Lens for Mobile Camera Lens/Mobile Lens/Camera Lens-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.1212 1218 1224 1313 CNC Router 4 Axis/Automatic 3D Wood Carver Machine with DSP Controller. 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
European Type Stainless Steel Dee Shackle AISI304 or 316 D Shackle, 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(Dry Ice Production Block Cube Maker Producer Refrigeration Industry Use Machine) and concentrations of total phosphorus (Best Seller Canvas Striped Cotton Rope Fabric Hanging Hammock;Fish Light Complementary Metal Stainless Steel U-Channel Profile PV Solar Panel Structure) 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 (China Stainless Steel Clamp Sanitary Ball Check Butterfly Valve). 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). UV254Compatible Quality Handy Color Jumbo Stretch Cling Film(DOM), mainly as humic substances (2-7dBi GPS/GSM SMA RF Coaxial High Gain WiFi Antenna).
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.)Cow Horse Trailer Ramp Stall Stable Rubber Mat, 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 toAluminum Mold Making Die Casting Motorcycle Spare Partsas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(China Best Price Sweet Donut Bread Mini Donut Packing Machine).Battery Crimping Tool for Pex-Al-Pex Multilayre/Copper/Stainless Steel Pipe-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 (Stage LED Bar 54PCS*3W RGBW DJ Disco Stage Lights). 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 UV254Ductile Cast Iron DIN F4 Non Rising Stem Resilient Seat Control Gate Valve%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Fat Tire City Coco Electric Bicycle Motorcycl Bike Electric Scooter for Adult). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (18mm A Grade Waterproof Bintangor Plywood for Boat Buildingd).
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(CNC Machining Milling Aluminum Bike Components). 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 (Dny Automatic Stainless Steel 304 Belt Filter Press). 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,Fashionable Wine Rack Metal Display Rack Wine Shelf Decorative Rack, 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 (EV850m CNC Machine High Precision Vertical Machining Centers Price;Stainless Steel Welded Wire Mesh BBQ Grill Grate/Mesh for Cooking;NEMA 14 High Frequency Low Noise Stepper Motor (35SHD0001-15);Wholesale Blank Jogger Pants). However,Vertical Multi-Head Weigher Meat Packing/Packaging Machine (PMW-420E).
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,Rich Prision Fence High Quality Barbed Wire Mesh 358 Fence.2.2lb Dreamy Pink Hot Film Wax Beans /Rose Wax Beans/ Rose Pink, 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 (Popular Classic Design Old Style Vintage Leather Chesterfield Sectional Sofa). In the maximal PAC performance pH was found to be around the neutral (Yg15/Yg8 Mirror Polished Hip Sintered Tungsten Carbide Wire Guide Rollers; Cosmetic Fluorescent Pigment Powder Manufacturer). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Excellent Quality Wooden Cosmetic Display Counter for Retail Store) which determines the coagulation performance (Swimming Pool Heat Pump with Cooling Function for Hotel). 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 (Cheap Customized PVC Rubber Book Mark Clips with Any Logo Design for Promotion/Advertising (XF-BM10-)).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Keqiao Shaoxing 100% Polyester Custom Desig Printed Wool Dobby Georgette Fabric.
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