eed Beds are essentially constructed wetlands that use the common reed, Phragmites australis, as their "active ingredient."  In a typical municipal sludge application, Reed Beds will reduce water content from 95% or so for the incoming sludge, to less than 55% for the final product.  This is accomplished through the combined actions of percolation, surface evaporation and, most significantly, leaf evapo-transpiration.  Also important: the development of a rich micro-flora in the root zone helps to break down over 95% of the bio-solids into water and carbon dioxide, with a corresponding reduction in volume.  And an added bonus is that volatile compound content is typically reduced to 25% or even less.

Sounds great!  But how do Reed Beds stack up against other means of sludge disposal in a cost/benefit analysis?  The answer depends on numerous factors, such as the makeup of the incoming sludge, local land and labor costs, local costs of hauling and disposal, whether constructing from the ground up or converting existing drying bed, etc. (Click here for more detail about RBS' services.)  Based on our experiences with scores of Reed Bed installations, we made up the following two scenarios to present a range of typical considerations and circumstances that exist out there in the real world.  We tried to use fairly typical numbers and costs, but please use these examples as boilerplates for your own analysis, based on your own local costs and considerations (and please don't hesitate to contact us if you have any questions or concerns):

Success story #1 -- converting existing beds:
In a nutshell: low initial capital outlay can yield good long-term savings...and FANTASTIC long-term savings, especially if operators are forced to choose between Reed Beds or hauling away liquid sludge because of looming restrictions on, or unavailability of, landfill.

A municipal sewage district somewhere in rural Pennsylvania, serving a community of about 3,500-4,000 people, generates an average of 400,000 gallons per year of aerobically-digested sludge with a 2% solids content.  They had been using a 10,000 square foot sand drying bed from which they typically removed and disposed of an average of 45 tons of sludge five times per year (every 4-6 weeks from May through October).  Digging up the dried sludge each time would usually take 1 1/2 days, with a contractor using a Bobcat to load an average of four trucks.  At a cost of $55/ton for excavation and transportation plus $50/ton for landfill charges their costs would be about $4,700 each time, or about $23,000 annually (plus labor).  They were reaching a time when landfill was no longer going to be an option for their sand-dried sludge:  strict limitations that were going to be imposed by in-state landfills, and the cost of shipping out of state would be prohibitive.  So  their only two viable options were going to be either having their liquid sludge hauled (for land-application or incineration) or converting to Reed Beds.  They chose Reed Beds based on the following analysis:

Hauling liquid sludge would have involved almost no initial capital outlay, and would have knocked their labor costs down from a cumulative seven or eight days a year to only one of two days a year.  But, at local hauling costs of 10¢/gallon it would have cost them $40,000/year to dispose of their sludge, almost doubling their annual costs.

Converting to Reed Bed technology, on the other hand, would initially cost them about $25,000 in fees to RBS.  As they were converting their existing drying beds their construction costs would be a relatively inexpensive $40,000 to local contractors.  So, their initial capital outlay is $65,000.  Over the next eight-year cycle of their Reed Beds they would save a total of $184,000 versus the  costs of operating their sand beds (and, as with hauling liquid, they would save 5-7 days/year of labor costs).  Less the $65,000 initial capital outlay, and less one complete excavation of the Reed Beds at $35,000, they would actually end up saving $84,000, or an average annual savings of more than $18,500 over subsequent years (versus continuing to operate their sand beds...if that had been an option).

Since they really only had a choice between hauling liquid sludge or converting to Reed Bed technology, let's run those numbers: converting to Reed Beds instead of to hauling liquid sludge, over the first eight years (one Reed Bed cycle), would end up saving them $220,000, or an average savings of over $27,000/year, and $285,000 over the subsequent eight years, or an average annual savings of almost $36,000 (about 9¢/gallon of sludge).

The bottom line?
 Reed Beds are the obvious choice!
 

Success story #2 -- new construction:
In a nutshell: more expensive up front, of course, but can save a bundle in the long run!

At this site the operator has a facility serving a population of about 10,500-11,000 in semi-rural South Dakota, generating 1,000,000 gallons/year of anaerobically-digested liquid sludge with 4% bio-solids content.  They had no existing drying beds and were paying 10.5¢/gallon to have their liquid sludge hauled at an annual cost of $105,000.  They constructed 40,000 square feet of all-new Reed Beds (four 10,000 square foot beds) at a cost of $70,000 in fees to RBS and $480,000  in construction at $12/sq. ft. local construction costs (labor and materials).  Over the course of their first eight-year Reed Bed cycle they had an initial capital outlay of $550,000, and paid $150,000 to have their accumulated sludge hauled at the end of the cycle, for total costs of $700,000.  On the up side they saved $105,000/year over their previous cost of disposing of liquid sludge for  gross savings of $840,000.  Less the costs, they netted savings of $140,000 for the first eight years, or about $17,500 annually.  Over the next eight-year period they will save another $840,000 (versus hauling liquid sludge).  But their costs this time will only include the one-time $150,00 fee for hauling, resulting in net savings of $710,000 over the second eight years, or an average net savings of about $89,000 per year  (about 9¢/gallon of sludge) -- and this rate of savings will continue over the subsequent life of the facility!

Once again, Reed Beds save the day!

Note: Climate Considerations:
Reed Beds can be effectively used through most of North America, but are most effective in climates where there is a least one good freeze per winter.  One reason is that the freeze-thaw cycle helps to further break down the bio-solids in the sludge.  Secondly, a hard freeze allows for easy access onto the frozen sludge for the annual winter harvest of the reed stems and leaves -- without a freeze the harvest can still be accomplished (e.g., by laying boards onto the sludge), but can involve considerable additional time and effort (e.g., cost).