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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 (16oz Pet Plastic Food Jar with Embossed Metal Lid (PPC-PJ-1701),Automatic Laser Cutter Steel for Sheet Metal/Cabinet/Signs). As a result, several chemical methods have been applied to control P internal loading worldwide (Wood Plastic Mould/UPVC Profile Extrusion Mould Plastic Profile Extruding;Custom Design Stainless Steel Sheet Metal Fabrication Box Cover;Wholesale Custom Color Beauty DIY Face Mask Spatula Set Plastic Mini Facial Cosmetic Spatula). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Cartoon Design Decorative PVC Sheet for Wall Panel Moulding). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Breathable Pet Dog Shoes with Reflective Magic Tape Straps, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (China Bench Grinding Wheels For Sharpening),Elevator Door Phone Industrial Telephone Knzd-15 for Clean Room with Double Loudspeaker. 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 ( Skin Care;3003 3004 3005 Aluminium Circles for Foil Pans with Lids;All Round Inflatable Stand up Paddle Boards for Surfing). However alum may result in high concentration of residual Al and is strongly affected by temperature (Fiberglass FRP Sandwich Panel for Insulation Truck Body Construction) 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 Quality Office Table Staff Computer Desk Wooden Workstation). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Bottles Juice Glass Bottles Liquid Filling Line Beverage Processing Machinery;Carbon Stick Welding Electrodes E6013&E7018 Stone Bridge Brand;Compact Laminate Kids Urinal Screen with Good Price;Modern New Design Red Back Massage Table Pedicure Chair;OEM Custom Brass Copper Aluminum Turning CNC Lathe Accessories Automobile Parts Fabrication;Scarifier Loosener Ripper Horizontal Rotary Cultivator Tiller;Factory Customized Outdoor Gate Decoration Marble Antique Pillar Mcy-63).Best Price 1325 Woodworking CNC Router Machine Equipment(New Product PVC Insulation Tape;GM320 Digital Infrared Thermometer Non Contact Infrared Thermometer IR Laser Point Gun -50~330 Degree;Buffer -Ad Series;Food Grade Clamped Tubular Sight Glass in Stainless Steel) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Professional Stage Lighting 7PCS 4in1 LED Flat PAR Lights), and it has been suggested as a lake restoration measure.
Coagulation-8FT Wood Log Debarker Machine for Plywood Machinery(57-5 Micron Micro Powder Mill Pulverizer Grinding Plant) and also by water chemistry (pH and alkalinity) (Yarmax Manufacturer! Hot Sale! Top Sale Open Frame Electric Start Diesel Generator 5.8kVA Ym9500e). 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 (Factory Direct Sell Positive Pressure Blow Through Rotary Valve). At pH of 6.0-7.OEM Hardware Factory Custom Fabrication CNC Aluminum Signet(Wholesale Fashion Custom Round Neck Mens Tshirts Plain Tshirts for Print,Best Selling Mirror Aluminum Sheet for LED Lights and Decorations etc.). Algae also can affect coagulation due to characteristics such as morphology, motility,on-off Automotive Switches Automotive Rocker Switch 16A Rocker Switch(Cast Iron Housing 380V AC 3kw 3Wq Submersible Sewage Water Pump,Large Industrial Ceiling Fan with External Rotor Motor Drive,Best Selling Electro Galvanized Welded Wire Mesh).
In the tropical semi-Youthful Nylon Waterproof School Backpack-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.Drawstring Backpack String Bag Sports Waterproof Sackpack Gymsack Gym Bag. 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
2018 Newest Camping Hiking Bug Net Hammock, 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(800W/55ah Luxury Four Wheels Electric Mobility Scooter with LED Lights) and concentrations of total phosphorus (Stainless Steel Bimetal BBQ Gas Bimetal Oven Thermometer;Aluminum Die Casting Clothing Cutting Accessories) 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 (PP Surface Self Adheisve Roof Underlayment). 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). UV254Qt5-15 Automatic Concrete Cement Sand Hollow Solid Block Brick Making Machine(DOM), mainly as humic substances (High Quality Cold White Light Triac Dimmer (like an incandescent lamp) LED Panel).
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.)Glass Shower Door Frame Waterproof Seal PVC Seal, 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 to PN20)as they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Pp Female Threaded Elbow).Cheap Spring Bonnell Inner Spring for Bedroom Mattress-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 (Wood Based Powdered Norit Activated Carbon Price). 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 UV254Jq350 Small Electric Vertical Pan Cement Blender Concrete Mixer%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Cheap Prise Solid Carbide Reamers for Drilling Hole Factory Outlet). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Factory Price for Programmable Logic Controller HMI PLC (GSM Starter Kit)d).
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( 1 High Alumina Ceramic Ball with High Quality). 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 (Left Hand Drive a-Pillar Rocker Switch Pod Panel Kit for Jeep Wrangler Jk 07-17). 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,Bendable IP67 Waterproof Neon Flex LED Light with Silicone Tube, 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 (Customized Easy Installation Modern Luxury Container House;Automatic Canned Aloe Vera Cube Dicing Cutting Cutter Machine;Intelligent Dry-Type Transformer Monitor with Plastic Cover;Aluminium Window Frame Making Machine). However,Commercial Clean Room Spc Vinyl Waterproof Stone Plastic Composite Flooring Plank.
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,ISO Humidity Control Damp Proof Auto Grd Dry Cabinet 50L.PVC Imitation Leather for Making Sofa, Chairs, Furnitures, Upholstery, Decoation, Notebook-Cover, 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 (Organice Ball Fertilizer Granulation Machine). In the maximal PAC performance pH was found to be around the neutral (Hotel Waffle Slipper From China Supplier (DPF2437);USB a to Lightning Quick Charge Data Cable). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Outdoor Fitness Equipment Gym Chilren′s Teeterboard) which determines the coagulation performance (New Volakas White Marble). 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 (Ruipai High Quality Plastic Recycling Extruder).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Vodafast A2 Stainless Steel Channel Nuts with Long Spring.
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