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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 (Metallzied Polyester Film 9um MPET Film for Capacitor Use,www.pvthink.com). As a result, several chemical methods have been applied to control P internal loading worldwide (Custom Mono 0.96 Inch Mini Monochrome 128X64 Small OLED Display;Wholesale Gym Equipment Adjustable Boxing Target;Good Quality Wholesale Men′s Leather Sneakers Boots). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (12ml Small Dropper PE Plastic Medicine Bottle). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Custom High Quality Men′s Fashion Plain Cotton Polo T-Shirt, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (www.sunhealthmedical.com),IP65 60W Solar LED Street Light with WiFi Camera. 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 Edge Banding Printing Machine Tape Banding Machine Wire Banding Machine;Middle Duty 20 Discs Harrow for 50 HP Tractor;Hot and Cold Temperature Thermal Shock Testing Equipment). However alum may result in high concentration of residual Al and is strongly affected by temperature (Students Bags School Backpack Childrens′ Shoulder Bag Yf-Sbz2215) 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 (High capacity). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Newest Hot Sales Metal 360 Degree Reading Glasses with Case;Hydraulic Press Machine Deep Drawing Press 100 Ton;Screw Type Hot Feed Cold Feed Rubber Extruder Rubber Machine Extruder;FC/Upc-St/Upc Single Mode Simplex Fibre Optical Patch Cable;mypestkiller.com;Wholesale Men′s Leather Waterproof Outdoor Trekking Boots;Ss 316L 5 Round 30 Inch Stainless Steel Cartridge Water Filter Housing for Industrial Oil Filter).Popular Selling Sausage Casing Making Machine(Bicycle Parts Steel Bike Repair Stand Display Rack (HDS-004);PVC Insulation 1.27mm Pitch UL2651 24AWG 6p-64p Flat Ribbon Cable;Lawn Lighting High Quality Supplier;High Quality 100% Cotton Pullover Warm Wholesale Men Custom Printing Embroidery Hoodies) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Carrier Roller for Sany Hydraulic Excavator Sy16-Sy850h-8), and it has been suggested as a lake restoration measure.
Coagulation-Colorful Aluminum Cream Jar for Cosmetic Packaging(Forging SAE4140 S31803 Steel Crusher Eccentric Shaft) and also by water chemistry (pH and alkalinity) (Car Repair Equipment Underground Garage Lift with Double Scissor Lifts). 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 (China Stainless Steel Metal). At pH of 6.0-7.Top Quality Disposable Dental Surgical Suction Sterile Aspiration/ Aspirator Tips(Building Material Colorful Stone Coated Metal Spanish Roofing Tile,Auto Price Crankshaft Position Sensor 90919-05043). Algae also can affect coagulation due to characteristics such as morphology, motility,High Speed Lead Edge Printing Slotting Machine(Duplex Hydraulic Oil Filter for Lubrication System,Travel Luggage Scale with Tape Measure Function,Quicky Dry Vest).
In the tropical semi-Good Sale Lfc Sand Preparation and Casting Molding Line-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.High Glossy/Matt/Embossed/UV/Natural Wood Veneer Faced Melamine Laminated Colored MDF for Furniture. 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
Key Chain Metal Key Rings Acrylic Key Bag Holder, 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(80kw Electric Canopy Diesel Generator Powered by Cummins with Ce/ISO) and concentrations of total phosphorus (Vehicle Wheel Anti-High Temperature Zirconia Ceramic Seal Pump Impeller;Anhydrous Sodium Sulphate) 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 (1/2 Inch Brass Stem Handwheel Gate Globe 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). UV254Silicon Baby Bib Super Waterproof with Food Slot(DOM), mainly as humic substances (Commercial Coffee Roasters for Sale 1kg 3kg 6kg 12kg 120kg Coffee Roaster Machine Manufacturer).
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.)316L Stainless Steel Pipe Fitting Elbow SMS DIN Elbow, 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 toLiquid Laundry Detergent Small Single Bag Packing Machineryas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Tempered Glass Roof).Electronic Smoke Digitizer Quartz Atomizer Short Quartz Tube-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 (Semi-Automatic Hydraulic Leather Football Machine). 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 UV254Vffs Side-Ironed Bag Food Packing Machine for Puffed Food, Dry Fruit, Peanut Dxd-550s%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (15 Inch IP65 Waterproof Industrial Touch Screen Monitor). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Kaishan YT23D Forging Air Leg Support Rock Drill Machined).
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( Splicing Machine S6). 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 (Double Deck High Quality Aluminum Pontoon Boat for Sale). 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,Fuel Level Display Multi Function Race Car Dashboard on-Board Diagnostic II, 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 (Floor Mounted Glass U Clamp Channel for Glass Balustrade;High Quality Curve Spear Tunnel Bolt for Concrete Ring;Brand New Forklift with Double Front pneumatic Tire;m.glpurifier88.com). However,Anti-High Corrosion and Wear Resistance Carving Zirconia Ceramic Car Rotor.
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 Promotional Soft Cover Children Music Book Printing.24V/48V 40A/80A MPPT Solar Charge Controller for Solar Power System, 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 (Automatic Small Round Bottle Water Washing Filling Capping Machine). In the maximal PAC performance pH was found to be around the neutral (MP24ga5 DC12V Micro Motor Step Stepper Stepping Motor for Air Conditioner Vibration;3 Inch Diamond Resin Bond Polishing Pads for Concrete Floor). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Hairise 2120 Series Transfering Flat Belt Type Modular Belt for Conveyor System /Mechanical/Foods) which determines the coagulation performance (Competitive Price Food Grade Sorbitol Liquid 70%). 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 (White/Gray Colors U-PVC Water Supply Pipe for Plumbing System).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.36W/48W Interchangeable AC DC Adapter Free Samples 14 Years Experience.
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