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| What the experts say |
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| Possible environmental impacts Part 3: |
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By Russell Bassett
Discharging effluent, sewage treated at a municipality’s wastewater plant, into a river is not a new concept.
In the 1930s and ‘40s, Oregon cities would discharge their untreated sewage directly into rivers, and while the practice of discharging raw sewage has mostly stopped, discharging treated sewage is standard operating procedures for many cities in Oregon.
Salem and Eugene are two of several municipalities that discharge into the Willamette, Portland discharges into the Willamette and the Columbia, Estacada is one of several cities that discharge into the Clackamas, and Medford discharges into the Rogue, to name just a very few.
In fact, if an Oregon city lives along a river, it is more likely than not that it discharges its effluent into the river.
Ask water quality and fishery experts if effluent is damaging the environment, and they say it’s a concern but one way down on the list.
“Sewage treatment is a fairly well-controlled process by-and-large compared to agricultural runoff, urban runoff, dairy operations and paper mills can be a concern,” said Chauncey Anderson, hydrologist with the United States Geological Service and one of the state’s top water quality experts.
One of the Pacific Northwest’s leading environmental watchdogs, Tracy Collier, the Environmental Conservation Division director with the National Oceanic and Atmospheric Administration’s Northwest Science Center in Seattle, wouldn’t even comment on the impact of effluent on the environment, because his people are focused on other polluters.
“We really have not studied that in our office,” he said. “It hasn’t been a priority of ours.”
Dr. Stan Gregory, an Oregon State University professor of fisheries and one of the state’s leading experts on the Willamette River fishery, said he is more concerned with the possibility of untreated sewage getting into a river, than he is concerned with treated sewage.
“A lot of sewage effluent that has tertiary treatment is fairly clean water, sometimes cleaner than the river itself,” he said. “The question is: Are storm flows causing raw sewage to go directly into the river?”
The Molalla River is a tributary of the Willamette River, and Chinook salmon and steelhead trout are federally listed as threatened species in the Willamette basin. In order to spawn in the Molalla, the premier fish have to travel through the most polluted part of the Willamette.
Gregory is directly involved in trying to increase fish populations in the Willamette River, and he did not list effluent in his top five reasons for fish decline.
He said the main reason for the decline of native steelhead and Chinook numbers is “hardening and channelizing of the river, loss of flood plain forest and riparian wetlands,” followed by “toxic chemicals from agriculture, pesticides and industry” and “the introduction of invasive species such as smallmouth bass and carp.”
Anderson’s focus is water quality, but he noted that “I’m an Oregonian, so I’m concerned about salmon.”
The hydrologist also did not list effluent in his top five reasons for fish decline.
“Habitat destruction, habitat destruction and habitat destruction are the first three,” he said. “I think the loss of feeder streams and riparian vegetation around streams and probably temperature is a big one.”
Below habitat destruction, Anderson listed “changes to aquatic food webs, significant changes in nutrients or an excess of algae growth and other plants that can change the food web.” Followed by “a tie between toxics and introduced species.
“I’d put (effluent) below those other factors that I mentioned, but with the caveat that nutrients from treated wastewater is a contribution to the fourth one — potential changes to aquatic food webs,” he said. “But I think that’s gotten better. What makes (effluent) a little lower on all these scales is it is something we can get a handle on. We know the permitted amounts and can regulate what is going in (the rivers). We can make predictions of loading nutrients and chemicals that are coming in from wastewater plants. The other sources we are talking about are harder to get a handle on.”
Concerns
Despite not putting effluent in their top five reasons for fish decline, both Anderson and Gregory, as well as Collier did have some concerns with discharging effluent into a river.
“It is an issue,” Collier said. “There are issues that come up with treated sewage and its discharge. There are a lot of PSBs (Photosynthetic Bacteria), dioxins and so forth that can come out of a treatment plant.”
“With treated sewage effluent, the question is the degree to which it will be treated and the certainty that accidents will not happen and the potential for direct release during flooding,” Gregory said. “Treatment plants can only handle so much when storm drains get flooded.”
“A mixing zone does have the potential to be a dead zone,” Anderson said. “With any luck, it will not block the whole river, and the fish have a way around.”
More specifically, there are several environmental concerns directly related to the discharge of effluent into a river system. They include, but are not limited to, the possibility of increased water temperature; decreased oxygen levels; increased pH levels; too-high levels of ammonia, chlorine, phosphorous and nitrogen; toxins from urban runoff; increased turbidity; and the introduction of endocrine disrupters, drugs and hormones into an ecological system.
Gregory said his biggest concern with effluent is the possibility of an increase to water temperature.
“Let’s assume you are having treated sewage effluent that is working to design specifications, the only major influence I am concerned with is temperature,” he said. “During summer, is it higher than the state will allow?”
The city of Molalla plans to only discharge into the Molalla River during the winter months, from Nov. 1 to April 30, while irrigating Steve Coleman’s ranch with the reclaimed water in the summer months; however, the city has in the past regularly requested and received an exception from the Oregon Department of Environmental Quality to discharge to Bear Creek into May and June.
“The Molalla River has water temperature issues during the summer time, and we are talking about (the city of Molalla) dumping (effluent) in the summer time,” said Friends of the Molalla River member Mark Schmidt. “November to April is an unusual year. It’s actually more like November to mid-June” when the city has discharged into Bear Creek in the past.
“(City Manager) Gene Green said in mitigation that ‘if Coleman doesn’t want irrigation, (the city) will keep dumping in the river,’” said fellow Friends member Tom Derry. “It would be rare if anyone needed water to irrigate in May, or June for that matter on many years.”
Molalla Wastewater Plant Operator Otis Phillips countered, “There is going to be no effect with our water warming up the river.”
Oxygen
Another concern experts raised with effluent discharge into a river is decreased oxygen levels. Untreated sewage decreases dissolved oxygen levels and increases the Bacterial Oxygen Demand or BOD in a river.
Gregory said in the 1930s and ’40s, when cities discharged raw sewage into the Willamette River, fish would die in a matter of minutes because oxygen levels were so low.
“Most of the fish around here and invertebrates require high oxygen levels,” he said. “They require about 5 parts per million of dissolved oxygen. If you get down to 2 to 3, it is toxic.”
Anderson noted that most treatment plants are built so as to not decrease oxygen levels in their discharge streams.
“If there is no oxygen, the fish can’t live,” he said. “That is the first thing treatment plants look at, and the engineering solutions to that are fairly well understood.”
Phillips noted that DEQ has specific standards for dissolved oxygen and BOD rate in effluent, and the Daily Monitoring Station to be built at the outfall site on the Molalla River is designed to help ensure that the city does not violate those regulations.
Opponents to the city’s plan point to past BOD violations at Bear Creek.
Ammonia, chlorine and
other compounds
Other possible impacts to the environment are increased levels of ammonia, phosphorous and nitrogen, which all occur naturally in a river system, and at proper levels can be beneficial. The concern is that effluent has the potential to make the levels too high.
“There are three main concerns with ammonia,” Anderson said. “One of which is that ammonia, due to a biological process with bacteria, can actually cause a very large oxygen demand. Bacteria takes ammonia and converts it to nitrate, and that process consumes huge amounts of oxygen. Two, a lot of ammonia in a treatment plant has a high toxicity. Ammonia in and of itself can be toxic under the right conditions. And the third one, ammonia along with nitrite and phosphorous, can fuel the growth of algae to where it can be a nuisance and harm the river.”
Anderson noted that urine naturally has high levels of ammonia, and feces has high levels of nitrogen, but treatment plants are designed to break those compounds down.
“The process of sewage treatment is the process of taking complex organic material and breaking it down to its smaller parts, and what that means is that essentially in respect to nutrients, you are going from organic material to inorganic nutrients,” he said. “Ammonia, however, can bind to other substances and not be completely broken down.”
“Compared to natural streams, treated sewage can have relatively higher concentrations of ammonia,” Gregory added, noting that 20 parts of ammonia per million of water can be lethal to fish.
DEQ Environmental Engineer Garry Sage said Molalla’s effluent averages 11.5 parts of ammonia per million of water, with a maximum of 25.9 parts per million.
City of Molalla officials originally asked to have ammonia limits increased but later dropped the proposal.
“I’m concerned about ammonia,” Sage said. “(The city of Molalla) has ammonia levels in their permits now, and I’m skeptical that they will make that. Well, that is why they had initially made this inquiry about changing the permit limits. ... What kills them every time is oxygen-depletion criteria. They can’t deplete oxygen in the river by .1 milligrams, (and) the BOD and ammonia figure into that, so they have to keep ammonia low.”
Phillips said the city’s effluent averages 14 parts of ammonia per million during the summer months and 3 to 5 parts per million in the winter.
“Nitrates are zero, nitrites are zero, phosphorous is zero,” he said.
Unlike the aforementioned compounds, chlorine does not naturally occur in a river nor in human waste; however, chlorine is added at the treatment plant to kill bacteria, similar to why chlorine is added to swimming pools.
“Chlorine can be toxic in high quantities (and) it can be caustic, causing irritation to gills and the skin of aquatic animals,” Anderson said.
“One of the concerns people have with chlorine and sewage is that if you mix chlorine with organic waste like feces — and urine is high in nitrogen — if you add chlorine with those compounds, you can create toxic substances, such as chloramines, which are highly toxic, and you can also form dioxin,” Gregory said.
Anderson added that chlorine “is another thing that is fairly well documented in treatment plants, and they should be able to do a good job with it.”
While the city of Molalla did not de-chlorinate its effluent when discharging into Bear Creek, its new permit requires that it de-chlorinate before discharging into the Molalla River.
“If everything goes through, de-chlorination will occur prior to discharging into the Molalla River,” Phillips said. “We will have a Daily Monitoring Station that will have samplers and meters to take samples. We will have dissolved oxygen monitoring, pH monitoring, temperature monitoring, chlorine monitoring.”
Other concerns
The experts say effluent has the potential to change pH levels in the discharge stream.
Anderson said most natural systems operate at an acidity of 7. Plus or minus a couple points can be detrimental to a river’s ecological system.
Like oxygen levels, pH levels in the city’s wastewater are monitored and regulated.
Not only does the city’s wastewater treatment plant treat sewage and other wastewater from homes, it also treats rain runoff that infiltrates into the city’s collection system.
During the summer months, the plants treat an average of 600,000 gallons a day, but during the winter, that number rises to 1.3 million a day, due mostly to rain runoff, according to Phillips.
“There are issues with lawns and streets and exhaust emissions, gasoline and other solvents and pesticides from urban runoff,” Anderson said. “Those are additional concerns with discharging wastewater into a system.”
Increased turbidity is another possible negative impact of the city’s plan, but Phillips noted that the “diffuser” to be placed underneath the Molalla River should alleviate turbidity concerns.
While the aforementioned concerns have been researched extensively over the past several decades, endocrine disrupters and other hormones and drugs are just starting to be looked at, and no one really knows for sure what possible effect they will have the environment.
“The research community is getting a better idea of the potential for compounds to make their way into streams, usually resulting from sewage treatment plant releases,” Anderson said. “So we are starting to get an idea of what levels might occur in the environment, but what we don’t have a good feel for is how to interpret the levels we see and what the ecological consequence of estrogen or other hormones are. ... The concern is that some contamination from synthetic chemicals or hormones from people might cause feminization of fish such that their reproductive capability is diminished.”
Collier said a lot of research has been done in England that shows rivers that have raw sewage discharged into them have “some populations of fish that have very few males and many females, but there is not a lot of research saying treated sewage has the same effect.”
Phillips said he has kept up with the research, and from what he has read, using Granular Activated Carbon as a media in treatment plant filters has been shown to decrease levels of hormones and drugs in wastewater.
According to Phillips, the city plans to start using the media in the near future.
We all contribute
The wastewater plant operator noted that effluent can’t be stored indefinitely.
“You’ve just got to have a place to put it,” Phillips said.
“We all contribute to sewage, and sewage has to go some place,” Anderson agreed.
Opponents argue that the risk to the Molalla River is not worth the benefit of having the river as a discharge point.
“Nobody knows the impact of wastewater on our fishery and our river,” Derry said. “DEQ doesn’t know what the impact is going to be. The guy who runs the plant doesn’t know what the impact is going to be. I’m just not ready to take the risk that there could be an impact.”
Opponents point to an alternative to the city’s plan, which would, they say, not only disallow discharge into the river but rehabilitate Bear Creek.
(In Saturday’s Pioneer, Bear Creek revisited, a look at the opponents’ dream alternative to discharging into the Molalla River.) |
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