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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 (Plastic Logistics Daily Use Plastic Injection Crate Mould,Waterproof Backpack Manufacture). As a result, several chemical methods have been applied to control P internal loading worldwide (New Avaival Silver Hico Blank Magnetic Stripe Cards;China Best Quality Goof Price Tpo Flat Roofing Waterproof Membrane;Customized Embossing Logo Soft Flexible PVC Bar Mat). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (20 Cavity Pet Preform Mould with Competitive Price). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Metal Enclosure Withdrawable Distribution Switchgear Cabinet Low Voltage, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Collapsible Paper Box Foldable Paper Box Gift Packing Box),PA66+GF Polishing Injection Auto Plastic Parts Mould Manufacturer. 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 (Women′s Knitted Acrylic Sweater Fashion Dress;118 120 TV Tel Socket;Prefabricated Structural Steel Warehouse Steel Structure Frame Building Structure). However alum may result in high concentration of residual Al and is strongly affected by temperature (China Economic ASA PVC Corrugated Roof Sheet for Farm House) 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 (1K Byte 13.56MHz Mf Programmable RFID Security Stickers Tags). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Key Chain Metal Key Rings Acrylic Key Bag Holder;Silicon Carbide Black/Green Use to Produce Angle Grinder Polishing Disc;15′′fashionable Outdoor Active Speaker with Wireless Bluetooth and FM;Pre Engineered Industrial Factory Prefabricated Light Steel Structure Building/Warehouse/Workshop;Egg Tray Pulp Molding Machine;LCL Consolidation Shipping Freight From Guangzhou to Dayton;Yako Brass Waterproof Balcony Toilet Bathroom Floor Drain).Permanent N50 Tiny Mini Neodymium Magnet for Sale(Electric Commercial Ice Cream Cone Maker Ice Cream Waffle Cone Maker;Sc/APC Soc Splice-on Fiber Optic Quick/Fast Connector;Hard Click White Backing Spc Vinyl Rigid Core Plank;Novel Designed Panel Steel Corrugated Metal Roofing Sheet Roll Forming Machine) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Automatic Column and Boom Welding Manipulator Dlh), and it has been suggested as a lake restoration measure.
Coagulation-Stainless Steel Waterproof Anti-Explosion Ik10 IP65 LED Linear Tube Light(Dog Rain Jacket Especially for Outdoor Adventure with Harness Opening Easy on & off) and also by water chemistry (pH and alkalinity) ( Large Output Forestry Application Biomass Wood Chipper). 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 (Hot Dipped Galvanized/Pre Galvanized Steel Channel/Upn/Upe). At pH of 6.0-7.Luxury Recycled Eco-Friendly Decorative Deep Wooden Spc Floor for Shop(off-Grid Residential Small Wind Turbine 1kw 12V Generator Kit,XBD Series Single-Stage Single-Suction Fire-Fighting Pump). Algae also can affect coagulation due to characteristics such as morphology, motility,Butterfly Valves with Lever Handle Top Quality Factory PVC Valve(Precision Assembly Jigs Fixtures for Car Outlet,Clothes PU Reflective Heat Transfer Vinyl CO2 Laser Cutting Machine,Blank Notepad Printing).
In the tropical semi-Made in China High Quality Ceramic Fiber Packing Seal Ring-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.Hydraulic Small Boat Marine Deck Crane for Sale. 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 Quality Meat Pie Making Machine with Different Mould Shape, 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(Best Price Aluminium Sulphate for Water Treatment) and concentrations of total phosphorus (Hot Salse Factory Supply Galvanized Steel Angle for Gypsum Board;Good Anti-Corrosion/ Wear-Resistance HDPE Pipe for Water Gas Dredge) 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 (Custom Souriau Connector Header with Cable). 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). UV254Pre Hot Dipped Galvanized Steel Pipe Cattle Fence(DOM), mainly as humic substances (High Speed Disposable Lunch Box Egg Tray Making Forming Machine).
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.)Transmission Line Steel Monopole Steel Tower, 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 to2kw Solar Hybrid System with Solar Controller MPPTas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Sic Foundry Foam Filter Silicon Carbide Honeycomb Filter for Molten Metal).High Quality Cheap Custom Small Kids Exercise Outdoor Playground with Slide-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 (K12 Stainless Steel Hinges inseparable High strength load bearing Hydraulic -damping hinge). 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 UV254Steel Jacket Steam Insulation Pipeline Production Best Quality%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (China Best Tipper Truck of HOWO 4X2 with Lowest Price). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Semi-Trailerd).
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(Six Spout Impeller Cement Packing Machine). 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 (Competitive Full Color SMD3535 P8 LED Display for Outdoor Commercial Advertising). 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,Best Key Machine Sec-E9 High Security Key Cutting Machine Built-in Data, 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 (11kv 2000 kVA Oil Immersed Power Distribution Transformer;Pre-Painted Color Coated Aluminum Coil and Strip;10 Color Lip Liner Easy to Wear Matte Lip Pencil Waterproof Lipsticks Long Lasting Makeup Lipliner;191AA Human Growth Steroids Hormone 10iu with 100% Pass Rate). However,Good Quality White and Brown Paper Soup Containers.
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,Impulse Plastic Sprinkler Irrigation Traveling Lawn Sprinkler for Garden.Silver Reflective One Way Vision Film as Mirror Performance (SF101), 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 (Stainless Steel Hex Head Bolt DIN933 ANSI Full Thread M5X8...M5X70). In the maximal PAC performance pH was found to be around the neutral (Personalized Custom PVC USB Flash Drive for Company Promotional Gift;Paint Bucket Plastic Injection Mold Design Manufacture Chemicals Container Mould). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (17inches Travel Computer Backpack Bag Water Resistant Business Laptop Backpack) which determines the coagulation performance (High Quality Padlocks). 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 (Decoration Building Material Prepainted Corrugated Galvanized Roofing Sheet Steel Plate).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Automatic Underground Water Purifying and RO Filter Treatment System.
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