Nitrogen in the form of organic nitrates, nitrites and ammonia is a major component of residential wastewater and fertilizers. It also is a major problem in coastal ponds where nitrogen from septic systems within the watershed area can contribute 60 to 80% of a pond’s nitrogen load. Another 10 to 20% derive from fertilizer runoff. Too much of a good thing often turns into a bad thing, and so it is with the nitrogen and phosphates in water bodies. Both are nutrients needed for life on land and in water -- it’s what microorganisms and plants but not animals can do: convert nitrogen and phosphorus into organic forms. But supply too much and a pond may respond to the overabundance of nutrients with a bloom of algae that then can kill aquatic plants and animals by depriving them of oxygen. Denitrifying (nitrogen-removing) septic systems would be a solution (see Part 1 below); they are expensive and are not (yet) required by law even in high-nitrogen load areas. But if you follow the advice on fertilizer use (see Part 2 below), you can at least avoid runoff from fertilizers.
What for septic systems? (For your health!)
Until recently, septic systems have been designed with purely sanitary reasons in mind, namely to prevent bacteria and viruses in the waste water from contaminating human food and drinking water sources. Typically, household waste water is channeled into an underground treatment (septic) tank and from there distributed into a leaching field, the size and composition of which depends on the quality of the soil (so called Title V systems). Most soil in general is a pretty good filtration medium, preventing the diffusion of microbes and even viruses over large distances. For safety, a setback of 100 foot from surface waters (wetlands) is stipulated now by Falmouth bylaw for septic systems.
What goes on inside? (A microbial paradise as long as no bleaches and other germicidal agents get there!)
The septic tank is a hotbed of chemical activity, mainly driven by bacteria, that break down and/or convert a lot of the constituents of human waste. The rich stores of nitrogen and phosphorus in the organic waste matter are attacked and released to the water in soluble form. Much other stuff (for instance fats, soaps, detergents) gets metabolized, some toxins are rendered harmless thereby, but occasionally harmless stuff gets converted into nasty stuff. Insoluble larger stuff stays as sludge, which builds up if not pumped out in regular intervals, and eventually clogs the septic system (toilets won’t drain! Yuckk!). The stuff in solution and in suspension reaches the leaching field, where the microbes, viruses and tiny solids are filtered out (the microbes and viruses die there eventually) and where some chemical constituents such as phosphates are retained to a significant extent. Nitrogen, however, in the form of nitrates, nitrites and ammonia, reaches the groundwater -- and from there the ponds -- basically undiminished.
How to trap or divert nitrogen? (Gassify it!)
Ever since the number one problem with ponds, streams and lakes has been identified as the overabundance of nutrients -- in salt ponds the accusing finger points at nitrogen whereas in freshwater ponds it points at phosphates – there has been a scramble under way to develop denitrifying (nitrogen removing) or denutrifying (nitrogen and phosphorus removing) septic systems. How do they do it? Although by different procedures, they all convert the nitrogen compounds into nitrogen gas, a natural and harmless constituent of air, that gets vented to the atmosphere. In denutrifying systems, in addition the phosphorus compounds are converted into forms that then react with the sandfilters and soil.
Who should install a denitrifying system? (Ideally, every homeowner whose home is not connected to a central waste water treatment facility!)
Once nitrogen reaches the groundwater, it stays with it until it surfaces as drinking water or as a spring feeding stream or pond. For drinking water, the tolerance level is quite high, also for streams and freshwater ponds and lakes as long as phosphates are low. Brackish and saltwater ponds, however, are quite sensitive to nitrogen and respond at rather low levels with rapid growth of algae and the detrimental process begins.
Why don’t we? ? (Why should I be the one?)
As long as there is no law mandating denitrifying septic systems, it, as usual, is a matter of $$$. A denitrifying system costs up to $10,000 more than a new Title V system; some require maintenance and have associated maintenance costs. The most cost-effective scenario is a cluster system, where several housing units are tied into one denitrifying septic system: the per-unit cost would be considerably less, and sufficient waterflow (required for most effective treatment) would be guaranteed.
When is the best time? (Some times are better than others)
It definitely would be the right thing to do when constructing a new home. A new home constitutes a new, additional, nitrogen source for the groundwater and the pond. It also should be seriously considered when upgrading the current system to Title V which is required by law when a house changes ownership, or when a failed system needs replacement. If you need to dig up your underground oil tank, that may be another time to consider upgrading your septic system – the yard is being torn up anyway.
Any fringe benefits? (Indeed, there are!)
With a denitrifying system the size of the leaching field may be reduced considerably – a bonus if there’s a space problem, especially where setback regulations have to be satisfied. If you are building new or remodeling, with a denitrifying system you may be allowed more bedrooms. And, of course, there is the satisfaction and the great feeling that comes from knowing that you are doing a good thing, the right thing, for our groundwater, ponds, bays, fish, …..
Which system? (Stay tuned!)
A Falmouth citizen’s committee is investigating the efficacy of various denitri/denutrifying systems. F.A.C.E.S. (Falmouth Associations Concerned with Estuaries and Salt Ponds) has several members on that committee, and together they have sponsored public informational sessions on the issue. Soon, a report will be isued by them. We shall keep you informed! In the meantime, why not check out the locally produced Ruck systems which do not require maintenance?
by Birgit Rose
Part 2: Fall is for Frugal Fertilization
When? (It’s a cool thing to do!)
If you have trouble remembering when to fertilize your lawn, just remember that F stands for both Fall and Fertilizer. Why is fall fertilization best? Weeds don’t grow very well during the cool autumn weather, but the fertilized grass will grow and turn nice and green. In contrast, some grass varieties don’t grow very well in the summer heat, and fertilization then mainly feeds the fast-growing weeds. Fall fertilization also helps the grass be in a healthy condition for surviving the winter. This Watershed issue may arrive a little late for 1999 fall fertilization, but if the winter temperatures and snow hold off for some more time, a light application may still be possible and worthwhile in early December.
Spring fertilization is almost as effective as fall fertilization (although the alliteration doesn’t work here): temperatures in March, April, and May are cool enough that the weeds won’t be able to take great advantage of the fertilizer, whereas the grasses will.
What kind? (Slowly does it!)
When choosing a fertilizer, look for "slow release" or organic fertilizers. The slow release fertilizers have a coating that dissolves gradually, so that the fertilizer only gradually becomes available to the grass over the course of days or weeks following your application. Organic fertilizers are also slow acting, because the soil microorganisms must first convert the organic forms of the nutrients into forms that the grasses can use. Dehydrated steer manure is another option which is not as rich in nutrients as commercial fertilizers, but it will add humus to the soil as well as gradual and modest doses of the needed nutrients. Applying manure may seem repugnant, but actually, the dehydrated stuff has no odor, and you wouldn’t know it was manure if the package didn’t say so.
How much? (Less is more!)
The other F to remember is for Frugal. Unlike the good old days when Brillcream advertised that only "a little dab’ll do ya," today’s marketing usually recommends over-indulgence, and the instructions on fertilizer packages are no exception. Rather than apply the full dose recommended on the package, apply half in the fall and the other half in the spring. Or if you think that your lawn is really starved of nutrients, apply half of the recommended dose in early spring and the other half in the late spring. In other words, two smaller doses spread out over a few months during the spring or fall is better than one big dose. The reason is simple: the grass and the soil are limited in how much fertilizer they can take up in a short period of time. The excess, often over half of what is applied, runs off into the street, the streams, and ponds. The lesson is: more of the fertilizer will stay on the lawn if given in small doses.
Why care? (Green lawns are healthy lawns but green ponds are sick ponds!)
The emphasis on ponds in the preceding paragraph should explain why advice on fertilizing your lawn is appearing in this newsletter. When nitrogen and phosphorus from the fertilizer end up in the pond instead of in your grass, it promotes the growth of algae. Some algal blooms get so big the pond turns green. When the algae die, their decomposition uses up the oxygen in the pond water. That leaves no air for the aquatic animal life which then suffocates from lack of oxygen. Anyone living near a pond should be especially careful about fertilizer application on their property.
Who? (It’s up to you!)
Even though fertilizers contribute only about 20% of the nutrients entering the pond, that 20% is the easiest part to cut down. (Septic systems contribute 60-80% – but that’s another, longer story.) All that’s needed is a little bit of behavior modification on the part of the homeowners: If every one of us applied fertilizer only in the spring and fall and applied only half as much as recommended on the fertilizer package, we could make a substantial dent in the nutrient load of the pond and help prevent harmful algal blooms.
If a lawn HMO takes care of your lawn/yard for you, you need to make sure that he/she understands that protecting the pond is equally if not more important to you (yeah, yeah!) than having a super lush lawn and yard. You are the boss, and you can instruct them to apply less fertilizer and less often.
What’s the prize? (Yes, prize, not price!)
Applying only as much fertilizer as the grass can use, and at the times of year when it competes best for the nutrients, will properly feed your green blades while cutting down on your ugly weed problems. This, in turn, will reduce your need to use herbicides, which can also run off into the pond where they could have hazardous effects. So you actually save money on fertilizer, herbicides, and reduced labor cost and instead you get a healthier yard and a healthier pond.
by Eric Davidson
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