Flocculators VELP Scientifica has developed a complete line of instruments to support the lab technician working in the environmental sector and for the separation of pollutants in waste-water treatment plants. FP4 Portable Flocculator Portable flocculator that allows standard conditions to be adopted for jar test, that are the basic requirement for reproducible results. Flocculators, or jar testers, are designed for a range of applications — Testing the efficiency of flocculation or precipitation agents — Leaching test, made on solid wastes to be sent to the dump that uses diluted acetic acid or carbon dioxide-saturated water to detect the presence of toxic heavy metals — ASTM D c method Jar testing entails adjusting the amount of treatment chemicals d the sequence astn which they are added to samples of raw water held in jars or beakers The sample is then stirred so that the formation, development, and settlement of floc can be watched just as it would be in the full-scale treatment plant Why perform a jar test? This standard is not included in any packages.
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All polyelectro- lytes are classified anionic, cationic or nonionic, depending upon their composition. These aids may have the ability to produce large, tough, easily-settled floc when used alone or in conjunction with inorganic coagulants.
A small dosage under 1 mgIL may permit a reduction in the dosage of, or complete elimination of, the coagulant. In the latter case, the polyelec- trolyte would be considered the prime coagulant rather than a coagulant aid. Aids come in powdered and liquid form. Powdered aids should be prepared as 0. Always add powdered aids to the dissolving water rather than the reverse, and add slowly to the shoulder of a vortex created by stirring.
If a vortex is not formed, the dry powder will merely collect on the surface of the water in gummy masses and become very difficult to dissolve. Dissolving time may vary from several minutes to several hours. Liquid forms can be readily prepared to the above strength without difficulty. Procedure As many sample portions may be used as there are positions on the multiple stirrer. Locate beakers so that the paddles are off-center, but clear the beaker wall by about 6A mm V4 in.
Record the sample temperature at the start of the test. Use one rack for each series of chemical additions. Make up each tube in the rack to a final volume of 10 mL, with water, before using.
There may be a situation where a larger volume of reagent will be required. Should this condition prevail, fill all tubes with water to a volume equal to the largest volume of reagent in the reagent rack.
When adding slurries, it may be necessary to shake the rack to produce a swirling motion just prior to transfer. Add the test solution or suspensions, at predetermined dosage levels and sequence. Flash mix for approximately 1 min after the additions of chemicals. Record the flash mix time and speed rpm.
Slow mix for 20 min. Record the time for the first visible floc formation. Every 5 min during the slow mix period , record relative floc size and mixer speed rpm. If coagulant aids are used, mixing speed is critical because excessive stirring tends to break up early floc forma- tion and may redisperse the aid. Record the time required for the bulk of the particles to settle. In most cases this time will be that required for the particles to settle to the bottom of the beaker; however, in some cases there may be interfering convection currents.
If so, the recorded settling time should be that at which the unsettled or residual particles appear to be moving equally upward and downward. Record the sample temperature. By means of a pipet or siphon, withdraw an adequate sample volume of supernatant liquor from the jar at a point one half of the depth of the sample, to conduct color,5 turbidity, pH and other required analyses, Note 1 determined in accordance with Test Methods D or D for turbidity and D for pH.
A suggested form for recording results is appended see Fig.