Global Warming

Discussion in 'Earth Science' started by Mind Over Matter, Mar 13, 2011.

  1. adoucette Caca Occurs Valued Senior Member

    But it doesn't support your contention that Septic tanks are a major contribution to our dead zones.

    While they point out that Septic tanks represent about 1/5th of our Phosphorus, when they examine Nutrient loading of Streams and Estruaries they don't even list Septic tanks (non point sources) as one of the causes of Nutrient Impairment.

    Of the Estruaries (only ones related to dead zones)

    % Assessed 72%
    % Nutrient Impaired 22%
    % Impaired by agricultural sources 10%
    % impaired by WWTP discharges 17%

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  3. Trippy ALEA IACTA EST Staff Member

    I'm sorry Arthur, but this is weak sauce - where, precisely, in any of these posts, do I claim that Septic tanks are a major contribution?

    Trick question - I didn't. I simply listed them as a form of non-point discharge, and suggested that they are a contributing factor which can not be ignored - IE Significant, but significant (versus insignificant) doesn't neccessarily qualify as major.

    Yes, and there's a good reason for that, but it's not because it's insignificant. It's because it's painfuly difficult to quantify in the recieving environment because of the nature of the discharge. Agricultural discharges can be quantified easily, there's a couple of different ways of doing it. Likewise, WWTP discharges are trivially quantifiable - you know the end of pipe discharge quality, the rate of discharge, and the rate of flow in the stream, but non point discharges from sources such as septic tanks are difficult to quantify because, well, they're diffuse. Both Agricultural discharges and WWTP discharges represent high dosage rates over small areas, septic tanks represent small dosage rates over large areas (not the best way of putting it, but i'm going to trust you understand what I mean - even though the mass flow from an individual tank might be low, there's a large number of them, and they're widely distributed).

    Also, take a moment to think about what the numbers say - IE that of the 22% of estuaries that were imparied, 73% of those were not impaired by WWTP discharges, or by agricultural sources.
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  5. adoucette Caca Occurs Valued Senior Member

    I don't think that's how you interpret that, but when I went to the source and found that it referenced a 1997 EPA report, but in it's references in the end, it failed to include that reference and a search of the EPA's database did not find the original report that that chart came from

    So I went looking for specific info on the issue I thought we were discussing (at least I was) the primary cause of our Dead Zones and as I suggested before, in our major dead zone, the Mississippi, it's Agricultural run off by a wide margin for both N and P.

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  7. Trippy ALEA IACTA EST Staff Member

    Yeah, I have the report open beside this window.
    Like you, I went looking for the original chart, and about the most useful information that I did manage to gather was that the WWTP category appears to include industrial WWTP's as well as municipal STP's - at least, as far as I could discern.

    I can't really see any other way of interpreting that chart though, seeing as how 25+5≠14; 19+7≠20 and 10+17≠22.
    Nor, for that matter do 22+10+17 = 72, or 72+22+17+10=100.

    To use Estuaries as an example, I read the column headings as:
    "Percentage of Estuaries assessed"
    "Percentage of Assessed Estuaries that were nutrient impaired"
    "Percentage of Nutrient impaired Estuaries that were impaired by Agricultural sources"
    "Percentage of nutrient impaired Estuaries that were impaired by WWTP discharges"
    Because Logicaly, linguisticaly, and mathematicaly, that was the interpretation that made the most sense.

    I've never questioned that.

    In fact if you want to get pedantic about my original post, then infer priority from the order the items were presented in. Agricultural runoff was the first thing that I listed, followed by effluent disposal, with human effluent included as a subset, included in brackets, which presents it as an afterthought.

    Biological polishing of effluent runoff at the point of entry into the waterway was mentioned, to which I suggested or implied that because of the diffuse nature of non-point source discharges such as septic tanks that such polishing would be of dubious value.

    If you want to get into the nitty gritty of it, my main motivation for septic tanks was because it's one of several diffuse sources of nutrients, that I am aware of, that I know have demonstrably caused problems with eutrophication of waterways because people have underestimated the net effects of it. And it happens to be the one that I'm working with primarily at the moment. I've spent the last two or three months modelling septic tank densities here in Otago, trying to identify areas that are at risk of surface water or groundwater contamination, so that I can then attempt to quantify the environmental impacts of these discharges, and maybe motivate politicians into doing something about it. But I seem to have a long road ahead of me because I don't think even my Director fully grasps the extent of the problem, or what causes septic tanks to operate inefficiently.

    If we had had this discussion say three months ago, I might have specifically named Sheep, Beef, and Venison farming as being a similarly signifcant but understimated source fo diffuse discharges of nutrients into the environment.
  8. chimpkin C'mon, get happy! Registered Senior Member

    And you weren't thinking of feedlots or factory farming, were you?

    I rode through the state of Indiana on a Family Vacation

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    and the whole place...all you see is corn, all you smell is pig $hit. For hours. And I guess that all ends up down the Mississippi.
  9. Trippy ALEA IACTA EST Staff Member

    Nope, I'm thinking of a bunch of beef cattle standing around in a field having a crap when the urge strikes them.

    Pretty much, one way or another.

    But there are ways of managing it, and reducing the nutrient load that makes it into the water ways. Riparian margins are one example of this, the look nice to boot.

    But even where you have tile drains, discharge quality can still be managed, it just requires the land owner to give enough of a damn to make the required investment.
  10. adoucette Caca Occurs Valued Senior Member

    I was having trouble with the math though.
    Just didn't make sense.

    Particularly this line

    Streams & Rivers

    Assessed 19%
    Impaired 14%
    Nutrient impaired 25%
    WWTP impaired 5%

    Because if the numbers were interpreted as you suggested, then 70% of the impairment wasn't even specified.

    Which makes no sense since we know Nutrient impairment is huge.

    But I agree, given the data, how else could you interpret it as clearly they were positioning the 25% Nutrient Impairment to be a subset of the 14% they said was impaired.

    Which is exactly how you did interpret it: -
    Indeed, the implication is what wasn't stated swamped what was.

    Which is not typically how reports work.

    So I finally tracked down the original report: EPA 1997 and the presentation of the figures leads to this misinterpretation.

    First of all it had the Percents surveyed listed and that matched the table from that report so I knew I had found the right EPA data (its the 1996 National Water Quality Inventory Report but it was published in 1997).

    For the Streams, sure enough 19% were surveyed.

    For types of impairment they grouped them into 11 catagories with Septic Tanks lumped into "Land Disposal" that also included Land Fills and Haz waste sites.

    Now here's where it gets a little funky.

    Of the 19% of the River Miles surveyed, 36% of them were listed as being Impaired, but neither of those numbers are in your mini chart.

    BUT, all the percents after that refer to PERCENT of Surveyed River Miles.

    The 14% for Nutrients, that's under the heading Leading Pollutant/Stessor and means 14% (of the 19% of our Rivers Surveyed) had Nutrients in them that were at the level of impairment.

    There are 7 other pollutant/stressors and a combination of them could cause a river to be considered Impaired.

    The 25% for Agricultural Sources, that's under a different heading called Leading Sources and means 25% (of the 19% of our Rivers that were Surveyed) had some pollution from Agriculture Sources (But there are multiple sources like Nutrients, Pesticides, Silation etc)

    But here's the kicker, for the Rivers, of the 11 Sources of Impairment, they only listed 8 as the leading sources (lowest impaired 3%) and Land Disposal which included Septic Tanks wasn't one of the 8 listed (and a river could be impaired by multiple sources).

    So our original Article, which was all about Septic Systems, seens to have been playing fast an loose with the data and implying Septic systems were involved when in fact they didn't even make the cut for River Pollution.

    So to restate it:

    See report and see if you agree with this interpretation. page&MaximumPages=1&ZyEntry=3#

  11. Trippy ALEA IACTA EST Staff Member

    Yeah - part of my point - 70% of the nutrient impairment comes from non-point source pollution.
    It's not that it's not specified, it's just not specifically tested for in the original data source.
    Some of it is from sources such as septic tanks.
    Some of it is from effluent management practices on farms.
    Some of it is from land management practices - for example, grazing right up to the waters edge.
    Some of it is from natural sources.

    There are other sources as well, but if you think about it, just from those 4 considerations, even though they might make up 70% of the remaining impairement, that's only a contribution of an average of 17.5% from each of them, which would place Septic tanks below agricultural runoff.

    See report and see if you agree with this interpretation.

    Cool, I'll comment on the rest of your post subsequent to that.
  12. adoucette Caca Occurs Valued Senior Member

    But that's not what the original EPA report says.
    Indeed, from the way the data is presented in the original report there is no way to determine percent of nutrient impairment from non-point sources.

    For our rivers, they say that 25% of the surveyed rivers are polluted by agriculture, but not what kind of agricultural pollution it is.

    They also say that 5% of the surveyed rivers are impaired by Municiple Point sources, but again, not what they pollute with.

    So while they do say that 14% of the surveyed rivers are polluted by nutrients, they don't turn that around and say what contribution each method of pollution makes to that 14%.

    What they DO say though is that SEPTIC TANKS, the issue I thought we were discussing as regards our dead zones, isn't even one of the sources that makes the list of issues for our streams, and since it's this nutrient load in our streams that causes the dead zones, what the report does make clear is that it isn't septic tanks that are causing the nutrient problem in our streams.

    Now when you add in the other much more recent report that I linked to that was specifically about our dead zones, it's clear that the problem in the US is in fact pretty much an Agriculture issue, which with a side dose of atmospheric deposition of Nitrogen makes up 86% of the Nitrogen load and 80% of the Phosphorus load all by itself.

    Last edited: Apr 7, 2011
  13. Trippy ALEA IACTA EST Staff Member

    Context, Arthur.
    I was addressing a specific point that you made that was phrased within what now appears to be an erroneous frame work, however, I was addressing it within the context of the seemingly erroneous framework to illustrate how your objection might be addressed within that.

    Based on the limited information I have been able to track down myself (information about the layout and contents of the original dataset, but frustratingly not the dataset itself) I'm not sure this is correct. The original dataset contained results for BOD[sub]5[/sub], TP, TN, E. coli, I have a feeling it might have had information about Secchi disk depth, DRP, AMM-N, and metals as well - I don't recall, I don't have the file in front of me, but I do recall that it had 'the usual suspects' in it (IE BOD[sub]5[/sub], TP, TN, E. coli).

    So that information is precisely determinable if the researchers at Lombardo had access to the original dataset as well as the USEPA report (this would be how I personally would approach the problem as well, because it seems to me to be the most logical method of approaching the matter).

    Given the above, I'm not sure that this follows.

    As I believe I have previously mentioned, USEPA does not test for septic tanks for a number of reasons mostly relating to the difficulties I have previously outlined. Also consider that, like heavy metal contamination from storm water runoff from roofs and roads, the nutrient contribution of septic tanks to waterways is something that up until recently has been underestimated and poorly understood.

    Again, we come back to the point that at no stage have I questioned the role of agriculture in this matter, merely asserted that some factors are more important than most people seem to understand.
  14. adoucette Caca Occurs Valued Senior Member

    And in that EPA report you can see that septic tanks do make the list for Lakes and particularly the Great Lakes.

    Why they aren't much of an issue for our dead zones (percentage wise) is simply because the drainage area for the Mississippi is mostly the part of our country that is heavy into Corn agriculuture for which Nitrogen is heavily applied.

    Notice how the areas where Corn is heavily grown maps to the very heavy Nitrogen dispostion, but at the same time, these areas tend to be quite rural and thus not a lot of septic tanks per square mile.

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    At the same time, the major population concentrations in the regions are almost exclusively on the banks of the Mississippi, and thus (New Orleans, St Louis, Memphis, Minneapolis/St Paul) have to deal with very low water tables such that Municiple Waste treatment is much more common than septic systems.

  15. Trippy ALEA IACTA EST Staff Member

    In the Lombardo report you linked to earlier, you'll see that Septic tanks are capable of delivering as much as 15-17 kg/ha/yr, which equates to 150-170 kg/km[sup]2[/sup]/Yr in areas where Phosphorus based detergents have been banned.

    EPA Guidelines are that more than 40 septictanks/km[sup]2[/sup] is considered high density.

    So anywhere on this map:

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    Where a density of more than 40 is indicated, the potential for problems exists - where reticulation is not present.

    There are two things that suggest to me that the EPA is aware of the problem, as well as various state level governments.

    The bans on detergents containing phosphorus, and the law changes with regards to what can and can't be done with septic tanks.

    You'd think so, wouldn't you.

    But let's back up a minute here.
    You aknowledge that failing septic tanks have the capacity to cause dead zones in lakes, streams and Fjords right (eg Hood Canal - a Fjord in Washington).

    Incidentally, as it turns out, another reason why you might not find septic tanks mentioned specifically in discussions on human waste and nutrient contribution is because municipal waste sources are used as a guide to the total.

    Consider this excerpt:

    So there are authors that have considered septic tanks a significant enough contributor to the Gulf of Mexico Hypoxic zone to test the assumptions that have been made in terms of sources.

    And, apparently, Mississippi State University considers "Pumping out your septic tanks on a regular schedule" important enough to mention as an "Additional action homeowners and city planners can take to prevent non point-source pollution" that they explicitly anbd specifically mention it in a section called "How can I help prevent the gulf or mexico hypoxic zone"[sup]1[/sup].

    I appreciate this debate, incidentally, it's making me think about the issue harder which can only help the report that I have to write up sooner or later.
  16. KilljoyKlown Whatever Valued Senior Member

    I just wanted to say I have been following the debate and also very much appreciate it. Thank you two very much.

    I'd like to hear more about that report your going to write up sooner or later. Who's going to read it and what is it's purpose. What are the chances it will make a real difference?
  17. Trippy ALEA IACTA EST Staff Member

    Arthur, just to make sure that we're on the same page, allow me to, quite literally, illustrate my point using Figure 5 from this Source

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    My sole point with the role of septic tank in the gulf of mexico hypoxic zone is, was, and will always be that even if they form the least part of the contribution to the problem, they still have a role that can not be ignored, especially when remedying that, and removing their contribution is actually pretty trivial.

    It's as simple as improving disposal fields, setting (and enforcing) a minimum standard and encouraging good maintenance.
  18. Trippy ALEA IACTA EST Staff Member

    At this point it looks like it's going to be a committee report, although I suspect before I can do that I'll have to write a prelimenary report outlining the extent of the problem, and what I think we need to do to better quantify the impacts septic tanks are having in Otago.

    At this stage what I know is that in Otago, according to my estimates there are something like 20,000 properties that are likely to be on septic tanks. Of those I've identified 4,000 properties in areas where there is vulnerable groundwater or surface water (unconfined, shallow aquifers; Streams, Rivers & lakes, or Easturine environments). Among those there's a handful where I'm aware of annecdottal, or, shall we say circumstantial evidence where the presence of those septic tanks is having a detrimental impact on the quality of the water - for example there's two locations that I can think of off the top of my head where following rainful events the microbiological quality of the water has been so poor that you shouldn't really have swam it (it failed to meet primary contact recreation guidelines). One of those locations also had anomalous levels of flouresence in the water - which is potentially indicative of FWA's in the water, which are added to laundry powders, and don't occur naturally. One of the other locations there's evidence in the groundwater chemistry that contamination is occuring, and IIRC the water fails to reach microbiological drinking water standards.

    I write a report outlining what I think we need to do to establish environmental effects.
    The spending gets approved.
    The testing gets carried out.
    I interpret the results and write another report outlining how I think we can improve the situation.

    This last step is the step that I expect to have the most difficulty with. My prefered method will be expensive, but should be the most effective, and the most cost effective, it should also result as a long term solution. The costs should be recoverable from rates payers, however doing anything like what I'm thinking of may require what amounts to a law change, which could have wider implications and ramifications, but there is precedent in NZ for it, albeit under circumstances involving worse pollution than anything I seem to be dealing with, I suspect it will also be unpopular with the politicians, who, ultimately are the people I need to convince.

    But before I can try and convince any of them I need to convince my Director who at this point - inspite of the approach having been adopted elsewhere and encouraged/considered by the central government (but they shelved it as being too hard), does not see the potential benefits from what I've been considering.
  19. adoucette Caca Occurs Valued Senior Member

    Not really, because there is not one septic system per person.

    Indeed, in the country you would probably need a population density of over 120 per km to reach that level of density of septic systems if everyone was on a septic system, but the main population centers, Memphis, St Louis, New Orleans and Minneapolis that reside on the banks of the Mississippi are all very low areas where septic systems aren't normally used (you do have to pass a Percolation Test to install one). All four of those cities indeed have extensive systems of city sewers.

  20. adoucette Caca Occurs Valued Senior Member

    Well I agree that they should not be ignored, and my experience tells me that homeowners don't ignore them because there is no way one can live near a septic tank that isn't draining properly. The Hydrogen Sulfide gas that is emitted is absolutely noxious even in very tiny quantitites and the neighbors (or the wife), even a quarter mile away simply would not put up with it, and the good news, is the remedy, pumping out the tank and/or putting in a new drain field simply isn't that expensive.

  21. Trippy ALEA IACTA EST Staff Member

    Yeah, I knew that to :facepalm:
    I've spent too long looking at my own maps which are based on population density, but are based on houses/km[sup]2[/sup] rather than people/km[sup]2[/sup].

    Let's put this one down to a momentary lapse of reason induced by sleep deprivation related to a 1am nappy and sheet change - not to mention the related autoclave moment.

    This bit:
    " do have to pass a Percolation Test to install one..."
    Generally it's not the new ones that are the problem.
    The new ones generally treat to at least a secondary standard, and are generally AWT's, rather than straight out septic tanks.

    It's the old, single chamber septic tanks with cracked walls and lids, no floors and a straight pipe discharge into a nearby waterway, or into a cess pit that generally cause the problems.
  22. Trippy ALEA IACTA EST Staff Member

    My experience on the law enforcement side of things suggests otherwise, althouhg what you say may be true of the majority of owners, it's certainly far from being exclusively true.

    I've seen some horrific photos of what people have lived with - both in the US and here, because they haven't realized that their tank and/or disposal field has failed, or is failing, and have just assumed that the odour and/or runoff is normal. My recollection seems to be though that it tends to happen in situations where everybodies is performing equally poorly.

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    (Source) septic for web.jpg

    Those aren't even the worst I've seen photos of (or seen personally for that matter).

    Ultimately though, even a properly operated and maintained septic tank still leaches nutrients into the environment that are capable of causing dead zones.
  23. adoucette Caca Occurs Valued Senior Member


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