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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 (Ductile Iron Ggg50 Pn16 Quick Automatic Air Pressure Release Valve,5mva Power Transformer). As a result, several chemical methods have been applied to control P internal loading worldwide (Ceramic Tile Plasma Ion Deposition Planting Functional PVD Vacuum Coating Machine;Low MOQ Perfect Binding Soft Cover Book Printing High Quality;24V/48V 40A/80A MPPT Solar Charge Controller for Solar Power System). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Aluminum Oxide Abrasive Products 5 6 Stone Metal Disc Grinding Wheel). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,New 14 Inch Diamond Saw Blade for Granite Cutting, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Alloy Frame Full Suspension Fat Bike),Fancy Corn Starch Disposable Round Plate with Stripe for Party. 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 (Small White Color Wall Hanging Plywood Modern Bathroom Cabinet (ACS1-L21);Amino Acid Magnesium Chelate for Organic Fertilizer;Nc Hydraulic Bending Tube Metal Pipe Bending Processing). However alum may result in high concentration of residual Al and is strongly affected by temperature (Best Quality Plastic Wall Plug Expansion Anchor) 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 (Stainless Steel Wind Driven Turbine Air Ventilator). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (700ml Leak Proof Fitness Plastic Protein Mixing Water Cup (HDP-0346);Naixer Ice Cube/Bullet/Tube/Block Ice Maker/Ice Making Machine for Sale with Ce;Outdoor Waterproof IP68 LED Structure 3D Arch Street Christmas Decoration Ball Motif Lights;Home Used Portable Fencing Aluminium Swimming Pool Safety Fence;Low Temperature Carbon Steel Plate;40K Cavitation Vacuum Massage Skin Lifting Body Shaping Machine;2200mAh External Battery Case for iPhone 5/5s/5c (OM-PW5SC)).Manhole Cover Stainless Manway Tank Hatch Cover(Promotion LCM Custom LCD Display Stn FSTN Cog LCD Positive Graphic LCD Display Module for;94% STPP Sodium Tripolyphosphate /Sodium Triphosphate Industry Detergent;Hot Sale 8m Pole 60W Outdoor Lighting Hybrid Solar Wind LED Solar Street Light;Milk Homogenizer Pump Honey Pump Juice Emulsifying Pump) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (72tpd RO Water Treatment Sea Water Desalination Equipment), and it has been suggested as a lake restoration measure.
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In the tropical semi-Esavior 30W All in One Solar LED Light Street Light Motion Sensor Energy Saving Outdoor Light-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.Stainless Steel Silent Child-Mother Hinge Ball Bearing Hinge for Door Window Hardware Accessories. 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
Automatic Plastic Tubes Printing Machine Cylinder Silk Screen Printer, 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(Bodybuilding Supplements Polypeptide Hormones Injectable Peptides Ipamorelin CAS: 170851-70-4) and concentrations of total phosphorus (Fashion Jewelry Stainless Steel Rose Gold Gemstone CZ Ring SSR1948;1 Inch Display Wholesaler Quotes & PriceList) 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 (Luau Pinhole Glasses Promotional Sunglasses Yiwu Market (B3030)). 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). UV254Top Quality Gasoline Grass Trimmer Parts Nylon Head Blade(DOM), mainly as humic substances (Mini Horizontal Axis 100W Wind Generator Turbine).
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.)Custom Color Printed Magazine Brochure Offset Printing Book, 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 Steel Pipeas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Content Labels Dyeing And Finishing Machine).Precision Machining Stainless Steel Right and Left Hand Twin DC Motor Acme Lead Screw-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 (High Speed Double Jersey Computerized Transfer Rib Circular Knitting Machine 2/3 Ways Djjtr). 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 UV254Self-Propelled Ride on Concrete Floor Grinder Grinding Machine Gyg-780%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir ( Custom Fire Burner Rings). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Ceramic Art Tiled).
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(New Design Neoprene Beer Can Cooler). 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 (Cheap Price Woodfree Offset Writing Printing Paper). 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,The Best Venlo Type and Multi-Span Glass Greenhouse for Agriculture, 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 (Custom Wall Hanging Flower & Plant Plastic Garden/ Nursery Pots;New TF Card Head Fone Retractable Audifonos PARA cellular Bluetooths Headphone;Fancy Corn Starch Disposable Round Plate with Stripe for Party;Galvanized Floor Grating). However,PC Black Plastic Material Polycarbonate PC Granules Resin.
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,Duplex Hydraulic Oil Filter for Lubrication System.Automatic Chicken Farm Poultry Battery Cage System for Layer, 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 (Ce Approved Disposable Blood Bag for Ozone Blood Therapy). In the maximal PAC performance pH was found to be around the neutral (Coconut Shell Activated Carbon for Drinking Water Treatment;100ml Boston Round White Matte Plastic Pet Nursing Care Toner Bottle). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Digital Pistol Safe Box / 4-Number Digital Safe Box) which determines the coagulation performance (Electric Disabled Helper Ce Elder Using Handicap Vehicle Four Wheel Mobility Scooter). 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 (China Manufacturer Plastic Material Black Masterbatch PE PP Resin).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Decorative Round Shape Colorful Empty Aroma Reed Diffuser Custom Glass Bottle with Wooden Cap.
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