Equipment and Supplies: Automatic pumping samplers--Tests of efficiency of Manning and ISCO samplers In Reply Refer To: November 28, 1980 EGS-Mail Stop 412 QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 81.06 Subject: Equipment and Supplies: Automatic pumping samplers-- Tests of efficiency of Manning and ISCO samplers Enclosed is a brief unpublished report of tests performed by the U.S. Forest Service, Redwood Sciences Laboratory, Arcada, California, of the Manning and ISCO pumping samplers. The tests indicate the importance of frequently checking the sampler efficiency of any pumping sampler that you may be using. We believe that sampler efficiency is reduced as the concentration of sandsize material increases. If the water-sediment mixture being sampled is mostly fine material, the sampler efficiency should be close to 100 percent. We believe that you should be aware of the potential for erroneous samples under some circumstances if either of these two samplers is used. Please distribute this memo to all District and research personnel who are working with pumping samplers or pumping-sampler data. R.J. Pickering Chief, Quality of Water Branch Enclosure Superseded memoranda: None. Key words: Water quality, sampling, samplers, pumping samplers. WRD Distribution: A, B, FO, PO. Pumping Sampler Cross Contamination Test Purpose The purpose of this test was to determine the response of two commonly used portable pumping samplers to sudden changes in suspended sediment concentration. The two samplers tested were: 1. Manning - model S-4050 as modified by the factory in the summer of 1980. (Modifications included a change in the electronics which control a pinch valve to empty the measurement chamber, and changes in the "plumbing" to improve the control of pressure and vacuum.) This is a pressure/vacuum sampler with an intake nozzle at the end of a 25' long - 3/8" i.d. plastic tube. The sampler is operated by a 12 volt battery. It was set to collect samples of about 260 ml with a velocity setting of 6 (line speed of 3.3 ft/sec) and a head of 4.2'. 2. ISCO model 2100. This sampler has a peristaltic pump, and 22' of 1/4" i.d. intake hose with nozzle. For the test a 110 volt battery charger replaced the 12 volt battery. The sample volume setting was 240 ml, the line speed was 5.0 ft/sec, and the suction head 6'. Experimental facility Lacking a flume, a 30 gallon plastic drum was fitted with a rack to support the intake of the sampler being tested. The intake was mounted vertically about 3 1/4 inches from the side of the drum with its center about 7 1/4 inches from the bottom. The drum was partly filled with a made-up water/sediment mixture which was kept in motion by a paddle mounted in a variable speed drill press. Immediately "in-front" of the sampler intake, a j-shaped reference nozzle - having the same i.d. as a DH-48 nozzle - was oriented into the flow, passed out through the wall of the drum, and was connected to a short piece of tubing outside which had a pinch valve to allow collecting reference samples simultaneously with the pumped ones. The water velocity in the drum at the nozzle location was about 1.8 ft/sec, as best that could be determined using a pigmy current meter. We are not very sure of this due to the velocity gradient from the center to the edge of the drum, and since the meter was used with its cups in a vertical plane. The "zero sediment" samples were taken from another 15 gallon drum containing tap water. The samples were, in turn, mounted at the upper end of a gently sloping ramp which held the hoses. Care was taken that the hoses led downhill all the way from the sampler to the nozzle. Data Collection The large drum was filled with 56.16 L of water and 56.16 g of sediment (less than 2 mm) taken from the stilling ponds at Caspar Creek. This made a nominal concentration of approximately 1000 mg/l in the drum as a whole. The paddle was operated for one minute before each sequence of 4 high sediment samples was taken (24 bottles in each sequence). A new water/sediment mixture was mixed for each batch of 24 bottles. The clear water drum was refilled for each batch. Two batches of 24 bottles were run for each sampler giving 48 samples total for each machine. Sets of 4 samples each were taken alternately in the high sediment and zero sediment drums starting with the high sediment. That is, for each sampler there were 6 sets of 8 sample patterns consisting of 4 high sediment followed by 4 zero sediment samples. The 4 samples at each sediment level were intended to show how many samples were required for a sampler to adjust to a new sediment level. The measurement chamber in the Manning sampler was rinsed before the test was begun. For the high sediment samples only, a reference sample was taken simultaneously with the pumped sample. The concentration in the clear water drum was assumed to be zero. Before sampling began for each batch, eleven 750 ml samples were removed from the high sediment drum while the paddle was rotating. After each pumped and concomitant reference sample (which together totalled about 750 ml) were taken, one of these 11 samples was returned to the drum to maintain the approximate volume and concentration. Standard gravimetric lab analyses were done on all pumped and reference samples.