Running the OUR test is quite simple to do but it does take some relatively sophisticated and expensive laboratory equipment. I use Hach instruments exclusively. I have no personal or professional connection to Hach, but, as an actual user, I cannot speak highly enough about the Hach field equipment I use on a frequent basis. Over the years the equipment discussed and shown here has proven to be extremely reliable and durable, and I ship these instruments back and forth across the United States many times each year. All of the test equipment you need to run OURs in the field is detailed below with photos and pricing provided. Everything you see here can be purchased from Hach (www.hach.com) with the exception of the magnetic stirrer which I buy through Amazon (www.amazon.com).
The Hach HQd Field Case is shown in Figure 1 and I highly recommend this case if need to travel. Really, the case is worth it even if you don’t travel because it provides storage and protection for your OUR meter and probes when not in use. This case measures approximately 15.5-in (long) x 7.5-in (wide) x 7.5-in (height). It houses most of what you need but not all since you also need BOD bottles and a magnetic stirrer. The top half of the case shows two LDO probes and the bottom half shows a Hach HQ30d hand-held meter. LDO stands for luminescent dissolved oxygen. In this case it refers to Hach’s membrane-free luminescent optical DO probe which provides very accurate, trouble-free operation.
Figure 1: Hach HQd Field Case for Portable OUR Test Equipment
The complete setup needed for doing oxygen uptake rate testing is shown in Figure 2. Any magnetic stirrer will do. The one shown below is a portable unit that gets packed up in a separate case so that I can travel easily with all of this equipment. Note the photo shows a glass BOD bottle but I travel with several of Hach’s plastic, disposable BOD bottles.
Figure 2: OUR Test Equipment
Equipment pricing is provided in Table 1 (updated periodically but you’ll have to confirm pricing for yourself because it is always changing). As I said, I use the plastic, disposable BOD bottles. If you don’t travel you may prefer the reusable glass BOD bottle and the part number and cost for that is shown. I offer two different magnetic stir bars and which one you use doesn’t matter. But you do need the MLSS in the BOD bottle to be completely mixed for the duration of the 15-minute OUR test and a stir bar is required. Do not rely on the tiny stirrer at the end of the LBOD probe itself. It is too small to provide the required degree of mixing for the test. About once a year, perhaps longer, you will need to replace the sensor in your LBOD probe and that item is shown as well. Finally, you can buy the rugged, small Hanna magnetic stirrer or you can use any larger, lab-quality stirrer that you might already have. I like the Hanna because of its size and weight, both of which make it easy to travel with.
Table 1: OUR Test Equipment Pricing
Note: If you want to make your ordering easier, by getting everything from Hach, including the magnetic stirrer, Hach does offer two lab-quality stirrers. The 4 x 4-in unit is $351 and the 7 x 7-in unit is $368. Clicking on the link for either unit will open up a PDF document from Hach with more information including the part number and price.