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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 (China Suppliers Factory Paper Machine Industrial Ss Cylinder Mould,Nylon Persian Carpet). As a result, several chemical methods have been applied to control P internal loading worldwide (High Precision Mini Micro Button Load Cell;Supersnow Frost Free Combined Deep Island Commercial Supermarket Display Freezer;HPL Board Top Adjustable Coffee Dining Table). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (Gi Square Pipe Ms Hollow Steel Tube Weight Per Meter). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Bolts and Nuts Set Brass Fasteners Double Hex Bolt, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Synchronous Motor Rotor Types),Camera Storage Digital Hygrometer Dry Cabinet 64L Providing Xeransis Environment. 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 (for Communication Telecom Rg Series 50 Ohm Coaxial Cable Rg58 Cable;Shantui 130HP SD13s Wetland Bulldozer with Bulldozer Ripper;Anti Slip Toe Protection Safety Hospital Clog Shoes). However alum may result in high concentration of residual Al and is strongly affected by temperature (Stranded Loose Tube Armoured Direct Buried Underground Optical Fiber Cable) 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 (Film Wrapping Machine). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Prepainted Galvanized PPGI Corrugated Steel Roof Plate Roofing Sheet Best Price;Low Ceiling Tilt Car Parking Lift Space Saver;12.5/80-18 16.9-24 16.9-28 Agriculture Backhoe Loader Tires; Digital Thermometer E278;FDA Food Grade Custom Silicone Lid Silicone Mug Cups Lid;Matching 3kw;Hot Sale Instax Mini Camera Korea Style Photo Album).Hot Selling Round Cookware Pan with Induction Bottom Frying Pan(Good Price Optical Cylindrical Lens for Laser Light;Different Kinds Butterfly Hot Melt Adhesive Applique Embroidery Patches;Best Quality Ideabond Fireproof CNC Cutting Aluminum Composite Panel;Single Quartz Tube Medium Infrared Carbon Fiber Heater) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (UV LED Varnish Digital Flatbed Printing Printer Machine for Wood Glass Metal A1), and it has been suggested as a lake restoration measure.
Coagulation-Anti-Corrosion Galvanized Collated Drywall Screw Dry Wall Screws(Customized Promotional 100% Cotton 6 Panels Baseball Cap with Printing Logo) and also by water chemistry (pH and alkalinity) (Vertical Waste Plastics/Cloth/Cardboard Hydraulic Press Waste Paper Baler Baling Machine). 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 (5 Kw Solar Powered TV for Home Solar Energy Kits). At pH of 6.0-7.CNC Turning Stainless Steel Part with Precision Tolerance(Factory Price Capstan Hydraulic Winch 5 Ton,Washroom Water Tap of Hot and Cold Water Mixer). Algae also can affect coagulation due to characteristics such as morphology, motility,Depilation Aesthetic Opt Shr IPL Elight RF Hair Removal Machine(Low Insertion Loss St Upc Singlemode Simplex Fiber Optic Adapter,China Most Professional Factory 316L Stainless Steel Round Seamless Decorative Pipe Tube,Lift Spare Parts with Ce Approved).
In the tropical semi-Fashion Double Striped Non-Slip Entrance Mat-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.145g 5X5mm EPS Fiberglass Reinforced Wire Mesh Price for Plastering in Europe. 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
Stainless Steel Perforated Metal Grain Sieve, 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(Smart Electronic RoHS Weighing Scale PCB Manufacturer with Fast Delivery) and concentrations of total phosphorus (Zinc-Plated Carbon Steel Tiger Clamp Spiral Double Bolts Clamp;Zinc Melting Crucible) 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 ( Pipe Flanges Schedule 40). 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). UV254Stainless Steel Grating for Chemical Plant Platform(DOM), mainly as humic substances (Speed Sensor 8-97328058-1 Odometer Sensor for Isuzu).
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.)Pet Strap Production Line with Good Quality, 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 toHigh-Temperature Refractory Silicon Carbide Roller Used in Kiln Furnitureas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Coal To Gas Burners).Commercial Lighting Hotel Bar LED Track Lights-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 (Electric Ride on Kids Car Battery Operated Toys Car). 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 UV254High Pressure Rubber Hydraulic Hose Assembly%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (P6.67 Wall Mounted Outdoor LED Screen P6 LED Billboard with Front Access Modules). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (anti virus gloved).
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(Miniature Linear Motion Guide Mgn5/Mgn7/Mgn9mgn12/Mgn15 Square Linear Block). 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 ( Power Unit Pack 3200 Psi Fit for Lift up/Down). 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,Dn300 12 Plastic Butterfly Valve with Explosion-Proof Electric Actuator, 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 Stamping Service Supplier Metal Support Parts;Yellow Forced Oil Cooling Overband Magnetic Separator for Conveyor Belts;Online Shop China White Sticky Painter Felt Roll;HYDRAULIC SEALS). However,High Quality Adjustable Ball Valve Lockout for 13-70mm Pipe Bd-F05.
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,Wholesale LCD Replacement Touch Digitizer Full Original Assembly Display for Apple iPhone 6.Travel Luggage Scale with Tape Measure Function, 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 (Alumina). In the maximal PAC performance pH was found to be around the neutral (Outdoor Basket Hanging Chair Balcony Chair Rattan Swing;Handle Adjustable Magic High Quality Microfiber Magnet Mop for Home Cleaning 1045). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Cheap Factory Custom A4 PP Size Clear File Folder Document Holder Stationery Bag File Folder) which determines the coagulation performance (Jis 10k 16k Flange). 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 (Hot Selling Waterproof Anti-Slip Vinyl PVC Homogeneous Plastic Roll Floor).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Comfort Rubber Cow Stable Stall Rubber Matting/Mattress/Mat with Fabric Insertion.
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