First-flush sample

In urban areas, sampling strategies for storm water runoff from industries and municipalities are of specific importance. The United States Federal Storm Water Regulations of 1990 specify protocols for such storm water nmoff sampling. These regulations define two separate samples that must be collected when a storm occurs. A first-flush sample is to be collected during the first 30 min of the storm event. A flow-weighted composite sample must be collected for the entire storm event or at least the first 3 h of the event [8]. 

The first-flush sample and the flow-weighted composite sample must be analyzed for the pollutants listed in Table 1.3. In general, the sample volume required for laboratory analysis depends on the particular pollutants being monitored and varies for each application. As a general rule, a 3 L sample volume for both first-flush and flow-weighted composite sample usually is sufficient for the majority of applications [8]. 

In operation, a spark source is normally first flushed with argon to remove loose particulate matter from any previous analysis. The argon flow is then reduced, and the cathode is preheated or conditioned with a short bum time (about 20 sec). The argon flow is then reduced once more, and the source is ran for sufficient time to build a signal from the sample. The spark is then stopped, and the process is repeated as many times as necessary to obtain a consistent series of analyses. The arc source operates continuously, and sample signal can be taken over long periods of time. 

A qualitative measure of the corrosion rate can be obtained from the slope of the curves in Fig. 2. Z INT is given in units of s ohm" . Owing to the presence of the uncompensated ohmic resistance and lack of values for Tafel slopes [Eq. (2)], data in Fig. 2 should be viewed as indicative of significant changes in corrosion rates. Corrosion loss remained low during the first 2 months, followed by a large increase for both flushed samples and controls. The corrosion rate increased when the surface pH reached values of 1 or less. Total corrosion loss as determined from integrated Rp data was less for the control than for the flushed sample. 

Fecal coliform density reached extremely high levels in Terrieu Creek and both wells directly after the creek began to flow and again several days later (Fig. 3b). The first peak in bacteria in Terrieu Creek coincided with the TSS peak in the first flush of streamflow. The second increase occurred when creek flow slowed and the water began to pond, peaking just before the creek ceased to flow. Samples of ponded water were not collected after cessation of flow. 

There is still room for art in this style of catalyst development. It will usually come up in the first flush of the discovery of a new catalyst, when major effects are visible from sample to sample. Moreover art or intuition will normally guide the creativity of the researcher in making decisions requiring judgment. However, the refinement and rational design of previously optimized catalyst formulations, those well established in industry, will surely best be done on the basis of good science. 

NOTE A sample taken by the consumer cannot be considered a true random daytime sample, as the consumer is likely to take a sample with extreme stagnation time (either a first draw sample or a fully flushed sample). 

Corrosion losses remained low during the first two months followed by a large increase for both the flushed sample and control. Increased corrosion rates of embedded steel electrodes occurred when surface pH reached values of 1 or less due to accumulation of sulfuric acid (H2SO4). 

The determination of radium by the emanation method is based on the production of radon as a decay product of radium. From a liquid sample, the radon is first flushed out with a carrier gas. The end of the flushing is taken as the starting time for fresh radon accumulation in the sample. After a suitable time, the radon reaches equilibrium in the sample... 

Do YOU USE THE WATER IMMEDIATELY OR DO YOU LET THE WATER RUN FOR AWHILE FIRST (If water lead levels are elevated in the FIRST FLUSH, BUT LOW IN THE FLUSHED SAMPLE, RECOMMEND FLUSHING THE WATER AFTER EACH PERIOD THE WATER HAS REMAINED STANDING IN THE PIPE FOR MORE THAN 6 HOURS.)... 

Test water (first-draw and flush samples). 

Table 3.15 Speciation of lead in two first flush tap water samples (based on [34]).

The appropriate sample volume depends on the elements or substances required to be analyzed on their expected concentration in the sample and on the required quantification limits. For trace metal analyses sample volumes of about 100 mL are sufficient in most cases. For the analysis of organic chemicals (e.g., pesticides) 1 L samples are commonly used. A 3 L sample volume has been suggested for both first-flush and flow-weighted... 

First-Flush Grab Sample Flow-Weighted Composite Sample How-Weighted Composite Sample... 

A 1.2.7 Steps A1.2.S and A 1.2.6 are repeated three times for a total of four sampling, each taking 10 to IS mL of the sample. The first three samplings are used to flush the system clean. The fourth sample is held in the expansion chamber to thermal equilibrium. 

K a sample is taken through this valve, first flush out 1-5 gal of TDI (for proper disposal procedure, see Handling Spills and Leaks below). Flushing ensmes that a representative sample is being taken. This is particularly important in determining if aromatic polyurea or dimer (white precipitate) is present. 

Another example of multi-column analysis has been demonstrated for the determination of impurities in styrene. The marked compounds in the styrene sample (Figure 12.15(a)) were solvent flushed via a splitline, with the analysis being carried out with a cryotrapping separation (CTS) (see Figure 12.15(b)). The first column, was an Ultra-2 (25 m X 0.32 mm i.d., d( = 0.25 p.m) precolumn, while the main column was a DB-WAX (30 m X 0.32 mm, d = 0.25 p.m) with an FID being employed as the detection system. 

A prepolymer is made first by charging Pluracol E2000 [1000.0 g, 1.0 eq., poly(ethylene oxide), 56 OH, BASF] to a suitable container equipped with a mechanical stirrer and a nitrogen gas inlet. Flush the container with dry nitrogen and add Desmodur W (264.0 g, 2.0 eq., 4,4 -methylene-bis(cyclohexyl isocyanate), 31.8% NCO, Bayer). While maintaining a positive N2 pressure on the reaction mixture, stir and heat at 80°C for 2 h. Cool the product to room temperature and check the NCO content (theory = 3.32 %). It might be necessary to warm the highly viscous prepolymer to take samples for titration. To a portion of this prepolymer (250.0 g, 0.2 eq.), add Dabco T-12 (0.25 g, dibutyltin dilaurate,... 

Accessibility to Cu sites was determined by temperature programmed desorption of NO (NO TPD), using an experimental setup similar to that used for TPR, except the detector was a quadrupole mass spectrometer (Balzers QMS421) calibrated on standard mixtures. The samples were first activated in air at 673 K, cooled to room temperature in air, and saturated with NO (NO/He 1/99, vol/vol). They were then flushed with He until no NO could be detected in the effluent, and TPD was started up to 873 K at a heating rate of 10 K/min with an helium flow of 50 cm min. The amount of NO held on the surface was determined from the peak area of the TPD curves. 

---