Question
In our community a central located pond is surrounded by landscaped lawns.
The nitrate runoff in the ground water combined with the duck excrement
promotes pond weed growth.

Any suggestions to eliminate the nitrates and have reasonable lawns?

Answer
I have limited experience with solving this problem -- I work more along the lines of ounce-of-prevention -- but I'd like to give you somewhere to begin.

Of course you know that Nitrates come from Nitrogen fertilizer.  This is a serious problem.  Phosphates come from Phosphorus fertilizer.  These chemicals are running off into your duckpond etc.  Don't even think what the Weedkillers are doing to the duckpond.

All this fertilizer is a waste of time and money.  It is UN-necessary.  But it makes a lot of people money, so they sell it.  No one needs fertilizer.  What you need is rich Soil.  Fertilizer won't do that for you.  But it will destroy the microbes in the Soil, by making it Salty (by definition, Fertilizers are Chemical Salts, which is why they burn roots and leaves if you use too much too soon).  Earthworms HATE Fertilizer.  Fungi love the weak tissue it produces and when you get the right weather, you end up with Fungus attacks.

It is highly un-likely however that anyone will stop using Fertilizer.  Those commercials just make it toooooo tempting.  And there are so many other, more urgent problems in the world right now, your Fertilizer seems so, well, de minimus.

The solution:

There is a service called the 'Ion Exchange Process' that fiddles with the positive and negative charges in polluted water to remove most Nitrates.  The process is described in the report by a company called Alpha Water Systems on 'Nitrates Polluion of Groundwater'; look for the paragraphs on 'CLEAN-UP OF NITRATE FROM WATER':

www.reopure.com/nitratinfo.html

They point out: 'In dealing with the Nitrate problem in subsurface Waters, there are two options for achieving safe Nitrate levels.

First of all there are non-treatment techniques that consist of blending drinking waters, or changing water sources.

The second alternative is the use of treatment processes, such as Ion Exchange, Reverse Osmosis, Biological Denitrification and Chemical Reduction to actually remove portions of the pollutant.

However, the most important thing to note about these clean-up procedures is that neither of these methods are completely effective in removing all the Nitrogen from the water.  Treatment can remove some of the Nitrate, but with varying efficiencies, much of which can depend on other substances found in the Water.  The non-treatment processes attempt to bring the nitrate concentration down to a safer level, through blending with cleaner waters.'

My favorite solution is the one called 'Bio-chemical Denitrification', which they describe thusly:

'By using denitrifying Bacteria and Microbes, the Nitrate ion can be reduced into its elemental state of N2.  These organism are able to carry out this process through a reaction such as:

6H+ + 6NO3- + 5CH3OH -> 3N2 + 5CO2 + 13H2O (Zajic, 328).'

My Fishtank used to work something like this.  Any of you people have an aquarium at home?

They explain: 'By using a chemical such as Ethanol, the removal of Nitrate is possible.'

Most of the time.

Sometimes, more is needed, they say: 'it is necessary to convert the Nitrogen from the Ammonium ion into Nitrite with the use of Nitrosomas (specialized Bacteria) to facilitate the removal of all Nitrogen from the solution (Shuval, 1977).  The Nitrite compound is then oxidized to Nitrate, which can then be eliminated by the reaction shown above.'

Another technique: Use of Photosynthetic Algae to take the Nitrates out of the Water.  A bit complicated.  But they endorse both solutions.

Note, they point out, that Oxygen-consuming microbes are injured or destroyed by any poisonous chemicals floating around in the water.  Those chemicals screw up everything.  They add, however, that 'Nitrates are, in most cases, rapidly oxidized by Chlorine.'  Best of all, they say, 'The Nitrogen is completely removed in its gaseous elemental form (Organization for Economic Co-Operation and Development, 1974).  There is no residue or problems with disposal.'  I'll drink to that.

THE LONG ISLAND GARDENER