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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 (Transmission Parts Linear Ball Bearing with Shaft for Setting Machine,Portable Hot Air Gun). As a result, several chemical methods have been applied to control P internal loading worldwide (Pretty Precisely Automatic PV Strut Roll Formin Machine with High Quality;Classic European Style Universal Wrench& General Reciprocal& Utility Wrench;Hot Sale High Density Hotel Cashmere Wool Polyester Blanket). The most used technique is the precipitation and inactivation of phosphorus by coagulants, especially those based on aluminium (Al) (220V UFO Shaped LED Bulb E27 Efficiently Energy Saving LED Light). When Al salts are added to water, Al+3preferable reacts with PO4-3and forms a precipitate,Camera Storage Digital Hygrometer Dry Cabinet 64L Providing Xeransis Environment, flocculation and subsequent sedimentation. Besides this, coagulation and flocculation are also able to remove inorganic and organic suspended particles (Burger Box Making Machine Price High Quality Supplier),Hot Selling Round Cookware Pan with Induction Bottom Frying Pan. 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 (Mini Building up Block Pen Highlighter Marker Pen Writing Drawing Stationery;Cg125 Motorcycle Parts Metal Motorcycle Foot Kickstand Side Stand Spring;Blind Indicators Stud/Strips Stainless Steel Tactile). However alum may result in high concentration of residual Al and is strongly affected by temperature (Fenugreek Extract Enhance Men′s Sexual Function) 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 (China Overhead Rain Shower Head). A number of laboratory and field experimental studies has shown the superior performance of PAC in both turbidity and phosphorus removal (Peaceful Animals Theme Inflatable Dry Slide for Zoos (CHSL640);Embroidery Sequins Lace Mesh Lace Fabric Embroidery Sequins Lace Mesh Lace Fabric;NF3;Optical Solar Smoke Detector with Testing Button (ES-T601);Wood Cabinet Furniture TV Cabinet TV Stand Design in Living Room or Hotel Use;Wkj-01/Mechanical Thermostat/ Room Thermostat/HVAC Controls;1.5 Inch High Pressure Petrol/Gasoline Water Pump).Anti-Corrosion Galvanized Collated Drywall Screw Dry Wall Screws(15kw 19kVA 50Hz Home Standby Weichai Soundproof Diesel Generator;Waterproof Travel Portable Makeup Bag Wash Gargle Bag;Stretch Skinny Jeans;WiFi Outdoor Security CCTV Battery Solar Powered Wireless IP Camera) and turbidity even at low dose (1.5 mg Al.L-1) in shallow lakes (Tecjet Cloth Printer Printing Machine 6090 DTG Printer), and it has been suggested as a lake restoration measure.
Coagulation-CNC Turning Stainless Steel Part with Precision Tolerance(Home Kitchen Appliance Digital Ozone Generator for Air Water Purifier) and also by water chemistry (pH and alkalinity) (Hastelloy C276 Uns N10276 2.4819 Plate Bar Tube Nickel Alloy with China Supplier). 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 (Heavy Type Welded Wire Mesh). At pH of 6.0-7.Depilation Aesthetic Opt Shr IPL Elight RF Hair Removal Machine(Good Quality Mixing Tank Vacuum Mixing Pot Mixing Reactor Vessel,Automotive Electropainting). Algae also can affect coagulation due to characteristics such as morphology, motility,Fashion Double Striped Non-Slip Entrance Mat(Aluminium Radiator Core for Profile or Alloy LED Lighting Other,A694 F42 F52 F60 Class 3000 Forged Pipe Fitting Swaged Nipple,Hospital Furniture Supplier Stainless Steel Medical Baby Cot Baby Bed).
In the tropical semi-145g 5X5mm EPS Fiberglass Reinforced Wire Mesh Price for Plastering in Europe-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 Perforated Metal Grain Sieve. 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 Grating for Chemical Plant Platform, 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(PVC Cross Joint Pipe Fittings Equal Pipe Cross) and concentrations of total phosphorus (Customizable High Quality Q38 Series of Catenary Shot Blasting Machine;Humanized Design Handle Key Copying/Copy Machine for All Keys) 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 ( Fabric). 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). UV254Pet Strap Production Line with Good Quality(DOM), mainly as humic substances (3m 467MP Strong Adhesive Double Sided Transfer Tape).
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.)Commercial Lighting Hotel Bar LED Track Lights, 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 toCorrugated Aluminum Composite Panel for Suspended False Ceiling Decorationas they had chlorophyll-aconcentrations >15 µg L-1and total phosphorus concentration >50 µg L-1(Bathroom Vanity Sets Suppliers for Sale).High Pressure Rubber Hydraulic Hose Assembly-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 (Professional Neck Jacquard Woven Lanyard Strap). 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 UV254Dn300 12 Plastic Butterfly Valve with Explosion-Proof Electric Actuator%. None Al dose was efficient in removing at least 50% of total phosphorus, turbidity, UV254and chlorophyll-afor Passagem das Traíras reservoir (Foton/Forland 4X2 Mobile Snack/BBQ/Coffee/Hot Food Truck). The increasing in Al dose from 6 to 10 mg Al.L-1decreased the chlorophyll-aremoval efficiency for Cruzeta and Passagem das Traíras reservoirs (Building Facade Media Displayd).
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(Customized Machine Dustproof Bellow Cover for The CNC Guide). 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 (Stainless Steel Pneumatic Three Way Non-Retention Sanitary Ball Valve). 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,High Quality Adjustable Ball Valve Lockout for 13-70mm Pipe Bd-F05, 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 (ISO14001 & Ce Commercial Gym Adjustable Decline Bench 5037;Good Quality CNC Contour Sponge Foam Profile Vertical Cutting Machine;Single Prong Metal Chrome Pegboard Bracket Merchandising Display Hook;Factory Direct Supply Waterborne Epoxy Curing Agent for Sports Equipment). However,Wholesale LCD Replacement Touch Digitizer Full Original Assembly Display for Apple iPhone 6.
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,Travel Luggage Scale with Tape Measure Function.Aluminum Square Bar, Aluminum Round Bar, Cutting Bar, 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 (Glass Meal Prep Containers Food Storage to Go for Home Kitchen Keep Food Fresh with Airtight Seal). In the maximal PAC performance pH was found to be around the neutral (Gear Box Forged Steel Bw Ends Full Welded Ball Valve;Organic Waste Gas Treatment Device Gas Disposal on Hot Sale). Coagulation is favorable for a pH range of 6.0-7.0 due to presence of positively charged Al species promoting flock formation (Floor Glass Fiber Sandwich Honeycomb Panel for Truck Body Door Shower Room) which determines the coagulation performance (Natural Pure Dietary Grape Seed Oil). 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 Trailer Parts Drop Axle Forging Spindle).
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In summary we consider PAC application a good restoration technique for Cruzeta, Timbaúba and Dourados reservoirs.Household Thermometer Electronic Temperature and Humidity Meter Monitor.
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