Almost unnoticed in the "real world," an unusual sort of "political revolution" has been gaining momentum on the Caribbean island of St. Croix. This tiny island is in the midst of a "poo-litical revolution"a fight over wastewater. The people are literally marching because they know their money, their water, and the future of their island itself is at stake.
We have seen a vigorous discussion of wastewater issues in the Source recently, and I heartily agree with the conclusion expressed recently by Steve Nisky: Solutions don't have to be difficult. However, when it comes to the subjects of primary treatment and constructed wetlands, his comments offer more evidence that education is still the biggest barrier facing sustainable solutions in the world today.
Even after more than 30 years of successful experience around the world, a simple fact remains: Gaining access to appropriate, accurate real world experience with constructed wetlands is often much more difficult than understanding these "technologies" themselves. Kelly Gloger did a great job of clarifying several misconceptions about excessive land requirements, odors, mosquitoes, and other "wildlife" issues that continue to confuse people to this day.
Subsurface wetlands have been designed to successfully accommodate "multiple-use" objectives, like animal grazing, etc. For 14 years, I have installed subsurface wetland systems some less than 30 feet from expensive, high-end family retreats in Aspen Colorado. I have also placed them next to patios at private homes and ecotourist lodges—some nearly 10,000' above sea level, with absolutely no odor complaints in over a decade of operation. In fact, owners of the Mt. Elbert Lodge in Colorado proudly display their beautiful flower-filled constructed wetland in advertising and promotional brochures. Surrounded by the beauty of rocky mountain scenery, 99 percent of guests at the lodge fail to distinguish the wetland from natural surroundings, even enjoying lunch at a picnic table sitting directly on top of system itself!
Constructed wetlands offer enormous potential benefits to the Island of St. Croix. Given the obvious potential for water recycling (i.e. subsurface landscaping irrigation), I think it is unfortunate that existing debate has seemingly focused on "wetlands" vs. "concrete and steel".
As currently presented, both of these 'options' share more in common than is generally known. Both systems rely on the same fundamental concept: "centralized" sewer collection. This mindset, (building piping networks to carry our wastes "away") has pervaded engineering practice since the Romans invented pipes. However, few people realize that the cost of collecting sewage and transporting it through vast underground pipe networks is often significantly more expensive than the cost of the actual treatment plant itself.
Over time, sewage collection pipes deteriorate, draining clean groundwater into sewage lines, reducing treatment plant capacity. Broken sewer mains can also unintentionally discharge raw sewage directly into groundwater, potentially jeopardizing the very resources they were intended to protect. In short, in terms of initial construction and long-term maintenance, sewer collection systems are often significantly more expensive than the mechanical treatment plants they are connected to.
Wetlands = 'Legos' for sewers
Confining the use of constructed wetlands to central treatment areas overlooks one of their principle advantages: Constructed wetlands are especially unusual in the wastewater world because the lined, gravel-filled 'wetland cells' can be adapted to virtually any wastewater type/volume. Like the Lego blocks we played with as children, 'modular' wetland designs can be built in ever-increasing sizes, and have proven successful treating sewage flows less than 1,000 gallons/day to over 10 million gallons per day. Unlike conventional concrete and steel "activated sludge" treatment plants, constructed wetlands do not need economies of scale to make them 'affordable'.
Transforming mechanical treatment "plants" into odor-free landscaping amenities, sewage treatment infrastructure can be installed close to the wastewater source. Completely hidden within subsurface irrigation systems, reclaimed water can often be safely and economically recaptured or discharged on site, completely eliminating the cost of the sewage collection system altogether, and potentially passing those savings on to the constituents.
LESS is MORE!
Traditional engineering practices dictate construction of an expensive collection system throughout the 'feasible' areas of the island, connected to a high-tech treatment facility. While this approach may very well be appropriate in areas with high-density development, outside urban areas, decentralized management should prevail.
A decentralized or 'modular' approach would utilize a number of smaller, simpler alternative collection systems, each equipped with a low tech, passive treatment component, (i.e. sand filter, wetland, etc.). Modular methods 'centralize' the management, NOT the infrastructure. Individuals and 'clusters' would be connected together by the Internet, instead of through expensive sewer mains. Scarce financial resources would be diverted back to the treatment and responsible recovery of precious water—where they belong!
ECONOMICAL AND ECOLOGICAL
In much the same way as the existing centralized sewer collection system removes all the wastewater from the island and dumps it into the sea, the construction teams and engineering 'experts' behind conventional solutions siphon millions of dollars off the Island in a one-way stream. By contrast, implementation of a decentralized network of constructed wetlands in a modular management system would be an environmental and economic win-win for St. Croix.
Unlike traditional centralized collection/treatment systems which import virtually all piping and mechanical materials, decentralized wetlands and modular treatment networks can be constructed using smaller local construction companies, material suppliers, etc. For example, some constructed wetland designs utilize a clay liner, so in many ways the natural clay soils in the area may actually be a benefit to such projects. Should the practice of constructing wetlands begin to boom in the Caribbean, perhaps someday we would see a clay liner 'spin off' industry created on the island!
In the end, Mr. Nisky may be on the right track asking for a treatment wetland in Frederiksted, Christiansted and mid-island. However, the most sustainable solution for St. Croix would more likely be a combination both centralized and decentralized treatment systems. Managed collectively, a necklace of emerald green wetlands would establish St. Croix as the true environmental jewel of Caribbean.
JUST Environmental Services
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