Beaker Screening Tests

Two methods of capsule formation were employed static beaker tests and atomizer screenings. In the beaker tests, which comprised the first phase of the screening (Step 2 of Fig. 1), a small volume of inner polymer solution was extruded from a Pasteur pipette as a droplet (nominally 2-3 mm) into a receiv- 

Permeability measurements have also been described elsewhere. 

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In the screen tests, each coagulant or flocculant is added to the beaker samples of representative slurry or hquor in a dropwise fashion, while the sample is mixed with a spatula, stirrer, or 3-6 jar stirrer mechanism. The amount of coagulant or flocculant required to initiate floe particle formation is noted along with relevant notes as to the size of the floe, capture of fines, resultant liquor clarity, and stabihty of the floe structure. The dosage is typically noted in g/t solids if the sample is primarily solids (thickener design), or in mg/L liquor if the sample is primarily for clarification and the solids concentration is low. 

Screening tests are used to determine the best chemical and its approximate dosage. It is usually convenient to use small, graduated beakers and sample quantities in the range of 50 to 150 mL. The chemical may be added with a syringe or medicine dropper and a note made of the quantity used, together with the results. The experimenter should filter and wash the flocculated sample on any convenient, small. 

Two sets of equipment were used for coagulation experiments - a conventional jar testing apparatus with six 500 mL cylindrical beakers with an overhead stirrer each, and a Heidoloph RZ R2021 overhead stirrer. The paddle was identical for both stirrer types (1 cm by 4 cm rectangular plate). The jar tests were used for screening tests and MF experiments. In that case the FeCl r was added from a 20 mM (5.4 gL FcCls 6H2O) stock solution, the soludon was then rapidly mixed at 100 rpm for 2 minutes and then at 25 rpm for 20 minutes. The method was adapted from Dennett et al. (1996). 

Gelation is a complex process affected by many variables. There is a need for simple, yet quantitative screening tests to evaluate a large number of samples and to predict performance of gel systems prior to the more difficult and time consuming core tests. We have developed beaker tests for gel time, gel strength and gel stability. 

There are two basic types of aquatic single-species toxicity tests acute and chronic. Acute toxicity tests have been the workhorse of aquatic toxicologists for many years. These tests are relatively simple, take little time, and are cost-effective. A large historical database exists for many chemicals and effluents. Acute toxicity tests are most often used to quickly screen toxicity or to determine the relative sensitivities of different test species. Mortality is the effect monitored during the test duration of 48 h (invertebrates) or 96 h (fish). In a typical acute toxicity test, 5-10 organisms are exposed under static conditions in glass test beakers to five test concentrations. A control is included. The experiments with test concentrations and control are conducted in triplicate. Daily observations are made on survival, and dead organisms are removed. 

Examples of comparative gel tests with a hydrolyzed polyacrylamide are presented below. The screening experiment discussed above indicated that polymer molecular weight and salinity are important in the gel reaction. The comparative tests are used to define the magnitude of these variable effects. In addition, the results demonstrate the usefulness of the simple beaker tests described earlier. 

Selected systems have been studied to compare the trends observed in beaker tests to core performance. If correlations can be developed between beaker test measurements and core test results, the screening of polymer/crosslinker systems can be expedited. These tests would ideally... 

Vastly different methods are available for cultivation of biofilms. Basically, these can be described as either batch-mode or continuous mode methods. In batch studies, growth substrata in the form of coupons or glass slides are placed in e.g. Petri-dishes or other holders filled with medium. Under the action of undefined shear forces, investigations in so-called beaker reactors are conducted. A further test system which operates in batch mode and continues to become prominent is the miniaturized test system comprising microtitre plates, in which 96 wells enable the simulation of various experimental conditions simultaneously under static conditions (Geneveaux et al., 1996 O Toole et al., 1999). In general, biocide tests in batch systems are simpler to run, have shorter durations, and are very simple to carry out. Therefore, they are well-suited for initial comparisons or screenings of different biocides, or different concentrations and contact times of a particular biocide. 

One PVC disk and one test animal were placed in glass beakers filled with seawater. Each beaker was covered with fiberglass screen to prevent the animals from escaping and then placed back into flowing seawater. Individual animals were allowed to feed until about 50% of either pellet on a disk was consumed. Remaining portions of treatment and control pellets were cut away from the disk at the Velcro interface and weighed to determine loss to consumers. Controls to account for variance in pellet mass unrelated to the activity of the consumers were also conducted the mass of treatment and control pellets not exposed to consumers did not differ. This method was used with hermit crabs, shrimp, and a gastropod. 

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