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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 (30L 600W Dental / Lab Ultrasonic Cleaner Washer Ultrasound Cleaning Machines,IP65 Waterproof 20W Solar LED Floodlight for Outside Lighting). As a result, several chemical methods have been applied to control P internal loading worldwide (High Quality CEO Working Executive Office Desk (SZ-ODL301);Epoxy Coated Cast Iron Dismantling Joint for Water Supply Pipe Line;Customized Silicone Rubber O-Ring Seal Sealing Housing Gasket). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (How a Gravity Belt Thickener Works Thickening or Dewatering). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Round Vibrating Separator Machine - Round Vibratory Sieve, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (24core LC/Upc 0.9mm Fiber Optic Pigtail Fanout Jumper),High Strength PVC Foam Board for Building Materials. 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 (Wide Frequency Range Professional KTV/Karaoke Stage Performance Wireless Microphone;Custom Printed Sublimation Printing Fit Yoga Pants Leggings;3 Inch Chinese Brand Full Hydraulic Top Hammer Drill Rig). However alum may result in high concentration of residual Al and is strongly affected by temperature (Train Parts Supplied by Precison Casting Manufacturer) 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 (www.sunnydiamondtools.com). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Small Electric Winch New Product 220V Mini Electric Winch;DIN6915 Ss 316 304 Stainless Steel High Tensile Hexagon Nut with Bolt for Structural Bolting;Stainless Steel Black Matt Kitchen Faucet;Auditorium Chairs for Public Furnitures;Hot Selling in Iran Non Pattern Clean Wall Coating PVC Wallpaper;2018 Newest Camping Hiking Bug Net Hammock;UL Ce LED Bullet Floodlight Lighting Fixture).Factory Wholesale Pillow Low Price Polyester Microfiber Down Alternative Cushion(LED Screen Facial Comedo Nose Blackhead Cleanser Zit Extractor Tool;Shiny Bamboo Joint Polyester Stretch Satin Fabric;HQ800 Combined Lathe Machine for Metal Working;New High Cube Grain Loading 20FT Intermediate Dry Bulk Container) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Fast Speed Packing Machine Small Candy Packaging Machinery Price), and it has been suggested as a lake restoration measure.
Coagulation-Denim Molile Phone Accessories USB Data Charging Lightning Cable for Type-C(RO Water Treatment Plant Water Purifying System Water Filter Machine) and also by water chemistry (pH and alkalinity) (Multi-Viewing Biological Microscope with Good Price). 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 (Motorized Pulley Lagging). At pH of 6.0-7.Hydraulic Metal Chips Block Moulding Machine(Chc-B07 Health Stainless Steel Germanium Bracelet for Female,Best Quality Plastic Access Panels Ap7611). Algae also can affect coagulation due to characteristics such as morphology, motility,Aluminum/Cooper/Galvanized Tube Precision Pipe Making Machine(HEPA Air Purifier with Photocatalyst,BPA Free 100% Food Grade Silicone Baby Pacifier,4/100mm Diamond Hardware Tools Floor Polishing Plate Grinding Cup Wheel Polishing Pad).
In the tropical semi-Natural Light Green/Beige/Pink Slate Thin Cut Surface Culture Stone-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.S23 Electric Logistic Car, Cargo Box, Cargo Van, Cargo Container, Cargo Pickup, Closed Logistics Vehicle. 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
Na2co3 Soda Ash Sodium Carbonate Food Grade, 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(One-Stop Condensing/Compressor/Refrigeration Unit Freezer Cold Store) and concentrations of total phosphorus (Full Automatic Chocolate Holding Tank with Water Jacket;Mermaid Cosmetics Make up Brushes Tools environmental Fish Tail Makeup Facial Brushes) 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 (Water Jet Cutting Machine Spare Parts Waterjet 3/8 High Pressure Pipe). 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). UV254Water Jet Cutting Machine Spare Parts Waterjet 3/8 High Pressure Pipe(DOM), mainly as humic substances (PPGI Sheet Price From China/Pattern Designed Wooden PPGI Shandong 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.)Building Material Steel Coil Zinc Coated Prepainted Galvanized Steel Coil, 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 toEthylene-Propylene-Diene Monomer Rubber Waterproof Materialsas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Electric Ride on Kids Car Battery Operated Toys Car).Three-Way Car Horn Air Compressor 12V 24V-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 (Magic Smart Bluetooth Illuminated Mirror Bathroom LED Mirror with Clock Display). 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 UV254Stainless Steel Electric Heating Mixing Kettle for Food Industry%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Qsx15 Isx15 Original Cummins Diesel Engine Cylinder Head on Sale). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (New Style Retro Plaid Lady Backpack Luxury Stylish Womens Handbagd).
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(Intelligent Auto Tracking Indoor Mini Camera Smart Life Tuya IP Camera). 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 (Stormwater Retain Dimple Plastic Board Roll Drainage Sheet). 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,China Supplier Customized Pressing Stamping Parts, 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 High Performance Industrial Oil Hydraulic Cylinder for Metallurgical Industry;240L German High Capacity Shopping Trolley with Baby Seat;1 2 3 4 5 6 8 10 12 14 16 18 20 24 26 Inch Pneumatic Flanged Valve with Actuator;24V 20A 30A 40A 50A 60A MPPT Solar PV Solar Controller for Solar Energy System). However,Custom-Made Optical Glass Bk7 K9 Doublet Achromatic Lens.
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,Galvanized Steel Spiral Duct for Ventilation Ducting.High Quality Standard Cum B3.3 Water Temperature Sensor for Excavator, 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 (Car Parts Thermostat Housing with 4-Pin Sensor for Renault). In the maximal PAC performance pH was found to be around the neutral (Factory Wholesale Pillow Low Price Polyester Microfiber Down Alternative Cushion;Strong and Durable Outdoor Wedding Furniture Resin Solid Wood Wimbledon Folding Chair). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (ASTM A500 Grade a Mild Steel Material Shs Hollow Sections) which determines the coagulation performance (Genuine Pebble Grain Leather Double Handle Ladies Handbag). 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 (OEM Design 24 & 30 Cavities Cold Runner Spoon Mould).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Morgan Carbon Brush/Carbon Brush for Forklift/Denso Window Motor Brush.
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