Jar tests

Vacuum filters are usually simulated with a Buchner funnel test or filter leaf test (54). The measured parameters are cake weight, cake moisture, and filtration rate. Retention aids are usually evaluated using the Britt jar test, also called the Dynamic Drainage Jar, which simulates the shear conditions found on the paper machine and predicts performance (55). 

The design of the sludge-blanket clarifiers used primarily in the water industry is based on the jar test and a simple measurement of the blanket expansion and settling rate (12). Different versions of the jar test exist, but essentially it consists of a bank of stirred beakers used as a series flocculator to optimize the flocculant addition that produces the maximum floc-setfling rate. Visual floc-size evaluation is usually included. 

Researchers had noted the release of formaldehyde by chemically treated fabric under prolonged hot, humid conditions (85,86). The American Association of Textile Chemists and Colorists (AATCC) Test Method 112 (87), or the sealed-jar test, developed in the United States and used extensively for 25 years, measures the formaldehyde release as a vapor from fabric stored over water in a sealed jar for 20 hours at 49°C. The method can also be carried out for 4 hours at 65°C. Results from this test have been used to eliminate less stable finishes. 

Control of Formaldehyde Release. Once the sealed-jar test became a factor in measuring the formaldehyde release of fabrics suppHed to garment cutters, limitations were placed on the allowable limits acceptable to the garment producers. These limits brought to the fore two classes of reagents those based on DMDHEU, and those based on the /V, /V- dim ethyl o1 ca rh am a tes (4) (88). 

Figure 46. Settling curves obtained from jar tests.

Zeta potentials of floe produeed in the plant may also be measured as a means of eontrol. The zeta potential value for optimum eoagulation must be determined for a given wastewater by aetual correlation with jar tests or with plant performance. The control point is generally in the range of 0 to 10 millivolts. If good correlations can be obtained between some zeta potential values and optimum plant performance, then it is possible to make rapid measurements of particle charge to compensate for major variations in wastewater composition due to storm flows or other causes. 

Reactions between alum and the normal constituents of wastewaters are influenced by many factors hence, it is impossible to predict accurately the amount of alum that will react with a given amount of alkalinity, lime, or soda ash which may have been added to the wastewater. Theoretical reactions can be written which will serve as a general guide, but in general the optimum dosage in each case must be determined by laboratory jar tests. 

In the Jar Test , an initially uniform, homogeneous suspension of partieles slurries settles out under the foree of gravity into distinet zones, as illustrated in Figure 2.6. 

Figure 2.6 Sedimentation zones during slurry settling (The Jar Test ). A, initial uniform concentration, B, zone of increasing concentration, C, sediment or sludge, D, clear liquor...

The settling rate and settling time ean be estimated using e.g. the Riehardson and Zaki equation (2.42). For slurries of irregular partieles, however, the assumptions in the eorrelation are exeeeded and the settling rate then beeomes more diffieult to ealeulate. Consequently, the Jar Test (see Chapter 2) is frequently used to determine R and /r in praetiee. 

Probe-zleben, n. sampling, -zieber, m. sampler. -zinn, n. standard tin. -zylinder, m. trial jar test tube. 

As with alum, it is necessary to conduct jar tests to identify the most suitable product and optimum application rates, pH level, and so forth. Testing with ferrous sulfate typically requires a starting point application level of around 50 ppm (as 100% active product), while ferric sulfate requires around 25 ppm (as 100% active product). 

Use jar tests to determine the most suitable types of polymers and potential application rates. Tests must be conducted on-site with fresh, representative water samples and fresh reagents. 

A guide for jar testing polymer samples is first, a rapid mix of 1 to 3 minutes at 80 to 200 rpm to evenly distribute the polymer and provide energy for coagulation. Second, a slow mix of 2 to 5 minutes at 25 to 40 rpm to allow the floe to build up. Third, a settling period of 2 to 5 minutes with little or no mixing to permit floe settlement. 

Evaluate jar tests on a 0 to 10 rating (10 = optimum result) for clarity, floe size, and settling rate, with the control given a rating of 5 for each area. 

Fig. 10. Diagram showing the efficiency of an organoclay in removing different mineral oils from water, using the jar test or single-point isotherm. After Alther (2002).

Jarlite, 2 3641 meta-Jarlite, 2 364t Jar molding, 12 732-733 Jarosite process, 26 567-568 Jar test, 22 56... 

Laboratory-scale test procedures consisting of jar test studies have been used for years, and the test methodology developed is such that full-scale designs can be developed from these studies with a high degree of confidence. A jar test is a series of bench-scale laboratory procedures made on 1- or 2-1 water samples to determine the most effective water treatment method. Tests are performed to identify the most effective coagulants, optimum dosage, optimum pH, and most effective order in which to add various chemicals. 

Schematic representation of coagulation observed in jar tests using aluminum(III) or iron(III) salts at constant pH.

An improvement in the flocculation ability of the purified cationic lignin ether due to an increase in the molecular weight is clearly seen in Figure 5. The same figure reveals a moderate gain in the flocculation performance relative to Praestol 41 IK when the cationic lignin ether had 3.4% N instead of 2.9% N as in the jar test shown in Figure 3a. 

Spread out thinly and allow to continue to air dry. The leaves will absorb the residual liquid. Allow to air dry thoroughly until free of all solvent odor and if possible until dry to the touch. Break up any clumps. Finally, the extract should be spread out thinly on an oven proof plate and placed in a 150 to 170 degree F oven for an hour. Exposure to this temperature will not destroy salvinorin but should remove any residual traces of solvent. The oven door should be cracked open an inch during this final desolventing . Store in a sealed jar. Test by opening the jar after a day and smelling. If a solvent odor is present there is still residual solvent in the material and further drying is required prior to use. 

Bottle/jar tests do have limitations. It can be difficult to reproduce the actual process temperature, pressure, and flow conditions, so in some cases the results may not scale-up to actual operational conditions. Mikula and Munoz [68] show the differences in jar test performance that can result from wall effects alone. 

Beyond the bottle/jars tests and their acceleration by centrifugation, other methods have been applied to the study of emulsion stability including [100-102] ... 

Emulsions An empirical test in which varying amounts of a potential demulsifier or coagulant are added into a series of tubes or bottles containing sub-samples of an emulsion or other dispersion that is to be broken or coagulated. After some specified time, the extent of phase separation and appearance of the interface separating the phases are noted. This test has many variations. For emulsions, in addition to the demulsifier, a diluent can be added to reduce viscosity. In the centrifuge test, centrifugal force can be added to speed up the phase separation. Other synonyms include jar test, beaker test. 

Water treatment A standard test method in which either the coagulant dosage is varied or the solution pH is varied for a given coagulant dosage, to optimize the coagulation of solids. Frequently termed jar test . 

---