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Frequently Asked Questions - Sampling Equipment
  • When should I use to draw my samples? Automatic Sampler vs. Grab Sampling?
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    • Collecting samples of water is commonly required as for permit compliance and process control. Samples of influent, effluent, wells, sludge, and so forth are used for laboratory testing procedures. Collection of the samples can generally speaking be per performed in 2 ways:
      Grab sampling: Single, individual samples that are collected at a specific spot or site over a short time span (typically seconds or minutes) - as defined by Standard Methods for Water/Waste Water, and tested separately. Special grab samples can be taken when unexpected COD/BOD loads are being detected etc. or where an automatic sampler is impractical Note: Some parameters require a grab sample; i.e. pH, chlorine, colifom, FOGs (Fats, Oils, Greases)
      Automatic Composite Sampling: specially designed devices that draw (pump) a specific volume of water into container over a period of time, independent of an operator.
      24 hour composite sampling (drawing a sample once an hour, every hour) is a common application. Unless the plant has 3 shifts, the only option is an automatic sampler.
      Regardless of the sampling process used, all samples are recommended to be tested as close to the time drawn as possible. Some parameters require analysis with specific time frames; i.e. BOD, coliform etc.
  • Do I need to cool my samples?
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    • Samples collected from a waste stream nearly always need some form of preservation in order to be used in further testing. Preservation, simply stated, means keeping a parameter in a sample from degrading or changing unfavorably from the state it was in when drawn.
      Some preservation techniques involve addition of chemicals, but the most universal form is cooling. If a sample must be held until finished, such as in a 24 hour composite, most common procedures indicate a temperature of 4 degrees C (39.2 degrees F) must be maintained in order for that sample to be usable. Freezing should not occur as this can damage or influence the water sample.
      Quickly collecting a grab sample and transferring to a refrigerator or cooler is common. Automatic samplers with built in compartments for ice are also common. For short-term storage, coolers packed with ice are generally acceptable. Keep in mind temperature will fluctuate, and will not be as constant as a refrigerator. Also, as the ice melts, possible cross contamination can occur if bottles are not sealed tightly and left to sit in ice water. It is never recommended to use dry ice as complications with off gassing and freezing may occur.
      Sampling with an automatic sampler that has an EPA recommended temperature setting of 4 degrees C would be the best option for proper temperature.
      Some applications do not allow for a large refrigerated sampler, such as sampling inside manholes.
      Contact USABLUEBOOK to discuss which procedure will work best in your application.
  • How do I decide what sampler to use or if I can use one?
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    • In order to choose a sampler that will fit your application properly many things must be considered.
      You local regulatory committee (EPA, DEQ etc) along with a copy of Standard Methods will aid in determining if an automatic sampler can be used. Depending on the test procedures that are intended for the sample, grab samples may be required.
  • What types of water can I use a sampler in?
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    • Samplers may be used in raw influent or treated effluent, water; industrial waste etc. There is no sampler that can fit into every single sampling application. However, most units targeted for the water/waste water industry will perform very well in either application.
  • How far away can I locate my sampler from the water I intended to draw?
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    • Most samplers will pull as expected up to 22 feet of head. Peristaltic samplers (those utilizing a pump with a “tube” that produces suction) will still function beyond that, but will generally require manual adjust of draw time and volume in order to obtain the proper “deposited” volume. Vacuum samplers work on a slightly more complicated principal, but can usually obtain draws of 28 ft of head or more before requiring manual adjustment.
  • Is there a difference between portable and stationary type samplers?
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    • Portable samplers, are exactly that, portable. They are samplers that are easily and readily movable. They are generally battery operated, but offer the option of AC power as well. Most portables do not offer refrigeration, but can be packed with ice or cooling packs. Stationary and All Weather Samplers are usually powered with 120vac, though some offer battery power and battery backups. They are not intended to be moved frequently. They do however offer a fully refrigerated compartment. Others offer a heating package to keep the controller and sampling line from freezing during winter months.
  • Should I use flow proportional or timed sampling?
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    • During different times of year, some applications will require flow proportional sampling. Other applications require samples to be drawn on a strict set time. (24 hour composite sampling for example.)
      To achieve flow proportional sampling most automatic samplers are equipped or offer an add on accessory that will accept an input signal from a flow meter. When the flow varies, the sampler will draw more or less of a sample over a specific time frame. This is helpful when rain events or heavy flows occur. This is also useful in helping to determine where new contaminates, or heavy BOD loads are coming from. (i.e. a local industry with private treatment plants emptying into a municipal sewer.)
      Timed sampling can be thought of as an average based over a specific time frame. Regardless of the flow rate, a timed sample will draw a specific volume at a specific time daily, hourly etc. This is very useful in determining long term trends, chemical feed rates, BOD loadings at various times of year etc.
  • How can I determine my sludge level?
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    • Determining when to waste sludge or determination of sludge blanket levels can be easily achieved by taking a “core sample”.
      Depths up to 25 feet can be sampled with a CorePro sampler. (Most other “core sampler” type products are not recommended for use above 20 ft.) To obtain a representative sample, simply keep the sampler in an upright position and allow it to settle to the bottom of your tank. Each section divided into 5 foot sections, with markers at each foot. This makes determining a sludge blanket level much easier.
      Once filled, remove the unit in an upright, hand over hand motion. As a 20-25 ft column of water can be unruly, you may need to secure the sampler, or utilize reinforcements close to the connections for each section. (Small pieces of angle iron or 2" x 4" zip tied near each connect can help.) After reading your blanket level, make sure the valve at the bottom is close to your tank, and release the water sample back to the tank.