Water Online

September 2014

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wateronline.com ■ Water Online The Magazine location, weather, and source water. At PWD, Jellison and colleagues replaced the biofilm sampler every two weeks simply to coincide with the EPA-approved filter sampling. As both the biofilm samplers and the filters were drawn from the watershed at the same time, results of the samples were compared. Samples were routinely taken in the source water prior to entering the intake of the PWD water treat- ment plant (WTP) and from a location farther upstream. Over the course of a full year (July 2013 to July 2014), the frequency of detection was remarkably similar (see Table 1). This comparison study suggests that, with regard to oocyst detection, the biofilm method is on par with the EPA- approved filter method. The pilot project did not include the seeding of oocysts and therefore does not speak to the variability of recovery — an established flaw with the filter method, but a complete unknown with the biofilm method. Volume concentrations of the water passing through the biofilm sampler are another unknown. It's because of the many as-yet unknowns that Jellison calls biofilm sampling a "long way" from becoming EPA- approved. Outside of LT2 testing, however, biofilm samplers can have significant impact. "It's cheaper, so you can sample in more locations at a higher frequency, over longer spans of time, and really understand where the sources of crypto are in your water- shed," summarized Jellison. In other words, instead of the snapshot image, water qual- ity managers can now get the big picture. By obtaining rela- tive data on oocyst concentrations — where and when they appear — mitigating actions such as source water protection plans or the installation of best management practices (BMPs) can be developed in areas where they will be most effective. How To Build A Biofilm Sampler To start monitoring oocysts and the threat of cryptospo- ridium in your own watershed, you need only a sturdy container and standard microscope slides. The container will need two open sides to permit water flow, as well as slots to hold the slides in place; mesh or a similar material should also be used to cover the open sides and prevent large debris from breaking the slides (see Figure 1). The PWD team utilized two weighted PVC pipes to keep the units submerged in the watershed (see Figure 2), but they collected samples from the source water just prior to the WTP intake by hanging the biofilm sampler from a rope off a dock. Once the biofilm sampler is retrieved, the slides are sim- ply scraped to remove the biofilms; by contrast, the second step of the standard method requires the filtered content to be eluted. The remaining steps are exactly the same as with the filter method under EPA Method 1623: immunomagnetic separation (IMS) followed by immunofluorescent micros- copy (IFA) — steps familiar to any utility that has done previ- ous crypto/LT2 monitoring. The Future Of Crypto Detection The next step on the road toward validation for the biofilm filter is to have more utilities try it out in the field to help gather information, work out the kinks, and develop best practices. A sticking point, so to speak, is how biofilms behave in different areas. "Is any biofilm going to be equally sticky for cryptosporid- ium, or are there specific things about the biofilm that make crypto more or less likely to attach? That's what we need to figure out," Jellison explained. She has already made some inroads, finding that "rough" biofilms catch more oocysts than smooth ones, as they tend to get caught in the crevices. Ultimately, she hopes to develop a synthetic surface that can be used anywhere, with a known attachment efficiency. Until then, she welcomes the participation of others and is optimistic that there will be benefit for other "do-it-yourselfers." "I think it's absolutely worth trying," she said. "And based on what we see here [in Philadelphia], I think it will give good information. If other people want to use it in their watersheds and share their findings, I see that as a really useful collaboration on both ends." For more information (or collaboration), contact Kristen Jellison at kjellison@lehigh.edu. Reference McCuin, R.M. and J.L. Clancy. 2003. Modifications to USEPA methods 1622 and 1623 for detection of Cryptosporidium oocysts and Giardia cysts in water. Applied and Environmental Microbiology 69:267-274. Feature 32 Water Source Biofilm Sampler 46% positive (18/39) Filter (EPA) Method 43% positive (17/40) Table 1. The biofilm sampler and EPA-approved filter method returned a similar frequency of oocyst detection at two collection points. Figure 1. The simple construction of the PWD biofilm sampler includes slots for six slides and protective mesh siding. Figure 2. Weighted PVC pipes help keep the biofilm samplers in place.

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