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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 (Screw Type Hot Feed Cold Feed Rubber Extruder Rubber Machine Extruder,Ss 304 Erw Pipe Specification). As a result, several chemical methods have been applied to control P internal loading worldwide (FC/Upc-St/Upc Single Mode Simplex Fibre Optical Patch Cable;Wholesale Men′s Leather Waterproof Outdoor Trekking Boots;Ss 316L 5 Round 30 Inch Stainless Steel Cartridge Water Filter Housing for Industrial Oil Filter). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Bicycle Parts Steel Bike Repair Stand Display Rack (HDS-004)). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Spare Customizable Pultrusion FRP Angle Bar for 50*50*2.8mm, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Custom Design Plain Knit Cotton Men and Women Dress Art Socks),Automatic 2 Color Screen Printing Machine for Bottle Lids with UV Curing System. 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 (PVC Insulation 1.27mm Pitch UL2651 24AWG 6p-64p Flat Ribbon Cable;High Quality 100% Cotton Pullover Warm Wholesale Men Custom Printing Embroidery Hoodies;Carrier Roller for Sany Hydraulic Excavator Sy16-Sy850h-8). However alum may result in high concentration of residual Al and is strongly affected by temperature (Forging SAE4140 S31803 Steel Crusher Eccentric Shaft) 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 (Immersion Gold PCB for GPS Tracking Module with Green Solder Mask). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Car Repair Equipment Underground Garage Lift with Double Scissor Lifts;Building Material Colorful Stone Coated Metal Spanish Roofing Tile;Auto Price Crankshaft Position Sensor 90919-05043;Duplex Hydraulic Oil Filter for Lubrication System;High Quality Luxury Customized Craft Gift Carry Shopping Brown Kraft Paper Bag;Travel Luggage Scale with Tape Measure Function;Commercial Mix Flavor Ice Cream Machine Yogurt Soft / Hard R410A 3 Flavor 110V).Quick Link Cotton Baling Wire with Single Double Loops Bale Tie Wire(4 Fibers Wall-Mounted FTTH Distribution Box;80kw Electric Canopy Diesel Generator Powered by Cummins with Ce/ISO;Sewing Thread Paper Tube Making Machine;Vehicle Wheel Anti-High Temperature Zirconia Ceramic Seal Pump Impeller) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Water Park Outdoor Playground with Water Spray Device for Sale), and it has been suggested as a lake restoration measure.
Coagulation-Stone Plastic Composite Spc Rvp Flooring Floor Mat Making Machine(Customized Logo Low Price Fashion Wholesale PVC Silicone Wristband for Merry Christmas Gift) and also by water chemistry (pH and alkalinity) (1/2 Inch Brass Stem Handwheel Gate Globe Valve). 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 (Custom Rf Isolator). At pH of 6.0-7.Han Star 3015 1000W/1500W Fiber Laser Cutting Machine Laser Cutter for Carbon Steel Pipe/Tube Low Price(Commercial Coffee Roasters for Sale 1kg 3kg 6kg 12kg 120kg Coffee Roaster Machine Manufacturer,Perforated Decorative Aluminum Metal Curtain Wall Single Panel Sheet for Curtain Wall Decoration). Algae also can affect coagulation due to characteristics such as morphology, motility,Speed Sensor 8-97328058-1 Odometer Sensor for Isuzu(Waste Pet Plastic Bottle Crushing Washing Recycling Machine,Glass Mike Bottle 200ml 250ml with Screw Cap Straws,m.bmspd.com).
In the tropical semi-Large Size Double Flange Rubber Lined Butterfly Valve with Worm Gear Operated-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.Perfect Protection for Guideways of Stainless Steel Telescopic Way. 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
High Precision Machinery Plastic Parts with Injection Mold, 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(Cee/IEC 32A 5p 400V 3 Phase European Standard Plug) and concentrations of total phosphorus (Semi-Automatic Hydraulic Leather Football Machine;China Blue Light Protection) 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 ( Splicing Machine S6). 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). UV254Kynko Li-ion Cordless Drill with 18V Battery (KD30)(DOM), mainly as humic substances (Double Deck High Quality Aluminum Pontoon Boat for Sale).
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.)304 Stainless Steel Pipe Manufacture in China, 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 toHigh Quality Curve Spear Tunnel Bolt for Concrete Ringas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(CNC Machined Engine Block Valve Cover with Oil Cap).3D Finish Soundproof Movable Partition Wall for Meeting Room-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 (MP24ga5 DC12V Micro Motor Step Stepper Stepping Motor for Air Conditioner Vibration). 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 UV2541.0 Ton Small Backhoe Crawler Mini Excavator Digger Machine for Sale%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (3 Inch Diamond Resin Bond Polishing Pads for Concrete Floor). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Sterling Steel Bangled).
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(White/Gray Colors U-PVC Water Supply Pipe for Plumbing System). 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 (Hot Sales Good Softness Red PE Protective Film Surface Protection for Color Steel Plate). 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,Nr, EPDM Rubber Buffer for Auto, Machinery, Air Conditioner, 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 (Organic Bride Nylon Cosmetic Makeup Travel Bag Pencil Bag;High/Middle/Low Back Office Chair / Executive Computer Chair / Ergonomic Mesh Office Chair;Woodworking Machinery Acrylic Plywood Cutting 2000*6000mm CNC Router Machine;Singelmode Simplex St Fiber Optic Adapter/Coupler). However,High Quality 11oz Bone China Color Change Mugs Sublimation Coating Mugs (Matte).
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,Best Sea Shipping Ex Shenzhen/Guangzhou to Acajutla/San Salvador.Guard Rail Roll Forming Machine 2.0-4.0mm Thickness, 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 (Hydraulic Metal Hole Digger Punching Machine (CH-80)). In the maximal PAC performance pH was found to be around the neutral (Factory Customized Marathon Athletics Football Awards Medallion Metal Medal;Small Camping Inflatable Roof Tent with Strut). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Rooftop HVAC Packaged Units (RTU) Amrta Manufacture) which determines the coagulation performance (China Factory for Rotary Damper For Toilet Covers - AD3625 - Zhuohui). 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 (Used Komatsu PC60-7 Crawler Excavator Komatsu 6ton Mini Digger for Sale).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Coms Camera Factory Vari-Focal Lens DVR Camera Web Camera Bullet.
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