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Safety of Rainwater for Irrigation
16 Plays2 years ago
What are the food safety risks of using harvested rainwater? In this episode, Mariel Borgman and Micah Hutchison talk with Dr. Rachel Rosenberg Goldstein about her research on harvested rainwater quality and whether or not it's safe to use for irrigation.
Additional Resources
Rachel's article on harvested rainwater quality from a first flush system:
https://www.sciencedirect.com/science/article/abs/pii/S0048969722040736?via%3Dihub
WOW lab website: https://sph.umd.edu/research-impact/laboratories-projects-and-programs/water-quality-outreach-and-wellness-wow-laboratory
Video showcasing harvested rainwater use in Baltimore City urban agriculture: https://youtu.be/r5rXSyu5J0c
Webinar series for Baltimore City Agricultural Irrigation Water Quality Project:
- Water Quality and Food Safety, Nov 16, 2022 07:00 PM Eastern Time (US and Canada)
Register in advance for this meeting: https://umd.zoom.us/meeting/register/tJ0ude6sqDMpGteyNMG57Xu3eSodOAsRNauW - Water Treatments, Nov 29, 2022 07:00 PM Eastern Time (US and Canada)
Register in advance for this meeting: https://umd.zoom.us/meeting/register/tJIvc--opzIuHtAWgnjG3ClrqW5KqJ8agKfu - Rainwater Harvesting at Baltimore Farms, Dec 8, 2022 07:00 PM Eastern Time (US and Canada)
Register in advance for this meeting: https://umd.zoom.us/meeting/register/tJUpd-6grj8iHdM_g3PAz5YdaTTWyrgFVY_2
Funding for this podcast was made possible in part by the Food and Drug Administration through grant PAR-16-137. The views expressed in the posted materials do not necessarily reflect the official policies of the Department of Health and Human Services, nor does any mention of trade names, commercial practices or organization imply endorsement by the United States Government.
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Transcript
Introduction to Produce Safety
00:00:00
Speaker
Hello, and welcome to the Agri-Food Safety Produce Bites podcast, where we discuss all things produce safety and dive into the rules and regulations surrounding the Food Safety Modernization Act Produce Safety Rule.
FSMA Rule with Micah Huncheson
00:00:13
Speaker
My name is Micah Huncheson. I am a produce safety technician located in the Genesee Conservation District, and I work in Southeast Michigan with fresh produce growers on the implementation of the FSMA Produce Safety Rule.
Community Food Systems with Mariel Borgman
00:00:28
Speaker
I'm Mariel Borgman with Michigan State University Extension. I'm a community food systems educator, and I work in the Southwest part of the state. And I do a lot of different things related to food systems, but food safety is kind of a topic that weaves its way through all of those things.
Water Quality with Rachel Rosenberg Goldstein
00:00:45
Speaker
My name is Rachel Rosenberg Goldstein, and I'm an assistant professor in the Maryland Institute for Applied Environmental Health.
00:00:54
Speaker
at the University of Maryland School of Public Health. And I'm also the director of the WOW Lab, which stands for Water Quality Outreach and Wellness. And I do research mostly on water quality and effectively communicating about water quality to communities.
Significance of Rainwater in Urban Agriculture
00:01:14
Speaker
Yeah, so today we're here to talk about rainwater, and we're going to specifically talk about rainwater from the context of urban farmers.
00:01:22
Speaker
and the significance of rainwater for urban agriculture and talk a little bit about what we know from the science around produce safety and compare that to kind of some of the general understanding of rainwater and kind of talk about what that all means for growers in urban areas. Micah, how have you seen urban farmers using rainwater in growing produce? I mostly see rainwater collection in growing produce for like the irrigation needs of the farm.
00:01:53
Speaker
Yeah, typically for irrigation, and I would say a lot of the time it's sort of a supplemental or additional source. I've seen few farms that have that as their sole source for water on the farm, but it's typically used or collected off of a hoop house or something like that on the farm. Have you seen that as well? Yeah, I've
Cost Benefits of Rainwater for Urban Growers
00:02:15
Speaker
seen a lot of hoop house collection as well as just standalone collection units.
00:02:22
Speaker
How do those standalone collection systems work? So what I've seen most frequently is the model utilized by Keep Growing Detroit, where you have a standalone structure. So something that has four posts and a roof that is slanted. There's gutters on the back of the structure where rainwater is then collected into barrels. Interesting. I don't think I've seen a system like that.
00:02:49
Speaker
Marielle, how important is rainwater to your growers? Yeah, so I would say it's important not
Rainwater: Challenges and Viability
00:02:56
Speaker
only as a supplemental source for irrigation water, but more in principle than anything. The cost of water is an issue. Urban growers have to pay the same cost to use water as
00:03:11
Speaker
household and those bills can add up really quickly. And obviously for agricultural uses, especially when we have times of drought, you're using a lot more water than an average household would to irrigate your crops. And if you need to use water for any other purposes like wash packs, sprays, et cetera, we know there are many, many uses for water on the farm so that rainwater can really help supplement and offset some of those costs.
00:03:38
Speaker
Additionally, many of the growers have values around conservation of resources, environmental sustainability, and so collecting rainwater as a way of practicing conservation is really important as well. Have you seen other areas of importance in your
Rainwater Contamination Risks under FSMA
00:03:59
Speaker
work, Micah?
00:03:59
Speaker
I think what I see the most and what I hear the most are definitely related to what you said earlier with cost. Locally in the community I live in, we have the option to rent hydrant meters from the city of Flint, but the initial cost for any grower
00:04:17
Speaker
is $600. Also, I've seen a lot in Southeast Michigan urban areas, there isn't a lot of access available to growers. Not every community has the option to rent a hydrant. So rainwater helps alleviate some of those access issues. Absolutely. That's something I've seen in Kalamazoo recently working with an urban grower there. It took a full growing season to get water hooked up to the site.
00:04:46
Speaker
So she did eventually have access, but it was a whole season before that was installed. So really relying on some of those other sources of water, whether that's rainwater or bringing in water from offsite or borrowing from a neighbor, these are all strategies that urban growers are employing to irrigate their crops. Okay, so Micah, what has been the general understanding of the risk level of this practice among growers and service providers? How risky have we thought rainwater to be?
00:05:17
Speaker
Mariel, I don't know about you, but since working in produce safety, I've assumed that the risk level of the practice was pretty high. The rain barrels I've seen a lot with screens, no solid protection. So it was my understanding that if a bird pooped on the screen or some other animal that contaminated all of the rainwater, making it riskier to use, what is your understanding, Ben?
00:05:43
Speaker
Yeah, same here. I would say in the produce safety circles, it's been thought of as pretty risky for those reasons that you stated. I think in general growers that I've talked to seem to think of it as less risky. But once they've gone through some produce safety trainings, I think that that has changed their mind a little bit. So I think there's definitely this pre-existing knowledge that it may be more risky in both of those communities. So how would
00:06:12
Speaker
the FSMA produce safety rule classify rainwater as you interpret it. Yeah, so I've always interpreted it as surface water because it's not a closed loop system coming directly from a well as you would have with groundwater or a municipal system. And so it really kind of falls into that surface water category.
00:06:34
Speaker
Essentially too, as you had mentioned, a lot of those units are kind of open to the environment. They maybe have a screen on top or some kind of filter, but it definitely is open to the environment. So really putting it in that surface water category has made the most sense in terms of FSMA. I agree. I definitely talk with growers about treating any rainwater they've collected as surface water. So mainly like
00:07:02
Speaker
using it to irrigate crops, not using it in post-harvest activities, drip if possible, reducing any contact with the harvestable portion of the crop, because I've assumed it's introduced a big risk. Yeah, so Rachel, what pathogens of human health significance could there be in rainwater? Yeah, so it's a great question because there is so much interest in harvesting rainwater and using it.
00:07:32
Speaker
for irrigation, just more generally, but also for urban agriculture. And we want to make sure that if we're using a water source that we have some idea about how risky it can be.
00:07:46
Speaker
When we think about rainwater, we're less concerned about rainwater just as it falls from the sky. There could be pathogens that are aerosolized and in that water, but really the work that I do is focused on rainwater that's collected from a surface. So the risks there are that there could be, as you mentioned, ec's on the surface. If we think about roofs or hoop houses, you know, a bird poops,
00:08:15
Speaker
on the surface then the rainwater as it runs along that surface and is collected could pick up some of those feces which could potentially have pathogens in it. And when we think about feces we're really talking about things like enteric pathogens so
00:08:32
Speaker
bacteria and other microorganisms that can live in the guts of animals. So this is something like E. coli is a common example of an enteric pathogen. We also know that when we talk about birds, in particular salmonella is endemic in bird populations and it's also a leading cause of foodborne illness. So that's something that we need to really evaluate.
00:09:00
Speaker
Yeah, those are some of the common ones we bring up in a lot of our food safety training. So they should be familiar to our listeners. Yes. So Rachel, how have you applied your research to reclaimed rainwater used for irrigation? Yeah, so through my
Recommendations for Safe Rainwater Use
00:09:17
Speaker
WOW Lab, we have the RAPER program, which stands for
00:09:21
Speaker
rooftop runoff irrigating produce eaten raw. And this program or project really started because farmers in Maryland were asking us if it was safe to use harvested rainwater to irrigate their produce. And when we looked at the literature, this started back in about 2018. There really wasn't that much in the literature showing what the risk was or what type of pathogens might be in.
00:09:49
Speaker
harvest rainwater. So we started by doing a pilot project at a site in Frederick, Maryland, that was already collecting rainwater from a roof surface and using a first flush diverter. So taking the first volume of water coming off the roof and discarding that and then using the rest of the water to irrigate some raised vegetable garden beds. And we actually just published the results of that study this past June.
00:10:20
Speaker
And the good news is that we didn't find any salmonella or listeria monocytogenes, which were two pathogens that we were looking at. We didn't find either of those pathogens in the water that was being harvested. We also, we took it one step further. We wanted to look at possible pathogens and E. coli in the soil that was contacted by that water and the produce being grown with that water.
00:10:48
Speaker
The good news is that when we looked at E. coli, all of the average E. coli for all of our harvested rainwater samples were below the good agricultural practices guidelines and also, you know, the FISMA standard of 126 colony form units per 100 mils. And then we only found a very small percentage of our produce had any E. coli present on it.
00:11:18
Speaker
So we're trying to follow that up. We know that we can't generalize just from one site. So we're currently working in Baltimore City, which has
00:11:29
Speaker
many, many urban farms, over 30 now, and about 300 community gardens. And we're working with people who are already harvesting rainwater, and we're evaluating what the quality of that water is. Because what we know is there's variability in the systems. Like you all were saying, some of these systems, the barrels are open to the environment. Some are closed.
00:11:55
Speaker
there's all different volumes and so we want to understand from a wider sample what is the water quality of harvested rainwater.
00:12:05
Speaker
Yeah, so knowing that there's a lot of different systems out there and different techniques for collecting rainwater,
Sustainable Practices and Research Findings
00:12:11
Speaker
Rachel, have you come up with a list of maybe some best practices for rainwater collection that would help to minimize the potential of any microbial contamination? Yeah. I mean, I think there are just some good practices maintaining your rainwater harvesting system. So emptying your barrel.
00:12:32
Speaker
Every now and then, we usually say around two weeks. And then also just checking your system, making sure that there aren't leaks, that there aren't cracks that could be openings for different contaminants. And then we also have been suggesting that people clean their rainwater harvesting system, their barrels, every year.
00:12:53
Speaker
either with a mixture of soap and vinegar or dish soap or a less than 5% bleach solution. We've also seen from our work, both with harpsichord rainwater, but with other water sources too, that different types of treatments can be effective. So these can be sustainable, low-cost things, sometimes things that farmers are already doing, like a sand filter can effectively reduce pathogens and E. coli
00:13:22
Speaker
the first flush system that we tested in our study, which was just a 35-gallon barrel to remove that first volume of water coming off the roof. And then there are other sustainable technologies that we're interested in looking into, and we're currently gearing up to test things like zero valent iron, which is
00:13:44
Speaker
using recycled iron shavings. So think of it kind of like a brighter filter, but just some sort of filter to improve the quality of water even more. When you did your research, were you doing drip irrigation? So the system that we did our pilot study on in Frederick, Maryland was a really unique system. And it was based on a design that they were using in Australia. So it was actually subsurface irrigation.
00:14:14
Speaker
So we think, you know, that could have also reduced some of the transfer of any potential E. coli from water to the produce. But, you know, you all know that drip irrigation is a less risky form of irrigation too. So I would say really for any water type using drip irrigation is a good idea, even with harvested rainwater.
00:14:43
Speaker
Yeah, I was just going to ask Rachel, was there anything else that came out of your research that you feel might be important for growers to know? Yeah, I think, you know, along with our water quality research, we also asked urban farmers in Baltimore City
00:15:03
Speaker
were they interested in harvesting rainwater and what their concerns were. And we found that there was a lot of interest in rainwater harvesting, but the concerns were mainly around the cost of the system and water quality. So I think it's just important that we keep up this work of water testing so that we can really confidently tell urban farmers if harvesting rainwater could be another alternative irrigation water source for them.
00:15:30
Speaker
My only question would, and this is again, sorry to, don't want to divert the conversation. But just for clarity, there weren't anything being like sanitizers or antimicrobials being used in the collected rainwater. It was just what was in the barrel. That's right. It was just, there was no additional treatment. It was just the water was being collected off the roof.
00:15:54
Speaker
the first 35 gallons were being diverted and then it was being sent to those raised garden beds with subsurface irrigation. Is that a practice that you would recommend as well, diverting some of that water prior to using it for irrigation?
00:16:09
Speaker
Yeah, I mean, I think that there's a lot of research showing that the first volume of water often has more contaminants, which makes sense if you think that there are contaminants like feces hanging out on the roof or whatever surface you're collecting from that they'd really be picked up in that first volume of water. So it's an easy, low-tech way to just reduce the risk of contamination.
00:16:35
Speaker
And I think also, just like a big picture takeaway is I really believe that rainwater harvesting could be this amazing sustainable water source for urban farmers because of all the different environmental benefits. And because what we've seen so far shows that it does meet the food safety guidelines. Will we have like a link to the research available for growers?
00:17:02
Speaker
Sure i'm happy to share a link to the article that we just published and then my wow lab has a website where we try to regularly
Conclusion and Resources
00:17:11
Speaker
update.
00:17:15
Speaker
Links to anything referenced in this episode are provided in our show notes, which can be accessed on the website at canr.msu.edu slash agri-food underscore safety. Thank you to everyone for listening, and don't forget to tune in next month for another episode of our Produce Bites podcast.