Tuesday, 22 August 2017
Technology

Advantages And Disadvantages Of Reed Beds For Leachate Treatment

A controversial subject like using reed beds for leachate treatment inspires strong feelings in many people, on both sides, for and against. Putting emotional feelings aside, it is best to evaluate each side as logically and cool-headedly as is possible. Having said that, let’s look calmly and analytically at the positions held and also the reasons in support of both sides:

Okay, let’s get started. On one side you have the “Pro”, the positions in favor:

The 1st point in support of reed beds for leachate treatment will be that they are cheap to operate, in fact they cost almost nothing to run and look after for at least the first three years, after which the banks and reed material build-up may require some attention, but that is all.

A 2nd point in favor would be they are very low energy consumption, making the carbon footprint for a reed bed treatment system much lower than alternatives, and they are a far more sustainable solution than any of the high-tech processes which require pumps, and mixers, and aerators, etc.

The third supporting point is going to be that they don’t consume expensive chemicals such as reagents, flocculents, anti-foaming agents etc.

A 4th support point in favor will be they are good for wildlife.

And last (but not necessarily least) we’ve got the 5th point in support they are quite good if something goes wrong and for a short period of time a higher strength of contamination arrives in the flow, they will usually absorb the additional loading and not discharge it, of course there are limits to this, but a high-tech process in their place would most probably have been overwhelmed by a shock loading much sooner than a reed bed.

And on the other side, for balance, the Con side, against:

The primary point against reed beds for leachate treatment is that the beds have to be sized and designed and built with a high degree of knowledge of what they can be expected to treat, and treated with respect, certainly when freshly planted so that there is no overloading while the roots (rhizomes) grow and establish the necessary root mass.

The second point in contra is going to be the best beds are low permeability when first built and the flow put through must be limited for the first period of use while the root grows and develop the growing media that they are planted into into a well oxygenated complex of live roots with a higher permeability

The 3rd point in contra will be you must avoid overland flow and short circuiting of the flow through a red bed for full treatment.

A fourth negative point will be in very cold climates in winter if there is no build-up of insulating snow over the beds and the effluent which flows through a bed becomes cold, a bed may freeze into the root mass. If this occurs treatment will be compromised until warm weather defrosts the bed, so a keen eye may be needed in winter with a backup treatment process method in the event of reed beds becoming too cold.

And 5th and last, but not necessarily the least, consideration against is the initial construction cost is quite high, although not usually as high as the alternative tank an reactor type processes.

So there you have it, the good qualities along with the cons, the points in favor along with the points against.

And so, who won? What can we conclude? Is reed beds for leachate treatment more good than bad? or more bad than good?

The answer seems to be “Yes” to both questions! reed beds for leachate treatment seems to be both good AND bad! It ought to be left up to you, the reader to decide. Which side, the good or the bad, has got the preponderance of weight of opinion?



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